Citation
Vogtia malloi, a newly introduced pyralid (Lepidoptera) for the control of alligatorweed in the United States

Material Information

Title:
Vogtia malloi, a newly introduced pyralid (Lepidoptera) for the control of alligatorweed in the United States
Creator:
Brown, John Lee, 1944- ( Dissertant )
Habeck, Dale ( Thesis advisor )
Parkins, B. David ( Reviewer )
Reynolds, John E. ( Degree grantor )
Place of Publication:
Gainesville, Fla.
Publisher:
University of Florida
Publication Date:
Copyright Date:
1973
Language:
English
Physical Description:
71 leaves : ill. ; 28 cm.

Subjects

Subjects / Keywords:
Diameters ( jstor )
Eggs ( jstor )
Infestation ( jstor )
Insects ( jstor )
Internodes ( jstor )
Lakes ( jstor )
Larvae ( jstor )
Moths ( jstor )
Nutrients ( jstor )
Streams ( jstor )
Dissertations, Academic -- Entomology and Nematology -- UF
Entomology and Nematology thesis Ph. D
Herbicides ( lcsh )
Weeds -- Control -- Research ( lcsh )
City of Gainesville ( local )
Genre:
bibliography ( marcgt )
non-fiction ( marcgt )

Notes

Abstract:
Vogtia malloi pastrana was introduced into the United States in the spring of 1971 as a biological control agent of alligatorweed, Alternanthera philoxeroides (mart.) Griseb. Vogtia populations were established and survived the winter as far north as Columbia, S. C. , and as far south as Fort Lauderdale, Florida. Vogtia populations dispersed randomly from release sites, and at one location in 1971 reduced the number of aerial stems/ft.^ from 52.5 to 4.0 in four generations. Studies reported herein include: a canonical analysis which describes the insect-host plant relationship between two insects and alligatorweed, the relationship between nutrient levels and alligatorweed grov^th, and a comparison of alligatorweed growing in lakes and in streams; a multivariate regression analysis which measures the significance of each of 12 measured variables in influencing the growth and spread of alligatorweed. Also included are measurements of alligatorweed productivity in greenhouse studies and in field plot studies during the spring and summer growth periods.
Thesis:
Thesis--University of Florida, 1973.
Bibliography:
Includes bibliographical references (leaves 68-70).
General Note:
Typescript.
General Note:
Vita.
Statement of Responsibility:
by John Lee Brown.

Record Information

Source Institution:
University of Florida
Holding Location:
University of Florida
Rights Management:
Copyright [name of dissertation author]. Permission granted to the University of Florida to digitize, archive and distribute this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.
Resource Identifier:
029978488 ( AlephBibNum )
37852656 ( OCLC )
ACG1107 ( NOTIS )

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Full Text












7c1T : ] . Y :T. LIP. ODLUCFD

PYPALID (L... TDOPTE:iJ) Z uR L;: ;O' TOL OF ALLIGOAIC ..".LEO


















By

JOHN LEE BROWN


A DISSERTATION RESENTED TO THE

GRADUATE COUNCIL OF TH'E UNIVERSITY OF FLORIDA

IN PARTIAL FULFILL.i'ENT OF THE .RQUIREMENiTS

FOR THE DEGREE OF DOCTOR OF PHILOSOPHY



T t .,-.--^^ I -~ -.


1973













TABLE OF CONTENTS

Page

ACKNOWLEDGEMENTS...................................... v

LIST OF TABLES.......................................... vi

LIST OF ILLUSTRATIONS................................. viii

ABSTRACT............................................... ix

INTRODUCTION....... ...... .............................. 1

LITERATURE REVIEW........................................ 3

Alligatorweed .................................... 3

Vogtia malloi .... ................................. 4

Biology.................................... ... 5

METHODS AND MATERIALS................................ 7

Biology and Behavior of Vogtia malloi............ 7

Fecundity and Fertility..................... 7

Oviposition......... ......................... 7

Egg and Larval Mortality.................... 8

Greenhouse Colony.................................. 9

Field Releases..................................... 10

1971......................................... 10

1972........................................... 15

RESULTS AND DISCUSSION.................................. 17

Biology and Behavior of Vogtia malloi............ 17

Fecundity and Fertility..................... 17










Oviposition ................................

Egg and Larval Mortality ....................

Behavior ....................................

Field Releases...................................

1971 ........................................

1972 ........................................

ALLIGATORWEED PRODUCTIVITY............................

Introduction......................................

Methods and Materials.............................

Greenhouse Studies..........................

Field Studies................................

Results and Discussion ............................

Greenhouse Studies............................

Field Studies...............................

INTERRELATIONSHIPS BETWEEN ALLIGATORWEED AND TWO

INSECTS- Vogtia and Agasicles.........................

Introduction.....................................

Methods and Materials............................

Results and Discussion...........................

Insect-host plant relationship..............


Nutrient levels and alligatorweed char-

acteristics .................................

Comparison of Lakes and Streams.............

Analysis of variance of Plant Char-

acteristics.................................

.............................................


SUMMARY..


iii


Page

19

19

20

22

22

29

31

31

31








Page

LITERATURE CITED ...................................... 68

BIOGRAPHICAL SKETCH.................. .................. 71












ACKNOWLEDGMENTS


I wish to express my appreciation to the numerous

individuals who have assisted in this study.

I am grateful for the technical assistance given by

Ted Center, Joe Balciunas, and Debbie Beasley both in

laboratory and field studies.

I wish to thank Neal Spencer and the U. S. Department

of Agriculture for providing space and the necessary equip-

ment to carry out this program.

I am also indebted to my committee chairman, Dr. Dale

Habeck, for his assistance in the preparation and submission

of this dissertation.













LIST OF TABLES


Table Page

1. Egg placement by V. malloi female moths caged

over alligatorweed............... ............... 19

2. Nutrient levels in water tables used for

productivity studies ............................. 34

3. Net productivity of alligatorweed in green-

house tests ................................... 34

4. Field studies of alligatorweed productivity..... 37

5. Variables used in canonical correlations with

mean and standard deviations.................... 43

6. Canonical variates in analysis I................ 44

7. Canonical coefficients for individual varibles,

analysis I....................................... 44

8. Canonical variates in analysis II............... 46

9. Canonical coefficients for individual

variables, analysis II.......................... 47

10. Variables used in canonical correlations III.... 48

11. Canonical variates in analysis III.............. 49

12. Canonical coefficients for individual

variables, analysis III.......................... 50

13. Computer reclassification of lakes and streams.. 52

14. ANOV for plant height........................... 54

15. ANOV for internode length ....................... 55







Table Page

16. ANOV for internode diameter...................... 57

17. ANOV for stem density............................ 59

18. ANOV for leaf area missing....................... 61

19. Overall effect of variables on alligatorweed..... 63


vii














LIST OF ILLUSTRATIONS


Figure Page

1. Vogtia release sites, 1971 and 1972............... 11

2. Log number of Vogtia eggs laid plotted

against time..................................... 18

3. Vogtia population build-up and its effect on

alligatorweed, Lake Alice, 1971 .................. 23

4. Vogtia population build-up and its effect on

alligatorweed, Lake Alice, 1972.................. 26
1^


viii











Abstract of Dissertation Presented to the
Graduate Council of the University of Florida in Partial
Fulfillment of the Requirements for the Degree of Doctor of Philosop!



VOGTIA MALLOI, A NEWLY INTRODUCED PYRALID (LEPIDOPTERA)
FOR THE CONTROL OF ALLIGATORWEED IN THE UNITED STATES



By


John Lee Brown


December 1973



Chairman: Dr. Dale Habeck

Major Department: Entomology


Vogtia malloi pastrana was introduced into the United

States in the spring of 1971 as a biological control agent

of alligatorweed, Alternanthera philoxeroides (mart.)

Griseb. Vogtia populations were established and survived the

winter as far north as Columbia, S. C., and as far south as

Fort Lauderdale, Florida.

Vogtia populations dispersed randomly from release

sites, and at one location in 1971 reduced the number of

aerial stems/ft.2 from 52.5 to 4.0 in four generations.

Studies reported herein include: a canonical analysis

which describes the insect-host plant relationship between













two insects and alligatorweed, the relationship between

nutrient levels and alligatorweed growth, and a comparison

of alligatorweed growing in lakes and in streams; a

multivariate regression analysis which measures the signi-

ficance of each of 12 measured variables in influencing the

growth and spread of alligatorweed. Also included are

measurements of alligatorweed productivity in greenhouse

studies and in field plot studies during the spring and

summer growth periods.












INTRODUCTION


Alligatorweed, Alternanthera philoxeroides (Mart.)

Griseb., a vascular aquatic plant in the family Amaranthaceae,

was probably introduced into the United States in the 1890's

(Weldon 1960). In recent years alligatorweed has become one

of the most troublesome weeds in fresh water ecosystems in

the southeast, and by 1970 more than 66,000 acres were

infested (Gangstad and Guscio 1970).

Alligatorweed may occur as a terrestrial plant in low-

lands, as a semi-aquatic plant along streams or lake shores,

or as an emersed aquatic plant. Floating mats which may

extend 50 feet or more out over the surface of the water are

formed of interwoven stems rooted near the shore. The stems

are marked by nodes at intervals of about 2-6 in. each of

which is capable of producing a new plant.

Most aquatic plants cannot compete with alligatorweed

where it has been introduced and are quickly crowded out

(Weldon 1960)

Alligatorweed is not as susceptible to herbicides as

some of the other aquatic plants, requiring application at

higher rates and shorter intervals.

The lack of a suitable chemical control and the alien

status of alligatorweed led to consideration of biological

control as a possible solution. In 1959 the U. S. Army






Corps of Engineers provided funds to the Agricultural

Research Service, USDA, to explore the possibilities of

importing natural enemies of alligatorweed capable of

suppressing its growth and spread (Vogt 1960, Zeiger 1967,

Maddox et al. 1971). As a result of these studies, three

insects have been introduced into the southeastern region

of the United States. A Chrysomelid beetle, Agasicles

hygrophila Selman and Vogt, introduced in 1964 has been

very effective in controlling alligatorweed in certain

areas (Zeiger 1967, Maddox et al. 1971). Amvnothrins

andersoni O'Neill, a thrips, was introduced in 1967, and

although still present in some release areas, it has not

caused significant damage to alligatorweed (Maddox et al.

1971).

The release and establishment of the third insect,

Vogtia malloi Pastrana, the so-called alligatorweed stem

borer (Lepidoptera: Pyralidae: Phycitinae), is the

subject of this dissertation.












LITERATURE REVIEW


Alligatorweed


Alligatorweed, also known as "Lagunilla" in South

America, was probably introduced into the United States

in the ballasts of sailing ships late in the nineteenth

century. It was first recorded in Florida in 1894 (Weldon

1960). Mohr (1901) discovered the plant completely filling

a creek near Mobile, Alabama in September 1897. He states

that the source of the introduction was from the West

Indies and Brazil.

According to Weldon (1960), the species was first

described in 1826 as Bucholzia philoxeriodes Mart. and in

1897 it acquired its present name, Alternanthera

philoxeroides (Mart.) Griseb.

Vogt (1960) studied over 1500 herbarium specimens of

Alternanthera and related genera including approximately

80 species of Alternanthera.

Penfound (1940) described the anatomy and the life

history of alligatorweed along with its aquatic growth

habits in Alabama while Arceneaux and Herbert (1943)

reported on alligatorweed growth in the cultivated fields

of Louisiana.








Weldon (1960) extensively reviewed the literature

concerning past chemical and mechanical controls for

alligatorweed.


Vogtia malloi

The moth Vogtia malloi (Pyralidae: Phycitinae) was

named in 1961 when Jose A. Pastrana described it as a new

genus and species. Vogtia may be recognized by the

following characteristics: large labial palpi, three

times the diameter of the eye, pointing forward with

loose, thick scales and an obtuse third joint; no maxillary

palpi are present; ocelli are present; the front wing has

smooth scales, a slightly curved edge, and ten veins. The

wingspan is 20-22 mm and the wings are straw-colored,

dashed with brown scales on the edge and tip of the wing.

This insect was discovered by George Vogt in his

surveys in South America for natural enemies of alligator-

weed for possible introduction into the United States.

Vogtia was one of the four insects considered by Vogt (1961)

as a major suppressant of alligatorweed in South America.

He found that Vogtia was almost coextensive with alligator-

weed, both geographically and ecologically occurring as far

south (La Plata, Argentia) and as far north (Georgetown,

British Guiana) as his survey extended.

Vogt (1961) reared Vogtia from Alternanthera

philoxeroides and from Alternanthera hassleriana, the plant

he considered most closely related to alligatorweed.








Field.observations in Argentina and starvation tests

in the laboratory (Maddox and Hennessey 1970) indicated

that Vogtia could not complete its life cycle on plants

outside the genus Alternanthera. Plants were selected for

feeding tests on the basis of their.taxonomic relationship

to or ecological association with alligatorweed, or their

economic importance. In field observations (1962-1967) 51

native and introduced species of plants were examined for

feeding damage by Vogtia and 30 plant species were examined

in starvation tests for larval feeding and survival (Maddox

and Hennessey 1970).


Biology

Egg---Eggs are deposited singly on the upper portion

of the aerial stems of alligatorweed. The average length

and width of Vogtia eggs was 0.69 mm and 0.37 mm respectively

(Maddox 1970). When the egg was first deposited, it was opaque

white; as it aged it gradually changed from white to light

yellow to amber. The head capsule was visible through the

chorion usually after the second day. Maddox (1970)

reported the average incubation period was 3.6 days at

an average of 32.90C and 41.4 % RH.

Larva---According to Maddox (1970), head capsule

measurements indicated that there were five instars. The

first stage larva was-approximately 2.25 mm long with a dark

brown to black head capsule about 0.27 mm in diameter

(Maddox 1970). In later stages the head capsule was brown

to light tan, and tan wavy longitudinal lines appear








on the dors.um and pleura of the thorax and abdomen. The

mature fifth stage larva averaged 13.7 mm long with an

average head capsule width of 1.25 mm (Maddox 1970). Larval

development required 24 days at 23C and 64 % RH (Maddox

1970).

Prepupa--As with most holmetabolous insects, a rela-

tively inactive larval period immediately proceeded pupation.

The larva becomes shorter, thicker, and may appear greenish

in color at the time the cocoon was constructed.

Pupa--The pupa was amber or light tan when first formed.

It gradually turned a dark brown or almost black just prior

to emergence. Pupal length varied from 9 to 10 mm and the

width from 1.5 to 2.0 mm (Maddox 1970). The-pupal period

averaged 9.5 days at 23.30C and 49.7 % RH (Maddox 1970).

Adult--The adult is approximately 13-14 mm long with

light tan scaled (both sexes). Variation occurs in both

the size (females are usually larger) and in the definition

of the color patterns of the adult moth. Females often

have scales with a reddish tan hue forming indefinite

patterns, and the males often have black or gray scales

forming definite spots along the front margin and tip of

the wings.












METHODS AND MATERIALS


Biology and Behavior of'Vogtia malloi


Fecundity and Fertility

In laboratory studies newly emerged adults were con-

fined in pint and gallon ice cream cartons covered with a

fine mesh net. One female and two males were placed in

each container and fed a 1:10 honey-water solution. There

were 10 replications using the pint containers and 25 repli-

cations with the gallon containers. Eggs were deposited on

the net covers which were changed daily and the eggs counted.

The temperature and RH were maintained at 270C and 72 %.

To determine hatchability, as an indicator of fertility,

447 eggs collected from the moths in the gallon containers

and 1079 eggs collected from the pint containers were held

at 310C and 60 % RH for 6 days. After 6 days the unhatched

eggs were removed and counted.


Oviposition

To duplicate natural conditions in the placement of

Vogtia eggs for field releases it was necessary to deter-

mine the ovipositional preference of the female moth.

One male and two female adults were confined in a 15 X

15 X 18 in. screen cage which contained a bouquet of 10 to

15 alligatorweed stems in water.








Egg and Lar-val Mortality

Studies were conducted at Lake Lawn, Orlando, Fla. to

determine the percentage of (1) the eggs oviposited that hatch

and (2) the larvae that survive and successfully enter the stems

of alligatorweed. One hundred Vogtia eggs were placed singly

with a camel's hair brush in the axils of terminal leaves

at the rate of 1 egg per stem, along about 30 linear feet

of a continuous mat of alligatorweed. These stems were

then marked with red flagging tape for later recovery.

Five days later, the number of surviving first instar

larvae was determined by locating the marked stems and

recording the number of plants injured within a radius of

about 10 in. around each flagged stem.

In a separate study at Lake Alice Vogtia eggs in

groups of 50 or more attached to strips of cloth were

pinned to stems of alligatorweed to detect and collect

egg parasites. The eggs were left in the field for two

days, after which they were collected and held in the

laboratory for emergency of moth larvae on parasites.

Larvae, prepuase, and pupae collected from the Lake

Alice samples were removed to the laboratory where they

were observed for parasitism. In this study, approximately

250 larvae and 45 pupae or prepupae were collected.








Greenhouse Colony


Permission to release V. malloi in the United States

was obtained in 1970. Pupae or eggs were collected from

the Buenos Aires area of Argentina, an area with climatic

conditions similar to the gulf coast states, and shipped to

the USDA quarantine facility in Albany, California. One

generation of Vogtia were reared at the Albany laboratory

to exclude parasites and diseases. Eggs collected from

that laboratory were shipped to the USDA laboratory in

Gainesville, Florida where a greenhouse colony was estab-

lished on alligatorweed growing in water tables to obtain

sufficient numbers for field release.

Vogtia was first released in Florida in the spring of

1971 and later in the year in Georgia, North Carolina, and

South Carolina.

In 1972 specimens were collected 450 km south of

Buenos Aires, the latitudinal equivalent of Richmond,

Virginia, to broaden the genetic base of populations

already established and perhaps obtain a more winter-hardy

strain.

Specimens from the southern area of Argentina were

released at Fort Jackson (May 10, 1972), Twin Lakes (July

12, 1972), and Garden's Corner, S.C. (May 20, 1972).

Vogtia from this colony were also released in Tennessee

Valley Authority projects and in North Carolina by indiv-

iduals employed in these areas.








Field Releases


1971

During the summer of 1971, Vogtia were released at the

following locations (Fig. 2): Lake Lawn, Orlando, Fla.;

Lake Alice, Gainesville, Fla.; USDA Plant Introduction

Station, Savannah, Ga.; Black Lake, Melrose, Fla.; Fort

Pierce, Fla.; Ashapoo River at Hwy. 17, S.C.; Savannah

River, near Savannah, Ga.; unnamed ditch, Gainesville,

Fla.; Santee Reservoir, near Lone Star, S.C., and Greenfield

Lake, Wilmington, N.C. Populations at the Ashapoo River,

the Savannah River, and the unnamed ditch sites were

destroyed by flooding, and the Fort Pierce site was destroyed

by dredging.

Lake Alice, Fla.-- At Lake Alice, on the University of

Florida campus, conditions were similar to those found at

Lake Lawne, i.e. high nutrient levels and a luxuriant

growth of alligatorweed. The Vogtia releases were made in

a small stream, about 20 ft. wide flowing into Lake Alice

from a sewage treatment plant. At the time Vogtia were

released, alligatorweed extended out 5-10 ft. from the

banks on either side of the stream for a linear distance

of about 100 ft. A similar area, about 150 ft. upstream

from the release area, was designated as a control area.

No Vogtia were released there and there was no attempt to

prevent the spread of Vogtia to this area.

On May 18, 1971 small strips of cloth (ca. 2 in.2), on

which Vogtia eggs had been deposited (a total of 64), were




























GA.


Garden's


savannah River


N e' Wilmington

)ia

XTwn Lakes


!shepoo River
.vannah









le

Orl ndo
Orl ndo


x iort Pierce


X Fort Lauderdale


Fig. 2. Vogtia Release sites, 1971 and 1972







taped to apical tips of alligatorweed. A second release

on June 6 consisted of 81 eggs or newly hatched larvae

(ca. 10 of the eggs had hatched). In this release the

strips of cloth were pinned to the aerial stems in a yd2

area near the shore. Additional releases of 200 eggs on

July 20 and 580 eggs on July 26 were made as in the second

release. These releases were made a few yards upstream

from the first two.

The Vogtia population was sampled during the larval

period of each of the 4 generations which occurred at this

site following the original release (sample dates: July 5,

August 28, September 29, and October 26). A sample con-

sisted of a 1-ft." area of alligatorweed, from which aerial

stems were removed and counted. Samples taken on July 5

were evenly spaced along arcs 1 yd. and 4 yds. out from the

point of release. Seven samples were taken along the 1 yd.

arc and 5 were taken along the 4 yd. arc. Subsequent

samples were taken by randomly throwing a ft.2 wooden frame

on the mat of alligatorweed at 15 ft. intervals along

either side of the stream.

On January 27 after the first frost the Vogtia popula-

tion was checked to determine mortality due to cold and

again on May 2 to determine winter survival. These samples

were taken by randomly selecting injured stems.

Lake Lawne, Fla.-- Lake Lawne is a 33 acre lake located

in Orlando, Florida. Sewage effluent from the surrounding

community drains into the lake creating severe nutrient








pollution which contributes to the luxuriant growth of

alligatorweed extending out 50-60 ft. from the shore in

some areas at the time of the releases.

On April 5 and May 20, 1971, 232 and 150 eggs respec-

tively, were placed on alligatorweed in the northwest corner

of the lake. Small strips of cloth, each with 10-15 Vogtia

eggs attached, were taped to aerial stems. Five days later

the eggs and stems were inspected. On June 23, a 2 x 4 ft.

section of alligatorweed mat was removed from the lake and

replaced by a Vogtia-infested mat of the same size from the

greenhouse colony. The infested mat and the surrounding

alligatorweed were inspected weekly to determine the number

of Vogtia larvae percent. Releases of adult Vogtia were

made in the same general area on July 23, August 13, August

18, and August 26 of 10, 7, 40 and 21 moths, respectively.

The Vogtia population was monitored periodically by

counting the number of injured plants in the release area.

Black Lake, Melrose, Fla.-- Alligatorweed growth on

this 20-25 acre lake was much less vigorous than at other

sites when Vogtia were released. The stems were smaller

and more fibrous and the alligatorweed supported several

(Sacciolepis striata (L.) was the dominant species) species

of grass and weeds. The lake was encircled by alligator-

weed mats 5-20 ft. wide. On August 20, 1971, 19 adults

were released in a 3-ft.2 screen cage placed on the

alligatorweed mat. Seven days later after the moths had

completed oviposition the cage was removed. No further








releases were made at this site. Counts of larvae or wilted

tops were made November 15, 1971 and January 28, February 11,

and April 17, 1972 from randomly selected sites.

Savannah, Ga.-- The only release at the USDA plant

Introduction Station consisted of Vogtia eggs placed in 3

screened plots (5 X 6 ft.) containing terrestrially-rooted

alligatorweed by Mr. Willey Durden on April 14, 1971 (Willey

Durden, personal communication).

Greenfield Lake, Wilmington, N.C.-- Vogtia eggs and

larvae were placed in a small stream 20-30 ft. wide flowing

into the northern end of the lake. The stream was completely

covered by a solid mat of alligatorweed for several hundred

feet. On August 2, 1971, a 4-ft.2 section of mat was removed

and replaced by a Vogtia-infested mat of the same size from

the greenhouse colony. The mat was wrapped in 6 mil poly-

ethylene and a small amount of water added for transporting.

Santee Reservoir, S.C.-- Vogtia were released on the

south side of the reservoir, near the town of Lone Star.

Alligatorweed at the release site appeared as rooted plants

in shallow water. The stems were small and fibrous, a

condition often observed in rooted alligatorweed. On August

3, 1971, a 2-ft.2 section of Vogtia-infested mat from the

greenhouse colony was placed in the stand of alligatorweed

after a section was removed.








Field Releases


1972

Releases were made in 1972 at the following locations:

Fort Jackson (Upper Legion Lake, Columbia, S.C.), Twin Lakes,

S.C., Peeples' Pond (Garden's Corner, S.C.), and a roadside

ditch (Fort Lauderdale, Fla.) (Fig. 2).

Fort Jackson, S.C.-- Upper Legion Lake is a small man-

made lake (10-15 acres) ringed with alligatorweed extending

out 5-20 ft. from the shore. On May 10, 72 larvae were

released on the east side of the lake, by placing them in-

dividually, with a camel's hair brush in the terminal leaves

of alligatorweed stems.

During the summer, 1972, the Vogtia release site was

subjected to malathion fog, used in mosquito abatement, and

to Diquat at 2 lbs./acre sprayed in alternating strips.

The Vogtia population was sampled September 11 and November

15, 1972 and June 16, 1973.

Twin Lakes, S.C.-- Twin Lakes consists of two ponds,

about 5 acres each, connected by an old riverbed and located

near Summerville, S.C. Alligatorweed normally covers all

but a small area in the center of both ponds.

On July 12, 100 adults were released in the norther-

most pond where alligatorweed was 16 to 18 in. tall in

relatively dense stands. The Vogtia population was sampled

on September 12 and November 15, 1972.

Garden's Corner, S.C.-- Peeples Pond is approximately

10 acres in size and ringed with alligatorweed extending








20 30 ft. out from the shore. On May 20, 150 Vogtia

eggs were placed on the aerial stems of alligatorweed and

25 adults were released.

Both Agasicles and Vogtia populations were sampled on

July 13, and September 11, 1972 and June 16, 1973.

Fort Lauderdale, Fla.-- On April 19, 85 first instar

larvae collected in the wilted tops of alligatorweed at the

Melrose, Fla. (Black Lake) site were released in the road-

side ditch (20 to 30 ft. wide) alongside the Sunshine State

Parkway 1/2 mile north of exit 16. Three months later,

July 18, 125 adults from the greenhouse colong were released

in the same general area. Alligatorweed grew luxuriantly

along the ditch for approximately 0.5 mile on either side

of the release site.

The Vogtia population was sampled July 18 and September

20, 1972 and April 26, 1973.















RESULTS AND DISCUSSION


Biology and Behavior of Voytia malloi


Fecundity and Fertility

According to Maddox and Hennessey (1970), the female

moth lays an average of 267 eggs with 6, 34, 18, 15, 12, 6,

5, and 4% of the total laid from the first through the eighth

day, respectively.

In laboratory studies 25 female moths held in gallon

containers laid only 132 eggs (average). The adults used in

the test were taken from a crowded greenhouse colony and may

reflect a reduced activity due to crowding. This study confirm.

Maddox's findings that the greatest percentage (69) of the

eggs were laid on the second day following emergency (Fig. 1).

Although some eggs were laid on the first day, most were

apparently infertile and did not hatch.

Only 84.3% of the eggs collected from moths in gallon

containers hatched. Of 1079 eggs from moths in pint containers,

the percentage was only 49.7%, presumably from a lack of mating

in the small containers.

A mated female, held for observation in a pint con-

tainer, laid 47 eggs in one period which began at 11:00 PM.

The average time interval between eggs was 17.3 seconds.












Y axis


Linear regression analysis

y = a(o) + a(1) x


log .1 6
of
eggs
laid


1.2





0.8





0.4






_____ __X axis
2 4 6 8
DAYS

Fig. 1. Log number of Vogtia eggs laid plotted against
time.








This moth was very active during oviposition, flitting

around the container and stopping only long enough to

deposit an egg.


Oviposition

Host of the eggs (60.6%) were deposited on the under-

side of the terminal leaves, with progressively fewer eggs

being placed on leaves of the lower nodes (Table 1). These

data confirmed Maddox's earlier report that eggs are de-

posited on the underside of a leaf in the first through

fourth pairs of apical leaves on the host plant.


Table 1. Egg placement by J. malloi female moths caged

over alligatorweed.

Margin Midrib Axil Total % Total

Terminal 17 19 24 63 60.6
leaves

Below 1st 3 8 8 19 18.3
node

Below 2nd 4 4 7 15 14.4
node

Below 3rd 2 1 4 7 6.7
node
26 32 43 104



Egg and Larval Mortality

The expected egg viability as indicated by laboratory

studies was 85%. The number of damaged stems recorded

indicated that 41% of the eggs produced larvae which caused

visible injury to the alligatorweed stems, leaving 44% of

the Vogtia eggs or larvae lost to predation or other








environmental factors.

Several specimens of the egg parasite Trichogramma

perkinsi Girault (identified by L. R. Ertle USDA) were

collected from the Vogtia eggs attached to alligatorweed

for 2 days.

Six internal parasites belonging to 2 species of

ichneumonids were reared from the Vogtia larvae and pupae

collected from Lake Alice: 4 were Gambrus bituminosus

(Cushman) and the other 2 were G. ultimus (Cresson) (determi-

ed by R. W. Carlson USNM). Both species have been collected

from a number of Lepidoptera in the United States (Muesebeck

et al. 1951).


Behavior

Upon hatching, the first stage larva enters and girdles

the alligatorweed stem, usually at the second internode.

Later in the season, the aerial stems may become tough and

fibrous, and the young larvae may descend on a silk strand

to the axillary shoots growing farther down the stem which

are still tender (Brown and Spencer 1973).

Within a few hours, the girdled top is wilted, and

within a few days it usually breaks off at the node just

below the girdle and falls onto the supporting mat of

alligatorweed with the young larva still inside. The

larva soon leaves the dead top and bores into another stem,

or the same stem at a lower level, and the process is repeated.

As the larva matures the process of girdling and feed-

ing on the interior of the hollow stems above the girdle

may be repeated many times (as many as 9 stems were reported








destroyed by a single larva, Maddox 1970). The mature larva

is known as a roving stem borer because of its characteristic

feeding habit. The larger the larva, the farther down the

stem it girdles, and frequently mature larvae are found

feeding below the water line, protected from drowning by

the air-filled cavity of the hollow stems.

When the Vogtia larva bores into a stem it quickly

seals the entry hole with silk strands to make it water-

proof. The exit holes however are never sealed leaving

the plant open to attack by other organisms.

Just prior to pupation the mature larva enters an

internode and seals off both ends at the nodes. A small

"window" is chewed in the stem wall, leaving only a thin

layer of the outer epidermis intact. The larva spins a

cocoon and orients itself so that the head region is

adjacent to the window, through which the adult will

eventually emerge.








Field Releases


1971

Lake Alice, Fla.-- Larval counts taken at Lake Alice

(July 5) along arcs 1 yd. and 4 yds. from the release area

were not significantly different, and no directional move-

ment was indicated; the mean number of larvae/ft.2 along

these arcs were 5.4 and 5.2, respectively. The standard

deviation of insect counts in the 12 samples was 2.84.

The population, within this limited area was distributed

with X = 5.3, S2 = 8.06, S2 / = 1.52, and K = 10.19.

Adult dispersal appeared to be random. Counts from later

samples indicated that the population expended at a nearly

uniform rate in all possible directions with each new

generation. Population density increased to 9.4 larvae/ft.2

by the second generation in the immediate release area and

then began a steady decline as the attractiveness of the

alligatorweed was reduced and the number of available egg

deposition sites diminished (Fig. 3).

During the first two generations the area of infesta-

tion was not significantly expanded based on observations

of wilted tops. The mean number of healthy aerial stems of

alligatorweed/ft.2 was reduced from 52.5 to 36.9. An

invasion of the test area by the southern beet webworm,

Herpetogramma bipunctalis (F.), occurred during the second

generation which resulted in partial defoliation of many of

the aerial sters. Although webworm damage was temporary,

it may have influenced the observed movement of V. malloi










































AUG. 28


SEPT. 29


30

2E-


20 P
1-


OCT. 26


Fig. 3. Vogtia population build-up and its effect on
alligatorweed, Lake Alice, 1971.


6/




4




2





0
JUL. 5








adults from the release area to the nearby control area

during the second generation, a distance of 150 yds.

In the third generation samples (Septenber 29), the

number of larvae.ft.2 had dropped to 6.3, with the number of

healthy aerial stems reduced to 17.4/ft.2. By the middle

of the fourth generation (October 26), the mean number of

larvae and aerial stems/ft.2 had dropped to 3.4 and 4.0,

respectively. With this damage the alligatorweed mat was

beginning to break up in the release area and was no longer

increasing. Other semiaquatic plants began to move in over

the submersed portion of the alligatorweed mat.

A one-way analysis of variance showed that the reduc-

tion in the number of aerial stems between sample dates

was statistically significant (0.01 level) but there was

no significant difference between insect counts for these

dates, probably due to the wide variation between samples.

The January 27, 1972 data consisted of superficial

observations only. The lack of alligatorweed stems due to

the cold and to Vogtia and Agasicles damage made detailed

samples impractical. Ten first and second instar larvae

collected from wilted stems in 2 small mats of alligator-

weed were not in diapause, but were actively feeding.

On April 25, 1972, the alligatorweed had attained a

height of 15 in. when the Vogtia population was sampled.

The mean number of larvae/ft.2 was 3.3 at the release site;

therefore a substantial number of Vogtia survived the winter.








In 1972 the Lake Alice population duplicated the 1971

response, i.e. the Vogtia population peaked at about the

same density and then began a decline (Fig. 4).

ake Lawne, Fla.-- The first releases made in this

area (April 5 and May 20, 1971) were probably unsuccessful

since no damaged stems were found, a result of the newly

hatched larvae becoming entangled in the tape. The second

attempt to establish a Vogtia population in Lake Lawne

(June 23) was likewise unsuccessful; no larvae were found

after the first week. Most of the Vogtia present in the

infested alligatorweed were probably drowned due to flood-

ing of the cut stems. A few larvae were found the following

week but they apparently did not survive to reproduce. On

July 23, 10 adults were released at the same location from

which a small larval population became established. Three

additional releases were made in August to supplement the

population.

The Vogtia population did not expand its numbers

rapidly. The population remained at low levels (ca. 0.1

larvae/ft.2) and larvae were never found more than 50 yd.

from the point of release during the summer of 1971. At

Lake Lawne where no frost occurred the alligatorweed

remained green throughout the winter. On May 21, 1972 the

population had increased to 3.7 Vogtia larvae/ft.2 in the

release area.

Black Lake, Fla.-- Only one release of 19 adults was

made at this site on August 20, 1971. On November 15












* LARVAE/FT2


10 L


- -


r- S /
STEMS/FT2


50



I



I N
-40



30

E-


*0-

MAY JUNE JULY AUG SEPT OCT NO---


Fig. 4. Vogtia population build-up and its effect on
alligatorweed, Lake Alice 1972.


/ a








numerous injured alligatorweed stems were found up to 50 ft.

from the point of release and a few injured plants were

found about 100 ft. away. By January 28, 1972-, the Vogtia

population had expanded to all areas infested by alligator-

weed in the lake. Vogtia larvae were active and still

feeding inside aerial stems recently killed by frost; most

of these were early instars. On February 11 the larvae

were found feeding below the frost-killed aerial stems on

green stems that were protected from frost. By April 17,

1972, the Vogtia population had attained a density of about

4.0/ft.2 around the entire lake.

By the end of the summer the alligator-weed at Black

Lake had been so reduced in area and density of the stems

that in many areas of the lake it was no longer the dominant

species. The suppression of alligatorweed at this site was

probably due to a combination of factors, i.e. insect

pressure, interspecific plant competition, and.-low nutrient

levels in the water.

Savannah, Ga.-- A Vogtia population became established

and survived the 1971-27 winter despite killing frosts on

terrestrially-rooted alligatorweed in experimental plots.

Mid-winter sampling failed to locate the overwintering

insects (Durden, personal communication). In South America,

Vogtia was found during the winter in the roots of terres-

trial alligatorweed (Vogt 1960).


*Willey C. Durden




28



Greenfield Lake, N.C. and Santee Reservoir, S.C.--

Vogtia has not been recovered at the 2 northermost release

sites. The method of release, i.e. the transfer of infested

mats, was proved unsatisfactory at Lake Lawne and may be one

reason for lack of establishment at these sites.








Field Releases


1972

Fort Jackson, S.C.-- By the end of 1972 only small

patches of alligatorweed remained at this site because of

the herbicidal treatment. The effect of removing most of

the alligatorweed on the Vogtia population was to concen-

trate the insects on the remaining mats of alligatorweed.

Samples taken November 15 indicated a population density
2
of 5 larvae/ft. .Earlier samples taken September 11

showed only 1 larva/ft.2

On June 16, 1973 after a severe winter in this area,

the Vogtia population was 0.6/ft. and the alligatorweed

was killed back to the water in most mats. A few protected

areas had healthy alligatorweed, and in one such area adult

Agasicles were found which had presumably survived the

winter as well.

Twin Lakes, S.C.-- The September 11 sample date showed

1.0 Vogtia larva/ft.2 with moderate defoliation by Agasicles

(approximately 50% of the leaf area missing). By November

15 the Vogtia population had increased to 2.6/ft.2. This

area was not sampled in 1973 because of spring flooding.

Garden's Corner, S.C.-- Garden's Corner was the only

site where Agasicles stripped all the foliage and many of the

small shoots from the aerial stems of alligatorweed after a

Vogtia population had become established. The Vogtia

population remained lo.: but was not elimianted. When the

Vogtia release was made (May 20, 1972) the Agasicles adult








population was 5 adults/ft.". By July 13 the alligatorweed

was under severe stress and the Agasicles population was

11 adults/ft.2 and the Vogtia population was 0.66/ft.2

Samples on June 16, 1973 indicated the Vogtia popula-

tion density was 1.6 larvae/ft.2 after a severe winter for

that area.

Fort Lauderdale, Fla.-- Samples on July 18 indicated

that the Vogtia population had attained a density of 0.43

larvae/ft.2 from the first release. A population of 3.4/ft.2

was recorded on September 20, 1972. In both cases the

sampling was done within approximately 100 yds. of the

release site. The population density declined as the dis-

tance was increased from the release area.

On April 26, 1973 just after spring growth had begun
2
the population was 2.25/ft. Therefore the population

.was probably not reduced significantly during the winter

period. This was expected since frost did not occur in

this area.













ALLIGATORWEED PRODUCTIVITY


Introduction

To evaluate the effects of stress caused by biological

control agents to growing plants, comparisons must be made

between that plant growing undisturbed, and that plant with

the additional stress factors added. Environmental condi-

tions, nutrient levels, and many other factors play a

significant role in regulating a plant's growth and spread.

This is especially true of plants such as alligatorweed

that are adapted to a wide range of conditions. With these

limitations in mind, attempts were made to determine the

net rate of biomass production in alligatorweed growing

under favorable greenhouse conditions, and in four lakes

which had varying levels of injury from biological control

agents.


Methods and Materials

Greenhouse Studies

Alligatorweed was grown in a 4 X 12 ft. X 6 in. green-

house table divided into three 4 X 4 ft sections. The two

end sections were covered with 6 mil polyethylene and

filled with tap water to a depth of 5 in. On December 13,

9.5 lbs of alligatorweed from the floating portion of a mat

of weeds taken from Lake Alice, Gainesville, Fla. were








placed in the water-filled sections. The middle section

contained a Henry J. Green hygrothernograph, which recorded

the temperature and relative humidity at the approximate

water level.

Artificial lighting, about 3000 ft. candles, was

supplied by 12 Sylvania 40w VHO cool white florescent

bulbs and 24, 75w incandescent lamps attached to a light

board and suspended 11 inches from the table top. An

Intermatic model T101 timer controlled the 12 hour photo-

period.

Each plant section was initially filled with tap

water to which 150g milorganite and 200g of 20-20-20 soluble

plant food was added. On January 4 another 180g of the

same fertilizer plus 45g of 1.82% iron supplement were

added to each section.

Half of the growing mat in each section was removed

on January 10, the remainder on January 16, terminating the

study. To reduce experimental error, alligatorweed was

taken from alternate sides of the table. The plant material

was allowed to drain for 5 minutes and then weighed on a

Fairbanks Morse portable platform scales.

Water samples were taken at the beginning of the

experiment and on January 4. These samples were analyzed

for common nutrients, i.e. nitrates, phosphates, potassium,

chlorides, magnesium, manganese, iron, copper, and calcium

by the Soils Laboratory, IFAS, University of Florida.

The mean daily temperature was 29C, the mean daily RH








was 50.6%, and the pH of the water was 7.5. The water tem-

perature on the first sample date was 260C.


Field Studies

Standing biomass samples were taken in early spring,

before much growth had occurred (March 19, 20, 22, and 23),

in early summer (May 2, 10, 20, and 24), and in midsummer

(July 13, 18, 27, and August 1) at two lakes (Black Lake,

Melrose, Fla. and Garden's Corner, S.C.) and three streams

(stream flowing into Lake Alice, Gainesville, Fla., roadside

ditch, at Ft. Lauderdale, Fla., and Twin Lakes, S.C.).

Alligatorweed characteristically grows very rapidly in the

spring and then considerably slower during the rest of the

growing season. These samples represent both growth periods

for alligatorweed at these sites.

A stainless steel cylinder was constructed to extract

a 1.2 ft.2 core sample from the floating mats of alligator-

weed. One end of the cylinder was sharpened to facilitate

cutting through the mass of alligatorweed, and the other

end was covered with 1/4 in mesh hardware cloth. A sample

was removed from the water, after cutting, by inverting

the sampling device. The sample was allowed to drain for

5 minutes and then emptied into a plastic bag and weighed

with a hand-held scales. The same mat of alligatorweed was

used for all sample periods at each location. All samples

were taken half way between the shoreline and the leading

edge of the mat.








Results and Discussion


Greenhouse Studies

Although the study began December 13, the actual growth

period of the alligatorweed did not begin until several days

later. When the alligatorweed was transferred to the green-

house table the aerial stems were broken and disoriented to

such an extent that growth was effectively stopped until new

stems were produced. Therefore the first samples at 28

days showed little change (Table 3), since the plants had

been actively growing for 10 days or less. The increase in

biomass during the first period was 64%. The second sample

period, lasting only 6 days increased its biomass by 48%.

Nutrient levels (Table 2) were much higher than those

normally found in natrual lakes or streams. In Lake Alice,

for example, only phosphates were higher than in these water

tables (2.98 ppm). Iron was 0.25 ppm, nitrates were 5.3 ppm,

chlorides were 25.0 ppm, and the pH was 7.75 on May 2, 1972.


Table 3. Net productivity of alligatorweed in greenhouse
tests


Wet weight of samples (lbs)


Initial wt. 28 days 34 days % increase


Rep. 1 9.5 14 19 200
Rep. 2 9.5 11 18 189










Table 2. Nutrient levels in water tables used for productivity
studies (ppm)


Sample No3 P K Cl Mg Mn Fe Cu Ca


Rep. 1 22.0 0.25 70.9 92.0 1.43 .075 1.80 0.20 0.90
Rep. 2 22.0 0.30 70.0 92.0 1.28 .075 1.90 0.20 0.82

tap water 4.3 0.0 0.0 22.5 0.73 0.0 0.0 0.10 1.10



Field Studies

Alligatorweed productivity in the field did not approach

that in the greenhouse. The Twin Lakes site had a high

percent increase, but the growth period was 52 days, compared

with 34 days for the greenhouse study (Table 4).

The early summer daily increment factors for the five

sites were .104, -.003, .082, .035, and .028 for Twin Lakes,

Fort Lauderdale, Garden's Corner, Lake Alice, and Black Lake,

respectively. The daily increment factor for the greenhouse

alligatorweed was .26, or 2 1/2 times the hignest increment

factor recorded in the field.

On a per acre basis, the Twin Lakes growth rate was

equivalent of 3,775 lbs of biomass produced per acre per day.

In the 52 day period an acre of alligatorweed would produce

193,300 lbs of new growth. That is approximately twice as

productive as the most productive agricultural crop, in half

the time. Corn grown on muck soils produces 2-30 tons of

silage in about 100 days (Cunha and Rhodes 1965).




36



At Garden's Corner during the summer sample period, and

at Fort Lauderdale, to a lesser extent, the standing biomass

was reduced. The reduction at Garden's Corner corresponded

with a heavy attack of the Agasicles beetle, in which the

aerial stems of alligatorweed were completely stripped of

their foliage and small stems. The reduction at Fort Lauderdale

was less dramatic and may have been due, in part, to severe

interspecific plant competition.









Tab~ 4~Fie1d sfl-udies of all iaM-orww~t~ nronrlc1-Avitv v 1972 -


Daily increment (Lbs.)
Location Sample period To. days % increase Wt./1.2ft.2 Wt./Ac/day


Twin Lakes, Mar. 3 May 10 52 110 .104 3775
S. C.

Lake Alice, Mar. 23-May 2 40 42 .035 1270
Gainesville
Fla.
June 1-Aug. 1 61 24 .02 726

Garden's lar.20-May 20 61 73 .082 2976
Corner, S.C.
lay 20-Jul 13 54 -24 -.052 -1887

Black Lake, Mar 22-May 24 63 40 .028 1016
Melrose, Fla
Aay 31-Jul 27 57 6 .007 254

Ft. Lauder- April 20 -
dale, Fla. July 18 89 -6 -.003 -109


Table 4-














INTERRELATIONSHIPS BETWEEN ALLIGATORWEED
AND TWO INSECTS-- Vogtia and Agasicles


Introduction

Pioneering plants or opportunists such as alligatorweed

may because of their tolerance to wide environmental condi-

tions appear in different areas with very different growth

and morphological characteristics. Alligatorweed in some

areas may produce numerous, short, fibrous stems while in

other areas the aerial stems may be much less dense in

number and taller, thicker, and more rapidly growing. Under

these conditions, it becomes increasingly difficult to

evaluate the host plant-insect relationship, and almost

meaningless to compare insect population data between the

areas. Therefore .a.great number of samples (287.) from all

the release areas have been combined to provide an overall

estimate, or comparison, of the effect of a given parameter

on alligatorweed with the effect of all other parameters

considered at the same time. The variables representing

the two insects have been evaluated with and without the

influence of the other variables being included in the model.

Two stastical methods were used to show the interactions

between the Vogtia and Agasicles populations, between each

of these insects and alligatorweed, and between available

nutrients and alligatorweed growth.








In the canonical correlations program, 24 variables

were grouped into sets. The sets were then compared and

significant relationships were defined. The second program

was a full multivariate regression model which explained

the significance of each of the measured variables in

influencing alligatorweed growtn.

In canonical correlations, a set of independent vari-

ables may be compared with a set of dependent variables to

find the linear combination of variables in each set which

when correlated is maximum. The resultant variable is

known as a canonical variate. If some linear relationship

between the sets of variables still remains unaccounted for

by the first set of canonical variates, the process of find-

ing new linear combinations that would best account for the

resideual relationships between the sets can be continued.

This process can go on until there are no significant

linear associations left. Each canonical variate is

orthogonal to (or unrelated to) other canonical variates.

The chisquare test is used to evaluate variates for signi-

ficance.

In canonical correlations, variables in one set may

be combined to predict maximally the variations of the

variables in the other set. This process was utilized to

compare data from lakes and streams, and to predict the

number of samples that should occur in using different sets,

lakes or streams (See Morrison 1967) for detailed discussion

of canonical correlations and tests of significance). All








statistical.methods were analyzed by computer program, BND,

SPSS (Nie, 1970) on the University of Florida North East

Regional Data Center's IBM 370/165.


Methods and Materials

The Vogtia and Agasicles sampling procedure was described

in the section on colonization, i.e. a ft.2 frame was used to

determine the population density, as well as to gather plant

material for stem measurements. Sample sites were selected

either by a random process (Lake Alice, Black Lake, and Lake

Lawn) or by taking samples at preselected 15 feet intervals

(Garden's Corner, Ft. Lauderdale, and Twin Lakes). Aerial

stems which were selected for measurement were representative

of the sample in both height and diameter. In most cases,

the uniformity of the samples made multiple plant measure-

ments unnecessary.

Measurements for each of the sample sites included the

following: stem height, length of the fourth internode,

diameter of the fourth internode, stem density, percent

leaf area missing, Agasicles/ft.2, vogtia/ft.2 (expressed

as a total and as each of the instars as a separate variable),

pH, alkalinity, iron (ppm), turbidity (jtu) chlorides (ppm),

phosphates (ppm), nitrites and nitrates (ppm), hardness,

water depth, and whether the sample was taken from a lake or

stream. The fourth internode was chosen for plant measure-

ments because it was the first fully developed internode.








Water samples were analyzed for nutrients in the laboratory

with the use of a Hach water testing kit.

A total of 287 samples were taken from the six following

release sites, three of which were lakes and three were

streams. The number of samples taken from each site is shown

in parenthesis: Lake Alice, Gainesville, Fla. (76); Black

Lake, Melrose, Fla. (155); Lake Lawn, Orlando, Fla. (34);

Peeples Pond, Garden's Corner, S.C. (2); Roadside ditch,

Ft. Lauderdale, Fla. (17); and Twin Lakes, Summerville,

S.C. (3), (Fig. 2).








Results and Discussion


Insect-Host Plant Relationship

In the first analysis, the set of plant characteristics

was compared with the set of variables representing numbers

of Agasicles and Vogtia present and a measure of Agasicles

feeding damage. As a result of these correlations, 3 new

canonical variates were formed (Table 5 and Table 6). Each

of these new variates was significant at the .01 level of

probability, indicating that 3 independent and significant

linear relationships existed.

If we examine the coefficients of the individual

variables (Table 7), we can explain the combinations of

variables making up each of these associations. The first

canonical variable represents the most important of the

linear associations, and in this case there is a positive

association between plant height, internode length, inter-

mode diameter and the number of Agasicles and Vogtia, and

a negative association between the same plant characteristics

and Agasicles feeding. Therefore, both Vogtia and Agasicles

tend to occur more frequently in alligatorweed with larger,

taller stems. Vogtia, having a larger coefficient, probably

favors these conditions more than Agasicles. The negative

association between the plant characteristics and Agasicles

damage was expected. The more damage done by Agasicles,

the more stress is placed on the growing plants, resulting

in smaller unthrifty stems.









The second canonical variate of less importance than the

first, but equally as significant, consisted of a negative

association between Agasicles feeding and plant height, and

internode diameter. This may appear to be in contradiction

of the first canonical variate; however, the canonical

variates must be considered separately. Therefore, 2 rela-

tionships exist, one superior to the other. When plants

are heavily attacked by Agasicles, the upper internodes may

be damaged sufficiently to cause them to be dropped off

resulting in a condition described by this relationship.


Table 5. Variables used in.canonical correlations with
mean and standard deviations.


Variable

SET I

Plant Height

Internode-Length

Internode Diameter

No. Stems

Percent damage

SETII

No. Agasicles

No. Vogtia

1st Inst. Vogtia

2nd Inst. Vogtia

3rd Inst. Vogtia

4th Inst. Voqtia

5th Inst. Vogtia


Mean Standard Dev.


11.895

2.2250:

.12007

51.212

15.174


3.90

* 1.-321

.05771

21.85

26.328


1.536

3.515

1.268

0.651

0.498

0.456

0.41S


2.634

4.138

2.095

1.219

0.876

0.918

0.280


Cases


287

287

287.

287

287


287

287

287

287

287

287

287








Table 5 continued.

Variable

Vogtia Prepupae

Vogtia Pupae


Mean

0.066

0.177


Standard Dev.

0.288

0.465


Table 6. Canonical Variates in Analysis I

Number of Canonical Chi-Square
Variate Sets

1 156.99149

2 75.90101

3 12.57912


Cases

287

287


Degrees of
Freedom

12**

6**

2**


** indicates significance at .01


Table 7. Canonical Coefficients for
Analysis I


Plant Height

Internode Length

Internode Diam.

No. Stems

% Leaf-Area Missing

No. Agasicles

No. Vogtia


Can. Var. 1

0.345*

0.487

0.329

-0.027

-0.638

0.321

0.645


Individual Variables,


Can. Var. 2 Can. Var. 3

-1.152 -0.469

-0.022 0.628

0.726 0.188

-0.535 0.906

0.704 -0.554

0.394 0.979

0.443 -0.700


*Variables underlined contributed most significantly to
the linear relationship.


_ I ___ ____L___I__~C~~C 1








The third canonical variate, likewise independent of

the first 2 and of less importance, consisted of a positive

association between the number of Agasicles and internode

length and the number of stems. We can conclude from this

that adult Agasicles tend to occur more frequently in dense

stands of alligatorweed with samller stems, and the latter

condition is negatively correlated with the number of Vogtia

and with Agasicles feeding. The Agasicles feeding and stem

size association is in agreement with the first canonical

variable but much smaller in magnitude. The positive

correlation of Vogtia with stem size is expected since in

small stems the full grown larvae may be as large in diameter

as the stem itself and, therefore, not protected from para-

sites and predators or environmental factors.

It should be noted that 63.96% of the variation is

explained by canonical.variable 1,. 30.92%. by canonical:

variable 2, and only 5.12% of the variation is explained

by canonical variable 3. The most important associations,

therefore, are probably described by canonical variables

1 and 2.

In the second analysis, the same 4 plant characteristics

i.e. plant height, internode length, internode diameter, and

number of stems were used to compare with the number of

Agasicles, Agasicles feeding damage and each of the 7 immature

stages of Vogtia present.

In this correlation, 4 new canonical variables were

formed (Table 8). The first 2 were significant at the .01








level of probability. The third was significant at the .10

level of probability and, therefore, will not be considered

in this discussion. The fourth variate was not significant.

The first variate incorporates 61.22% of the total variation

and the second 29.87%.



Table 8. Canonical Variates in Analysis II.


Number of Canonical Chi-Square Degrees of
Variate Sets Freedom

1 195.18961 36**

2 94.64266 24**

3 23.28067 14

4 5.74528 < 6



** indicates significance at the .01 level of probability


An inspection of the canonical coefficients for the

individual variables (Table 9) reveals a positive associa-

tion between stem diameter and internode length with the

5th instar Vogtia. This relationship, as explained in the

first analysis, has been observed in the field in areas where

alligatorweed was under severe stress. During temporary

stress periods, the aerial stems may become small,with the

stems making up the mat remaining large. In this case,

the larvae can survive in the mat unless flooding occurs

which may drown the larvae. Another relationship occurring

in the first canonical variable is a negative association

between Agasicles feeding and stem size. This relationship,









also apparent in the first analysis, is a result of Agasicles

damage producing stress in the alligatorweed which resulted

in smaller, less thrifty plants.

The second canonical variate shows a negative associa-

tion between Agasicles feeding and plant height. As dis-

cussed earlier, reduced plant height with increased Agasicles

damage is a direct result of Aqasicles attack. Since the

plant suffers more damage in the top few internodes, the

more severely attacked plants are much more prone to break-

ing over, and to dropping these upper internodes.


Table 9. Canonical Coefficients for Individual
Analysis II

Variable Can. Var. 1

SET I

Plant Height 0.036

Internode Length 0.550

Internode Diam. 0.387

No. Stems -0.220

% Leaf Area Missing -0.359


SET II

No. Agasides

1st Instar Vogtia

2nd Instar Vogtia

3rd Instar Vogtia

4th Instar Vogtia


0.273

0.187

0.028

0.021

0.237


Variables,


Can. Var. 2



1.156

0.200

-0.561

0.578

-0 855


-0.195

0.141

-0.114

-0.145

-0.090








Table 9 continued.

Variable

5th Instar Vogtia

Vogtia Prepupae

Vogtia Pupae


Can. Var. 1

0.544

0.051

0.119


Can. Var. 2

-0.075

-0.147

-0.076


Nutrient levels and alligatorweed characteristics

In a similar program the same plant characteristics

were compared with the physical and chemical parameters

associated with water quality at each site. The second set

of parameters were: pH, alkalinity, iron, turbidity,

chlorides, phosphates, nitrates, hardness, depth of the

water, and the lake or stream origin of sample (Table 10).


Table 10. Variables used in canonical correlations III (IN)


Variable
SET I

Plant Height

Internode length

Internode diameter

No. stems


Mean



11. 89

2.225

.1201

51.21


S.D.


3.90

1.321

.0577

21.85


Cases


287

287

287

287


SET II


pH

alkalinity

iron

turbidity

chlorides


7.02

74.14

0.23

36.13

18.48


0.99

74.21

0.29

20.15

12.2


287

287

287

287

287









Table 10 continued.

Variable Mean S.D. Cases

phosphates 1.32 1.75 287

nitrites & nitrates 3.68 1.35 287

hardness 99.21 120.45 287



These canonical variates produced four linear relation-

ships which were significant at the .01 level of probability

(Table 11). As in the first program, each of these relation-

ships is independent of the others. The first and most

important association is a negative correlation between

water depth and plant height and a positive correlation

between plant height and turbidity. Since larger coeffi-

cients occur between water depth and plant height those are

likely the more important variates in this linear relation-

ship. Therefore, as water depth increases, plant height

tends to decrease. Secondarily, as turbidity increases

plant height also increases. The latter relationship

probably reflects nutrient pollution which would tend to

produce larger, more vigorous stems (Table 12).


Table 11. Canonical variates in analysis III

Variates Chi-sauare D.F.

1 526.21 40**

2 233.11 27**

3 76.46 16**

4 24.03 7**

** Indicates significance at the .01 level of probability








The second canonical variable shows a second positive

relationship between plant height and turbidity, independent

from the first. In this case however, the major emphasis

should be placed on the positive association between inter-

node diameter and water hardness, where as water hardness

increases, so does the diameter of the aerial stems.


Table 12. Canonical coefficients for individual variables,
Analysis III

Variable Can. Var. 1 Can. Var. 2 Can. Var. 3 Can. Var.4

SET I

plant Ht. -0.833 -0.701 -0.168 -0.784

internode L. 0.681 0.129 -0.145 -1.343

internode D. -0.430 1.086 0.779 1.204

No. Stems 0.124 -0.230 1.022 -0.245



SET II

pH 0.130 -0.038 0.861 -0.053

alkalinity -0.150 -0.226 0.808 -0.697

iron 0.129 0.186 -0.216 0.563

turbidity -0.773 -0.651 0.777 -1.003

chlorides -0.042 -0.088 0.056 0.140

phosphates 0.053 0.450 0.899 0.375

nitrates, -0.047 -0.113 -0.745 -0.117
nitrites

hardness 0.005 0.981 -1.740 0.612

depth 1.376 0.369 1.281 0.306


Underlined coefficients contributed most to the linear
relationship.








The third canonical variable indicates a negative

relationship between the number of stems and water hardness.

This, in conjunction with the second variable suggests that

water/hardness is normally associated with stems of larger

diameter and of lower density as opposed to a larger number

of stems of smaller size. Also important in this relation-

ship is the positive association between water depth and

stem density, indicating that as depth increases stem density

increases as well. Another part of this association is a

positive relationship between stem diameter and pH, phosphates

and alkalinity, indicating that as these variables increase,

the diameter of the stems increase similarly.

The fourth variable shows a negative relationship

between turbidity and internode diameter similar to the

second variable, and a positive relationship between tur-

bidity and internode length.. The .latter relationship would

be expected since a positive relationship has been shown

between turbidity and plant height. Internode length and

plant height are almost certainly related.


Comparison of lakes and streams

To determine if there was statistically significant

difference between alligaterweed growths in lakes and

streams a canonical discriminant analysis was utilized to

compare the 287 samples and group them according to their

origin (Cooley and Lohnes 1970). Three of the four plant

characteristics were significant between the two groups at

the .01 level of probability. These were: internode









length, internode diameter and stem density. The samples

were then weighted according to the relative importance of

these three characteristics and reclassified through the

use of the canonical discriminant function (Table 13).


Table 13. Computer reclassification of Lakes and Streams.


Original data

Lakes

191

Reclassified



Lakes

Streams

Reclassified
of the water



Lakes

Streams


set


Streams


96

according to plant characteristics

Lakes Streams

67 29 70%

30 161 = 84%

according to physical and chemical properties


Lake

93

0


s


Streams

3 = 97%

191 = 100%


Using plant characteristics 67 of the 96 lake samples

were classified correctly; 29 were reclassified as stream

samples thereby producing an accuracy of 70 percent. The

stream samples were reclassified with an 84 percent accuracy

(161 of the 191 stream samples). Thirty of the stream

samples were reclassified wrongly as lake samples.

The procedure of reclassification was repeated using

the parameters which measured water quality, all of which








were significant at the .01 probability level: PH, alkalinity,

iron, turbidity, chlorides, phosphates, nitrates, hardness,

and water depth. The result was an overall accuracy of 99

percent. Ninety-three of the 96 lake samples were reclassi-

fied correctly with only three appearing as stream samples

(97% accuracy). The stream samples were reclassified with

100 percent accuracy (Table 13).

The author is cognizant of the fact that with the

small number of sample sites these comparisons may not

represent a true picture of lakes and streams in general;

they are, however, valid for this study.


Analysis of variance of Plant Characteristics

Two analysis of variance tables were constructed for

each of the variables representing plant characteristics;

one which showed the statistical significance of the

dependent variable with all independent variables included

in the model, and the other an analysis of the dependent

variable with only the independent variables representing

the insect populations included in the model.

In each analysis, the sums of squares was broken down

using partial sums of squares to show how each of the

independent variables contributed to the variation of the

dependent variable. In each case the F test was employed

to determine statistical significance.

As shown in table 18 plant height was significant at

greater than the .01 probability level in both analysis.

The partial sums of squares indicate that iron, turbidity,








water depth, .nd Vorcia %.,ere .:.in' ficant at .01 in contribut-

ing to the variation of plant .heigqht. Alkalin.tv was signi-

ficant at the .05 prcIba I '- ; : .. te second nodcl

which inclu ec-,: cnl .- .::, I : h c-asicles

and ''o t. a sJrre sirni c- .. 14).



Table : !-
Source .. r. F Pron F

Regression 12 22.0 1.97 27.14 0.0001

Error 274 1- c C 7

correct- a : 235 i.


Source


pH

Alkalinity-

Iron

Turbidity

Chlorides

Phosphates

Nitrates

Hardness

Water depth

Lake or Stream

Vogtia

Agasicles


Partial SS


0.116

0 -j'

0.562

1.879

0.01

0.03

0.003

0.06

5.38

0.04

0.46

0.22


1.59

1.2

7.74

25.83

0.18

0.34

0.04

0.81

74.01

0.49

6.33

3.07


Prob F


0.205

0.040

0.005

0.000

0.677

0.57

0.84

0.63

0.00

0.509

0.01

0.08


_ ---~CIl-------IIC--- ----- - I








Table 14 continued.


ANOV for Plant Height with nutrient effects removed



Source DF SS MS F Prob F


Regression 2 3.98 1.99 14.25 0.0001

Error 284 39.63 0.14

Corrected Total 286 43.61



Source DF Partial SS F Prob F


Agasicles 1 1.53 10.97 0.0014

Vogtia 1 3.12 22.34 0.0001




The analysis in which internode length was the dependent

variable and with the same independent variables the analysis

of variance indicated significance at the .01 level (Table 15).

The partial sums of squares showed only one statistically

significant independent variable, Agasicles (.01). In the

insect only model both Agasicles and Voatia were significant

at the .01 probability level.


Table 15. ANOV for internode length


Source DF SS MS F Prob F


Regression 12

Error 274

Corrected total 286


149.96

349.84

499.80


12.50 9.79

1.28


0.0001









Table 15 continued.


Source DF Partial SS F Prob F


pH 1 0.061 0.05 0.821

Alkalinity 1 0.670 0.52 0.524

Iron 1 1.351 1.06 0.305

Turbidity 1 0.509 0.40 0.535

Chlorides 1 1.082 0.85 0.639

Phosphates 1 0.696 0.55 0.532

Nitrates 1 0.253 0.20 0.661

Hardness 1 1.659 1.30 0.254

Water depth 1 0.341 0.27 0.612

Lake or Stream 1 0.448 0.35 0.561

Vogtia 1 2.892 2.26 0.129

Agasicles 1 8.304 6.50 0.011


ANOV for Internode length with nutrient effects removed



Source DF SS MS F Prob F


Regression 2 81.65 40.82 27.73 0.0001

Error 284 418.15 1.47

Corrected Total 286 499.80


Source DF Partial SS F Prob F


Agasicles 1 11.32 7.69 0.0061

Vogtia 1 58.05 39.43 0.0001








The analysis of variance with internode diameter as

the dependent variable indicated significance at the .01

probability level both with all independent variables

included and with only the independent variables for insects

included. The partial sums of squares with all variables

included showed significance at .01 for water depth and

Agasicles. The partial sums of squares with only the insect

variables included resulted in Aqasicles not being statis-

tically significant and Vogtia significant at the .01

probability level (Table 16). The reversal in significance

for Agasicles is probably due to the correlation of Vogtia

with stem diameter (the simple correlation coefficient

was .51).


Table 16. ANOV for internode diameter


Source DF SS MS F Prob F


Regression 12 44.42 3.70 19.95 0.0001

Error 274 50.84 0.18

Corrected Total 286 95.26



Source DF Partial SS F Prob F


pH 1 0.001 0.00 0.95

Alkalinity 1 0.144 0.77 0.62

Iron 1 0.040 0.21 0.65

Turbidity 1 0.001 0.00 0.95

Chlorides 1 0.033 0.18 0.68









Table 16 continued.


Source


Phosphates 1

Nitrates 1

Hardness 1

Water depth 1

Lake and Stream 1


Vogtia

Agasicles


Partial SS


0.661

0.442

0.540

1.708

0.523

0.211

0.950


ANOV for internode diameter with nutrient effects removed



Source DF SS MS F Prob F


Regression 2 15.76

Error 284 79.49

Corrected 286 95.26
Total


7.88 28.16

0.28


Source DF Partial SS F Prob F



Agasicles 1 0.592 2.11 0.1429

Vogtia 1 13.58 48.53 0.0001



Table 17 shows the analysis of variance using stem

density as the independent variable with the same independ-

ent variables previously listed. Sten density was significant


Prob F


3.56

2.38

2.91

9.20

2.82

1.14

5.12


0.06

0.12

0.08

0.00

0.09

0.29

0.02


0.0001








at the .01 probability level in both analysis. The partial

sums of squares shows significance at .01 for the following

-variables: pH, alkalinity, nitrates, hardness, and water

depth- Significance at .05 was indicated for phosphates,

lake or stream variable, and Vogtia, The partial sums of

squares with only insect variables included showed signifi-

cance at .01 for Vogtia and no significance for Agasicles

(Table 17).


Table 17. ANOV for Stem density.


Source DF SS MS F Prob F


Regression 12 384.94 32.08 8.97 0.0001

Error 274 980.08 3.58

Corrected 286 1365.02
Total



Source DF Partial SS F Prob F


pH 1 40.77 11.40 0.00

Alkalinity 1 27.51 7.69 0.01

Iron 1 6.66 1.86 0.17

Turbidity 1 7.06 1.97 0.16

Chlorides 1 0.10 0.03 0.86

Phosphates 1 14.88 4.16 0.04

Nitrates 1 64.42 18.01 0.00

Hardness 1 71.90 20.10 0.00

Water depth 1 53.29 14.90 0.00

Lake or Stream 1 14.43 4.03 0.04








Table 17 continued.

Source DF


Partial SS


F Prob F


Vogtia 1 18.72 5.23 0.02

Agasicles 1 5.21 1.46 0.23




ANOV for Stem density with nutrient effects removed.



Source DF SS MS F Prob F


Regression 2 141.05 70.52 16.36 0.0001

Error 284 1223.S97 4.31

Corrected total 286 1365.02



Source DF Partial SS F Prob F


Agasicles 1 2.777 0.64 0.5710

Vogtia 1 126.53 29.38 0.0001



The last ANOV table was constructed for the variable

representing leaf area missing, in which case this was the

dependent variable. Leaf area was significant at .01 in

both analyses, i.e. in both the limited model and when all

independent variables were included in the model (Table 18).

The partial sums of squares indicated that the following

independent variables were significant sources of variation

at the .01 probability level: Alkalinity, iron, nitrates,

Vogtia and Agasicles. Turbidity and phosphates were








similarly significant but at the .05 level. The partial

sums of squares in the limited model shows both Agasicles

and Vogtia to be significant at the .01 probability level.


Table 18. ANOV for Leaf area missing.


Source DF SS MS F Prob F


Regression 12 616.05 51.34 10.29 0.0001

Error 274 1366.48 4.99

Corrected 286 1982.53
Total



Source DF Partial SS F Prob F


pH 1 0.54 0.11 0.74

Alkalinity 1 33.52 6.72 0.01

Iron 1 134.37 26.94 0.00

Turbidity 1 23.71 4.76 0.03

Chlorides 1 2.42 0.48 0.51

Phosphates 1 25.86 5.18 0.02

Nitrates 1 34.72 6.96 0.01

Hardness 1 0.05 0.01 0.92

Water depth 1 9.70 1.94 0.16

Lake or Stream 1 '1.18 0.23 0.63

Vogtia 1 36,86 7.39 0.01

Agasicles 1 91.99 18.44 0.00



ANOV for leaf damage with nutrient effects removed









Table 18 continued.

Source DF SS MS F Prob F


Regression 2 343.94 171.97 29.81 0.001

Error 284 1638.59 5.77

Corrected Total 286 1982.53



Source DF Partial SS F Prob F


Agasicles 1 288.82 50.06 0.0001

Vogtia 1 108.97 18.82 0.0001



In table 19 the overall effect of each of the independent

variables on the plant characteristics as a whole is shown.

Like the previous programs, F values were calculated using

all independent variables in the first model and secondly

with only the insect variables included. Pillai's Trace

with the F statistic was used as a test for significance.

When all variables were included only one independent

variable lacked significance, chlorides. Variables with

larger F values and therefore more important sources of

variation were: Iron, turbidity, nitrates, hardness, water

depth, and Agasicles. With only the insect variables

included, both Agasicles and Vogtia were significant at

greater than the .01 probability level.








Table 19. Overall effect of variables on alligatorweed


Variable DF F Prob F


pH 5 and 270 3.15 0.0091

Alkalinity 5 and 270 3.07 0.0104

Iron 5 and 270 6.42 0.0001

Turbidity 5 and 270 10.54 0.0001

Chlorides 5 and 270 0.38 0.8624

Phosphates 5 and 270 4.76 0.0006

Nitrates 5 and 270 8.44 0.0001

Hardness 5 and 270 5.92 0.0001

Water depth 5 and 270 26.91 0.0001

Lake or Stream 5 and 270 3.98 0.0020

Agasicles 5 and 270 8.89 0.0001

Vogtia 5 and 270 3.57 0.0042



Overall effect of insects with nutrient effects removed


Variable DF F Prob F


Agasicles 5 and 280 16.19 0.0001

Vogtia 5 and 280 15.08 0.0001















SUMMARY


Vogtia malloi was introduced into the United States in

the spring of 1971 with populations successfully established

in 1971 and 1972 at the following locations: Upper Legion

Lake, Columbia, South Carolina, Twin Lakes, South Carolina,

Garden's Corner, South Carolina, Black Lake, Melrose, Florida,

Lake Alice, Gainesville, Florida, Lake Lawne, Orlando, Florida,

and a roadside ditch, Fort Lauderdale, Florida.

Populations of Vogtia expanded randomly as alligatorweed

in the release area became damaged and less desirable.

Samples of the parasite populations at Lake Alice and Lake

Lawne indicated that the Vogtia populations were not seriously

reduced and only general parasites were observed.

Both Vogtia and Agasicles demonstrated their ability for

surviving frost and cold temperatures. At Columbia, South

Carolina both insects survived the 19-72-73 Winter with below

freezing temperatures recorded for 17 of the 28 days in the

month of February. With this degree of cold tolerance it

is probable that these insects can extend their range through-

out the northern limits of alligatorweed infestations.

At Garden Coner the Vogtia population was reduced but

was not excluded even when Agasicles had completely defoliated








the alligatorweed and almost destroyed it. When the Agasicles

population subsided, as expected during the hot months of

summer, the Vogtia population began to build up, keeping the

alligatorweed under stress for the entire growing season.

While Agasicles populations remained low in south Florida,

presumably because of high temperatures, the Vogtia population

was apparently unaffected, and will therefore probably surpass

Agasicles in its influence on alligatorweed growth in the

southern regions.

The use of canonical correlations, in conjunction with

a multivariate analysis has enabled us first to show the

interrelationships which occurred between Vogtia and Agasicles,

between each of these insects and alligatorweed, and between

the physical and chemical characteristics of the water and

alligatorweed, and secondly, to determine the significance

of -these-.factors in controlling alligatorweed growth.

As expected, a significant relationship existed between

Agasicles and plant height. Agasicles characteristically

begins feeding on the upper leaves and items of alligator-

weed resulting in shorter plants. Similarly, Agasicles adults

occurred less frequently in heavily damaged alligatorweed, as

did Vogtia larvae, a probable result of the food supply being

reduced.

In this study, as stem density increased Vogtia occurred

less frequently and Agasicles occurred more frequently. Since

alligatorweed may occur in relatively dense stands of stems








with small diameters, this indicates the preference of

Agasicles for the younger leaves, and with the positive

correlation between Vogtia larvae and stem size, the in-

ability of Vogtia larvae to survive in very small stems.

This is also indicated by the tendency of both populations

to occur in greater numbers with tall healthy plants.

As the depth of the water increased, aerial stems

tended to be shorter and more numerous, and as turbidity,

iron, and alkalinity increased plant height increased.

Also, as water hardness, pH, and phosphates increased the

plants tended to be larger. This simply indicates that

alligatorweed grows better in shallow, fertile ponds as

opposed to deep, clean water.

Samples from lakes and streams were more accurately

separated according to characteristics of the water than

to plant characteristics, suggesting that a greater differ-

ence occurs between lakes and streams than between stands

of alligatorweed growing in these areas.

The overall effect of the independent variables on

the plant characteristics as a whole resulted in all

variables, except chlorides, being significant at 0.01

The most important of these were: iron, turbidity, nitrates,

hardness, water depths, and Agasicles, as indicated by

larger F values.

The potential for seasonal control of alligatorweed

has been clearly demonstrated by both Agasicles alone

(Zeiger 1967), by Vogtia, and by Vogtia and Agasicles in








combinations. However, the resiliency of alligatorweed in

re-establishing itself is truly remarkable, and for this

reason no attempt has been made to predict the final

impact of these insects in reducing the overall area of

infestation of alligatorweed.

In many areas, the mats of alligatorweed have increased

over the years such that they now frequently occur 8-10 in.

in depth. Under these conditions, herbicides may be required

to facilitate insect pressure if alligatorweed is to be reduced

drastically in a short period of time.















LIJ' .. rD


Acreneaux, G. ?rd L. P. i:.r',,rr. .i43. Preliminary studies

of periodic flaming as a .; or controlling johnson

grass and alligator-.eed. on sugarcane lands. The Sugar

Bull. 21: 21-23.

Brown, J. L. ano N. R. S .encer. 1973. Vootia nalloi, a

newly introduced Pivcitine roth (Lepidoptera: P-vrelidae)

to control alligatoreed. J. Environ. Entonol. 2(4):

519-523.

Cooley, W. W. and P. R. Lohnes. 1970. uultivariate Data

Analysis. John Wilev and Sons. 369o.

Cunha, T. J. and G. N. Rhodes. 1965. Peef cattle in

Florida. Bulletin 28. Florida Denartnent of Acricul-

ture.

Gangstad, E. 0. and F. J. Guscio. 1970. Research planning

conferences for aquatic plant control. Tech. Rep.,

Chief of Engineers, U.S. Army Corps of Encineers.

Maddox, D. M. and R. D. Hennessey. 1970. The biology and

host range of Vogtia malloi Pastrana. Unpublished

manuscript, Agricultural Research Service, USDA, Albany,

California.

Maddox, D. '., L. A. Andres, R. D. Hennessey, R. D. Blackburn,


weua nv uatc ucosses in the Unte
'1C2G., ci 0;~~oiz arouatic ucosvstems in the United








States. Bioscience 21: 985-91.

Mohr, C. 1901. Plant Life of Alabama. Vol. 6, 921p.

Morrison, D. F. 1967. Multivariate statistical methods.

McGraw-Hill Co. New York. 338p.

Muesebeck, C. F. W., K. V. Krombein, and H. K. Townes.

1951. Hymenoptera of America North of Mexico. U.S.

Dep. Agric., Agric. Mono. no. 2. 1420 pp. U. S. Govt.

Printing Office, Washington, D. C.

Nie, N. 1970. Stastical package for the Social Sciences.

McGraw-Hill Co. New York. 338p.

Pastrana, J. A. 1961. Una nueva Phycitidae (Lep.) parasite

de la "Lagunilla". Rep'. Arg. Publ. Tec. 71, Inst. Nac.

Tec. Agropecuar., p 265-272.

Penfound, W. T. 1940. The biology of Achyranthes

philoxeroides (Mart.) Standley. American Midl. Nat.

24: 248-252.

Vogt, G. B. 1960. Exploration for natural enemies of

alligatorweed and related plants in South America.

U. S. Dept. Agric., Agric. Res. Serv., Entomol. Res.

Div., Special Report PI-4, 58p.

Vogt, G. B. 1961. Exploration for natural enemies of

alligatorweed and related plants in South America.

U. S. Dep. Agric., Agric. Res. Serv., Entomol. Res.

Div., Special Report PI-5, 50p.

Weldon, L. W. 1960. A summary review of investigations

on alligatorweed and its control. USDA, Agric. Res.

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70


Zeiger, C. F. 1967. Biological control of alligatorweed

with Agasicles n. sp. in Florida. Hyacinth Control

J. 6: 31-34.












BIOGRAPHICAL SKETCH


John L. Brown was born November 17, 1944 in Weiner,

Arkansas. He attended Weiner Public Schools from 1950

to 1962 and after graduation he enlisted in the U.S. Air

Force. In 1967 he enrolled in the school of Agriculture

at Arkansas State University. He received the Bachelor of

Science degree in 1969, and enrolled at Iowa State Univer-

sity. He received the Master of Science degree in entomo-

logy in 1971 and transferred his studies to the University

of Florida where he is completing the requirements for the

degree of Doctor of Philosophy.

John L. Brown is married to the former Delena Y.

Newmans and has two children, a son of 10 years and a

daughter of 5.

He is a member of the Entomological Society of America

and the Florida Anti-mosquito Association.

He was employed by the Florida Division of Health in

January, 1973 as director of the stable fly control program.









I certify that I have read this study and that in my
opinion it conforms to acceptable standards of scholarly
presentation and is fully adequate, in scope and quality,
as a dissertation for the degree of Doctor of Philosophy.




B. David Perkins
Assistant Professor of
Entomology



This dissertation was submitted to the Dean of the College
of Agriculture and to the Graduate Council, and was accepted
as partial fulfillment of the requirements for the degree of
Doctor of Philosophy.

December, 1973. /(


Dean, Graduate School




Full Text

PAGE 1

Vogtia xr.Sill or . ..7 "^?~P.ODUCFD PYPALID (LEPIDOPTERA) FOR THE CONTROL OF ALLIGATORWEED IN T\IF. UNITED STATES By J-OHN LEE BR0V7N A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL OF TPIE UNI\^RSITY OF FLORIDA IN ?ARTIi\L FULFILLIIENT OF THE PvEQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPY UT'IVEPSITY 1973

PAGE 2

TABLE OF CONTENTS Page ACKNOWLEDGEMENTS '. v LIST OF TABLES vi LIST OF ILLUSTRATIONS viii ABSTRACT ix INTRODUCTION. 1 LITERATURE REVIEW 3 Alligatorweed 3 Vogtia rnalloi 4 Biology 5 METHODS AND MATERIALS 7 Biology and Behavior of Vog tia raalloi 7 Fecundity and Fertility 7 Oviposition 7 Egg and Larval Mortality 8 Greenhouse Colony 9 Field Releases 10 19 71 10 19 72 15 RESULTS AND DISCUSSION 17 Biology and Behavior of Vogtia rnalloi 17 Fecundity and Fertility 17 ii

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Page Oviposition 19 Egg and Larval Mortality 19 Behavior , ^ . . . 20 Field Releases 22 19 71 22 1972 , . 29 ALLIGATORWEED PRODUCTIVITY 31 Introduction 31 Methods and Materials 31 Greenhouse Studies 31 Field Studies 33 Results and Discussion • 34 Greenhouse Studies 34 Field Studies. 35 INTERRELATIONSHIPS BETWEEN ALLIGATORVJEED AND TWO INSECTSVogtia and Agasicles 38 Introduction 38 Methods and Materials 40 Results and Discussion 42 Insect-host plant relationship 42 Nutrient levels and alligatorweed characteristics 48 Comparison of Lakes and Streams 51 Analysis of variance of Plant Characteristics 53 SUMMARY 64 111

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Page LITERATURE CITED 68 BIOGRAPHICAL SKETCH 71 IV

PAGE 5

ACKNOWLEDGMENTS I wish to express my appreciation to the numerous individuals who have assisted in this study. I am grateful for the technical assistance given by Ted Center, Joe Balciiinas, and Debbie Beasley both in laboratory and field studies. I wish to thank Neal Spencer and the U. S. Department of Agriculture for providing space and the necessary equipment to carry out this program. I am also indebted to my committee chairman, Dr. Dale Habeck, for his assistance in the preparation and submission of this dissertation.

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LIST OF TABLES Table . Page 1. Egg placement by V. nalloi female moths caged over alligatorweed „ 19 2. Nutrient levels in water tables used for productivity studies 34 3. Net productivity of alligatorv'/eed in greenhouse tests , 34 4. Field studies of alligatorweed productivity 37 5. Variables used in canonical correlations with mean and standard deviations 43 6. Canonical variates in analysis 1 44 7. Canonical coefficients for individual varibles, analysis I 44 8. Canonical variates in analysis II 46 9. Canonical coefficients for individual variables, analysis II 47 10. Variables used in canonical correlations III.... 48 11. Canonical variates in analysis III 49 12. Canonical coefficients for individual variables, analysis III 50 13. Computer reclassification of lakes and streams.. 52 14. ANOV for plant height 54 15. ANOV for internode length 55 VI

PAGE 7

Table , Page 16. ANOV for internode diameter 57 17. ANOV for stem density 59 18. ANOV for leaf area missing..,. 61 19. Overall effect of variables on alligatorweed 63 VI 1

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LIST OF ILLUSTRATIONS Figure Page 1. Vogtia release sites, 1971 and 1972 11 2. Log number of Vogtia eggs laid plotted against time ,. 18 ^* Vogtia population build-up and its effect on alligatorweed, Lake Alice, 1971 „ 23 ^' Vogtia population buiJd-up and its effect on alligatorweed, Lake Alice, 1972 26 Vlll

PAGE 9

Abstract of Dissertation Presented to the Graduate Council of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosopl: VQGTI A MALLOI, A NEWLY INTRODUCED PYRALID (LEPIDOPTERA) FOR ""the control OF ALLIGATORWEED IN THE UNITED STATES By John Lee Brown December 197 3 Chairman: Dr. Dale Habeck Major Department: Entomology Vogtia malloi pastrana was introduced into the United States in the spring of 1971 as a biological control agent of alligatorweed, Alternanthera philoxeroides (mart.) Griseb. Vogtia populations were established and survived the winter as far north as Columbia, S. C. , and as far south as Fort Lauderdale, Florida. Vogtia populations dispersed randomly from release sites, and at one location in 1971 reduced the number of aerial stems/ft.^ from 52.5 to 4.0 in four generations. Studies reported herein include: a canonical analysis which describes the insect-host plant relationship between IX

PAGE 10

two insects and alligatorweed, the relationship between nutrient levels and alligatorweed grov^th, and a comparison of alligatorweed growing in lakes and in streams; a multivariate regression analysis which measures the significance of each of 12 measured variables in influencing the growth and spread of alligatorweed. Also included are measurements of alligatorweed productivity in greenhouse studies and in field plot studies during the spring and i. summer growth periods..

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INTRODUCTION Alligatorweed, Alternanthera philoxeroides (Mart.) Griseb., a vascular aquatic plant in the family Amaranthaceae, was probably introduced into the United States in the 1890 's (Weldon 19 60) . In recent years alligatorweed has become one of the most troublesome weeds in fresh water ecosystems in the southeast, and by 1970 more than 66,000 acres were infested (Gangstad and Guscio 1970) . Alligatorweed may occur as a terrestrial plant in lowlands, as a semi-aquatic plant along streams or lake shores, or as an emersed aquatic plant. Floating mats which may extend 50 feet or more out over the surface of the v/ater are formed of interwoven stems rooted near the shore. The stems are marked by nodes at intervals of about 2-6 in. each of which is capable of producing a new plant. Most aquatic plants cannot compete with alligatorweed where it has been introduced and are quickly crowded out (Weldon 1960) . Alligatorweed is not as susceptible to herbicides as some of the other aquatic plants, requiring application at higher rates and shorter intervals. The lack of a suitable chemical control and the alien status of alligatorweed led to consideration of biological control as a possible solution. In 1959 the U. S. Army

PAGE 12

Corps of Engineers provided funds to the Agricultural Research Service, USDA, to explore the possibilities of importing natural enemies of alligatortveed capable of suppressing its grov;th and spread (Vogt 1960, Zeiger 19 67, Maddox et al. 1971). As a result of these studies, three insects have been introduced into the southeastern region of the United States. A Chrysomelid beetle, Agasicles hygrophila Selman and Vogt, introduced in 19 64 has been very effective in controlling alligatorweed in certain areas (Zeiger 1967, Maddox et al. 1971). Amynothrip s anderson i O'Neill, a thrips, was introduced in 19 67, and although still present in some reJ.ease areas, it has not caused significant damage to alligatorweed (-Maddox et al. 1971) . The release and establishment of the third insect, Vogtia malloi Pastrana, the so-called alligatorweed stem borer (Lepidoptera: Pyralidae: Fhycitinae), is the subject of this dissertation.

PAGE 13

LITERATURE REVIEW Alligatorweed Alligatorweed, also known as "Lagunilla" in South America, was probably introduced into the United States in the ballasts of sailing ships late in the nineteenth century. It was first recorded in Florida in 1894 (Weldon 19 60) . Mohr (19 01) discovered the plant completely filling a creek near Mobile, Alabama in September 189 7. He states that the source of the introduction was from the West Indies and Brazil. According to Weldon (1960) , the species was first described in 1826 as Bucholzia philoxeriodes Mart, and in 1897 it acquired its present name, Alternanthera philoxeroides (Mart.) Griseb. Vogt (19 60) studied over 1500 herbarium specimens of Alternanthera and related genera including approximately 80 species of Alternanthera . Penfound (1940) described the anatomy and the life history of alligatorTA?eed along with its aquatic growth habits in Alabama while Arceneaux and Herbert (1943) reported on alligatorweed growth in the cultivated fields of Louisiana.

PAGE 14

Weldqn (1960) extensively reviewed the literature concerning past chemical and mechanical controls for alligatorweed. Vogtia malloi The moth Vogtia malloi (Pyralidae: Phycitinae) was named in 1961 when Jose A. Pastrana described it as a new genus and species. Vogtia may be recognized by the following characteristics: large labial palpi, three times the diameter of the eye, pointing forward with loose, thick scales and an obtuse third joint; no maxillary palpi are present; ocelli are present; the front wing has smooth scales, a slightly curved edge, and ten veins. The wingspan is 20-22 mm and the wings are straw-colored, dashed with brown scales on the edge and tip of the wing. This insect was discovered by George Vogt in his surveys in South America for natural enemies of alligatorweed for possible introduction into the United States. Vogtia was one of the four insects considered by Vogt (1961) as a major suppressant of alligatorweed in South America. He found that Vogtia was almost coextensive with alligatorweed, both geographically and ecologically occurring as far south (La Plata, Argentia) and as far north (Georgetown, British Guiana) as his survey extended. Vogt (1961) reared Vogtia from Alternanthera philoxeroides and from Alternanther a hassleriana , the plant he considered most closely related to alligatorweed.

PAGE 15

Field .observations in Argentina and starvation tests in the laboratory (Maddox and Hennessey 1970) indicated that Vogtia could not complete its life cycle on plants outside the genus Alternanthera . Plants were selected for feeding tests on the basis of their . taxonomic relationship to or ecological association with alligatorweed, or their economic importance. In field observations (1962-1967) 51 native and introduced species of plants were examined for feeding damage by Vogtia and 30 plant species were examined in starvation tests for larval feeding and survival (Maddox and Hennessey 19 70) . Biology Egg Eggs are deposited singly on the upper portion of the aerial stems of alligatorweed. The average length and width of Vogtia eggs was 0.69 mm and 0.37 mm respectively (Maddox 1970) . When the egg was first deposited, it was opaque white; as it aged it gradually changed from white to light yellow to amber. The head capsule was visible through the chorion usually after the second day. Maddox (1970) reported the average incubation period was 3.6 days at an average of 32.9°C and 41.4 % RH. Larva According to Maddox (1970) , head capsule measurements indicated that there were five instars. The first stage larva was approximately 2.25 mm long with a dark brown to black head capsule about 0.27 mm in diameter (Maddox 1970) . In later stages the head capsule was brown to light tan, and tan wavy longitudinal lines appear

PAGE 16

on the dors.um and pleura of the thorax and abdomen. The mature fifth stage larva averaged 13.7 mm long with an average head capsule width of 1.25 mm (Maddox 1970). Larval development required 24 days at 23°C and 64 % RH (Maddox 1970). Prepupa — As with most holmetabolous insects, a relatively inactive larval period immediately preceeded pupation, The larva becomes shorter, thicker, and may appear greenish in color at the time the cocoon was constructed. Pupa — The pupa was amber or light tan when first formed, It gradually turned a dark brown or almost black just prior to emergence. Pupal length varied from 9 to 10 mm and the width from. 1.5 to 2.0 mm (Maddox 1970). Thepupal period averaged 9.5 days at 23.3°C and 49.7 % RH (Maddox 1970). Adult--The adult is approximately 13-14 mm long v/ith light tan scaled (both sexes) . Variation occurs in both the size (females are usually larger) and in the definition of the color patterns of the adult moth. Females often have scales with a reddish tan hue forming indefinite patterns, and the males often have black or gray scales forming definite spots along the front margin and tip of the wings .

PAGE 17

METHODS AND MATERIALS Biology and Behavior of Vogtia m alloi Fecundity and Fertility In laboratory studies newly emerged adults were confined in pint and gallon ice cream cartons covered with a fine mesh net. One female and two males were placed in each container and fed a 1:10 honey-v/ater solution. There were 10 replications using the pint containers and 25 replications with the gallon containers. Eggs were deposited on the net covers which were changed daily and the eggs counted. The temperature and RH were maintained at 27 °C and 72 %. To determine hatchability , as an indicator of fertility, 447 eggs collected from the moths in the gallon containers and 1079 eggs collected from the pint containers were held at 31 °C and 60 % RH for 6 days. After 6 days the unhatched eggs were removed and counted. Oviposition To duplicate natural conditions in the placement of Vogtia eggs for field releases it was necessary to determine the ovipositional preference of the female moth. One male and two female adults were confined in a 15 X 15 X 18 in. screen cage which contained a bouquet of 10 to 15 alligatorweed stems in water.

PAGE 18

Egg and Lar-val Mortality Studies v;ere conducted at Lake Lawn, Orlando, Fla. to determine the percentage of (1) the eggs oviposited that hatch and (2) the larvae that survive and successfully enter the stems of alligatorweed. One hundred Vogtia eggs were placed singly with a camel's hair brush in the axils of therminal leaves at the rate of 1 egg per stem, along about 30 linear feet of a continuous mat of alligatorweed. These stems were then marked with red flagging tape for later recovery. Five days later, the number of surviving first instar larvae was determined by locating the marked stems and recording the number of plants injured within a radius of about 10 in. around each flagged stem. * In a separate study at Lake Alice Vogtia eggs in groups of 50 or more attached to strips of cloth were pinned to stems of alligatorweed to detect and collect egg parasites. The eggs were left in the field for two days, after which they were collected and held in the laboratory for emergency of moth larvae on parasites. Larvae, prepuase, and pupae collected from the Lake Alice samples were removed to the laboratory where they were observed for parasitism. In this study, approximately 250 larvae and 45 pupae or prepupae were collected.

PAGE 19

Greenhouse Colony Permission to release V. malloi in the United States was obtained in 1970. Pupae or eggs were collected from the Buenos Aires area of Argentina, an area with climatic conditions similar to the gulf coast states, and shipped to the USDA quarantine facility in Albany, California. One generation of Vogtia were reared at the Albany laboratory to exclude parasites and diseases. Eggs collected from that laboratory were shipped to the USDA laboratory in Gainesville, Florida where a greenhouse colony was established on alligatorweed grov?ing in water tables to obtain sufficient numbers for field release. Vogtia was first released in Florida in the spring of 1971 and later in the year in Georgia, North Carolina, and South Carolina. In 1972 specimens were collected 450 km south of Buenos Aires, the latitudinal equivalent of Richmond, Virginia, to broaden the genetic base of populations already established and perhaps obtain a more winter-hardy strain. Specimens from the southern area of Argentina were released at Fort Jackson (May 10, 1972), Twin Lakes (July 12, 1972), and Garden's Corner, S.C. (May 20, 1972). Vogtia from this colony v/ere also released in Tennessee Valley Authority projects and in North Carolina by individuals employed in these areas.

PAGE 20

10 Field Releases 1971 During the siUBiner of 1971, Vogtia were released at the following locations (Fig. 2): Lake Lawn, Orlando, Fla. ; Lake Alice, Gainesville, Fla.; USDA Plant Introduction Station, Savannah, Ga.; Black Lake, Melrose, Fla.; Fort Pierce, Fla.; Ashapoo River at Hwy. 17, S.C.; Savannah River, near Savannah, Ga.; unnamed ditch, Gainesville, Fla.; Santee Reservoir, near Lone Star, S.C., and Greenfield Lake, Wilmington, N.C. Populations at the Ashapoo River, the Savannah River, and the unnamed ditch sites were destroyed by flooding, and the Fort Pierce site was destroyed by dredging. Lake Alice, Fla. — At Lake Alice, on the University of Florida campus, conditions were sim.ilar to those found at Lake Lawne, i.e. high nutrient levels and a luxuriant growth of alligatorweed. The Vogtia releases were made in a small stream, about 20 ft. wide flowing into Lake Alice from a sewage treatment plant. At the time Vogtia were released, alligatorweed extended out 5-10 ft. from the banks on either side of the stream for a linear distance of about 100 ft. A similar area, about 150 ft. upstream from the release area, was designated as a control area. No Vogtia were released there and there was no attempt to prevent the spread of Vogtia to this area. On May 18, 1971 small strips of cloth (ca. 2 in. ), on which Vogtia eggs had been deposited (a total of 64) , were

PAGE 21

11 Wilmington X Xort Pierce XjFort Lauderdale Fig. 2. Vogtia Release sites, 1971 and 1972

PAGE 22

12 taped to apical tips of alligatorv/eed. A second release on June 6 consisted of 81 eggs or newly hatched larvae (ca. 10 of the eggs had hatched) . In this release the strips of cloth were pinned to the aerial steins in a yd^ area near the shore. Additional releases of 200 eggs on July 20 and 580 eggs on July 26 v/ere raade as in the second release. These releases were made a fev7 yards upstream from the first two. The Vogtia population was sampled during the larval period of each of the 4 generations v/hich occured at this site following the original release (sample dates: July 5, August 28, September 29, and October 26). A sample consisted of a 1-ft.^ area of alligatorweed, f.rom which aerial stems were removed and counted. Samples taken on July 5 were evenly spaced along arcs 1 yd. and 4 yds. out from the point of release. Seven samples were taken along the 1 yd. arc and 5 were taken along the 4 yd. arc. Subsequent samples were taken by randomly throv;ing a ft. wooden frame on the mat of alligatorweed at 15 ft. intervals along either side of the stream. On January 27 after the first frost the Vogtia population was checked to determine mortality due to cold and again on May 2 to determine winter survival. These samples were taken by randomly selecting injured stems. Lake Lawne, Fla. — Lake Lawne is a 33 acre lake located in Orlando, Florida. Sewage effluent from the surrounding community drains into the lake creating severe nutrient

PAGE 23

13 pollution which contributes to the luxuriant growth of alligatorweed extending out 50-60 ft. from the shore in some areas at the time of the releases. On April 5 and May 20, 1971, 232 and 150 eggs respectively, were placed on alligatorweed in the northwest corner of the lake. Small strips of cloth, each with 10-15 Vogtia eggs attached, were taped to aerial stems. Five days later the eggs and stems were inspected. On June 23, a 2 x 4 ft. section of alligatorweed mat was removed from the lake and replaced by a Vogtia infested mat of the same size from the greenhouse colony. The infested mat and the surrounding alligatorweed were inspected weekly to determine the number of Vogtia larvae persent. Releases of adult Vogtia were made in the same general area on July 23, August 13, August 18, and August 26 of 10, 7, 40 and 21 moths, respectively. The Vogtia population was monitored periodically by counting the number of injured plants in the release area. Black Lake, Melrose, Fla. — Alligatorweed growth on this 20-25 acre lake was much less vigorous than at other sites when Vogtia were released. The stems were smaller and more fibrous and the alligatorweed supported several ( Sacciolepis striata (L.) was the dominant species) species of grass and weeds. The lake was encircled by alligatorweed mats 5-20 ft. wide. On August 20, 1971, 19 adults were released in a 3-ft.2 screen cage placed on the alligatorweed mat. Seven days later after the moths had completed oviposition the cage was removed. No further

PAGE 24

14 releases were made at this site. Counts of larvae or wilted tops were made November 15, 1971 and January 28, February 11, and April 17, 1972 from randomly selected sites. Savannah, Ga. — The only release at the USDA plant Introduction Station consisted of Vogtia eggs placed in 3 screened plots (5X6 ft.) containing terrestrially-rooted alligatorv;eed by Mr. IVilley Durden on April 14, 19 71 (Willey Durden, personal communication) . Greenfield Lake, Wilmington, N.C. — Vogtia eggs and larvae were placed in a small stream 20-30 ft. wide flowing into the northern end of the lake. The stream was completely covered by a solid mat of alligatorweed for several hundred feet. On August 2, 1971, a 4-ft.'^ section of mat was removed and replaced by a Vogtia infested mat of the same size from the greenhouse colony. The mat was wrapped in 6 mil polyethylene and a small amount of v/ater added for transporting. Santee Reservoir, S.C. — Vogtia were released on the south side of the reservoir, near the town of Lone Star. Alligatorweed at the release site appeared as rooted plants in shallow water. The stems were small and fibrous, a condition often observed in rooted alligatorweed. On August 3, 1971, a 2-ft. section of Vogtia infested mat from the greenhouse colony was placed in the stand of alligatorweed after a section was removed.

PAGE 25

15 Field Releases 1972 Releases were made in 19 72 at the folloxving locations: Fort Jackson (Upper Legion Lake, Coluinbia, S.C.), Twin Lakes, S.C., Peeples' Pond (Garden's Corner, S.C.), and a roadside ditch (Fort Lauderdale, Fla.) (Fig. 2). Fort Jackson, S.C.— Upper Legion Lake is a small manmade lake (10-15 acres) ringed with alligatorweed extending out 5-20 ft. from the shore. On May 10, 72 larvae were released on the east side of the lake, by placing them individually, with a camel's hair brush in the terminal leaves of alligatorweed stems. During the summer, 1972, the Vogtia release site was siobjected to malathion fog, used in mosquito abatement, and to Diquat at 2 lbs. /acre sprayed in alternating strips. The Vogtia population was sampled September 11 and November 15, 1972 and June 16, 1973. Twin Lakes, S.C. — Twin Lakes consists of two ponds, about 5 acres each, connected by an old riverbed and located near Summerville, S.C. Alligatorweed normally covers all but a small area in the center of both ponds. On July 12, 100 adults were released in the northermost pond where alligatorweed was 16 to 18 in. tall in relatively dense stands. The Vogtia population was sampled on September 12 and November 15, 1972. Garden's Corner, S.C.-Peeples Pond is approximately 10 acres in size and ringed with alligatorweed extending

PAGE 26

20 30 ft._ out from the shore. On May 20, 150 Vo gtia eggs were placed on the aerial stems of alligatorweed and 25 adults v/ere released. Both Agasicles and Vogtia populations were sampled on July 13, and September 11, 1972 and June 16, 1973. Fort Lauderdale, Fla. — On April 19, 85 first instar larvae collected in the wilted tops of alligatorweed at the Melrose, Fla. (Black Lake) site were released in the roadside ditch (20 to 30 ft. wide) alongside the Sunshine State Parkway 1/2 mile north of exit 16. Three months later, July 18, 125 adults from the greenhouse colong were released in the same general area. Alligatorweed grew luxuriantly along the ditch for approximately 0.5 mile on either side of the release site. The Vogtia population was sampled July 18 and September 20, 1972 and April 26, 1973.

PAGE 27

RESULTS PJ'^D DISCUSSION Biology and Behavior of Vogtia mallei Fecundity and Fertility According to Maddox and Hennessey (1970) , the female moth lays an average of 267 eggs with 6, 34, 18, 15, 12, 6, 5, and 4% of the total laid from the first through the eighth day, respectively. In laboratory studies 25 female moths held in gallon containers laid only 132 eggs (average) . The adults used in the test were taken from a crowded greenhouse colony and may reflect a reducted activity due to crowding. This study confirme( Maddox' s findings that the greatest percentage (69) of the eggs were laid on the second day following emergency (Fig. 1) . Although some eggs were laid on the first day, most were apparently infertile and did not hatch. Only 84.3% of the eggs collected from moths in gallon containers hatched. Of 1079 eggs from moths in pint containers, the percentage was only 49.7%, presumably from a lack of mating in the small containers. A mated female, held for observation in a pint container, laid 47 eggs in one period which began at 11:00 PM. The average time interval between eggs was 17.3 seconds. 17

PAGE 28

18 Y axis -2.0 log of eggs laid 1.6 1.2 Linear regression analysis y = a(o) + a(l) X p.s

PAGE 29

19 This moth was very active dujring cviposition, flitting around the container and stopping only long enough to deposit an egg. Oviposition Most of the eggs (60.6%) V7ere deposited on the underside of the terminal leaves, with progressively fev/er eggs being placed on leaves of the lower nodes (Table 1) . These data confirmed Maddox ' s earlier report that eggs are deposited on the underside of a leaf in the first through fourth pairs of apical leaves on the host plant. Table 1. Egg placement by V. malloi female moths caged

PAGE 30

20 environmental factors. Several specimens of the egg parasite Trichogramma perkinsi Girault (identified by L. R. Ertle USDA) were collected from the Vogti a eggs attached to alligatorweed for 2 days . Six internal parasites belonging to 2 species of ichneumonids were reared from the Vogtia larvae and pupae collected from Lake Alice: 4 were Gambrus bituminosus (Cushman) and the other 2 were G. ultimus (Cresson) (determied by R. W. Carlson USNM) . Both species have been collected from a number of Lepidoptera in the United States (Muesebeck et al. 1951) . Behavior Upon hatching, the first stage larva enters and girdles the alligatorweed stem, usually at the second internode. Later in the season, the aerial stems may become tough and fibrous, and the young larvae may descend on a silk strand to the axillary shoots growing farther down the stem which are still tender (Brown and Spencer 1973) . Within a few hours, the girdled top is wilted, and v/ithin a few days it usually breaks off at the node just below the girdle and falls onto the supporting mat of alligatorweed with the young larva still inside. The larva soon leaves the dead top and bores into another stem, or the same stem at a lower level, and the process is repeated, As the larva matures the process of girdling and feeding on the interior of the hollow stems above the girdle may be repeated raany times (as many as 9 stems were reported

PAGE 31

21 destroyed by a single larva, Maddox 1S)70) . The mature larva is known as a roving stem borer because of its characteristic feeding habit. The larger the larva, the farther down the stem it girdles, and frequently mature larvae are found feeding below the water line, protected from drowning by the air-filled cavity of the hollow stems. When the Vogtia larva bores into a stem it quickly seals the entry hole with silk strands to make it waterproof. The exit holes however are never sealed leaving the plant open to attack by other organisms. Just prior to pupation the mature larva enters an internode and seals off both ends at the nodes. A small "window" is chewed in the stem wall, leaving only a thin layer of the outer epidermis intact. The larva spins a cocoon and orients itself so that the head region is adjacent to the window, through which the adult will eventually emerge.

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22 Field Releases 1971 Lake Alice, Fla. — Larval counts taken at Lake Alice (July 5) along arcs 1 yd. and 4 yds. from the release area . were not significantly different, and no directional movement was indicated; the mean number of larvae/ft.^ along these arcs were 5.4 and 5.2, respectively. The standard deviation of insect counts in the 12 samples was 2.84. The population, v/ithin this limited area was distributed with X = 5.3, S^ = 8.06, S^ /X = 1.52, and K = 10.19. Adult dispersal appeared to be random. Counts from later samples indicated that the population expended at a nearly uniform rate in all possible directions v/ith each new generation. Population density increased to 9.4 larvae/ft. by the second generation in the immediate release area and then began a steady decline as the attractiveness of the alligatorweed was reduced and the number of available egg deposition sites diminished (Fig. 3) . During the first two generations the area of infestation was not significantly expanded based on observations of wilted tops. The mean number of healthy aerial stems of 2 alligatorweed/f t. was reduced from 52.5 to 36.9. An invasion of the test area by the southern beet webworm, Herpe to gramma bipunctalis (F. ) , occurred during the second generation v/hich resulted in partial defoliation of many of the aerial stem.s. Although v/ebworm damage was temporary, it may have influenced the observed movement of V. malloi

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23 .iJ/swais lYiHav o

PAGE 34

24 adults from the release area to the nearby control area during the second generation, a distance oC 150 yds. In the third generation sanples (September 29) , the number of larvae, ft. had dropped to 6.3, v/ith the nunber of healthy aerial stems reduced to 17.4/ft.^. By the middle of the fourth generation (October 26) , the mean number of larvae and aerial stems/ft. had dropped to 3.4 and 4.0, respectively. With this damage the alligatorweed mat was beginning to break up in the release area and was no longer increasing. Other semiaquatic plants began to move in over the submersed portion of the alligatorweed mat. A one-way analysis of variance showed that the reduction in the number of aerial stems between sample dates was statistically significant (0.01 level) but there was no significant difference between insect counts for these dates, probably due to the wide variation between samples. The January 27, 1972 data consisted of superficial observations only. The lack of alligatorweed stems due to the cold and to Vogtia and A gasicles dam.age made detailed samples impractical. Ten first and second instar larvae collected from wilted stems in 2 sm.all mats of alligatorweed were not in diapause, but were actively feeding. On April 25, 1972, the alligatorweed had attained a height of 15 in. when the Vogtia population was sampled. The mean number of larvae/ft.^ was 3.3 at the release site; therefore a substantial number of Vogtia survived the v/inter.

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25 In 19 72 the Lake Alice population duplicated the 19 71 response, i.e. the Vocjtia population peaked at about the same density and then began a decline (Fig. 4) . ^^•^ke Lawne, Fla. — The first releases made in this area (April 5 and May 20, 1971) were probably unsuccessful since no damaged stems were found, a result of the newly hatched larvae becoming entangled in the tape. The second attempt to establish a Vogtia population in Lake Lawne (June 23) was likewise unsuccessful; no larvae were found after the first week. Most of the Vogtia present in the infested alligatorweed were probably drowned due to flooding of the cut stems. A few larvae were found the following week but they apparently did not survive to reproduce. On July 23, 10 adults were released at the same location from which a small larval population became established. Three additional releases were made in August to supplement the population. The Vogtia population did not expand its numbers rapidly. The population remained at low levels (ca. 0.1 2 larvae/ft. ) and larvae were never found more than 50 yd. from the point of release during the summer of 1971. At Lake Lawne where no frost occurred the alligatorweed remained green throughout the winter. On May 21, 1972 the population had increased to 3.7 Vogtia larvae/ft. in the release area. Black Lake, Fla. — Only one release of 19 adults was made at this site on August 20, 1971. On November 15

PAGE 36

26 .i.^/SRaoLs ^vIHav c

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27 numerous injured alligatorweed srems were found \ip to 50 ft. from the point of release and a few injured plants were found about 100 ft. away. By January 23, 1972-, the Vogtia population had expanded to all areas infested, by alligatorweed in the lake. Vogtia larvae v;ere active and still feeding inside aerial stems recently killed by frost; most of these were early instars. On February 11 the larvae were found feeding below the frost-killed aerial stems on green stems that v/ere protected from frost. By April 17, 1972, the Vogtia population had attained a density of about 4.0/ft. around the entire lake. By the end of the summer the alligator>/eed at Black Lake had been so reduced in area and density of the stems that in many areas of the lake it was no longer the dominant species. The suppression of alligatorweed at this site v/as probably due to a combination of factors, i.e. insect pressure, interspecific plant competition, and low nutrient levels in the water. Savannah, Ga. — A Vogtia population became established and survived the 1971-27 v/inter despite killing frosts on terrestrially-rooted alligatorweed in experimental plots. Mid-winter sampling failed to locate the overwintering insects (burden, personal communication) . In South America, Vogtia v;as found during the winter in the roots of terrestrial alligatorweed (Vogt 19 60) . *Willey C. Durden

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28 Greenfield Lake, N.C. and Santee Reservoir, S.C. — Vogtia has not been recovered at the 2 northermost release sites. The method of release, i.e. the transfer of infested mats, was proved unsatisfactory at Lake Lawne and may be one reason for lack of establishment at these sites.

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29 Field Releases 1972 Fort Jackson, S.C. — By the end of 1972 only small patches of alligatorweed remained at this site because of the herbicidal treatment. The effect of removing most of the. alligatorweed on the Vogtia population was to concentrate the insects on the remaining mats of alligatorweed. Samples taken November 15 indicated a population density 2 of 5 larvae/ft. . Earlier samples taken September 11 showed only 1 larva/ft. . On June 16, 1973 after a severe winter in this area, the Vogtia population was 0.6/ft. and the alligatorweed was killed back to the water in most mats. A few protected areas had healthy alligatorweed, and in one such area adult Agasicles were found which had presumably survived the winter as well. Twin Lakes, S.C. — The September 11 sample date showed 2 1.0 Vogtia larva/ft. with moderate defoliation by Agasicles (approximately 50% of the leaf area missing) . By November 15 the Vogtia population had increased to 2.6/ft. . This area was not sampled in 1973 because of spring flooding. Garden's Corner, S.C. — Garden's Corner was the only site where Agasicles stripped all the foliage and many of the small shoots from the aerial stems of alligatorweed after a Vogtia population had become established. The Vogtia population remained low but v/as not elimianted. V7hen the Vogtia release was made (May 20, 1972) the Agasicles adult

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30 9 population was 5 adults/ft.". By July 13 the alligatorweed was under severe stress and the Agasicles population was 11 adults/ft. and the Vogtia population was 0.66/ft. . Samples on June 16, 197 3 indicated the Vogtia popula2 tion density was 1.6 larvae/ft. after a severe v;inter for that area. Fort Lauderdale, Fla. — Samples on July 18 indicated that the Vogtia population had attained a density of 0.43 2 9 larvae/ft. from the first release. A population of 3.4/ft. was recorded on September 20, 1972. In both cases the sampling was done within approximately 100 yds. of the release site. The population density declined as the distance was increased from the release area. * On April 26, 1973 just after spring growth had begun 2 the population was 2.25/ft. . Therefore the population was probably not reduced significantly during the winter period. This was expected since frost did not occur in this area.

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ALLIGATORWEED PRODUCTIVITY Introduction To evaluate the effects of stress caused by biological control agents to growing plants, comparisons must be made between that plant growing undisturbed, and that plant with the additional stress factors added. Environmental conditions, nutrient levels, and many other factors play a significant role in regulating a plant's grov;th and spread. This is especially true of plants such as alligatorweed that are adapted to a wide range of conditions. With these limitations in mind, attempts v/ere made to determine the net rate of biomass production in alligatorweed growing under favorable greenhouse conditions, and in four lakes which had varying levels of injury from biological control agents. Methods and Materials Greenhouse Studies Alligatorweed v/as grown in a 4 X 12 ft. X 6 in. greenhouse table divided into three 4X4 ft. sections. The two end sections were covered v/ith 6 mil polyethylene and filled with tap water to a depth of 5 in. On December 13, 9.5 lbs of alligatorv'/eed from the floating portion of a mat of weeds taken from Lake Alice, Gainesville, Fla. were 31

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32 placed in the water-filled sections. The middle section contained a Henry J. Green hygrothernograph, which recorded the temperature and relative humidity at the approximate water level. Artificial lighting, about 3000 ft. candles, was supplied by 12 Sylvania 40w VHO cool v/hite florescent bulbs and 24 f 75w incandescent lamps attached to a light board and suspended 11 inches from the table top. An Intermatic model TlOl timer controlled the 12 hour photoperiod. Each plant section was initially filled with tap water to v/hich 150g milorganite and 200g of 20-20-20 soluble plant food was added. On January 4 another 180g of the same fertilizer plus 45g of 1.82% iron supplement were added to each section. Half of the growing mat in each section was removed on January 10, the remainder on January 16, terminating the study. To reduce experimental error, alligatorv/eed was taken from alternate sides of the table. The plant material was allov/ed to drain for 5 minutes and then weighed on a Fairbanks Morse portable platform scales. Water samples were taken at the beginning of the experiment and on January 4. These samples v;ere analyzed for common nutrients, i.e. nitrates, phosphates, potassium, chlorides, magnesium, manganese, iron, copper, and calcium by the Soils Laboratory, IFAS, University of Florida. The mean daily temperature was 29°C., the mean daily RH

PAGE 43

33 was 50.6%, and the pH of the water was 7.5. The water temperature on the first sample date was 26°C. Field S^yudies Standing bioraass samples were taken in early spring, before much growth had occurred (March 19, 20, 22, and 23), in early summer (May 2, 10, 20, and 24), and in midsummer (July 13, 18, 27, and August 1) at two lakes (Black Lake, Melrose, Fla. and Garden's Corner, S.C.) and three streams (stream flowing into Lake Alice, Gainesville, Fla. , roadside ditch, at Ft. Lauderdale, Fla., and Twin Lakes, S.C.). Alligatorv/eed characteristically grows very rapidly in the spring and then considerably slower during the rest of the growing season. These samples represent both growth periods for alligatorv/eed at these sites. A stainless steel cylinder was constructed to extract a 1.2 ft.^ core sample from the floating mats of alligatorweed. One end of the cylinder was sharpened to facilitate cutting through the mass of alligatorweed, and the other end was covered with 1/4 in mesh hardware cloth. A sample was removed from the water, after cutting, by inverting the sampling device. The sample was allowed to drain for 5 minutes and then emptied into a plastic bag and v;eiqhed with a hand-held scales. The same mat of alligatorweed was used for all sam.ple periods at each location. All samples were taken half way between the shoreline and the leading edge of the mat.

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34 Results c:nd Discussion Greenhouse Studies Although the study began December 13, the actual growth period of the alligatorweed did not begin until several days later. When the alligatorv;eed was transferred to the greenhouse table the aerial steins were broken and disoriented to such an extent that growth was effectively stopped until nev; stems were produced. Therefore the first samples at 28 days showed little change (Table 3) , since the plants had been actively growing for 10 days or less. The increase in biomass during the first peri.od was 64%. The second sample period, lasting only 6 days increased its biomass by 48%. Nutrient levels (Table 2) were much higher than those normally found in natrual lakes or streams. In Lake Alice, for example, only phosphates were higher than in these water tables (2.98 ppm) . Iron was 0.25 ppm, nitrates were 5.3 ppm, chlorides were 25.0 ppm, and the pH was 7.75 on May 2, 1972. Table 3. Net productivity of alligatorweed in greenhouse tests Wet v/eight of samples (lbs) Initial wt . 28 days 34 days % increase Rep. 1 9.5 14 19 200 Rep. 2 9.5 '11 18 189

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35 Table 2. Nutrient levels in water tablc-s used for productivity studies (ppm) Sample No3 P K CI Mg Mn Fe Cu Ca Rep. 1 22.0 0.25 70.9 92.0 1.43 .075 1.80 0.20 0.90 Rep. 2 22.0 0.30 70.0 92.0 1.28 .075 1.90 0.20 0.82 tap water 4.3 0.0 0.0 22.5 0.73 0.0 0.0 0.10 1.10 Field Studies Alligatorweed productivity in the field did not approach that in the greenhouse. The Tv/in Lakes site had a high percent increase, but the growth period was 52 days, compared with 34 days for the greenhouse study (Table 4). The early summer daily increment factors for the five sites were .104, -.003, .082, .035, and .028 for Twin Lakes, Fort Lauderdale, Garden's Corner, Lake Alice, and Black Lake, respectively. The daily increment factor for the greenhouse alligatorweed was .26, or 2 1/2 times the hignest increment factor recorded in the field. On a per acre basis, the Twin Lakes growth rate was equivalent of 3,775 lbs of biomass produced per acre per day. In the 52 day period an acre of alligatorweed would produce 193,300 lbs of new growth. That is approximately tv/ice as productive as the most productive aggricultural crop, in half the time. Corn grown on muck soils produces 2-30 tons of silage in about 100 days (Cunha and Rhodes 1965) .

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36 At Garden's Corner during the summer sample period, and at Fort Lauderdale, to a lesser extent, the standing biomass was reduced. The reduction at Garden's Corner corresponded with a heavy attack of the Agasicles beetle;, in which the aerial stems of alligatorv^eed were completely stripped of their foliage and small stem.s. The reduction at Fort Lauderdale was less dramatic and may have been due, in part, to severe interspecific plant competition.

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37

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INTERRELATIONSHIPS BETWEEN ALLIGATORWEED AND TVv'O INSECTS— Vogtia and Agasicles Introduction Pioneering plants or opportunists such as alligatorweed may because of their tolerance to wide environmental conditions appear in different areas with very different growth and morphological characteristics. Alligatorweed in some areas may produce numberous , short, fibrous stems while in other areas the aerial stems may be much less dense in number and taller, thicker, and more rapidly growing. Under these conditions, it becomes increasingly difficult to evaluate the host plant-insect relationship, and almost meaningless to compare insect population data between the areas. Therefore a great number of samples (287) from all the release areas have been combined to provide an overall estimate, or comparison, of the effect of a given parameter on alligatorweed with the effect of all other parameters considered at the same time. The variables representing the two insects have been evaluated with and without the influence of the other variables being included in the model. Two stastical methods were used to shov; the interactions between the Vogtia and Agasicles populations, between each of these insects and alligatorv/eed, and between available nutrients and alligatorv/eed growth. 38

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39 In the canonical correlations program, 24 variables were grouped into sets. The sets were then compared and significant relationships were defined. The second program was a full multivariate regression model which explained the significance of each of the measured variables in influencing alligatorweed growth. In canonical correlations, a set of independent variables may be compared with a set of dependent variables to find the linear con±)ination of variables in each set which when correlated is maximum. The resultant variable is known as a canonical variate. If some linear relationship between the sets of variables still remains unaccounted for by the first set of canonical variates, the process of finding new linear combinations that would best account for the resideual relationships between the sets can be continued. This process can go on until there are no significant linear associations left. Each canonical variate is orthogonal to (or unrelated to) other canonical variates. The chisquare test is used to evaluate variates for significance. In canonical correlations, variables in one set may be combined to predict maximally the variations of the variables in the other set. This process was utilized to compare data frcm lakes and streams, and to predict the number of samples that should occur in using different sets, lakes or streams (See Morrison 0.961) for detailed discussion of canonical correlations and tests of significance) . All

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40 statistical, methods were analyzed by computer program, BND, SPSS (Nie, 197 0) on the University of Florida North East Regional Data Center's IBM 370/165. Methods and Materials The Vogtia and Agasicles sampling procedure was described in the section on colonization, i.e. a ft. frame was used to determine the population density, as well as to gather plant material for stem measurements. Sample sites were selected either by a random process (Lake Alice, Black Lake, and Lake Lawn) or by taking samples at preselected 15 feet intervals (Garden's Corner, Ft. Lauderolale , and Twin Lakes). Aerial stems v/hich were selected for measurement were representative of the sample in both height and diameter. In most cases, the uniformity of the samples made multiple plant measurements unnecessary. Measurements for each of the sample sites included the following: stem height, length of the fourth internode, diameter of the fourth internode, stem density, percent leaf area missing, Agasicles/ft. , vogtia/ft.'^ (expressed as a total and as each of the instars as a separate variable) , pH, alkalinity, iron (ppm) , turbidity (jtu), chlorides (ppm) , phosphates (ppm), nitrites and nitrates (ppm), hardness, water depth, and whether the sample was taken from a lake or stream. The fourth internode was chosen for plant measurements because it was the first fully developed internode.

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41 Water samples were analyzed for nutrients in the laboratory with the use of a Hach water testing kit. A total of 287 samples were taken from the six following release sites, three of which were lakes and three were streams. The number of samples taken from each site is shown in parenthesis: Lake Alice, Gainesville, Fla. (76); Black Lake, Melrose, Fla. (155); Lake Lawn, Orlando, Fla. (34); Peeples Pond, Garden's Corner, S.C. (2); Roadside ditch. Ft. Lauderdale, Fla. (17); and Twin Lakes, Summ.erville , S.C. (3), (Fig. 2).

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42 Results and Discussion Insect-Host Plant Relationship In the first analysis, the set of plant characteristics was compared with the set of variables representing numbers of Agasicles and Vogtia present and a measure of Agasicles feeding damage. As a result of these correlations, 3 new canonical variates were formed (Table 5 and Table 6). Each of these new variates was significant at the .01 level of probability, indicating that 3 independent and significant linear relationships existed. If we examine the coefficients of the individual variables (Table 7) , we can explain the combinations of variables making up each of these associations. The first canonical variable represents the most important of the linear associations, and in this case there is a positive association between plant height, internode length, intermode diameter and the number of Agasicles and Vogti a , and a negative association between the same plant characteristics and Agasicles feeding. Therefore, both Vogtia and Agasicles tend to occur more frequently in alligatorweed with larger, taller stems. Vogtia , having a larger coefficient, probably favors these conditions more than Agasicles . The negative association between the plant characteristics and Agasicles damage was expected. The more damage done by Agasicles , the more stress is placed on the growing plants , resulting in smaller unthrifty stems. *

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43 The second canonical variate of less importance than the first, but equally as significant, consisted of a negative association between Agasicles feeding and plant height, and internode diaraeter. This may appear to be in contradiction of the first canonical variate; however, the canonical variates must be considered separately. Therefore, 2 relationships exist, one superior to the other. When plants are heavily attacked by Agasi c les , the upper internodes may be damaged sufficiently to cause them to be dropped off resulting in a condition described by this relationship. Table 5. Variables used in 'canonical correlations with mean and standard deviations. Variable Mean Standard Dev. Cases SET I Plant Height 11.895 Internode Length 2.2250-: •. Internode Diameter .12007 • No. Stems 51.212 Percent damage 15.174 SETII No. Agasicles 1.536 No. Vogtia 3.515 1st Inst. Vogtia 1.268 2nd Inst. Vogtia 0.651 3rd Inst. Vogtia 0.498 4th Inst. Vogtia 0.456 5th Inst. Voatia 0.418 3.90

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44 Table 5 continue

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45 The th.ird canonical variate, likewise independent of the first 2 and of less importance, consisted of a positive association between the number of Agasicles and internode length and the number of stems. We can conclude from this that adult Agasicles tend to occur more frequently in dense stands of alligatorweed with samller stems, and the latter condition is negatively correlated with the number of Vogtia and with Agasicles feeding. The Agasicles feeding and stem size association is in agreement with the first canonical variable but much smaller in magnitude. The positive correlation of Vogtia with stem size is expected since in small stems the full grown larvae may be as large in diameter as the stem itself and, therefore, not protected from parasites and predators or environmental factors. It should be noted that 63.96% of the variation is e3q)lained by canonical variable 1, 30.92% by canonical, variable 2, and only 5.12% of the variation is explained by canonical variable 3. The most important associations, therefore, are probably described by canonical variables 1 and 2. In the second analysis, the same 4 plant characteristics i.e. plant height, internode length, internode diameter, and number of stems were used to compare with the number of Agasicles , Agasicles feeding damage and each of the 7 immature stages of Vogtia present. In this correlation, 4 new canonical variables were formed (Table 8). The first 2 were significant at the .01

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46 level of probability. The third was significant at the .10 level of probability and, therefore, will not be considered in this discussion. The fourth variate was not significant. The first variate incorporates 61.22% of the total variation and the second 29.87%. Table 8. Canonical Variates in Analvsis II. Number of Canonical Variate Sets 1 2 3 4 Chi-Square 195.18961 94.64266 23.28067 5.74528 Degrees of Freedom 36** 24** 14 6 * indicates significance at the .01 level of probability An inspection of the canonical coefficients for the individual variables (Table 9) reveals a positive association between stem diameter and internode length with the 5th instar Vogtia . This relationship, as explained in the first analysis, has been observed in the field in areas where alligatorweed was under severe stress. During temporary stress periods, the aerial stems may become small, v/ith the stems making up the mat remaining large. In this case, the larvae can survive in the mat unless flooding occurs which may drown the larvae. Another relationship occurring in the first canonical variable is a neaative association between Agasicles feeding and stem size. This relationship,

PAGE 57

47 also apparent in the first analysis, is a result of A gasicles damage producing stress in the alligatorweed which resulted in smaller, less thrifty plants. The second canonical variate shov/s a negative association between Agasicles feeding and plant height. As discussed earlier, reduced plant height with increased Agasicles damage is a direct result of A gasicle s attack. Since the plant suffers more damage in the top few internodes, the more severely attacked plants are much more prone to breaking over, and to dropping these upper internodes. Table 9. Canonical Coefficients for Individual Variables, Analysis II Variable Can. Var. 1 Can. Var. 2 1.156 0,200 -0.561 0.578 -Q..g55 SET I

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48 Can. Var. 1

PAGE 59

phosphates

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50 The second canonical variable shows a second positive relationship between plant height and turbidity, independent from the first. In this case however, the major emphasis should be placed on the positive association between internode diameter and water hardness, where as water hardness increases, so does the diameter of the aerial stems. Table 12. Canonical coefficients for individual variables, Analysis III Variable

PAGE 61

51 The third canonical variable indicates a negative relationship between the number of stems and water hardness. This, in conjunction with the second variable suggests that wate^-iiardness is normally associated with stems of larger diameter and of lower density as opposed to a larger number of stems of smaller size. Also important in this relationship is the positive association between water depth and stem density, indicating that as depth increases stem density increases as well. Another part of this association is a positive relationship between stem diameter and pH , phosphates and alkalinity, indicating that as these variables increase, the diameter of the stems increase similarly. The fourth variable shows a negative relationship between turbidity and internode diameter similar to the second variable, and a positive relationship between turbidity and internode. length.. The latter relationship would be expected since a positive relationship has been shown between turbidity and plant height. Internode length and plant height are almost certainly related. Comparison of lakes and streams To determine if there was statistically significant difference between alligaterweed growths in lakes and streams a canonical discriminant analysis was utilized to compare the 287 samples and group them according to their origin (Cooley and Lohnes 1970) . Three of the four plant characteristics were significant between the two groups at the .01 level of probability. These were: internode

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52 length, internode diameter and stem density. The samples were then weighted according to the relative importance of these three characteristics and reclassified through the use of the canonical discriminant function (Tab]c 13). Table 13. Computer reclassification of Lakes and Streams. Original data set Lakes Streams 191 96 Reclassified according to plant characteristics Lakes Streams Lakes 67 29 » 70% Streams 30 161 = 84% Reclassified according to physical and chemical properties of the water Lakes Streams Lakes 93 3 = 97% Streams 191 = 100% Using plant characteristics 67 of the 96 lake samples were classified correctly; 29 were reclassified as stream. samples thereby producing an accuracy of 70 percent. The stream samples were reclassified with an 84 percent accuracy (161 of the 191 stream samples) . Thirty of the stream samples v;ere reclassified v/rongly as lake samples. The procedure of reclassification was repeated using the parameters which measured water quality, all of which

PAGE 63

53 were significant at the .01 probability level: PH , alkalinity, iron, turbidity, chlorides, phosphates, nitrates, hardness, and water depth. The result was an overall accuracy of 99 percent. Ninety-three of the 9 6 lake samples were reclassified correctly v/ith only three appearing as stream samples (97% accuracy) . The stream samples were reclassified v;ith 100 percent accuracy (Table 13) . The author is cognizant of the fact that with the small number of sample sites these conparisions may not represent a true picture of lakes and streams in general; they are, however, valid for this study. Analysis of variance of Plant Characteristics Two analysis of variance tables were constructed for each of the variables representing plant characteristics; one which showed the statistical significance of the dependent variable with all independent variables included in the model, and the other an analysis of the dependent variable with only the independent variables representing the insect populations included in the model. In each analysis, the sums of squares v/as broken down using partial sums of squares to shov; how each of the independent variables contributed to the variation of the dependent variable. In each case the F test was employed to determine statistical significance. As shown in table 18 plant height was significant at greater than the .01 probability level in both analysis. The partial sums of squares indicate that iron, turbidity,

PAGE 64

54 water depth, and Vogtia were significant at .01 in contributing to the variation of plant height. Alkalinity was significant at the .05 probability mvtjj.. In the second model which included only the insect -rariables, both Agasicles and Vogtia were sicrnificnnt at .0]_ (Table 14). Table 14. ANOV for nlant Source

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55 Table 14 continued. ANOV for Plant Height with nutrient effects removed Source DF SS MS F Prob F Regression Error 2 3.93 1.99 14.25 0.0001 284 39.63 0.14 Corrected Total 286 43.61 Source DF Partial SS F Prob F Agasicles 1 ' 1.53 10.97 0.0014 Vogtia 1 3.12 22.34 0.0001 The analysis in which internode length was the dependent variable and with the sane independent variables the analysis of variance indicated significance at the .01 level (Table 15) The partial suras of squares shov7ed only one statistically significant independent variable, Agasicles (.01). In the insect only model both Agasicles and V oatia were significant at the .01 probability level. Table 15. ANOV for internode length Source DF SS MS F Prob F Regression 12 149.96 12.50 9.79 0.0001 Error 274 349.84 1 Corrected total 286 499.80 z.i

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56 Table 15 continued. Source

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57 The analysis of variance with internode diameter as the dependent variable indicated significance at the .01 probability level both v/ith all independent variables included and v/ith only the independent variables for insects included. The partial suras of squares with all variables included showed significance at .0,1 for water depth and Agasicles . The partial suras of squares with only the insect variables included resulted in Agasicles not being statistically significant and Vogtia significant at the ,01 probability level (Table 16) . The reversal in significance ^^^ Agasicles is probably due to the correlation of Vogtia with stem diameter (the simple correlation coefficient was . 51) . < Table 16. ANOV for internode diameter Source DF SS MS Prob F Regression 12 Error 274 Corrected Total 286 44.42

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Table 16 cdntinued, 58 Source DF Phosphates 1 Nitrates 1 Hardness 1 Water depth 1 Lake and Stream 1 Vogtia 1 Aqasicles 1 tial SS

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59 at the .01 probability level in both analysis. The partial sums of squares shows significance at .01 for the following variables: pH, alkalinity, nitrates, hardness, and water depths' Significance at .05 was indicated for phosphates, lake or stream variable, and Vogtia , The partial sums of squares with only insect variables included shov/ed significance at .01 for Vogtia and no significance for Agasicles (Table 17) . Table 17. ANOV for Stem density, Source DF SS MS F Prob F Regression

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Table 17 CQntinued, 60 Source

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61 similarly significant but at the .05 level. The partial sums of squares in the limited model shows both Agasicles and Vogtia to be significant at the .01 probability level, Table 18. ANOV for Leaf area missinq. Source

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62 Table 18 continued. Source DF SS MS F Prob F Regression 2 343.94 171.97 29.81 0.001 Error 284 1638.59 5.77 Corrected Total 286 1982.53 Source DF Partial SS F Prob F Agasicles 1 288.82 50.06 0.0001 Vogtia 1 108.97 18.82 0.0001 In table 19 the overall effect of each of the independent variables on the plant characteristics as a whole is shown. Like the previous programs, F values v/ere calculated using all independent variables in the first model and secondly with only the insect variables included. Pillai's Trace with the F statistic was used as a test for significance. When all variables v;ere included only one independent variable lacked significance, chlorides. Variables with larger F values and therefore more important sources of variation were: Iron, turbidity, nitrates, hardness, water depth, and Agasicles . With only the insect variables included, both Agasicles and Vogtia were significant at greater than the .01 probability level.

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63 Table 19. Overall effect cf variables on alligatorweed Variable

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SUMMARY Vogtia malloi was introduced into the United States in the spring of 1971 with populations successfully established in 1971 and 1972 at the following locations: Upper Legion Lake, Columbia, South Carolina, Twin Lakes, South Carolina, Garden's Corner, South Carolina, Black Lake, Melrose, Florida, Lake Alice, Gainesville, Florida, Lake Lawne, Orlando, Florida, and a roadside ditch, Fort Lauderdale, Florida. Populations of Vogtia expanded randomly as alligatorweed in the release area became damaged and less desireable. Samples of the parasite populations at Lake Alice and Lake Lawne indicated that the Vogtia populations were not seriously reduced and only general parasites were observed. Both Vogtia and Agasicles demonstrated their ability for surviving frost and cold temperatures. At Columbia, South Carolina both insects survived the 1972-73 VJinter with below freezing temperatures recorded for 17 of the 2 8 days in the month of February. With this degree of cold tolerance it is probable that these insects can extend their range throughout the northern limits of alligatorv/eed infestations. At Gardenfe Coner the Vogtia population was reduced but was not excluded even when Agasicles had completely defoliated 64

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65 the alligatorweed and almost destroyed it. When the Agasicles population subsided, as expected during the hot nonths of summer, the Vogtia population began to build up, keeping the alligatorweed under stress for the entire growing season. While Agasicles populations remained low in south Florida, presumably because of high temperatures, the Vogtia population was apparently unaffected, and will therefore probably surpass Agasicles in its influence on alligatorweed grov/th in the southern regions. The use of canonical correlations, in conjunction with a multivariate analysis has enabled us first to shov/ the interrelationships which occured between V ogtia and Agasicles , between each of these insects and alligatorv/eed, and between the physical and chemical characteristics of the v;ater and alligatorweed, and secondly, to determine the significance of these factors in controlling alligatorweed growth. As expected, a significant relationship existed between Agasicles and plant height. Agasicles characteristically begins feeding on the upper leaves and items of alligatorweed resulting in shorter plants. Similarly, Agasicles adults occured less frequently in heavily damaged alligatorweed, as did Vogtia larvae, a probable result of the food supply being reduced. In this study, as stem density increased Vogtia occurred less frequently and Agasicles occurred more frequently. Since alligatorweed may occur in relatively dense stands of stems

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66 with small diameters, this indicates the preference of Agasicles for the younger leaves, and with the positive correlation between Vogtia larvae and stem size, the inability of Vogtia larvae to survive in very small stems. This is also indicated by the tendency of both populations to occur in greater numbers with tall healthy plants. As the depth of the water increased, aerial stems tended to be shorter and more numerous, and as turbidity, iron, and alkalinity increased plant height increased. Also, as water hardness, pH , and phosphates increased the plants tended to be larger. This simply indicates that alligator^veed grows better in shallow, fertile ponds as opposed to deep, clean water. < Samples from lakes and streams were more accurately seperated according to characteristics of the water than to plant characteristics, suggesting that a greater difference occurs between lakes and streams than between stands of alligatorweed growing in these areas. The overall effect of the independent variables on the plant characteristics as a whole resulted in all variables, except chlorides, being significant at 0.01 The most important of these were: iron, turbidity, nitrates, hardness, water depths, and Agasicles , as indicated by larger F values. The potential for seasonal control of alligatorweed has been clearly demonstrated by both Agasicles alone (Zeiger 1967) , by Vogtia, and by Vogtia and Agasicles in

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67 combinations. However, the resiliency of alligatorweed in re-establishing itself is truly remarkable, and for this reason no attempt has been made to predict the final impact of these insects in reducing the overall area of infestation of alligatorv/eed. In many areas, the mats of alligatorweed have increased over the years such that they now frequently occur 8-10 in. in depth. Under these conditions, herbicides may be required to facilitate insect presure if alligatorweed is to be reduced drastically in a short period of time.

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LITEFi; CITED Acreneaux, G. and L. P. Herbert. 1943. Preliminary studies of periodic flaming as a means of controlling Johnson grass and alligatorweed on sugarcane lands. The Sugar Bull. 22: 21-23. Brown, J. L. ana N. R. Spencer. 19 73. Vogtia malloi , a newly introduced Phycitine moth (Lepidoptera: Pyralidae) to control alligator^-zeed. J. Environ. Entomol. 2(4): 519-523. Cooley, W. W. and P. R. Lohnes . 1970. Multivariate Data Analysis. John Wiley and Sons. 359d. Cunha, T. J. and G. N. Rhodes. 1965. Beef cattle in Florida. Bulletin 28. Florida Department of /igriculture. Gangstad, E. 0. and F. J. Guscio. 1970. Research planning conferences for aquatic plant control. Tech. Rep., Chief of Engineers, U.S. Army Corps of Engineers. Maddox, D. M. and R. D. Hennessey. 19 70. The biology and host range of Vogbia malloi Pastrana. Unpublished manuscript, Agricultural Research Service, USDA, Albany, California. Maddox, D. Zl. , L. A. Andres, R. D. Hennessey, R. D. Blackburn, and M. R, Spencer. IP" nsects to control alligatorweed, an xnvaaer of aquatic ecosystems in the United CQ

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69 States. Bioscience 21: 985-91. Mohr, C. 1901. Plant Life of Alabama. Vol. 6, 921p. Morrison, D. F. 1967. Multivariate statistical nethods. McGraw-Hill Co. Nev; York. 338p. Muesebeck, C. F. W., K. V. Krombein, and H. K. Townes . 19 51. Hymenoptera of Anerica North of Mexico. U.S. Dep. Agric, Agric. Mono. no. 2. 142 pp. U. S. Govt. Printing Office, Washington, D. C. Nie, N. 1970, Stastical package for the Social Sciences. McGraw-Hill Co. New York. 338p. Pastrana, J. A. 1961. Una nueva Phycitidae (Lep.) parasito de la "Lagunilla". Rep'. Arg. Publ. Tec. 71, Inst. Nac. Tec. Agropecuar., p 265-272. Penfound, W. T. 1940. The biology of Achyranthes philoxeroides (Mart.) Standley. American Midi. Nat. 24: 248-252. Vogt, G. B. 1960. Exploration for natural enemies of alligatorweed and related plants in South America. U. S. Dept. Agric, Agric. Res. Serv. , Entomol. Res. Div. , Special Report PI-4, 58p. Vogt, G. B. 1961. Exploration for natural enemies of alligatorweed and related plants in South America. U. S. Dep. Agric, Agric. Res. Serv., Entomol. Res. Div., Special Report PI-5, 50p. Weldon, L. W. 19 60. A summary review of investigations on alligatorweed and its control. USDA, Agric. Res. Serv., Crops Res. Div., CR 33-60, 41p.

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70 Zeiger, C. F. 19 G7. Biological control of alligatorweed with Agasicles n. sp. in Florida. Hyacinth Control J. 6: 31-34.

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BIOGRAPHICAL SKETCH John L. Brown was born November 17, 19 44 in Weiner, Arkansas. He attended Weiner Public Schools from 1950 to 1962 and after graduation he enlisted in the U.S. Air Force. In 19 67 he enrolled in the school of Agriculture at Arkansas State University. He received the Bachelor of Science degree in 1969, and enrolled at Iowa State University. He received the Master of Science degree in entomology in 19 71 and transferred his studies to the University of Florida where he is completing the requirements for the degree of Doctor of Philosophy. John L. Brown is married to the former Delena Y. Newmans and has two children, a son of 10 years and a daughter of 5. • • " He is a member of the Entomological Society of America and the Florida Anti-mosquito Association. He was employed by the Florida Division of Health in January, 1973 as director of the stable fly control program. 71

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I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a dissertation for the degree of Doctor of Philosophy. .-^iM-^^^^i B. David Perkins Assistant Professor of Entomology This dissertation was submitted to the Dean of the College of Agriculture and to the Graduate Council, and was accepted as partial fulfillment of the requirements for the degree of Doctor of Philosophy. December, 19 73 Dean, Graduate School