• TABLE OF CONTENTS
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 Front Cover
 Front Matter
 Title Page
 Table of Contents
 Important pests of chrysanthem...
 Less important pests of chrysa...
 Pesticide use and pesticide...
 References
 Back Cover














Group Title: Bulletin - Agricultural Experiment Station. University of Florida ; 881
Title: Management of insect and mite pests of Florida chrysanthemums
CITATION THUMBNAILS PAGE IMAGE ZOOMABLE
Full Citation
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Permanent Link: http://ufdc.ufl.edu/UF00086516/00001
 Material Information
Title: Management of insect and mite pests of Florida chrysanthemums
Series Title: Bulletin
Physical Description: 19 p. : col. ill. ; 28 cm.
Language: English
Creator: Price, J. F ( James Felix )
Poe, S. L ( Sidney LaMarr ), 1949-
Publisher: Agricultural Experiment Station, Institute of Food and Agricultural Sciences, University of Florida
Place of Publication: Gainesville Fla
Publication Date: 1991
 Subjects
Subject: Chrysanthemums -- Diseases and pests -- Control -- Florida   ( lcsh )
Insect pests -- Control -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references (p. 17-19).
Statement of Responsibility: James F. Price and Sidney L. Poe.
General Note: Cover title.
General Note: "Printed 3/91"--P. 4 of cover.
Funding: Bulletin (University of Florida. Agricultural Experiment Station) ;
 Record Information
Bibliographic ID: UF00086516
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 26898563

Table of Contents
    Front Cover
        Front Cover
    Front Matter
        Front Matter
    Title Page
        Title Page
    Table of Contents
        Table of Contents
    Important pests of chrysanthemums
        Page 1
        Page 2
        Page 3
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
    Less important pests of chrysanthemums
        Page 16
    Pesticide use and pesticide labels
        Page 17
    References
        Page 17
        Page 18
        Page 19
    Back Cover
        Back Cover
Full Text
,o
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Management of insect and mite pests
of Florida chrysanthemums
James F. Price and Sidney L. Poe


I
/


Central Scien
Library
Sep 81 982


versity of Florida






Agricultural Experiment Station
Institute of Food and Agricultural Sciences
University of Florida
J.M. Davidson, dean


Bulletin 881
























CIEPA
LM P.,'.'"












































James F. Price is an associate professor of Entomology, Gulf Coast Research and Education Center, Bradenton, FL 34203; and
Sidney L Poe is a former professor, Department of Entomology and Nematology, Gainesville, FL 32611; respectively, University of
Florida.














Management of insect and mite pests
of Florida chrysanthemums
James F. Price and Sidney L. Poe















... .'. .- ...








Contents
Introduction ............................................................................................................................................................. 1
Pest status of arthropods ........................................................................................................................................ 1
Integrated Pest M anagem ent (IPM ) ....................................................................................................................... 1
Important pests of chrysanthem um s......................................................................................................................1
M ites ....................................................................................................................................................................2
Leafminers ...........................................................................................................................................................3
Aphids ..................................................................................................................................................................6
Thrips ................................................................................................................................................................... 7
Beet armyworm and other Lepidoptera ........................................................................................................9
Plant bugs .......................................................................................................................................................... 12
Fungus gnat ....................................................................................................................................................... 13
W hiteflies ........................................................................................................................................................... 14
Less important pests of chrysanthemum s ........................................................................................................... 16
M ealybugs .......................................................................................................................................................... 16
Garden fleahopper ............................................................................................................................................. 16
Field crickets and m ole crickets .......................................................................................................................16
Snails and slugs ................................................................................................................................................. 17
Pesticide use and pesticide labels .................................................................................................................... 17
References .............................................................................................................................................................. 17








Introduction
Florida is a major, United States producer of
three chrysanthemum products: cut flowers, potted
flowers, and stem tip cuttings for production of cut
and potted flowers. Approximate values during
1986 were: cut flower chrysanthemums, $3.6
million; potted chrysanthemums, $8.9 million; and
cuttings, $18 million. These combined products
were produced by 42 growers on 336 acres (Waters
et al. 1987).
Chrysanthemums produced in Florida may be
subject to losses from microbial, nematode, weed,
and arthropod pests. This publication addresses the
arthropod pests affecting production of chrysanthe-
mums in Florida.
Arthropods are animals that possess jointed legs
and an exterior skeleton. These include insects,
mites, symphylans, spiders, millipedes, centipedes,
ticks, and other groups. Insects and mites are the
arthropods that usually damage chrysanthemums.
Chrysanthemums are produced in environments
that always contain arthropods, regardless of the
precautions exercised.

Pest status of arthropods
Although arthropods are always present in a
chrysanthemum crop, they become economically
damaging only when they reduce the amount or
quality of the chrysanthemums sold (Price et al.
1980). Some arthropods associated with chrysan-
themums never attain that status. For example,
the metallic blue or green "long-legged flies"
(dolichopodids) are often abundant among chrysan-
themums but do no damage and are rarely found on
the shipped product.
Other arthropods can attain pest status depend-
ing on the type of crop produced (potted flower, cut
flower, or cuttings), regulatory restrictions, or crop
demand and supply available. For instance, even
sparse populations of fungus gnats are intolerable
on potted chrysanthemums nearing harvest but are
of little consequence on cut chrysanthemums. The
presence of a few leafminers is usually not impor-
tant to the appearance of cut flower chrysanthe-
mums since most leaves are removed for floral
arrangements. However, regulatory restrictions
may require that shipments be entirely free of
leafminers. Prices offered for cut flower chrysanthe-
mums may be unaffected by small amounts of
leafminer damage when flower supplies are limited,
but they may be lowered when supplies of unaf-
fected flowers are sufficient.


Integrated
Pest Management (IPM)
Successful arthropod management requires an
understanding of tolerable population densities, life
cycles, feeding behavior, methods of dispersal, and
means of detection of important arthropods. Effi-
cient management can be attained through inte-
grating the following:
* regulatory controls imposed over regions;
* sanitation measures within the crop and its
environs;
* production from high quality cuttings;
* exclusion of pests through design, maintenance,
and management of greenhouses and
shadehouses;
* production from resistant cultivars;
* manipulation of irrigation, fertilization, and
other components of culture to provide the least
advantages to pests;
* scouting for pests;
* biological control by beneficial organisms;
* judicious use of pesticides;
m education of buyers to accept certain arthropods
and their effects.
The most effective tactic for managing a poten-
tial arthropod pest is to prevent its establishment
in the region. Regulatory measures that prevent
the introduction of exotic, potential pests have
become important since chrysanthemums are
moved daily among world regions. The failure of
effective regulatory measures permitted Liriomyza
trifolii (Burgess), a leafminer pest in Florida and
nearby areas, to develop into a cosmopolitan pest
(Parrella and Keil 1984). Regulatory procedures
should be strengthened to ensure that pests are not
moved into areas where they do not already exist.

Important pests of
chrysanthemums
Many arthropods attack chrysanthemums at one
time or another, but only the more important can
be discussed here. This publication identifies and
provides details of those arthropods that present
greatest limitations to successful production. No
specific pesticidal recommendations are presented
but are available from the University of Florida,
IFAS (Short and Price, 1989).









Mites


Mites in advanced juvenile and adult stages are
eight-legged, usually smaller than the period at the
end of this sentence and about as wide as long.
Unlike insects, mites are always wingless.
The twospotted spider mite (Tetranychus urticae
Koch, "red spider mite," "red spider," or "two spot")
is probably the most common pest of chrysanthe-
mums (Fig. 1). This mite is usually pale, translu-
cent yellow or slightly green but during cold
weather may be orange or reddish purple. There is
a distinctive dark patch on each side of the abdo-
men that gives rise to the common name,
"twospotted spider mite." Eggs are round, translu-
cent green or creamy and too small to be seen
without magnification. They are laid on the under-
side of leaves, often along the midrib, under almost
undetectable webbing.


Figure 1. Twospotted spider mite adult, egg and white feeding
marks.
An infestation may begin after introduction of
contaminated cuttings or plants, after movement of
mites from older infested plants, or after entry of
adults airborne on silk strands. Once the
twospotted spider mite is present in one part of the
range, it is easily carried to other portions by
workers, equipment, relocated plants, or air cur-
rents.
The twospotted spider mite is most troublesome
during warm, dry weather. Developmental time
varies with temperatures, but at 810F (27C), each
female can lay an average of 8 eggs per day for
almost 3 weeks. Eggs hatch into six-legged larvae
in about 2 days, then develop through 3 resting
periods and 3 active stages each with 8 legs. About
10 days are required for a newly laid egg to hatch,
the mite to develop and, if female, the mite to lay
its own eggs. (Poe 1971, Shih et al. 1976). Thus, a
potted chrysanthemum with a few mites at the


time of sale, could be heavily infested 2 weeks later
in a warm, dry home.
Spider mites feed by sucking cell contents. They
attack the leaves but also may attack buds and
flowers at the top of plants when populations are
dense. Spider mite feeding may cause leaves to
become silvery or russety and may cause flower
petals, particularly on outside florets, to appear
water-soaked and to desiccate.
Chrysanthemums should be scouted at least
weekly to find potentially damaging spider mites.
Earliest infestations are detected by looking for the
mites, their stipple marks, or silvering on the lower
surfaces of lower leaves. IPM scouts should pay
particular attention to plants along perimeters of
shade houses and near entrances and air intakes of
greenhouses.
Mite densities that require chemical treatment
vary according to temperature, type and age of
crop, effectiveness of miticides, and other factors.
Miticides often lose much of their effectiveness
within 1 or 2 days and may have little effect on
eggs and resting stages. In many cases it is neces-
sary to make at least two applications, about 3-5
days apart. Systemic miticides may be required to
kill mites protected by florets or other plant parts.
Sprays should cover the underside of leaves for best
control of mite populations.
Biological control of twospotted spider mites on
cut-flower chrysanthemums has been achieved on a
few farms in Europe. The tactic can involve intro-
ducing twospotted spider mites into the crop first,
then introducing a predatory mite, Phytoseiulus
persimilis Athias-Henriot (Osborne et al. 1985). By
this technique, spider mites always will be present,
but at a little- noticed level. Pesticides for other
arthropod and microbial pests must be compatible
with the use of biological control for mites; this
requirement limits use of predatory mites (Foster
1980; Osborne et al. 1985).
Mite populations are affected by crop culture,
and alterations in culture may be practical to
reduce mites. Water- stressed host plants are
susceptible to mite attack, so adequate soil mois-
ture to ensure good chrysanthemum growth can
retard mite population development (Price et al.
1982). Furthermore, in the absence of miticides,
crops grown by trickle irrigation have higher spider
mite populations than those crops watered by
overhead sprinklers. With miticides, the opposite
effect occurs, probably because chemical residues
remain active longer on plants not watered over-
head. (Price et al. unpublished data).








Fertilization is also important to spider mite
population development. Increased nitrogen fertili-
zation, but not phosphorous or potassium, is
associated with increased levels of twospotted
spider mites in cut-flower chrysanthemums (Price
unpublished data). Gibberellin has reduced mites
in treated plants (Poe 1971), perhaps due to the
chemical's reduction of nitrogen in leaves.
Cyclamen and broad mites also are occasionally
important. They cannot be seen with the unaided
eye, but their presence may be suspected when
young leaves become thickened and cupped, and
malformed flowers develop. These mites live among
the developing tissues of the bud or in tight folds
where humidity is high. Those protective sites
require specific miticides to be applied in high
volume sprays.

Leafminers
No chrysanthemum pest has caused more
concern in recent years than the so called "veg-
etable leafminer," (L. trifolii). Prior to the 1970s,
this leafminer affected chrysanthemums only in
Florida and the neighboring Caribbean countries.
Eventually the leafminer was shipped throughout
the United States, into Kenya, Colombia, Europe,
and then throughout much of the remaining
world.
Adult L. trifolii leafminers are insects and about
the size of the fruit flies seen around rotting fruits.
Yellow and black markings of the head and thorax
(Fig. 2) distinguish this fly from similar ones on
chrysanthemums. Larval forms are yellow maggots
(Fig. 3) not much larger than the type on this page.
Immobile pupae (Fig. 4), found on production
surfaces, are smaller than larvae and barrel-
shaped. Pupae change from bright yellow to light
brown with age.
Leafminers in newly planted chrysanthemums
may originate from cuttings bearing eggs or larvae,
from flies within an older planting, or from flies
entering the production area from weeds or other
hosts. A new generation begins from eggs laid in
punctures on upper surfaces of leaves. Punctures
are formed with the egg laying organ, the oviposi-
tor, but only a portion actually receives eggs.
Developmental rates depend upon temperatures
and have been examined by several scientists
(Charlton and Allen 1981, Velez et al. 1980, Prieto
and de Ulloa 1980). At 770F (25C) the egg requires
almost 4 days to hatch. Larvae feed under the leaf
cuticle within the upper tissues and develop
through 3 instars in less than 5 days (Charlton and


Allen 1981). This creates the winding, white mine
for which this pest is known.
Once developed fully, the larvae cut through the
upper cuticle and drop to the soil or bench surface.
The skins of the third stage larvae harden to form
puparia protecting the pupae inside. After about 8
more days (Charlton and Allen 1981) adults
emerge, mate and begin to lay eggs.
Economic losses to the leafminer are usually
from punctures and mines (Fig. 5) that reduce
appeal. Additionally, punctured and mined tissue
can be more vulnerable to diseases such as bacte-
rial leaf spot (Price, Harbaugh and Stanley 1982,
Poe 1983, Matteoni and Broadbent 1988) (Fig. 6).
Other losses may occur as a result of regulatory
measures to inhibit the movement of leafminers
within and among regions.


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Figure 2. Adult L trifoli (bottom) and L huidobrensis (top)
leafminers.







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Figure 3. Larval L. trifoliileafmlner In a mine.


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Figure 4. Pupal L. trifoali leafminer.
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Figure 5. Larval L. trifoli leafmines.


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Figure 6. Larval L trifolil leafmines and bacterial leafspot
infection.


Figure 7. Yellow sticky card trap for monitoring some flying
Insects.


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Monitoring this insect is important to determine
its initial arrival and population structure, and to
evaluate effects of controls. Flies are monitored by
placing 3 x 5 inch (8 x 13 cm) or larger canary
yellow cards, coated with an adhesive (Olson
Products, P.O. Box 1043, Medina, Ohio 44526) (Fig.
7) immediately above plants once or twice weekly.
Flies are attracted to the yellow cards and trapped
by the adhesive. Earliest detection usually occurs
when cards are placed among favored cultivars at
field margins and at greenhouse doors, windows,
and air-intake vents. Less formal methods of
detection include observation for flies or their
oviposition and feeding punctures on upper sur-
faces of leaves.
Information on population development is gained
by recording numbers of active or newly killed
larvae within mines, or completed mines with exit
holes (Price, Ketzler and Stanley 1981). These are
seen by holding leaves between a light and the
observer's eye. With the aid of a hand lens, an
observer can see living yellow larvae and their
black, sickle-shaped mouth hooks moving if tem-
peratures are above 60F (160C). Recently killed
larvae are motionless and yellow to brown. This
monitoring method provides important information,
especially concerning effects of pesticides, but is
time-consuming.
Once leafminers infest a crop, insecticides are
used to reduce losses. Insecticides available in the
past have killed adults or larvae, or inhibited egg-
laying. When scouting indicates that infested
cuttings will be planted, a systemic larvicide should
be applied immediately to prevent larvae from
entering the insecticide-tolerant, pupal stage.
Reapplication should occur 4-7 days later to kill
larvae developing from eggs present earlier. Addi-
tional applications should be determined by the
effective period of the insecticide and the vulner-
able portion of the leafminer population. For
instance, if all life stages are present in a crop to
which an adulticide with a 2-day period of activity
is applied, then additional protection may be
required in 2 days as younger leafminers reach the
adult stage. On the other hand, if only adults are
present, then the one-time application may be
sufficient.
Biological control has not been established on
chrysanthemum farms in North America or Eu-
rope, even though numerous parasitic wasps exist.
Some producers of cut-flower chrysanthemums in
Bogota and Piendamo, Colombia, have succeeded in
maintaining leafminers at acceptable levels with
parasitic wasps.


Cultural practices can affect the densities of
leafminer populations (Price and Harbaugh 1981),
and choice of cultivar is particularly important.
Levels ofleafminer susceptibility are known for
many cultivars and growers could determine
susceptibility for others (Webb and Smith 1969,
Schuster and Harbaugh 1979a, Schuster et al.
1981, Alverson and Gorsuch 1982, Oetting 1982,
Broadbent and Blom 1983). When practical, the
most susceptible cultivars should be eliminated or
isolated to reduce contamination of others and to
facilitate their special care.
Shadehouses and greenhouses can be con-
structed to exclude leafminers (Price and
Harbaugh 1981, Parrella and Jones 1987). The
chrysanthemum industry uses 20 X 20 mesh shade
cloth barriers (Begley 1989).
More leafmines and more rapid larval leafminer
development occur in chrysanthemums provided
with high nitrogen fertilization than in chrysanthe-
mums provided less nitrogen (Woltz and
Kelsheimer 1958, Poe et al. 1977, Harbaugh et al.
1983). Nitrogen is important to chrysanthemum
growth, but leafminer damage should be considered
in establishing regimes of nitrogen fertilization.
Leafmining in chrysanthemums appears unaf-
fected by normal variations in amounts of trickle
irrigation (Price et al. 1982). However, leafmining
increases under trickle irrigation compared to
overhead sprinkling (Price et al. unpublished data).
Sanitation measures performed during harvest-
ing can be very important when egg or larval
leafminers are present. Leaves left behind, on
stubble or stripped from stems, can continue to
produce adult leafminers and threaten the younger
crop (Price and Harbaugh 1981, Short and Price
1988). All crop residues should be incorporated into
the soil or otherwise be destroyed as quickly as
possible.
Chrysanthemums host two other potentially
important leafminers. Neither is known in Florida,
but precautions should be made to keep this region
free. Liriomyza huidobrensis (Blanchard), or the
pea leafminer (Fig. 2), mines the underside of
chrysanthemum leaves along major veins. This fly
is present throughout much of South America,
southern California, and Hawaii. Chromatomyia
syngenesiae (Hardy), the chrysanthemum
leafminer, is a pest in western Europe and Califor-
nia and occasionally occurs elsewhere.








Aphids
Four species of aphids that feed and reproduce
on chrysanthemums are particularly important in
Florida: the green peach aphid (Myzus persicae
(Sulzer)), the cotton aphid/melon aphid (Aphis
gossipii Glover), the spirea aphid (A. citricola Van
der Goot), and the chrysanthemum aphid
(Macrosiphoniella sanborni (Gillette) (Fig. 8). All
are pear-shaped, and the mature size is comparable
in size to the type on this page. They possess long
antennae and a rod-shaped protrusion on each side
of the posterior. The chrysanthemum aphid is
maroon or brown and the other three are green,
grayish, or yellowish green. A few winged adults
may occur, but most adults and all immatures
(nymphs) are wingless. Nymphs look like adults
but are smaller.
Aphids can develop on plants outside the produc-
tion area and enter the crop from there. Occasion-
ally infestations develop from aphids carried long
distances by wind or from those introduced on
cuttings. Wingless aphids tend to remain on the
plants where they were born but can walk among
plants within the range. When colonies are left
uncontrolled and crowding occurs, winged forms
are produced which disperse to other plants.
Flowing water from irrigation or rain may trans-
port aphids among plants.
The unique type of reproduction possessed by
aphids provides shortcuts to population develop-
ment and permits one aphid to create a large colony
rapidly. Unlike most chrysanthemum pests, aphids
are usually female and can reproduce without
mating. Offspring are usually females which are
able to produce young within 1 week. In addition,
the aphids bear living young, eliminating the time
required for eggs to hatch.
Aphid colonies usually grow on the tender, apical
tissues but may occur on the stem below. Aphids
also frequent mature leaves and flowers but usu-
ally not in large numbers. Adults and nymphs
insert needle-like mouthparts into vascular tissues
and remove sap. Sugary components, or honey-
dews, are excreted and fall onto upper surfaces of
leaves (Fig. 9). These substances are usually
washed away by overhead irrigation or rains but
otherwise become objectionable. Excretions remain-
ing on surfaces may attract ants or may become
colonized with an objectionable, dark-to-black,
sooty mold fungus (Fig. 10). Aphids or the skins
cast by growing nymphs also accumulate in this
sticky substance and further deteriorate plant
quality. Plant quality is also affected by aphid
feeding which sometimes deforms leaves.


I,


Figure 8. Chrysanthemum aphid adults and young.


Figure 9. Leaf with aphid honeydew (right) and without (left).


Figure 10. Leaf with sooty mold fungus (right) and without (left).


_p5 w 91M g








Aphid colonies tend to be scattered. IPM scouts
should look for aphids around buds and elsewhere
on the top 6 inches of stem. Sometimes droplets of
sugary excretions or white cast skins on upper
surfaces of leaves provide early indications of
infestations. Yellow sticky-card traps placed
throughout the crop, especially at entrances, are an
effective means to detect winged aphids. Population
levels requiring insecticidal treatment vary accord-
ing to several factors. More stringent control is
usually required for pot chrysanthemums and for
plants not regularly washed by irrigation or rain.
Since marketed flowers must be free of noticeable
aphids or skins and yet are susceptible to pesticide
damage, aphids should be controlled before flowers
show color.
Precise timing of insecticides is not as critical for
aphids as for some other arthropods since tolerant
pupae and eggs do not occur here. Systemic insecti-
cides are particularly effective because aphids
ingest large amounts of plant juices. Nonsystemic
aphicides usually are effective before flowers open
because aphids remain exposed on buds, stems, and
leaves. Aphids near bases of florets in open flowers
may be difficult to kill without systemic insecti-
cides.
Parasitic wasps exist that could control aphids,
but barriers such as parasite susceptibility to
agricultural chemicals limit practicality. Adult and
larval lady beetles and green and brown lacewings
often decimate colonies outside greenhouses but
usually after unacceptable damage has occurred.
Biological control of aphids by a microorganism
has recently become practical in the limited envi-
ronments of warm, humid greenhouses (Burges and
Hall 1983). Commercial preparations of the fungal
pathogen Verticillium leconii control aphids under
these conditions. The white aphid bodies remain on
plants after treatment, detracting from quality.
The management of non-crop plants in the
environs of production areas is important since
aphids may disperse from there. In addition, small
mesh screens on greenhouse openings or on
shadehouses can be especially helpful to exclude
aphids.

Thrips
Both flower and foliage thrips can injure chry-
santhemums. The latter are the less encountered
and will be discussed briefly at the conclusion of
this section.
Flower thrips recently have become a concern
throughout North America and Europe following


movement of the western flower thrips
(Frankliniella occidentalis (Pergande)) from the
western U.S. to new territories. Western flower
thrips has been found in a few greenhouses in
Florida but not in outdoor crops except in the
panhandle area. Another flower thrips, F. bispinosa
Morgan, continues to be a perennial nuisance
throughout the state in greenhouses and outside.
Adult flower thrips are tiny (shorter than half
the height of a letter printed on this page), narrow,
and usually yellow or brown (Fig. 11). Adults have
feather-like wings that when at rest, lie along the
length of the insect's back. Larvae look similar to
adults but have no wings.


Figure 11. Adult western flower thrips. (Photo courtesy R. D.
Getting.)
Development varies among flower thrips species,
but development in all species is similar to F.
bispinosa, the most common flower thrips in
Florida. The biology has been studied by Quintance
(1898) and Watson (1922). Eggs are laid in plant
tissues and hatch in about 3 days. Larvae emerge
and feed by piercing cells with their mouth parts
and then withdrawing liquids inside a mouthcone.
About 5 days after hatching, pupae form in the soil
and remain inactive for about 4 days before becom-
ing adults. Females begin to lay eggs in about 3-5
days. Adults feed as do the larvae. The egg-to-adult
portion of the life cycle varies from 10-18 days.
Most infestations begin from adults that fly or
are carried by air currents into the production
area. Enormous numbers can enter a crop in a
short time. They can enter shadehouses and
greenhouses through screening and sometimes can
be drawn through water and pad cooling systems.
Adults, larvae, and eggs also may be carried into
the production area on infested plants. Pupae may
gain entry via soil of potted plants.


s








Presently, the greatest losses are to flowers.
Thrips enter flowers soon after color shows and
feed on florets. Hidden there, thrips can cause
serious but unnoticed damage. Feeding produces
tiny, elongate spots initially with a water-soaked
appearance (Fig. 12). After a few days, the spots
turn brown (Fig. 13) and are easily recognized
when open flowers are broken apart. Live thrips on
flowers may be objectionable to consumers.
Flower thrips' feeding on developing foliage of
some cultivars may result in brittle, malformed
leaves with small, raised, star-shaped formations
(Fig. 14). This deformity is particularly important
in potted and garden varieties where leaves consti-
tute an important portion of the finished product.
Tomato spotted wilt virus, potentially one of the
most damaging viruses to the horticultural
industry, is transmitted among chrysanthemums
and other crops by the western flower thrips
(Matteoni et al. 1988). No infections are known in
Florida's chrysanthemums, but they do occur
elsewhere. Since the western flower thrips has been
found here recently, producers must learn to
recognize the disease this insect transmits and
develop measures to manage it.
Flower thrips may enter production areas daily
when citrus and wild flowers are blooming. Thrips
can be detected by sticky traps, by inspecting
plants, or by tapping open flowers onto a white
cloth. The yellow sticky traps used to monitor
leafminers, aphids, and other insects also catch
adult flower thrips. When placed near air intake
vents, entrances to greenhouses, and near margins
of shadehouses, these traps can detect invasions
early. Additionally, their presence may become
evident when workers complain about being bitten
by tiny insects.
In vegetative chrysanthemums, flower thrips
may be found among developing tissues of the bud
and at bases of young leaf axils. In flowering
plants, these thrips may be located around the
calyx and at petal bases. Thrips distribution within
a production range is affected by the developmental
stage and the chrysanthemum cultivar. Adult
thrips' mobility permits more uniform distribution
than that of many other arthropods.
Since flower thrips stay largely in protected
crevasses and feed from plant juices, systemic
insecticides potentially are most effective. Control
is dependent on coverage of upper portions of the
plant. Two applications in 5 days should be made
when flower thrips are detected (Robb and Parrella
1988). The second application should kill nymphs


or adults that were in protected egg or pupal stages
at the time of the first insecticidal application.
Numerous natural enemies feed upon thrips
(Ananthakrishnan 1984). The predatory anthocorid
bugs (minute pirate bug (Orius tristicolor (White))
and related insects) are frequent inhabitants of
flowers with thrips. However, natural enemies have
been unable to reduce thrips sufficiently to prevent
flower damage.
Since flower thrips develop upon many plants,
management of nearby, alternative hosts may be
beneficial. For example, problems with F. bispinosa
increase in chrysanthemums following the bloom-
ing period of nearby citrus. Also, white clover
(Trifolium repens L.), common in Florida's land-
scapes, may contribute thrips to chrysanthemum
crops during spring, particularly if the clover is
mowed after thrips populations have built up in
clover flowers. Pest control practices, mowing, and
other manipulations of these crops should be
performed in a manner most beneficial to chrysan-
themums.


Figure 12. Florets with (top) and without (bottom) flower thrips
injury.


























Figure 13. Flowers with (left) and without (right) severe flower
thrips Injury.


Two foliage thrips occasionally feed on chrysan-
themum leaves in Florida: greenhouse thrips
(Heliothrips haemorrhoidalis (Bouche')) and the
banded greenhouse thrips (Hercinothrips femoralis
(0. M. Reuter)) (Denmark 1976, Denmark 1985).
Both are usually dark, slowly increase in numbers,
and remain exposed on developed leaves. These
insects are controlled by several insecticides
commonly used in chrysanthemum culture.
Thrips palmi Karny attacks chrysanthemums
and is difficult to control (Sakimura et al. 1986). It
is clear yellow with black setae and often congre-
gates along leaf midribs where it causes leaf
silvering. This thrips does not occur in Florida, but
conditions may allow it to establish if introduced.
This insect is widespread in the Indian subconti-
nent, Far East, South Pacific, and Hawaii; and
measures to prevent the entry of T. palmi should be
practiced when importing plant material from
infected areas.

Beet armyworm and other Lepidoptera
The beet armyworm (Spodoptera exigua
(Hubner)) is the caterpillar most difficult to man-
age. Larvae are smooth-textured and up to 1 1/6
inches (3 cm) long (Fig. 15). They have 5 pairs of
short, stubby, abdominal prolegs in addition to 3
pairs of true legs near the head. A conspicuous line
along each side separates the differently shaded,
green-to-black, upper and lower halves. There is
usually a small dark spot above the middle pair of
thoracic legs. Adults are grayish brown moths
about 3/4 inch (2 cm) long and similar to other
moths attracted to outside lights. They hide during
the day.


Figure 14. Flower thrips Injury to a developing leaf.


Figure 15. Larval beet arrnyworm.








Beet armyworms may be brought into a range as
eggs or young larvae on cuttings. More often
however, moths are attracted to production lights
or security lights and enter production areas
through holes in structures or lay eggs on tops of
shadehouses from which larvae hatch and drop
inside.
Watson (1934) and Wilson (1932) reported on
beet armyworm biology in Florida. On warm
nights, moths lay about 100-150 eggs, often stacked
in piles and covered by hairlike material. Eggs are
usually laid on the underside of lower leaves and
hatch in about 2-6 days. Newly emerged larvae feed
for a short time on nearby leaf tissues then disperse
within 2 days to stem terminals less than 3 feet
(about 1 m) away. Young larvae spin webs loosely
over their bodies, often tying leaves tent-like over
themselves. As larvae mature, they may leave the
terminal and feed openly on older leaves.
After less than 2 weeks in the larval stage, beet
armyworms fall from the plant, form a loose cell in
the soil surface, and pupate. Less than 1 week
later, moths emerge, mate, and begin laying eggs
within 3 days. Time required between generations
is about 24 days.
Foliage losses to beet armyworms are rarely
significant. Heaviest losses occur as young larvae
feed on vegetative or flower buds. When buds are
damaged, flowers are not produced and axillary
shoots develop. Occasionally a small larva exca-
vates the developing petal tissues from young
flower buds. Under heavy infestations, older beet
armyworms may graze on flower petals, ruining the
flowering stem just before harvest.
Beet armyworms are particularly menacing from
April through October and their populations should
be monitored by IPM scouts to time insecticides
and gauge management success. One of the most
effective and widely used means is to observe moth
activity via a blacklight trap (Fig. 16). Pheromone
traps are available to monitor adult males. Traps
should be placed within greenhouses or
shadehouses that exclude the adults attracted from
outside. Catches should be counted daily.
Besides monitoring by means of light trapping,
IPM scouts can also search for egg masses or first
instars. Since economic damage occurs at low
densities, it is difficult to detect, by this method,
before losses occur. Scouting for later instars is not
desirable since these are difficult to kill.


The economically tolerable level of beet army-
worm larvae is low since each larva may eliminate
one or more stems. To achieve the greatest effect,
pesticides should be applied after eggs have
hatched but before small larvae form protective
webs. This begins about 6 days after large catches
of moths (Poe et al. 1973).
Residues toxic to first instars should be on leaves
and buds throughout egg laying. Beet armyworms
do not ingest large amounts of plant juices, thus
systemic insecticides are not advantageous. Since
eggs are often laid on the underside of leaves and
first instars likely will feed there, thorough cover-
age is important. Spray penetration of chrysanthe-
mum beds is difficult and limits control.
Numerous parasitoids exist (Oatman et al. 1983,
Schwartz et al. 1980, Tingle et al. 1978) that may
maintain this insect at low levels when pesticides
do not disrupt activity. Viral and nematode controls
for beet armyworms have been used commercially.
Further advances may make this aspect of biologi-
cal control available throughout the chrysanthe-
mum industry (Begley 1989).
Successful management requires that beet
armyworm not gain access to the crop. Cuttings
should be purchased free of eggs or larvae, and
ranges should be constructed, maintained, and
operated to exclude moths (Schuster and Harbaugh
1979b).
Numerous hosts grow near production sites and
serve as reservoirs for beet armyworms. These
include many other ornamentals, vegetables, field
crops, and weeds such as kenaf, lambs quarter,
pigweed, pokeweed, arrowroot, and sesbania. These
weed hosts must be managed to reduce their
impact on the chrysanthemum crop.

Other Lepidoptera affect production to a lesser
degree. The cabbage looper (Fig. 17), Spodoptera
spp. (Fig. 18 and 19) (in addition to S. exigua) and
the salt marsh caterpillar (Estigmene acrea
(Drury)) (Fig. 20 and 21) feed on leaves. The corn
earworm (Helicoverpa zea (Boddie)) may feed on
leaves or flowers, and leaftiers (Tortricidae) (Fig.
22) web large, terminal leaves together. Cultural
and exclusion practices performed for beet
armyworm are effective for other Lepidoptera.
Several pesticides are available to manage these
pests as they appear.














































Figure 16. Blacklight trap.


Figure 18. Larval southern armyworms (Spodoptera eridanla)
resulting from an egg mass.


Figure 19. Full grown larval southern armyworm.


I/


Figure 17. Larval cabbage looper.










r


Figure 20. Young larval salt marsh caterpillar.


--Fi( fr


ii j


Figure 21. Full grown larval salt marsh caterpillar.


Figure 22. Leaves tied by a leaftier.


*:
;i~
--


Plant bugs
Plant bugs, also known as capsids or lygus bugs,
suddenly can enter a range and devastate a crop.
Several species attack chrysanthemums, including
the tarnished plant bug (Lygus lineolaris (Palisot
de Beauvois)), green plant bug (Taylorilygus
pallidulus (Blanchard)), and Polymerus spp.
Appearances, biologies, and crop effects vary
slightly.
Plant bugs are usually 1/8 to 1/4 inch (3-6 mm)
long, about half as wide, and often brown or green.
The profile of the insect's top side angles down
obliquely about 2/3 the distance from front to
rear.
Almost all infestations are initiated by adults
flying short distances. Females lay cigar-shaped
eggs, one at a time, in the stem, leaf, and flower
tissue. Eggs hatch in about 7-10 days, resulting in
green, wingless nymphs resembling aphids.
Nymphs develop through 5 instars and feed and
damage plants near terminals. Nymphs become
adults in about 2 weeks.
Nymphs and adult plant bugs insert needle-like
mouthparts into developing terminals to feed and
may kill small areas of leaf tissues. The dead
tissues result in ragged edges and "shot holes"
when leaves expand (Fig. 23). Greater damage is
caused when the feeding damages the stem termi-
nals, resulting in unwanted axillary shoots and
delayed flowering (Fig. 24). Plant bugs also can
cause lateral flowers not to develop (Fig. 24) and an
S incomplete array offlorets (Fig. 25).
The deformed leaf is often the first sign of plant
bugs, but serious losses may have been caused
earlier. The presence of plant bugs, therefore, must
be known as quickly as possible.
There are some ways to detect adults soon after
they arrive. They are attracted to the yellow sticky
cards used for leafminers (Fig. 7). Cards should be
placed around field margins or structure entrances
and monitored once or twice weekly. IPM scouts
also can shake plants and observe adults as they
fly. Adults leave yellow-to-red fecal specks on
flowers (Fig. 26). IPM scouts should use fecal
remains as additional signs of plant bugs where
rain or irrigation do not interfere.
Each plant bug can ruin one or more stems, and
pesticides should be applied as soon as scouting
indicates their presence. Sprays should be applied
especially to terminals and top surfaces of upper
leaves where plant bugs are most active. Since
plant bugs consume plant juices, systemic insecti-
cides may be helpful.


,, .- ,


























Figure 23. Leaves damaged by green plant bugs. Figure 26. Orange fecal spec from green plant bug.


Figure 24. Green plant bug damage: Unwanted side shoot with
delayed flowers (left), stem with abnormal flower
and without axillary flowers (center), and normal
flower stem (right).


Figure 25. Green plant bug damage: Incomplete array of florets
(right) and undamaged flowers (left).


Plant bugs are abundant on many field crops,
grasses, and weeds, especially those in flower, and
easily can move to nearby crops. Special concern
should be given when hosts are harvested or are
senescing close to production areas. Properly
screened greenhouses and shadehouses can exclude
plant bugs.

Fungus gnat
Bradysia spp. fungus gnats are 1/8 inch (3 mm)-
long, spindly flies with long legs and long, thread-
like antennae. Larvae (Fig. 27) are translucent
white, about 1/4 inch (6 mm) long, worm-like with
no legs, and have distinctive, shiny, black heads.
These gnats can infest a crop from soil or algae
within the range, from contaminated potting soil,
or by flying into the production area from nearby.
Fungus gnats are almost always present in ranges,
at least at low densities.
Females live about a week and lay 30 to 120 eggs
singly or in batches of up to 30 on the soil. Eggs
hatch in 4-7 days (Steffan 1966). Larvae are usu-
ally located at the soil surface, especially in the
early morning, and develop fully in about 8-20
days. The resting pupal stage lasts about 3-5 days
near the surface.
The adult flies do not damage plants, but they
are objectionable to consumers and cannot be
tolerated on potted plants in hospitals, grocery
stores, or florist shops. The larvae feed on decaying
matter and on living roots in the soil medium (Fig.
28). Damaged roots provide conditions for root
diseases, further complicating fungus gnat manage-
ment and crop health.






























Figure 27. Larval fungus gnats.


Fungus gnat adults are attracted to yellow sticky
traps (Fig. 7). These traps can be used to detect
their presence, or IPM scouts can look for adults
moving on pot surfaces. Larvae can be found on the
surface of potting soil early in the morning. Larvae
build "nests" of tiny silk threads that collect
moisture at night. These nests with moisture
droplets can also be seen in the early morning.
Pesticides for controlling fungus gnats can be
applied as drenches to pots or as sprays to pots,
beds, or other soil surfaces. A biological control
agent, the Neoaplectana carpocapsae nematode, is
marketed by some providers of agriculturally
beneficial organisms to control fungus gnats in
potting media (Morton 1987). These are not widely
used however. Without pesticides, parasitic wasps,
occurring naturally in Florida, may establish to
regulate the populations.
Sound crop culture denies fungus gnats the
conditions necessary for development, reduces need
for pesticides, and promotes parasites. Fungus gnat
problems may result from over-wet conditions and
diseased roots and should alert growers to poor
culture. Potting media should be stored dry, and
pots and production areas must be well drained.
Fungus gnats can exist on soil fungi under benches.
Some growers apply hydrated lime to eliminate the
fungal food source.
Sprouting bean or grain seeds can be placed in
containers throughout the greenhouse as a trap
crop (Zepp 1981). Flies will lay their eggs in the
sprouting seeds. Seeds should be buried or burned
and replaced every 2 weeks.

Whiteflies
Two whiteflies are found on chrysanthemums in
Florida, sweetpotato whitefly (Bemisia tabaci
(Gennadius)) and greenhouse whitefly
(Trialeurodes vaporariorum (Westwood) (Osborne
and Price 1987)). Neither of these whiteflies
reaches the densities that occur in other crops.
Appearance, behavior, and biology of the green-
house whitefly is similar to the sweetpotato white-
fly discussed below.
Adults of both species are white, narrow, less
than 1/16 inch (2 mm) long and can be
distinguished usually by the positions of their
wings. Sweetpotato whiteflies (Fig. 29) hold their
wings parallel to and close to the sides of the
abdomen while greenhouse whiteflies hold their
wings more flat, in a deltoid position over the upper


Figure 28. Roots damaged by fungus gnats (right) and
undamaged (left).









surface of the abdomen. Eggs are cigar-shaped,
stand on an end, and are creamy white when young
but darken to light brown in about a day (Fig. 29).
Nymphs are translucent green or yellow and scale-
like (Fig. 30) but become opaque yellow and
mounded as pupae (Fig. 31).
All life stages occur on the underside of leaves
where adults and nymphs suck plant juices. Fe-
males lay about 6-12 eggs per day which hatch in
about 1 week. A first stage nymph ("crawler") (Fig.
32) emerges from the egg, moves about 1/16 inch (2
mm) and attaches to the leaf. The nymph develops
for 1 week in warm weather, then becomes a non-
feeding pupa. During this 1-week period the insect
changes to an adult whitefly.
All living forms, exoskeletal remains, and all
dead forms except adults usually stay on leaves
when the plant is sold. Customers object to the
appearance of plants with whiteflies. Nymphal and
adult whiteflies produce honeydews that can result
in sooty molds affecting the chrysanthemum's
appearance. Sweetpotato whiteflies can transmit
certain viruses among plants, but none are known
to be transmitted to chrysanthemums.
Scouting a crop regularly with yellow sticky
cards (Fig. 7) provides information on when the
whiteflies first arrive and the success of manage-
ment practices. Sticky cards should be placed near
doors, air-intake vents, field margins, and among
newly arriving plants. IPM scouts should check
cards once or twice weekly. Since most pesticides do
not kill pupae, young adults may be observed on
cards for about 1 week after spraying.


Figure 30. Advanced nymphal sweetpotato whitefly.


Figure 31. "Pupal" sweetpotato whitefly.


Figure 29. Adult and egg sweetpotato whiteflies.


Figure 32. Sweetpotato whitefly "crawler".








Whiteflies do not consume leaf surface tissue
that can be treated with insecticides. In addition,
immatures do not crawl long distances and conse-
quently have a reduced contact with toxic particles.
Therefore, nonsystemic insecticides must contact
the insects under the leaf. This is difficult with
ordinary spraying practices, as chrysanthemums
are closely spaced and basal leaves are close to
bench or bed surfaces. Insecticidal soaps are gener-
ally effective for whitefly control.
Parasitic wasps, especially Encarsia formosa, E.
transvena, and Eretmocerus spp. exist in Florida to
reduce greenhouse and sweetpotato whitefly
populations, respectively. The parasites are very
sensitive to pesticides, however, and are rarely
found in chrysanthemum culture. Biological control
of whiteflies is not feasible under Florida conditions
at this time.
Various practices can prevent, delay, or lessen
the severity of infestations. One of the most impor-
tant is to purchase noninfested cuttings. Whiteflies
can fly within a greenhouse from an infested crop to
a noninfested one. New crops should be planted
only after a previous infested crop has been re-
moved and the greenhouse has been maintained at
production temperatures and free of whitefly hosts
for several days. Removing the older hosts also will
remove all immature whiteflies and many adults.
The warm, host-free period will cause the remain-
ing adults to starve in a few days. Since it is im-
practical and difficult to maintain adequate white-
fly control on weeds and other noncrop plants in
and around the chrysanthemum range, nonessen-
tial hosts should be eliminated. Whiteflies are
attracted to yellow clothing and equipment. Moving
such articles among areas of an infested range also
could move whiteflies and ensure other plants
becoming contaminated.

Less important pests of
chrysanthemums
Additional arthropods occasionally may damage
chrysanthemums. Producers should be aware of
their existence and be able to recognize them in
order to take corrective action should they appear.

Mealybugs
Several mealybugs of the family Pseudococcidae
can infest chrysanthemums. These females are
wingless, oval, gray, soft-bodied insects covered with
a white, mealy, or filamentous wax. They are 1/5 to
1/3 inch (5-8 mm) long when mature. Eggs are
entwined with waxy filaments, sometimes called an


egg sac. Mealybugs are found on stems and under
leaves at axils, and each generation requires about
1 month.
Mealybugs do not fly. They enter production
areas, most commonly, on infested plants. Newly
hatched crawlers spread up to several feet. Nymphs
and adult females injure plants by sucking the sap
with their needle-like mouthparts causing yellow
spots on leaves. Mealybugs excrete honeydew
which hosts sooty mold and attracts ants. The
insects and their cottony egg sacs make the plant
unsightly.
Insecticides may be required to control an
infestation. Systemic insecticides are advantageous
since mealybugs consume plant juices and are
protected partially by their sessile habit and waxy
covering. Contact insecticides may require wetting
agents to penetrate the waxy material adequately.
Insecticides should be applied at 2-week intervals
until control is achieved.

Garden fleahopper
The garden fleahopper (Halticus bractatus (Say))
can cause damage when numerous. They are tiny
and black, have long legs and antennae, and look
like tiny field crickets. Nymphs occur with the
adults and are wingless, but hop when disturbed.
Fleahoppers infest chrysanthemums after
leaving weed hosts near the range. Damage is
usually seen in shadehouses near borders and not
in greenhouses. Fleahoppers cause a patch or
curving trail of white stipple marks on upper
surfaces of leaves. These pests are readily con-
trolled by numerous organic insecticides.

Field crickets and mole crickets
These two crickets damage young cuttings in soil
beds. Both are active at night, leaving damage
often attributed to cutworms.
The Gryllus spp. field crickets are dark brown
with long antennae and appear much like crickets
sold for fish bait. They enter shadehouses from
nearby weeds, stored plastic or wood, or refuse
piles. They are active on the soil surface and sever
stems of young cuttings just above the ground.
Weeds near affected crops should be mowed and
raked, and refuse and other shelter eliminated.
Field crickets are easily killed with insecticidal
baits. Scapteriscus spp. mole crickets are up to 1 1/
2 inches long (3.8 cm),tan, and have short, broad
front legs for digging. Mole crickets tunnel just
below the soil surface resulting in raised soil ridges








about 1/2 inch (13 mm) wide. Tunnels are promi-
nent on mornings following an evening rain
shower. The mole crickets themselves are rarely
observed.
Mole crickets invade shadehouses from nearby
weeds or are attracted from longer distances by
production lights or security lights. They burrow in
the root crowns of newly set cuttings, often killing
them. One insect can destroy several plants.
Tightly closed shadehouses can exclude mole
crickets if structural material is buried at perim-
eter bases. Soil insecticides or baits applied to
production and surrounding areas provide effective
control.

Snails and slugs
Snails and slugs are mollusks, not arthropods.
These mollusks are active at night under humid
conditions. Their damage is similar to caterpillars',
with interveinal leaf sections eaten. A slime trail on
a pot, bench, or leaf indicates snail or slug passage.
Removal of plastic, boards, and debris from the
soil surface and eliminating excess moisture are
important steps toward managing snails and slugs.
Where snails and slugs are a problem, potted
plants should be grown on mesh benches providing
air and light underneath. Molluscicide baits are
available and effective for control where required.

Pesticide use and pesticide
labels
Effective and properly registered pesticides
change frequently and are not enumerated in this
publication. Current IFAS recommendations are
presented in the regular revisions of the IFAS
Insect Control Guide.
Insects can develop resistance to pesticides.
Resistance is likely delayed when pesticides are
used in a rotation program based on the pesticide's
chemical class and the target insect's life cycle. A
single class of insecticide should be used for one
generation of the target pest (Parrella et al. 1987).
Following generations should be treated with
pesticides from different classes. The University of
Florida's IFAS provides information on classes of
permitted insecticides.
Restrictions to the use of certain highly toxic
pesticides to trained and licensed applicators was
introduced in the 1972 amendment to the Federal
Insecticide, Fungicide, and Rodenticide Act
(FIFRA). By this act, the label of a restricted


pesticide will clearly state "RESTRICTED USE
PRODUCT" in a prominent position. Labels also
bear the signal words "DANGER," "WARNING," or
"CAUTION" communicating the pesticides' level of
potential hazard to humans. The "DANGER"
statement indicates the most poisonous insecticides
and is always displayed with a skull and
crossbones.
Each label further bears specific directions for
use of the product such as rates, applications, and
precautionary measures. In order for a pesticide's
use to be permitted on chrysanthemums, the label
must state that the product is registered for use on
"chrysanthemum," "flower crops," "ornamental
crops," "nursery crops," or other group that would
include chrysanthemum. Note that pesticides can
not be used in greenhouses unless their labels
specifically permit.
All applicators should be thoroughly familiar
with the label of each product and adhere to the
specific directions for its use. Applicators who
follow label instructions will assure their safety
and successful control of pests.

References
Alverson, D. R. and C. S. Gorsuch. 1982. Evalua-
tion of chrysanthemum cultivars and insecticides
for control of damage by a leafminer, Liriomyza
trifolii (Diptera: Agromyzidae). J. Econ. Entomol.
75:888-91.
Ananthakrishnan, T. N. 1984. Bioecology ofthrips.
Indira Publishing House. Oak Park, Mich.
233pp.
Begley, J. W. 1989. How integrated pest manage-
ment has reduced pesticide applications at Yoder
Brothers Inc. Pages 8-18 in M. Daughtrey and J.
Begley, eds. Proc. of the Fifth Conf. on Insect and
Disease Management on Ornamentals. Soc.
Amer. Florists. Alexandria, Va. 138 pp.
Broadbent, A. B. and T. J. Blom. 1983. Compara-
tive susceptibility of chrysanthemum cultivars to
Liriomyza trifolii (Diptera: Agromyzidae). Proc.
Entomol. Soc. Ontario. 114:91-3.
Burges, H. D. and R. A. Hall. 1983. Recent progress
with a novel method of pest control. Grower
(Feb. supplement):83-7.
Charlton, C. A and W. W. Allen. 1981. The biology
of Liriomyza trifolii on beans and chrysanthe-
mum. Pages 42-9 in D. J. Schuster, ed. Proc.
IFAS-Industry Conf. on Biol. and Control of
Liriomyza leafminers. Univ. of Fla. IFAS. 235pp.








about 1/2 inch (13 mm) wide. Tunnels are promi-
nent on mornings following an evening rain
shower. The mole crickets themselves are rarely
observed.
Mole crickets invade shadehouses from nearby
weeds or are attracted from longer distances by
production lights or security lights. They burrow in
the root crowns of newly set cuttings, often killing
them. One insect can destroy several plants.
Tightly closed shadehouses can exclude mole
crickets if structural material is buried at perim-
eter bases. Soil insecticides or baits applied to
production and surrounding areas provide effective
control.

Snails and slugs
Snails and slugs are mollusks, not arthropods.
These mollusks are active at night under humid
conditions. Their damage is similar to caterpillars',
with interveinal leaf sections eaten. A slime trail on
a pot, bench, or leaf indicates snail or slug passage.
Removal of plastic, boards, and debris from the
soil surface and eliminating excess moisture are
important steps toward managing snails and slugs.
Where snails and slugs are a problem, potted
plants should be grown on mesh benches providing
air and light underneath. Molluscicide baits are
available and effective for control where required.

Pesticide use and pesticide
labels
Effective and properly registered pesticides
change frequently and are not enumerated in this
publication. Current IFAS recommendations are
presented in the regular revisions of the IFAS
Insect Control Guide.
Insects can develop resistance to pesticides.
Resistance is likely delayed when pesticides are
used in a rotation program based on the pesticide's
chemical class and the target insect's life cycle. A
single class of insecticide should be used for one
generation of the target pest (Parrella et al. 1987).
Following generations should be treated with
pesticides from different classes. The University of
Florida's IFAS provides information on classes of
permitted insecticides.
Restrictions to the use of certain highly toxic
pesticides to trained and licensed applicators was
introduced in the 1972 amendment to the Federal
Insecticide, Fungicide, and Rodenticide Act
(FIFRA). By this act, the label of a restricted


pesticide will clearly state "RESTRICTED USE
PRODUCT" in a prominent position. Labels also
bear the signal words "DANGER," "WARNING," or
"CAUTION" communicating the pesticides' level of
potential hazard to humans. The "DANGER"
statement indicates the most poisonous insecticides
and is always displayed with a skull and
crossbones.
Each label further bears specific directions for
use of the product such as rates, applications, and
precautionary measures. In order for a pesticide's
use to be permitted on chrysanthemums, the label
must state that the product is registered for use on
"chrysanthemum," "flower crops," "ornamental
crops," "nursery crops," or other group that would
include chrysanthemum. Note that pesticides can
not be used in greenhouses unless their labels
specifically permit.
All applicators should be thoroughly familiar
with the label of each product and adhere to the
specific directions for its use. Applicators who
follow label instructions will assure their safety
and successful control of pests.

References
Alverson, D. R. and C. S. Gorsuch. 1982. Evalua-
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