Citation
Insects and diseases affecting strawberries

Material Information

Title:
Insects and diseases affecting strawberries
Alternate title:
Bulletin 629 ; University of Florida. Agricultural Experiment Station
Creator:
Brooks, A. N. ( Albert Nelson )
Kelsheimer, E. G. ( Eugene Gillespie ), 1902-
Place of Publication:
Gainesville, Fla.
Publisher:
University of Florida Agricultural Experiment Station
Publication Date:
Copyright Date:
1961
Language:
English
Physical Description:
35 p. : ill. ; 23 cm.

Subjects

Subjects / Keywords:
Strawberries -- Diseases and pests -- Florida ( lcsh )
Strawberries -- Diseases and pests -- Control -- Florida ( lcsh )
Genre:
non-fiction ( marcgt )

Notes

General Note:
Cover title.
Statement of Responsibility:
A.N. Brooks and E.G. Kelsheimer.

Record Information

Source Institution:
University of Florida
Holding Location:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
AEN8092 ( ltuf )
18305084 ( oclc )
026159756 ( alephbibnum )

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Full Text


Bulletin 629

UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATIONS
J. R. BECKENBACH, Director
GAINESVILLE, FLORIDA



Insects and Diseases Affecting

Strawberries

A. N. BROOKS AND E. G. KELSHEIMER


























Fig. 1.-Strawberry leaf blight, show ario t of lesi The
leaflet at the top shows a typical fans e dead ar, m Agr.
Exp. Sta. Bul. 229.) I

Single copies free to Florida resi t
AGRICULTURAL EXPERIME N Sr
GAINESVILLE, FLORIDA










CONTENTS
Page
D ISEASES -............ ---- .. ........-. ........ ...... ................. 3
Anthracnose ..--.......-------------........ --......------- .......--.. 3
Rhizoctonia diseases ..-..----........ ..-------- ...-..--.-- ..-..-- ........------.....--- 4
Bud Rot ........----------........... .-------............. 5
Root Rot .....---------.. .......- ----......- .. .----...... 6
W eb Blight ...... ......------.......----.. --. ---.............. 6
Vein Infection ....--.----.--------...... .------- -----------.. 6
Leaf Spot Diseases ......------..............----...----------....-- 6
Common Leaf Spot ---....--.. ...--- --.-- ......-----..--..-- 6
Leaf Scorch ...........---------.........-----.. --... --........-..-- 7
Leaf Blight .....- ..--..... -----......---..-..-- -...----..... 7
Fruit Rots -..-..-....---......---- ....------- -------.. ...........-- 8
Leaks or Whiskers ............-- ----------.... .....-----.. ...--.. 8
Gray Mold or Brown Rot ...... ...------........ .. .....-------.. 8
Hard Brown Rot ---------......---..--..... ...-.-------.-..-- 10
Light Tan Rot --------....... -----..... ....--....-----.......... 10
Virus Infection .-.--------.......--...---......---------------. 10
Black Root .---..... .......----.............. ------..........-- 11
Sclerotium R ot .-...-... ... ..............--------------------------------------- 11
NEMATODES ....-- ....--.......--- .. ............ ----....----... -----......-...- 12
Bud Nematode .............. ---- ..-----... ----- ...... ... 12
Sting Nematode ....................-----------..-------- ....... 13
Root-knot Nematode .-----....- ----..............--------....... 14
INSECTS AND SPIDER MITES ...........----------------- -------..... ... ........ 16
Pests of Major Importance ............. .........- ......... ...... ... ----16
Spider Mites ..---...---.. ....... ...... .. ......-------- ...... 16
Wireworms .-......-..... .......------ .... .......---------.... 19
Lesser Cornstalk Borer ....--- ......-----.....------- ..-------... 22
Pameras ....-- -----.........---........-..........---- ------... 25
Mole-crickets ..............................--------------- ..... ---- 26
Florida Flower Thrips ..---. .......-----......--------------. 27
Cutworms and Armyworms .----........---....---.......--.. ----- 28
Insects of Lesser Importance ....-..........----- ..---.-----..... ....-.. --28
Crickets .-..---. ............... -------.......----.---- -.... --....-. --..... .... 28
Strawberry Flea Beetle ......------....-....------..... .. ---- ---------28
Strawberry Leaf Roller ..........-------.....--....-----.............-- ----- 29
Root Worms ---....... --..... . .....------........- ------29
Grasshoppers ...............-------------..-------....------ 29
Ants .....--....-- .....-------------- ----...........-- -..... .... 29
Root Aphids ............... ...- .-----..... ... .......-.--- .-- 31
W white Grubs .-... .-----............... ---. ---- -............... 31
Slugs and Snails .........----........----......... --------....- 33
Citrus Root W eevil .................. ...................................... 33
Time of Application of Insecticides ...------......-...-----..---------. 34
Precautions .-.......-................ -............. -...-. --- -..... ........... 35
Com patibilities ................. ---.......- -................. .-...............-- ...........- .... 35
Interval Between Insecticide Application and Harvest --..............---- 35

February 1961









Insects and Diseases Affecting

Strawberries

A. N. BROOKS 1 AND E. G. KELSHEIMER 2

Use of trade names in this publication is solely to provide specific in-
formation. It does not constitute a guarantee or warranty of the products
named and does not signify that they are approved to the exclusion of
others of suitable composition.

DISEASES
In the strawberry-growing areas of Florida there are several
important diseases. These will be described in detail according
to the time of year or weather conditions favoring their develop-
ment.
During the production of runner plants, especially in the sum-
mer period of abundant rainfall and high temperatures, a fungus
disease, anthracnose, causes a spotting and girdling of runners
and leaf stems and also a dry rot of the fleshy part of the plants.
During this same period any 1 of several soil-infesting fungi
may attack the plants and cause soft rots. Several different spe-
cies of nematodes may attack the roots and 1 attacks the buds
of plants.
During the fruiting season common leaf spot may appear on
leaves and gray mold on blossoms and on green and ripe fruit.

ANTHRACNOSE
This disease, which is most important in nursery beds, is
caused by the fungus Colletotrichum fragariae Brooks. The
fungus causes a spotting and girdling of runners and leaf stems.
It can grow from these parts into the fleshy part of the plant.
There it produces a dryrot which results in a wilting of the affect-
ed plant. The disease is most destructive during periods of high
temperatures and abundant rainfall. Runner spots are dark
brown to black and definitely sunken, with a rather sharp line of
demarcation between healthy and diseased tissue (Fig. 2). This
distinguishes them from similar spots on runners caused by sand
burn during periods of hot, dry weather. Sand burn spots are
lighter brown and sunken. Furthermore, the black spots caused
by the fungus can be definitely identified by examining them
under a 6X hand lens. Such spots are covered with tufts of
SPlant Pathologist in Charge, Strawberry Laboratory, Plant City.
2Entomologist, Gulf Coast Experiment Station, Bradenton.







4 Florida Agricultural Experiment Stations

small black bristles which are part of the fungus, and which are
readily distinguished from the lighter colored, large hairy struc-
tures of the strawberry runner.
Control.-Since the disease occurs during the rainy season,
it is most difficult to control and keep from spreading through-
out the nursery. It is readily spread by wind-blown spores and
also quite easily spread from
nursery to nursery by man or
"animal walking through a dis-
"eased nursery and then walking
into a disease-free nursery.
If the disease is noticed ear-
ly, some benefit can be achieved
by carefully removing the dis-
eased plants and runners from
the nursery and burning them.
Careful removal and complete
destruction are necessary so
that the fungous spores at-
tached to the diseased part of
the plants may not be scattered
to healthy plants.
A spray program will, to a
certain extent, keep the disease
from spreading, except during
prolonged rainy periods. Cop-
per spray materials, if used
with some good spreading and
sticking agent, may be applied
at weekly intervals or more
Soften if necessary. All plant
S- parts, esp ecially runners,
Fg. 2 r s g should be covered by the spray.
Fig. 2.-Anthracnose, showing
typical lesions on runners. T h e fungicidal residue will
stick to the plants and remain
effective if it thoroughly dries before rain falls.

RHIZOCTONIA DISEASES
There are 4 distinct diseases caused by different species of
the fungus Rhizoctonia. One disease, bud rot, occurs during the
winter months. The other 3, root rot, web blight and vein in-
fection, occur during late spring and summer.







Insects and Diseases Affecting Strawberries 5

BUD ROT
The fungus which causes this disease, Rhizoctonia solani
Kuhn, is quite prevalent in the soils of Florida and causes dis-
eases in many species of plant. It can attack any part of the
strawberry plant in contact with the surface of the soil, or it
can grow superficially over the plant surface and attack leaf
buds and flower buds. It is this latter phase that will be de-
scribed here. As yet, it has not been found attacking roots.
When strawberry plants with single-bud crowns are attacked
by the fungus, the bud is killed by dry-rot and may be pulled
easily from the remainder of the plant. The older leaves may
or may not be attacked. If attacked, they become dry-rotted at
the bases of the leaf stems, weakening the support of the leaves
and causing them to lie flat on the soil. In this position the
leaves may continue to grow and live out their normal span of
life. Death of the main bud results in death to the plant unless
lateral buds subsequently develop and are not themselves at-
tacked by the fungus.
When large plants with many buds in the crown are attacked,
the disease may go unnoticed for some time because diseased buds
are hidden by abundant foliage. Later, the disease will be no-
ticed when the lack of new vegetative growth and lack of fruit
production become apparent.
The fungus attacks not only leaf buds but also flower buds.
It attacks the buds in any stage of development from the early
forms to open blossoms. When the early forms are attacked,
the buds develop dry-rot and die. When open or nearly opened
blossoms are attacked, the petals remain white but the centers
become black, similar in appearance to frosted blossoms.
Bud rot is usually more prevalent during the winter months,
when air temperature is below 75 degrees and humidity is high.
The disease is favored by foggy weather and heavy dews, which
may keep the plants covered with moisture for long periods.
Large plants and plants set too closely together on the bed tend
to hold a moist atmosphere around the buds and thus favor the
disease. Moist soil surfaces favor the growth of the fungus
from plant to plant. This is especially true where the beds
are covered with mulch of any kind, such as straw, shavings or
plastic film.
Control.-To control the disease it is necessary to make the
environment as unfavorable as possible for the development







6 Florida Agricultural Experiment Stations

of the fungus. Frequent shallow cultivations around the plants
will keep the soil surface dry. Wider spacing of plants on beds
will give better air circulation and allow foliage and buds to
dry more rapidly.
Most fungicidal sprays are of little value in controlling rhiz-
octonia. One material is quite specific against the fungus, but
is toxic to strawberry plants if allowed to remain on the plant.
This material, pentachloronitrobenzene, can be used as a soil
treatment to kill the fungus.
Bud rot disease practically disappears when the weather
changes from high humidity and relative calm to low humidity
and more air movement.
ROOT ROT
This disease is caused by another species of Rhizoctonia and
occurs in the summer in nursery fields. It attacks the roots but
not the crowns of plants.
WEB BLIGHT
In this case the fungus, another species of Rhizoctonia, grows
superficially over the lower surface of leaves and may cause death
of some leaves.
VEIN INFECTION
The species of Rhizoctonia involved here infects the lower
surfaces of main veins. This retards or stops growth in the in-
fected area and causes the leaflets to curl downward.

LEAF SPOT DISEASES
There are 3 different leaf spot diseases of strawberry: com-
mon leaf spot, leaf scorch and leaf blight, the first being the most
important.
Copper spray applications at 7- to 10-day intervals will con-
trol these diseases in the nursery field. The captain spray pro-
gram to be outlined later for Botrytis rot control in the fruiting
field will also control leaf spot diseases.

COMMON LEAF SPOT
This leaf spot is caused by the fungus Mycosphaerella fra-
gariae (Tul.) Lindau. The spots are at first small, less than 1/8
inch in diameter and purplish red. They increase to a diameter
of approximately 3/16 inch. The centers become white or gray
(Fig. 3). The spots may number from 1 to many on each leaflet







Insects and Diseases Affecting Strawberries 7

and if extremely numerous cause death of the leaflet. If many
leaflets die, the plant itself may be killed.
Florida Ninety is susceptible
to this disease, Missionary is re-
sistant.
LEAF SCORCH
This leaf spot is caused by the
fungus Diplocarpon earliana (Ell.
and Ev.) Wolf. The
young spots appear
on the upper surfaces
of the leaves as small
purplish discolora-
tions which rapidly
enlarge into irregular
p u r p 1 i s h blotches
from 1/16 to 3/16
inch in diameter. In Fig. 3.-Common leaf spot on strawberries.
these spots are very
small black, glistening bodies which are the fruiting structures
of the fungus (Fig. 4). The spots on each leaflet may become so
numerous that they coalesce and give a dark reddish cast to the
entire leaflet. In severe
cases of infection t h e
edges of the leaflets curl
upward and the leaf tis-
sue dies and dries to a
tan color, progressively
from edge to midrib, giv-
ing the plant a scorched
appearance.

LEAF BLIGHT
This leaf
spot is caused
by the fun-
gus Dendro-
phoma obscu-
rans (Ell. and
ras (E. and Fig. 4.-Leaf-scorch.
Ev.) Ander-
son. The young spots of this disease are larger than the mature
spots of either common leaf spot or leaf scorch. From 1 to 5







8 Florida Agricultural Experiment Stations

spots may occur on a leaflet. The young spots are circular and
reddish purple. The older spots become zonated. The central
zone is dark brown, surrounded by a lighter brown zone which
in turn is bordered by a purplish zone which blends into the
normal green of the leaf. Mature spots may be circular, oval
or even V-shaped (Fig. 1). Small black dots, fruiting structures
of the fungus, appear in the central, dark brown zones of ma-
ture spots.
FRUIT ROTS
LEAKS OR WHISKERS
This rot, caused by the fungus Rhizopus nigricans Ehrenb.
ex Fr., is of most importance during the transportation and mar-
keting of strawberries, although it may also be found in the field.
It develops most rapidly under conditions of high temperature
and moisture.
The fungus readily attacks fruit that has been injured and
causes a collapse of the tissues and rapid loss of fruit juice,
which accumulates in the bottom of the container and drips out,
thus giving rise to the common name "leaks." The fruit settles
down until it fills about half the container. A loose cottony
growth of fungus appears over the surface of the fruit. This is
the "whiskers" stage (Fig. 5). This growth may hold the fruit
together so firmly that when the container is inverted the fruit
falls out in a solid block. Black dots appear scattered through-
out the cottony mass. These dots are the spore-bearing struc-
tures of the fungus.
During picking, preparing and transporting, fruit should
always be handled carefully to avoid bruising. Frequent chang-
ing of water used in washing fruit will greatly reduce the source
of infectious material. Since high temperatures favor the de-
velopment of this rot, fruit should be picked during the morning
and protected at all times from the sun. When the fruit reaches
market, the buyer should rapidly cool the fruit to a temperature
of 35 to 40 degrees before shipping it north by air, rail or truck.
Fruit thus handled will not develop this type of fruit rot.

GRAY MOLD OR BROWN ROT
This rot, caused by the fungus Botrytis cinere-a Pers., occurs
both in the field and during transportation of fruit. During pro-
longed periods of cool, wet weather this rot may become of prime








Insects and Diseases Affecting Strawberries 9

importance in the field, where it attacks strawberries in all stages
of development from blossom-stage to fully-ripe. At such times
a high percentage of the fruit is covered with "gray mold" and
has to be discarded.




























-- a r -

Fig. 5.-"Whiskers" or "leaks".

Under less severe conditions the fruit may be spotted. These
spots are at first light brown, later dark brown in color. The
flesh may become slightly soft at first, then hard and dry; never
"leaky." There is no distinct line of demarcation between dis-
eased and healthy tissue. Under moist conditions the infected
fruit becomes covered with "gray mold," which is the spore-bear-
ing stage of the fungus. Since this disease is spread from fruit
to fruit by wind-blown spores, plastic film bed mulch will not
keep it under control. It is necessary to follow a regular spray
program.








10 Florida Agricultural Experiment Stations

During the past several years experiments and experiences
of growers have shown that this rot can be controlled by the
use of captain sprays. Applications are made at 10-day intervals
from fall-setting of plants to blossoming time, and thereafter at
7-day intervals during the fruiting period. Use captain 50 per-
cent W.P. at the rate of 2 to 4 pounds per 100 gallons.
In preparing fruit for market all fruit infected with this rot
should be discarded because Botrytis will develop slowly, even
at temperatures of 35 to 40 degrees.

HARD BROWN ROT
The fungus which causes this rot of strawberry fruit is the
same 1 causing bud-rot in plants, Rhizoctonia solani. The fun-
gus produces no spores and hence cannot be spread from plant
to plant by air currents. The fungus grows in the soil and at-
tacks the fruit on the side in contact with the soil. Fruit in all
stages of maturity may be attacked. The infected spots are
light tan unless soil has become enmeshed in the fungal growth.
In this case the spots are of the same color as the soil adhering
to them. The line of demarcation between the tan-colored dis-
eased tissue and the pink healthy tissue is so sharp that the
diseased tissue can be cut away and the remainder of the fruit
will be edible.
Plastic film bed mulch will keep the fruit from coming in con-
tact with the soil and hence prevent infection by Rhizoctonia.

LIGHT TAN ROT
This fruit rot, the least important of the 4 rots in Florida,
is caused by the fungus Pezizella lythri Shear and Dodge, and
is easily distinguishable from the other rots.
The spots produced on the fruit are small, sunken and tan.
They increase but slowly in size. The infected tissue is a cone-
shaped core which, due to its corky texture and to the disintegra-
tion of the cells adjoining, can be removed intact from the sound
tissue.
VIRUS INFECTION
It is only within the past 15 years that the seriousness of
virus infection in strawberry plants in the eastern United States
has been recognized. It has been found to be present in most
varieties grown in the area. There are no definite leaf symptoms
of virus infection displayed in strawberry plants as is the case







Insects and Diseases Affecting Strawberries 11

with most vegetable varieties. Infected strawberry plants make
poor plant growth and runner production and produce low yields
of fruit. The Missionary variety of strawberry became infected
with viruses, with the result that yields of fruit were so low that
growers said the variety was "running out." The United States
Department of Agriculture has established a virus-free line of
Missionary.
As yet, virus infection has not been found in plants of the
Florida Ninety variety. Plant lines which have been maintained
in Florida stay clean because the insects which transmit virus dis-
eases of strawberry are never numerous in the plant-growing
areas of the State.
BLACK ROOT
Black root is not typically an injury. The condition prob-
ably is physiological, occurring on older plants. The root cortex
or bark may become dark brown to black. This dark colored cor-
tex readily peels off, showing that the central cylinder is still
white and alive. Such roots can put out new lateral roots and
under favorable growing conditions will support a vigorously
growing plant which will put on a good crop of fruit.
Black root occurs mainly on older plants in the nursery beds.
Two or 3 weeks before such plants are to be set in the field, loosen
the soil around them with a potato fork or pitchfork. This helps
to aerate the soil so that old black roots will put out new laterals,
and within 2 or 3 weeks plants will be in much better condition
for setting in the field.

SCLEROTIUM ROT
This rot is caused by a soil-inhabiting fungus, Sclerotium
rolfsii Sacc., which develops most rapidly during hot, moist
weather. For this reason, the disease is found mainly during
the summer months on plants in nursery fields, especially in
lower, wetter portions of these fields. The fungus grows through
the soil and attacks plants at the soil line. From there it pro-
gresses upward into the fleshy part of the plants and also down-
ward into the roots. Complete death of plants may be quite
sudden. Under conditions of high humidity and moist soil a
white mat of compressed cottony growth of the fungus may be
found around the base of the plant. Small round bodies, sclero-
tia, which are white at first and later dark brown appear scat-
tered over the surface of the white mat. These sclerotia, about







12 Florida Agricultural Experiment Stations

the size of strawberry seed, are most easily seen on diseased
leaf-stems.
The fungus can attack most of the cultivated crops and weeds
in central Florida. However, infection is seldom widespread.
Even in individual fields it is quite localized.
Control of this disease has been accomplished by the use of
pentachloronitrobenzene 3 as a spray at the rate of 10 pounds per
100 gallons. Only the diseased areas in the field are sprayed to
kill the fungus, since this fungicide is quite toxic to strawberry
plants if it remains in contact with the aboveground parts of the
plants.
NEMATODES
Three species of nematodes attack strawberry plants. The
root-knot nematode and sting nematode attack the roots. The
bud nematode infects buds and produces the disease known as
crimp or Frenchbud.
BUD NEMATODE
This nematode, Aphelenchoides besseyi (Ritzena Bos) Chris-
tie, does not actually get into the bud tissue. Instead it inhabits
the air spaces in the leaf buds and runner buds. It feeds by
puncturing the young tissues and sucking out the plant juices
by means of a stylet or tube. The saliva which it injects into
these young growing parts causes them to develop abnormally.
The young leaves are crimped, crinkled, darker green in color,
with reddish coloration on edges and veins (Fig. 6). The leaf
area may be greatly reduced; in some cases not much more than
mid-ribs develop. Plants infested with this nematode are prac-
tically worthless for fruit production.
The nematodes are most active during late spring to early fall,
when temperatures are well above 75 degrees. At the lower tem-
peratures occurring during late fall and winter the nematodes
are so sluggish that infested plants put on some normal growth.
Bud nematodes have been and still are spread from state to
state in shipments of nursery plants. The same thing happens
from field to field in local areas. Spread in individual fields is
accomplished by the nematodes swimming in the soil moisture
or being transported longer distances by heavy rains and flood
waters.
The nematodes can live in the soil for long periods. They
feed on 1 or more species of fungi which are present in the soil.
Terraclor.








Insects and Diseases Affecting Strawberries 13

Under favorable moisture conditions, both soil and atmospheric,
they are able to enter plant buds and produce the crimp disease.





















Fig. 6.-Frenchbud, showing crimping
of young leaves.

Land known to be infested with the nematodes should not
be used for plant production until it has been fumigated with
an effective nematocide. Land to be treated should be located
where it will not receive drainage from infested soil. Plants
used for setting in treated land should be free of nematodes.

STING NEMATODE
This nematode, Belonolaimus longicaudatus Rau, is an ex-
ternal root parasite. It does not enter the roots but feeds from
the outside by means of a stylet through which it sucks the
juices from the tissues of the very small roots and root tips.
This causes the death of these roots with the result that the
affected plants soon have no feeder roots, only brushes of coarse
roots. Such plants do not put out further growth. They may
remain semi-dormant for prolonged periods or may gradually
decline and finally die.
In the field these infested plants usually form circular to oval-
shaped areas which appear to increase in size as the season ad-








14 Florida Agricultural Experiment Stations

vances. This increase in size is due not to migration of nema-
todes from plant to plant but rather to the build-up in population
around each individual plant. The initial density of population
of nematodes in these infested areas depends upon the type of
cover crop growing there prior to preparation of land for straw-
berries.
If crab-grass is the cover, the population of sting nematodes
will be quite dense. Crabgrass roots favor the rapid multiplica-
tion of the nematode and are capable of supporting large popula-
tions, without having the grass show any signs of the nematodes
being present. Sesbania also is favorable for the nematode but
becomes stunted if too many are present on the roots. Velvet
bean and hairy indigo are not good host plants for the nematode
and should be used as cover crops for strawberry land.
In the fruiting fields satisfactory control of the nematode can
be obtained by in-the-row injection with D-D or ethylene dibro-
mide at the rate of 1 pint to 150 lineal feet. This must be done
at least 2 weeks before plants are set, as these materials are
toxic to plants. For the nursery fields nematode control is best
accomplished with 1,2-dibromo-3-chloropropane 4. Plants are set
out and soil is treated after plants are well established. The en-
tire bed is drenched with Nemagon at the rate of 2 gallons tech-
nical per acre.
ROOT-KNOT NEMATODE
The type of root injury caused by this nematode occurs on
roots of many of the vegetable crops in the South grown during
warm weather. On strawberries the disease is less severe. Fruit-
ing plants are not much affected, mainly because during the
fruiting season temperatures are comparatively low and the root-
knot nematode somewhat dormant. The disease can become
severe and cause considerable root injury and even death of plants
during prolonged periods of drought and high temperature, espe-
cially if the plants are being grown on light, sandy soil.
The microscopic eelworm or nematode, Meloidogyne sp., which
causes root-knot is quite common in the soils of Southern states.
It enters strawberry roots and causes galls 1/16 to 1/8 inch in
diameter, much smaller than those formed on roots of vegetable
crops (Fig. 7). These galls interfere with normal root function,
such as absorption of nutrient solutions from the soil. Plants
thus attacked become unthrifty and may eventually die.

Nemagon.








Insects and Diseases Affecting Strawberries 15

There are several methods which can be used to reduce the
number of root-knot nematodes in the soil. Some treatments may
even eliminate most of them. In all cases after soil has been so
treated it should not be set with plants which are themselves in-
fested with nematodes.

























Fig. 7.-Root-knot as it appears on strawberries.

One of the most economical methods for reducing the nema-
tode population is by the use of a resistant crop. Velvet beans,
crotalaria and hairy indigo are best for this purpose. Drill the
seed in rows 2 feet apart and cultivate the crop as long as pos-
sible to keep down growth of weeds which may be host plants.
The nematodes die of starvation because they have no suitable
plant roots upon which to feed.
Good results can be obtained by fumigating the soil with the
fumigants D-D, ethylene dibromide or Nemagon. All soils to
be treated should be well prepared and free of trash. At time
of treatment, soils should be at optimum moisture, neither too
wet nor too dry. Unless heavy rains ensue after treatment, the







16 Florida Agricultural Experiment Stations

land can be bedded 2 weeks from treating time and strawberry
plants set.
Each grower can treat his land himself by the row method
or bed method. Costs for this method are quite low. Full details
concerning this method can be obtained from County Agricultural
Agents, Florida Agricultural Experiment Stations or several of
the agricultural supply companies.


INSECTS AND SPIDER MITES

Insects and spider mites cause considerable damage to those
fields set to strawberry plants for fruit production. Insects are
of less importance in strawberry nurseries. The pests are listed
in the order of their importance. The first 7 should always be
considered as an annual menace to the strawberry grower.

PESTS OF MAJOR IMPORTANCE
SPIDER MITES
The problem of identifying infested plants in the field is of
primary importance. Symptoms of mite infestation become so
pronounced that it is hard to believe that so few mites present
could be responsible for the condition of the plant. Severe in-
jury consists of dwarfing and stunting of the plants. Medium
injury is characterized by wrinkled leaves and reduced plant
growth and yield. Slight injury causes a slight wrinkling of the
leaves and irregular folds of the leaf margins. Plants in the field
may turn brown or brownish red, but this condition cannot be
entirely attributed to mites because other factors could cause
these same symptoms.
Of the plant-feeding mites, the Tetranychidae or spider mites
are most widespread and most important economically. There is
hardly a plant that is not attacked by at least 1 species, and all
species apepar to be pests.
Mites are distributed by birds, wind and man. They may be
carried on clothing from 1 plant to another. Strawberry varie-
ties differ in their susceptibility. Missionary is quite susceptible
to mite attack and Florida Ninety to a lesser degree. None are
immune. The degree of susceptibility seems to be associated
with the plant's growth habit. An upright variety, as Florida
Ninety, with a fairly smooth lower leaf surface is more resistant
to mites than low-growing varieties having leaves flat on the








Insects and Diseases Affecting Strawberries 17

ground. Missionary, for example, is a prostrate variety with
lower leaves lying against the soil, making an ideal place for mite
infestation and making it very difficult for control measures to
be effective.
The Northern or green 2-spotted mite, Tetranychus telarius
(L.), and the Southern lobed mite, T. lobosus Boudreaux, are
2 common species. T. lobosus is referred to as the red spider
mite. These mites are found on many weeds, so infestation is
simple. The 2-spotted mite is found on nightshade, pokeweed,
hairy indigo, gladiolus and many other plants. Plants shipped
in from Maryland, Tennessee, Arkansas and other localities in
the North, even though arriving in a defoliated condition, may
possibly harbor mites or eggs in the crown of the plant. These
plants are set in the nurseries for next year's runners.
T. lobosus has been seen on strawberries in the Plant City
area for over 30 years. This species is readily controlled with
dusting sulfur and, as a result of the rigorous control measures
used against another species of mite, is difficult to find in any
large populations. The green 2-spotted mite, first noticed in 1950
on eggplants and later on strawberries, is difficult to control with
those measures successful against the red spider mite.
Control.-Most strawberries are set in the field by the middle
of October and, depending upon market and weather conditions,
are plowed under some time in March or April. The plants are
growing during the cooler portion of the year, and this makes an
ideal condition for mite development. Growers who think that
weather conditions are unfavorable for mites sometimes neglect
to keep up their control program during cold weather, which
allows the mites to increase in numbers to the point that every
effort must be used to combat the pests. Plants injured by mites
suffer a lasting damage and seldom recover their former vigor-
The low soil temperature and cool nights that are ideal for mites
make it difficult to obtain adequate control.
The presence of 2 or more mite species may account for the
failure of miticides to control all infestations. Dusting sulfur,
for example, has always been effective against the red spider mite,
but the appearance of another species may necessitate the use
of other materials.
Parathion 15W applied at 2 pounds to 100 gallons of water has
been as effective under the same conditions as 2 percent dust.
However, parathion failed to control heavy, established infesta-
tions. Parathion, too, is poisonous and should not be handled








18 Florida Agricultural Experiment Stations

carelessly. However, it is a good insecticide and miticide and
should be used where recommended. Malathion applied as a 5
percent dust or a spray of 1 pound active ingredient (4 pounds of
25 percent) per 100 gallons of water has proven effective under
some conditions. There is a short residual, so a follow-up treat-
ment must be made to kill newly hatched crawlers and adults
missed in previous treatment.
The most satisfactory control for mites has been 1,1-bis(4-
chlorophenyl) 2,2,2-trichloroethanol 5, a non-phosphatic material.
This is formulated as an emulsion concentrate, an 18.5 percent
wettable powder and in dusts. The wettable powder is used at 2
pounds to 100 gallons of water and as a 2 percent dust and to date
has proven effective against all species of mites. Kelthane kills
mites in the adult, larval and egg stages. Kelthane is relatively
safe for workers.
Control.-Once the plants are set in the seedbed area and leaf
out, spray thoroughly with Kelthane wettable powder at the rate
of 2 pounds to 100 gallons of water. Since varieties vary in sus-
ceptibility to mite injury, susceptible varieties should be sepa-
rated from the others in the seedbed and receive frequent thor-
ough sprayings. Repeat applications every week or 10 days
until ready for planting in the field.
If a grower does not spray as suggested above, he may try this
procedure. Prior to setting plants in the seedbed, dip them in
a Kelthane suspension made from the emulsion concentrate at
11/2 gallons to 100 gallons of water or 10 pounds of the wettable
powder to 100 gallons of water. Captan 50W may be included
at the rate of 2 pounds per 100 gallons to prevent the spread of
disease fungi. Completely immerse and shake the plants in
the liquid, remove and allow to drain into the same vat in which
they were dipped. As soon as they have drained, set out in the
field. Discard the liquid at the end of each day because of the
accumulation of soil and debris from the immersed plants. After
the plants are set in the field and have leafed out, they should
be sprayed with Kelthane at the rate of 2 pounds to 100 gallons
of water to control any mites not killed by dipping. Remember,
1 mite infested plant set in the field can cause much unnecessary
spraying. If dusting is preferred, use a 2 percent Kelthane dust.
Apply either dust or spray every 3 weeks.
As soon as the buttons appear on the plants, cease spraying
with Kelthane and use parathion wettable powder at 11/2 pounds
SKelthane.







Insects and Diseases Affecting Strawberries 19

per 100 gallons of water or a 2 percent dust with a sulfur carrier.
Parathion has been approved for use with 3 days as the mini-
mum between last application and harvest. If berries are picked
on Friday, follow immediately after picking with the spraying
or dust and by Monday, when the picking crews are in the field
again, all parathion residues will be at the minimum.

WIREWORMS
For years strawberry growers have been aware of the de-
struction caused by wireworms. Before the advent of the new
insecticides and soil fumigants, part of the crop in some years
was lost because of wireworm. Most of this damage was due to
injury to the plants. Wireworms were probably the "drill worms"
found in the fruit in past years. Wireworms are smooth, round
and shiny and vary in color from pale yellow to dark brown
(Fig. 8). This particular species is approximately 1/3 inch long.
Wireworms are classed as soil-inhabiting insects but are found
infesting berries.












Fig. 8.-Larvae of wireworm that enter strawberry fruits.

Conoderus falli Lane belongs to the click beetle family. The
adult is from 1/4 to 3/8 inch long and brown to black in color. The
adults are attracted to light. Judging from the numbers taken
at a light trap, July is the month of peak emergence. Little is
known of this species' history in Florida, but the larvae are
usually numerous at setting time. There is another beetle emerg-
ence in October and the larvae from this generation bore into
the fruit when it matures.
Wireworm damage results from the larvae boring into the
thickened portion of the plant and causing a severe stunting or
death. Wireworm damage to the fruit consists of the larvae bor-







20 Florida Agricultural Experiment Stations

ing into the ripened fruit (Fig. 9). Damage is due not only to the
actual hole bored into the fruit but also to rot organisms which
enter and hasten the decomposition of the berries (Fig. 10). This
damage is particularly noticeable when the berries are processed
as fresh chilled fruit. The larvae fall to the bottom of the con-
tainer. Worse yet is for the consumer to find the larvae entirely
within the fruit without its presence being noticeable from the
outside.




























Fig. 9.-Larva of wireworm on strawberry fruit.

Control.-Clean culture, crop rotation and thorough cultiva-
tion are helpful practices, but these alone are far from satisfac-
tory. Chemical control must be used. Chemical control will be
divided into 2 sections; control of the wireworm in the soil and
later control of the wireworm in the fruit.
For control of the wireworm in the soil, the following methods
are useful:








Insects and Diseases Affecting Strawberries 21

1. Chlordane Treatment.-Apply 5 pounds of active chlor-
dane either emulsion concentrate, wettable powder or granules.
Chlordane as an emulsion has 72 to 78 percent active chlordane
or 8 pounds active ingredient per gallon. Each pint contains 1
pound, so 5 pints per acre sprayed broadcast or in the row should
be applied. Granules are formulated at 5 or 10 percent, and
100 pounds of the 5 percent is equivalent to 5 pounds active in-
gredient. Wettable powder is usually formulated as a 40 percent
product, so 121/2 pounds are required for 5 pounds of active in-
gredient.
Chlordane may be applied with the fertilizer. Regardless of
formulation, these materials are applied to the soil surface and
disked in as deeply as possible. Setting may commence at once,
but a short wait of 2 or 3 days between treatment and setting
is preferred because insect activity, stirred up by the chlordane,
will have ceased by this time. This same application controls
mole-crickets, earwigs, ants, grubs, cutworms and armyworms
that might be in the soil.

Fig. 10.-Damage to strawberry fruits by wireworm and lesser
cornstalk borer.








*~^^~








22 Florida Agricultural Experiment Stations

Make the first application after plants start growing and the
second when the berries form. This may be a 5 percent dust at
20 pounds per acre, a spray using wettable powder at 1 pound
active ingredient per acre or 5 percent granules at 20 pounds per
acre in bands placed on both sides of the plant. Do not use the
emulsion concentrate because it may injure the plants. When
berries form, apply only the 5 percent granular material directly
to the plant and around it. The nature of the granular material
permits it to roll off the fruit so that there can be no residue
problem. The presence of the granule on the leaf or plant will
not have any effect on the residue that might be on the fruit.
2. Aldrin Treatment.-This material, similar to chlordane, is
also used by many growers. It has been effective against wire-
worm in other parts of Florida and in general throughout the
eastern United States. However, results have been erratic in
tests at Bradenton. For this reason aldrin is not listed as a fav-
orable control. It should be used at the rate of 4 or 5 pounds
active ingredient per acre. Formulations are a 2-pounds-per-gal-
lon emulsion concentrate, and 2 gallons per acre are required for
a 4-pound active ingredient application. The 25 percent wettable
requires 16 pounds.
Fertilizer and insecticide formulations are custom mixtures,
so make application as quickly as possible because fertilizer mix-
tures tend to break down the insecticides and the insecticides be-
come ineffective. Use all of your mixture.

LESSER CORNSTALK BORER
The lesser cornstalk borer, Elasmopalpus lignosellus (Zell.),
at times is a serious pest of strawberry plants and fruits. It is
found throughout Florida feeding upon various cultivated crops
such as corn, Southernpeas, pepper, strawberries, beans, sugar-
cane and gladiolus. There are several wild host plants, of which
a preferred 1 appears to be nutgrass.
Wilting of the younger leaves of a plant is usually the first
indication of its presence. A carefully dug and lifted plant will
reveal a silken tube connected with the entrance hole at the base
of the injured seedling (Fig. 11). This silken tube covered with
sand and excrement may easily be mistaken for a root of the
plant. If this tube is torn open, the slender, extremely active
bluish-green larva about 2/3 inch long marked with dark-brown
longitudinal bands is exposed. The larva is very active and
jumps like a piece of spring wire. The larva does not remain in








Insects and Diseases Affecting Strawberries 23

its burrow except for feeding. The remainder of the time is
spent in the silken tube.



















-.






Fig. 11.-Lesser corn stalk borer larvae (slightly enlarged).

Larvae not only burrow into a plant but can tunnel any place
along the runner, which will kill the young plant if it has not
rooted. Mature larvae construct a silken cocoon covered with
sand and excrement and transform to pupae. The moths emerge
in from 1 to 3 weeks, depending upon weather. There are sev-
eral generations a year.
Plants are damaged by the larva boring into the stem just
above or beneath the surface of the soil and encircling the plant
at the fleshy part, causing the newly set plant to wilt and die.
If the plant is not killed, it is left in a stunted, deformed condi-
tion incapable of producing berries. Lesser cornstalk borer dam-
age to the fruit consists of the larva's boring into the ripened
fruit (Figs. 10, 12).
Control.-Control measures are of no value to a stricken
plant but will protect the remaining plants. Where wireworm







24 Florida Agricultural Experiment Stations

control has been practiced, little damage should result from the
lesser cornstalk borer. At least 2 applications of chlordane at
the same rate as for wireworms should be made from the time
the plants are set until the berries first set. The spray boom
should be within 12 to 18 inches of the ground and the spray rig
driven so that a sufficient amount of coarse spray is directed to-
ward the ground where it will do the most good and wet the
ground with the spray. Pressure should not exceed 200 pounds.
































Fig. 12.-Larva of lesser cornstalk borer and its damage to strawberry fruit.

Fertilizer mixtures containing insecticides are of little ben-
efit against this pest because the material is normally placed in
the soil too deep to be effective against surface insects. After







Insects and Diseases Affecting Strawberries 25

the fruit has formed, use only chlordane granular formulation
because of the residue problem.

PAMERAS
Three species have been recorded in Florida, but Pachybrach-
ius bilobata (Say) is
the m o s t prevalent
/(Fig. 13). Pameras
\ belong to the chinch
bug family. The
S young resemble small
I yellow ants in size and
color but are much
more rapid in their
movements. The
ad u lts h av e d ark -col-
ored wings. They
breed so rapidly and
are so inconspicuous in
color, size and habits
that they often become
very abundant before
they are noticed.
Pameras cause
S"buttons"- berries in
the early stage of de-
velopment that cease
to grow and become
Fig. 13.-Pamera. hard, dry and brown.
The outer leaves of the
plant die first and dry up, turning a brownish color. If these
leaves are disturbed, the pameras scatter in all directions. Later
the insects attack the crown of the plant, which withers rapidly
and dies if the insects are numerous. They are prevalent in late
spring but sometimes occur as early as late November and De-
cember.
Damage from pameras has increased since there is less hand
work around the plant. The individual attention given to each
plant disturbed the hiding places of the insect by loosening the
leaves that had stuck to the soil, thereby facilitating insect con-
trol. Upright growing plants have less leaf area against the soil,
hence control is easier.







26 Florida Agricultural Experiment Stations

Control.-Pameras are controlled by dusts, granules and
sprays. On plants not fruiting apply 10 percent DDT at the rate
of 20 pounds per acre if single row or 35 pounds for a double row.
If DDT spray is preferred, use at 1 pound active per acre to 100
gallons of water. On fruiting plants use parathion or malathion.
Parathion 15W applied at 11/ pounds in 100 gallons of water has
been an effective control. A 2 percent parathion dust also has
proven effective. Malathion 5 percent dust or spray applied as
1 pound active per 100 gallons per acre is also effective. Two
treatments spaced 10 days apart have generally given satisfac-
tory control. It is generally windy when dusting is required for
insect control and for this reason a spray is preferred.




















Fig. 14.-The most widespread and destructive mole-crickets. Left,
change (Scapteriscus vicinus Scudd.); right, Southern mole-cricket (S.
acletus R. & H.).
MOLE-CRICKETS
The Southern mole-cricket, Scapteriscus acletus R. & H., and
the Puerto Rican mole-cricket or change, S. vicinus Scudd., quite
often cause considerable damage to strawberry plants (Fig. 14).
They are most destructive in the field in the fall. They can also
be destructive in nurseries. They affect the plant by destruction
of roots and drying out of soil (Fig. 15).
Control.-Control measures used for wireworms are effective
against mole-crickets. If control measures are for mole-crickets,








Insects and Diseases Affecting Strawberries 27

without consideration of other insects, apply chlordane as a spray,
using 21/2 pounds of 40 percent wettable powder in 100 gallons of
water per acre. A dust mixture of 5 percent chlordane in a dust-
ing sulfur base has proven very effective. Apply the dust at the
rate of 15 pounds per acre for a single row or 20 to 25 pounds
per acre for a double row.
Chlordane is also used in a bait made from a feed base con-
taining mostly wheat products, to which enough chlordane is
added to 100 pounds of bait to make a 2 percent product. To
make your own bait, use 4 pounds of a 50 percent chlordane or 5
pounds of 40 percent chlordane in 100 pounds of wheat feed.
Apply the bait only to soil that has been moistened. Bait should
be fresh and used at once. Apply bait in the late afternoon. If
mole-crickets are a problem after the berries have set, use 5
percent granular chlordane.

FLORIDA FLOWER THRIPS
This sucking insect, Frankliniella cephalica (Crawford), is
minute, soft-bodied, yellowish and quite active. The insects
sometimes are found in considerable numbers in blossoms, where

Fig. 15.-Mole-cricket "runs" on newly graded yard.








28 Florida Agricultural Experiment Stations

they feed on stamens, pistils and young berries. When numerous
they can cause blossom drop or the young berry may remain hard
and brown and fail to grow. They usually are found in the field
in the late spring after the picking season, but may infest blos-
soms.
Control.-Nicotine is the most effective control for flower
thrips. Dusts are very effective but the mixture must be fresh.
Nicotine dusts should be applied when it is warm (above 600 F.)
and quiet. These conditions are rarely present where needed, so
nicotine sulfate applied as a spray at 1 pint of the 40 percent
emulsion per 100 gallons of water is more satisfactory. In those
areas where parathion is used, apply 1 pound of the 15 percent
wettable per 100 gallons of water or else a 1.5 percent dust. Gen-
erally, 1 or at most 2 applications are all that is required after
flowering has begun.

CUTWORMS AND ARMYWORMS
Several species of cutworms and armyworms attack straw-
berries but no attempt is made here to separate the species.
Damage is caused by the larvae cutting off the young plants or
leaves. They also feed on the berries, sometimes cutting the
fruits from the plants. They are found in the field and in the
nursery, especially in early fall.
Control.-The control measures used against wireworms are
effective against cutworms and armyworms. Again, if these
pests appear when the fruit is set, use granular 5 percent chlor-
dane.
INSECTS OF LESSER IMPORTANCE

CRICKETS
Field crickets, Gryllus sp., in the past have been destructive
but now are seldom seen since the new organic insecticides have
been in use.
Control.-Apply 5 percent chlordane, 10 percent DDT dust
or 2 percent chlordane bait.

STRAWBERRY FLEA BEETLE
This flea beetle, Altica ignita (Illiger), is a bronze-colored in-
sect about 1/5 inch long that damages strawberry leaves by eat-
ing round holes in them. They are most frequently found in the
fall on early set plants.
Control.-Apply 10 percent DDT dust as for others.







Insects and Diseases Affecting Strawberries 29

STRAWBERRY LEAF ROLLER
The strawberry leaf roller, Ancylis comptana fragariae (W.
& R.), is more prevalent in nursery plantings than in the field.
The gradual change in color of the leaves from green to silver
in a nursery may be the first indication that this pest is present.
A heavy infestation results in many folded leaves with the color
changing from green to silver because the lower sides of the
leaves are exposed due to being webbed together. Later, as feed-
ing continues, the leaves have a scorched appearance.
The moth is about 1/4 inch long and 1/ inch wide, including
wingspan. The adult is a light brown or rusty brown. The larvae
are pale green at first, changing to grayish brown as they reach
maturity, when they are approximately 1/ inch in length. The
larvae pupate inside a folded leaf or leaves.
A newly hatched larva feeds on either side of the leaf, eventu-
ally feeding on the upper surface after pulling the leaf or leaves
together with silver threads to form an enclosure. The larvae
feed upon the surface of the leaves, which causes the entire leaflet
to turn brown and die. Newly formed leaves are often webbed
together.
Control.-Insects within a leaf enclosure are difficult to kill,
but parathion applied for other insects often effectively controls
many new infestations. Sometimes the parathion will drive the
pests out of the folded leaves where they may be more easily
controlled. DDT spray or dust is very effective if used when the
insects first appear. The pest is seldom seen in commercial plant-
ings, but may occur in home gardens when plants are set.

ROOT WORMS
The adult, Paria canella (Fab.), acts as a leaf beetle in the
fall on early set plants. Nothing is known of its larval habits.
Control.-Apply 10 percent DDT dust.

GRASSHOPPERS
The young nymphs are usually the most destructive.
Control.-Apply 5 percent chlordane dust or 2 percent chlor-
dane bait.
ANTS
Several species of ants damage plants by building mounds
over the buds, causing them to rot. Ants carry aphids from plant
to plant.







30 Florida Agricultural Experiment Stations

























Fig. 16.-Severe injury to strawberry plant caused by white grub.






















ig. .-Slugs (natural sie).




Fig. 17.-Slugs (natural size).







Insects and Diseases Affecting Strawberries 31

Control.-Apply 5 percent chlordane dust or 5 percent granu-
lar chlordane.
ROOT APHIDS
Aphis forbesi Weed, the strawberry root aphid, damages
strawberry plants by sucking the plant juice from the roots.
They are a very minor pest.
Control.-Same as for ants.




























Fig. 18.-Snails, Polygyra septemvolva Say (natural size).

WHITE GRUBS
White grubs are the larvae of May beetles. They are thick-
bodied, dirty-white, approximately 1 to 11/2 inch long when full
grown. They are always in a curved position. Larvae damage
the plant by cutting off the roots, frequently below the crown
(Fig. 16). Damage usually is most severe on new ground re-
cently cleared of a heavy stand of saw palmetto, Serenoa repens.






Fig. 20.Cse-up view of plants damaged by citrus root weevil.


.- .. ..-
* :C .. - .-.
r -












































IV7
S,.-I. -I I, -
1' ..' ,
.f- ~ .' ..-..


























A.,







Insects and Diseases Affecting Strawberries 33

Grub damage seldom, if ever, occurs on land that has been in
cultivation except with certain home gardens that are near
electric lights. The beetles or adults of the white grub are at-
tracted to lights and heavy infestation occurs in the vicinity of
the lights.
Control.-Chlordane applied at the same rate as for wireworm
control is effective against this pest.

SLUGS AND SNAILS
Home gardeners are especially plagued with these pests that
attack the strawberry fruit and eat out large portions (Figs.
17, 18). Heavy mulching makes a favorite hiding place for these
pests. They feed late in the afternoon or in the evening.
Control.-Chemicals that control slugs and snails are too
poisonous to humans to be used on strawberries, so hand picking
and sanitation are the only methods recommended.
















Fig. 21.-Adult of citrus root weevil (X2).

CITRUS ROOT WEEVIL
The larvae of the citrus root weevil, Pachnaeus litus (Ger-
mar), severely damage strawberry plantings in Dade County.
First observed in 1926 (Figs. 19, 20), it was then called the
crown borer. The adult is a greenish-blue snout beetle from
1/3 to 1/2 inch long (Fig. 21). The larvae are large, white, fat
grubs. The chief damage is caused by the larvae which tunnel
through the strawberry crown and kill or stunt the plants (Fig.







34 Florida Agricultural Experiment Stations

22). The larvae and pupae develop inside the crown of the plant,
usually below the soil surface.
Control.-The control measures used against wireworms
should prevent damage by these weevils.

TIME OF APPLICATION OF INSECTICIDES

The grower is given his choice of preventing a build-up in
population by applying insecticides on a schedule or of using in-
secticides for control only when needed, as determined by care-
ful inspection of the plants.
Do not dust when plants are wet, since a foliage burn may
result, especially when heavy deposits remain on the plant. It
is better to dust in late afternoon and evening when plants are
dry. Apply immediately after harvesting the berries, to allow
a 2- to 3-day interval between treatment and harvest.
Sprays should be applied after the plants have dried to prevent
excessive run-off of the spray material. These recommendations
apply to Kelthane, parathion, malathion and chlordane granules
where fruit is involved.
At present, none of the other insecticides or miticides men-
tioned may be used during the harvesting season because of
residue problems. However, they may be safely used up to the
time of fruit set.

Fig. 22.-Larva of citrus root weevil and its damage.








2A







Insects and Diseases Affecting Strawberries 35


PRECAUTIONS

All insecticides are poisonous. Handle them with care and
follow the directions and precautions on the container label.
Always work on the windward side of the crop. Do not chew
tobacco or smoke while handling parathion. Do not eat food
without washing hands carefully with soap and water after
handling parathion. Children and adult workers should not enter
a parathion-treated field for 24 hours after application. Children
working on hands and knees are in closer contact with the treated
plants than adults who stoop or bend over to pick the fruit. After
24 hours there is no danger to the pickers.
Store insecticides in closed containers out of reach of children
and irresponsible persons. Use only fresh materials. Buy only
amounts needed for 3 or 4 weeks.
If you accidentally swallow an insecticide, induce vomiting by
taking 1 tablespoonful of salt in a glass of warm water. Never
give oil. Repeat if necessary. Call a doctor and be sure to show
him or tell him the antidote printed on the label. Identify the
poison; then the doctor can act accordingly.

COMPATIBILITY

All materials mentioned herein are compatible with fungi-
cides and nutrients commonly used on strawberries. Do not
use with any alkaline materials such as hydrated lime.

INTERVAL BETWEEN INSECTICIDE APPLICATION
AND HARVEST

Wait 3 days after parathion application and 1 day after mal-
athion before harvesting again, and wash the berries before
packing. Wait 2 days after applying Kelthane before harvest-
ing fruit. The safe intervals between application and harvest
for the other materials have not yet been established.

ACKNOWLEDGMENT
Figs. 13, 21, 22 courtesy Lewis Maxwell.









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AGRICULTURAL EXPERIMENT STATION
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CONTENTS Page D ISEASES -............ ---.. ........-. ........ ...... .................. 3 Anthracnose ..--.......-------------........ --......------.......--.. 3 Rhizoctonia diseases ..-..----........ ..-------...-..--.-..-..-........------.....--4 Bud Rot ........----------........... .-------............. 5 Root Rot .....---------.. .......----........ .----...... 6 W eb Blight ...... ......------.......----.. --. .---.............. 6 Vein Infection ....--.----.--------...... .-----------------.. 6 Leaf Spot Diseases ......------..............----...----------....-6 Common Leaf Spot ---....--.. ...-----.-......-----..--..-6 Leaf Scorch ...........---------.........-----.. --... --........-..-7 Leaf Blight .......--..... -----......---..-..--...----..... 7 Fruit Rots -..-..-....---......---....-------------.. ...........-8 Leaks or Whiskers ............-----------.... .....-----.. ...--.. 8 Gray Mold or Brown Rot ...... ...------........ .. .....-------.. 8 Hard Brown Rot ---------......---..--........-.-------.-..-10 Light Tan Rot .--------....... -----..... ....--....-----.......... 10 Virus Infection .-.--------.......--...---......---------------. 10 Black Root .---..... .......----.............. ------..........-11 Sclerotium R ot .-...-... .... ..............--------------------------------------11 NEMATODES ....-....--.......--.. ............ ----....----... -----......-...12 Bud Nematode .............. ---..-----... ----...... ... 12 Sting Nematode ....................-----------..-------....... 13 Root-knot Nematode .-----....----..............--------....... 14 INSECTS AND SPIDER MITES ...........-----------------------..... ... ........ 16 Pests of Major Importance .............. .................. ...... ... .----16 Spider Mites ..---...---.. ....... ...... .. ......-------...... 16 Wireworms .-......-..... .......-----.... .......---------.... 19 Lesser Cornstalk Borer ....---......-----.....------..-------... 22 Pameras ....------.........---........-..........----------... 25 Mole-crickets ..............................--------------..... ---26 Florida Flower Thrips ..---........-----......--------------. 27 Cutworms and Armyworms .----........---....---.......--.. ----28 Insects of Lesser Importance ....-..........----..---.-----..... ....-.. --28 Crickets .-..---. ............... -------.......----.----.... .--....-. --..... .... 28 Strawberry Flea Beetle ......------....-....------..... .. ------------28 Strawberry Leaf Roller ..........-------.....--....-----.............-----29 Root Worms ---....... --..... .......------........------29 Grasshoppers ...............-------------..-------....-----29 Ants .....--....-.....-----------------...........--..... ..... 29 Root Aphids ............... ....-----..... ... ........-.--.-31 W hite Grubs .-... .-----............... ---. .-----............... 31 Slugs and Snails .........----........----......... --------....33 Citrus Root W eevil .................. ...................................... 33 Time of Application of Insecticides ...------......-...-----..---------. 34 Precautions .-.......-................ -............. -...-. ---..... ........... 35 Com patibilities ................. ---.......-................. .-...............-............... 35 Interval Between Insecticide Application and Harvest --..............---35 February 1961



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22 Florida Agricultural Experiment Stations Make the first application after plants start growing and the second when the berries form. This may be a 5 percent dust at 20 pounds per acre, a spray using wettable powder at 1 pound active ingredient per acre or 5 percent granules at 20 pounds per acre in bands placed on both sides of the plant. Do not use the emulsion concentrate because it may injure the plants. When berries form, apply only the 5 percent granular material directly to the plant and around it. The nature of the granular material permits it to roll off the fruit so that there can be no residue problem. The presence of the granule on the leaf or plant will not have any effect on the residue that might be on the fruit. 2. Aldrin Treatment.-This material, similar to chlordane, is also used by many growers. It has been effective against wireworm in other parts of Florida and in general throughout the eastern United States. However, results have been erratic in tests at Bradenton. For this reason aldrin is not listed as a favorable control. It should be used at the rate of 4 or 5 pounds active ingredient per acre. Formulations are a 2-pounds-per-gallon emulsion concentrate, and 2 gallons per acre are required for a 4-pound active ingredient application. The 25 percent wettable requires 16 pounds. Fertilizer and insecticide formulations are custom mixtures, so make application as quickly as possible because fertilizer mixtures tend to break down the insecticides and the insecticides become ineffective. Use all of your mixture. LESSER CORNSTALK BORER The lesser cornstalk borer, Elasmopalpus lignosellus (Zell.), at times is a serious pest of strawberry plants and fruits. It is found throughout Florida feeding upon various cultivated crops such as corn, Southernpeas, pepper, strawberries, beans, sugarcane and gladiolus. There are several wild host plants, of which a preferred 1 appears to be nutgrass. Wilting of the younger leaves of a plant is usually the first indication of its presence. A carefully dug and lifted plant will reveal a silken tube connected with the entrance hole at the base of the injured seedling (Fig. 11). This silken tube covered with sand and excrement may easily be mistaken for a root of the plant. If this tube is torn open, the slender, extremely active bluish-green larva about 2/3 inch long marked with dark-brown longitudinal bands is exposed. The larva is very active and jumps like a piece of spring wire. The larva does not remain in



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Insects and Diseases Affecting Strawberries 23 its burrow except for feeding. The remainder of the time is spent in the silken tube. -. Fig. 11.-Lesser corn stalk borer larvae (slightly enlarged). Larvae not only burrow into a plant but can tunnel any place along the runner, which will kill the young plant if it has not rooted. Mature larvae construct a silken cocoon covered with sand and excrement and transform to pupae. The moths emerge in from 1 to 3 weeks, depending upon weather. There are several generations a year. Plants are damaged by the larva boring into the stem just above or beneath the surface of the soil and encircling the plant at the fleshy part, causing the newly set plant to wilt and die. If the plant is not killed, it is left in a stunted, deformed condition incapable of producing berries. Lesser cornstalk borer damage to the fruit consists of the larva's boring into the ripened fruit (Figs. 10, 12). Control.-Control measures are of no value to a stricken plant but will protect the remaining plants. Where wireworm



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20 Florida Agricultural Experiment Stations ing into the ripened fruit (Fig. 9). Damage is due not only to the actual hole bored into the fruit but also to rot organisms which enter and hasten the decomposition of the berries (Fig. 10). This damage is particularly noticeable when the berries are processed as fresh chilled fruit. The larvae fall to the bottom of the container. Worse yet is for the consumer to find the larvae entirely within the fruit without its presence being noticeable from the outside. Fig. 9.-Larva of wireworm on strawberry fruit. Control.-Clean culture, crop rotation and thorough cultivation are helpful practices, but these alone are far from satisfactory. Chemical control must be used. Chemical control will be divided into 2 sections; control of the wireworm in the soil and later control of the wireworm in the fruit. For control of the wireworm in the soil, the following methods are useful:



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Insects and Diseases Affecting Strawberries 25 the fruit has formed, use only chlordane granular formulation because of the residue problem. PAMERAS Three species have been recorded in Florida, but Pachybrachius bilobata (Say) is the m o s t prevalent /(Fig. 13). Pameras \ belong to the chinch bug family. The young resemble small I yellow ants in size and color but are much more rapid in their movements. The S. " \· " adults have dark-colored wings. They breed so rapidly and are so inconspicuous in color, size and habits that they often become very abundant before they are noticed. Pameras cause ""buttons"-berries in the early stage of development that cease to grow and become Fig. 13.-Pamera. hard, dry and brown. The outer leaves of the plant die first and dry up, turning a brownish color. If these leaves are disturbed, the pameras scatter in all directions. Later the insects attack the crown of the plant, which withers rapidly and dies if the insects are numerous. They are prevalent in late spring but sometimes occur as early as late November and December. Damage from pameras has increased since there is less hand work around the plant. The individual attention given to each plant disturbed the hiding places of the insect by loosening the leaves that had stuck to the soil, thereby facilitating insect control. Upright growing plants have less leaf area against the soil, hence control is easier.



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Insects and Diseases Affecting Strawberries 13 Under favorable moisture conditions, both soil and atmospheric, they are able to enter plant buds and produce the crimp disease. Fig. 6.-Frenchbud, showing crimping of young leaves. Land known to be infested with the nematodes should not be used for plant production until it has been fumigated with an effective nematocide. Land to be treated should be located where it will not receive drainage from infested soil. Plants used for setting in treated land should be free of nematodes. STING NEMATODE This nematode, Belonolaimus longicaudatus Rau, is an external root parasite. It does not enter the roots but feeds from the outside by means of a stylet through which it sucks the juices from the tissues of the very small roots and root tips. This causes the death of these roots with the result that the affected plants soon have no feeder roots, only brushes of coarse roots. Such plants do not put out further growth. They may remain semi-dormant for prolonged periods or may gradually decline and finally die. In the field these infested plants usually form circular to ovalshaped areas which appear to increase in size as the season ad-



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Insects and Diseases Affecting Strawberries 9 importance in the field, where it attacks strawberries in all stages of development from blossom-stage to fully-ripe. At such times a high percentage of the fruit is covered with "gray mold" and has to be discarded. --a r Fig. 5.-"Whiskers" or "leaks". Under less severe conditions the fruit may be spotted. These spots are at first light brown, later dark brown in color. The flesh may become slightly soft at first, then hard and dry; never "leaky." There is no distinct line of demarcation between diseased and healthy tissue. Under moist conditions the infected fruit becomes covered with "gray mold," which is the spore-bearing stage of the fungus. Since this disease is spread from fruit to fruit by wind-blown spores, plastic film bed mulch will not keep it under control. It is necessary to follow a regular spray program.



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Insects and Diseases Affecting Strawberries 19 per 100 gallons of water or a 2 percent dust with a sulfur carrier. Parathion has been approved for use with 3 days as the minimum between last application and harvest. If berries are picked on Friday, follow immediately after picking with the spraying or dust and by Monday, when the picking crews are in the field again, all parathion residues will be at the minimum. WIREWORMS For years strawberry growers have been aware of the destruction caused by wireworms. Before the advent of the new insecticides and soil fumigants, part of the crop in some years was lost because of wireworm. Most of this damage was due to injury to the plants. Wireworms were probably the "drill worms" found in the fruit in past years. Wireworms are smooth, round and shiny and vary in color from pale yellow to dark brown (Fig. 8). This particular species is approximately 1/3 inch long. Wireworms are classed as soil-inhabiting insects but are found infesting berries. Fig. 8.-Larvae of wireworm that enter strawberry fruits. Conoderus falli Lane belongs to the click beetle family. The adult is from 1/4 to 3/8 inch long and brown to black in color. The adults are attracted to light. Judging from the numbers taken at a light trap, July is the month of peak emergence. Little is known of this species' history in Florida, but the larvae are usually numerous at setting time. There is another beetle emergence in October and the larvae from this generation bore into the fruit when it matures. Wireworm damage results from the larvae boring into the thickened portion of the plant and causing a severe stunting or death. Wireworm damage to the fruit consists of the larvae bor-



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34 Florida Agricultural Experiment Stations 22). The larvae and pupae develop inside the crown of the plant, usually below the soil surface. Control.-The control measures used against wireworms should prevent damage by these weevils. TIME OF APPLICATION OF INSECTICIDES The grower is given his choice of preventing a build-up in population by applying insecticides on a schedule or of using insecticides for control only when needed, as determined by careful inspection of the plants. Do not dust when plants are wet, since a foliage burn may result, especially when heavy deposits remain on the plant. It is better to dust in late afternoon and evening when plants are dry. Apply immediately after harvesting the berries, to allow a 2to 3-day interval between treatment and harvest. Sprays should be applied after the plants have dried to prevent excessive run-off of the spray material. These recommendations apply to Kelthane, parathion, malathion and chlordane granules where fruit is involved. At present, none of the other insecticides or miticides mentioned may be used during the harvesting season because of residue problems. However, they may be safely used up to the time of fruit set. Fig. 22.-Larva of citrus root weevil and its damage. 2A



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26 Florida Agricultural Experiment Stations Control.-Pameras are controlled by dusts, granules and sprays. On plants not fruiting apply 10 percent DDT at the rate of 20 pounds per acre if single row or 35 pounds for a double row. If DDT spray is preferred, use at 1 pound active per acre to 100 gallons of water. On fruiting plants use parathion or malathion. Parathion 15W applied at 11/ pounds in 100 gallons of water has been an effective control. A 2 percent parathion dust also has proven effective. Malathion 5 percent dust or spray applied as 1 pound active per 100 gallons per acre is also effective. Two treatments spaced 10 days apart have generally given satisfactory control. It is generally windy when dusting is required for insect control and for this reason a spray is preferred. Fig. 14.-The most widespread and destructive mole-crickets. Left, changa (Scapteriscus vicinus Scudd.); right, Southern mole-cricket (S. acletus R. & H.). MOLE-CRICKETS The Southern mole-cricket, Scapteriscus acletus R. & H., and the Puerto Rican mole-cricket or changa, S. vicinus Scudd., quite often cause considerable damage to strawberry plants (Fig. 14). They are most destructive in the field in the fall. They can also be destructive in nurseries. They affect the plant by destruction of roots and drying out of soil (Fig. 15). Control.-Control measures used for wireworms are effective against mole-crickets. If control measures are for mole-crickets,



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Insects and Diseases Affecting Strawberries 15 There are several methods which can be used to reduce the number of root-knot nematodes in the soil. Some treatments may even eliminate most of them. In all cases after soil has been so treated it should not be set with plants which are themselves infested with nematodes. Fig. 7.-Root-knot as it appears on strawberries. One of the most economical methods for reducing the nematode population is by the use of a resistant crop. Velvet beans, crotalaria and hairy indigo are best for this purpose. Drill the seed in rows 2 feet apart and cultivate the crop as long as possible to keep down growth of weeds which may be host plants. The nematodes die of starvation because they have no suitable plant roots upon which to feed. Good results can be obtained by fumigating the soil with the fumigants D-D, ethylene dibromide or Nemagon. All soils to be treated should be well prepared and free of trash. At time of treatment, soils should be at optimum moisture, neither too wet nor too dry. Unless heavy rains ensue after treatment, the



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8 Florida Agricultural Experiment Stations spots may occur on a leaflet. The young spots are circular and reddish purple. The older spots become zonated. The central zone is dark brown, surrounded by a lighter brown zone which in turn is bordered by a purplish zone which blends into the normal green of the leaf. Mature spots may be circular, oval or even V-shaped (Fig. 1). Small black dots, fruiting structures of the fungus, appear in the central, dark brown zones of mature spots. FRUIT ROTS LEAKS OR WHISKERS This rot, caused by the fungus Rhizopus nigricans Ehrenb. ex Fr., is of most importance during the transportation and marketing of strawberries, although it may also be found in the field. It develops most rapidly under conditions of high temperature and moisture. The fungus readily attacks fruit that has been injured and causes a collapse of the tissues and rapid loss of fruit juice, which accumulates in the bottom of the container and drips out, thus giving rise to the common name "leaks." The fruit settles down until it fills about half the container. A loose cottony growth of fungus appears over the surface of the fruit. This is the "whiskers" stage (Fig. 5). This growth may hold the fruit together so firmly that when the container is inverted the fruit falls out in a solid block. Black dots appear scattered throughout the cottony mass. These dots are the spore-bearing structures of the fungus. During picking, preparing and transporting, fruit should always be handled carefully to avoid bruising. Frequent changing of water used in washing fruit will greatly reduce the source of infectious material. Since high temperatures favor the development of this rot, fruit should be picked during the morning and protected at all times from the sun. When the fruit reaches market, the buyer should rapidly cool the fruit to a temperature of 35 to 40 degrees before shipping it north by air, rail or truck. Fruit thus handled will not develop this type of fruit rot. GRAY MOLD OR BROWN ROT This rot, caused by the fungus Botrytis cinere-a Pers., occurs both in the field and during transportation of fruit. During prolonged periods of cool, wet weather this rot may become of prime



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10 Florida Agricultural Experiment Stations During the past several years experiments and experiences of growers have shown that this rot can be controlled by the use of captan sprays. Applications are made at 10-day intervals from fall-setting of plants to blossoming time, and thereafter at 7-day intervals during the fruiting period. Use captan 50 percent W.P. at the rate of 2 to 4 pounds per 100 gallons. In preparing fruit for market all fruit infected with this rot should be discarded because Botrytis will develop slowly, even at temperatures of 35 to 40 degrees. HARD BROWN ROT The fungus which causes this rot of strawberry fruit is the same 1 causing bud-rot in plants, Rhizoctonia solani. The fungus produces no spores and hence cannot be spread from plant to plant by air currents. The fungus grows in the soil and attacks the fruit on the side in contact with the soil. Fruit in all stages of maturity may be attacked. The infected spots are light tan unless soil has become enmeshed in the fungal growth. In this case the spots are of the same color as the soil adhering to them. The line of demarcation between the tan-colored diseased tissue and the pink healthy tissue is so sharp that the diseased tissue can be cut away and the remainder of the fruit will be edible. Plastic film bed mulch will keep the fruit from coming in contact with the soil and hence prevent infection by Rhizoctonia. LIGHT TAN ROT This fruit rot, the least important of the 4 rots in Florida, is caused by the fungus Pezizella lythri Shear and Dodge, and is easily distinguishable from the other rots. The spots produced on the fruit are small, sunken and tan. They increase but slowly in size. The infected tissue is a coneshaped core which, due to its corky texture and to the disintegration of the cells adjoining, can be removed intact from the sound tissue. VIRUS INFECTION It is only within the past 15 years that the seriousness of virus infection in strawberry plants in the eastern United States has been recognized. It has been found to be present in most varieties grown in the area. There are no definite leaf symptoms of virus infection displayed in strawberry plants as is the case



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Insects and Diseases Affecting Strawberries 11 with most vegetable varieties. Infected strawberry plants make poor plant growth and runner production and produce low yields of fruit. The Missionary variety of strawberry became infected with viruses, with the result that yields of fruit were so low that growers said the variety was "running out." The United States Department of Agriculture has established a virus-free line of Missionary. As yet, virus infection has not been found in plants of the Florida Ninety variety. Plant lines which have been maintained in Florida stay clean bcause the insects which transmit virus diseases of strawberry are never numerous in the plant-growing areas of the State. BLACK ROOT Black root is not typically an injury. The condition probably is physiological, occurring on older plants. The root cortex or bark may become dark brown to black. This dark colored cortex readily peels off, showing that the central cylinder is still white and alive. Such roots can put out new lateral roots and under favorable growing conditions will support a vigorously growing plant which will put on a good crop of fruit. Black root occurs mainly on older plants in the nursery beds. Two or 3 weeks before such plants are to be set in the field, loosen the soil around them with a potato fork or pitchfork. This helps to aerate the soil so that old black roots will put out new laterals, and within 2 or 3 weeks plants will be in much better condition for setting in the field. SCLEROTIUM ROT This rot is caused by a soil-inhabiting fungus, Sclerotium rolfsii Sacc., which develops most rapidly during hot, moist weather. For this reason, the disease is found mainly during the summer months on plants in nursery fields, especially in lower, wetter portions of these fields. The fungus grows through the soil and attacks plants at the soil line. From there it progresses upward into the fleshy part of the plants and also downward into the roots. Complete death of plants may be quite sudden. Under conditions of high humidity and moist soil a white mat of compressed cottony growth of the fungus may be found around the base of the plant. Small round bodies, sclerotia, which are white at first and later dark brown appear scattered over the surface of the white mat. These sclerotia, about



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Insects and Diseases Affecting Strawberries A. N. BROOKS 1 AND E. G. KELSHEIMER 2 Use of trade names in this publication is solely to provide specific information. It does not constitute a guarantee or warranty of the products named and does not signify that they are approved to the exclusion of others of suitable composition. DISEASES In the strawberry-growing areas of Florida there are several important diseases. These will be described in detail according to the time of year or weather conditions favoring their development. During the production of runner plants, especially in the summer period of abundant rainfall and high temperatures, a fungus disease, anthracnose, causes a spotting and girdling of runners and leaf stems and also a dry rot of the fleshy part of the plants. During this same period any 1 of several soil-infesting fungi may attack the plants and cause soft rots. Several different species of nematodes may attack the roots and 1 attacks the buds of plants. During the fruiting season common leaf spot may appear on leaves and gray mold on blossoms and on green and ripe fruit. ANTHRACNOSE This disease, which is most important in nursery beds, is caused by the fungus Colletotrichum fragariae Brooks. The fungus causes a spotting and girdling of runners and leaf stems. It can grow from these parts into the fleshy part of the plant. There it produces a dryrot which results in a wilting of the affected plant. The disease is most destructive during periods of high temperatures and abundant rainfall. Runner spots are dark brown to black and definitely sunken, with a rather sharp line of demarcation between healthy and diseased tissue (Fig. 2). This distinguishes them from similar spots on runners caused by sand burn during periods of hot, dry weather. Sand burn spots are lighter brown and sunken. Furthermore, the black spots caused by the fungus can be definitely identified by examining them under a 6X hand lens. Such spots are covered with tufts of SPlant Pathologist in Charge, Strawberry Laboratory, Plant City. 2Entomologist, Gulf Coast Experiment Station, Bradenton.



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Insects and Diseases Affecting Strawberries 27 without consideration of other insects, apply chlordane as a spray, using 21/2 pounds of 40 percent wettable powder in 100 gallons of water per acre. A dust mixture of 5 percent chlordane in a dusting sulfur base has proven very effective. Apply the dust at the rate of 15 pounds per acre for a single row or 20 to 25 pounds per acre for a double row. Chlordane is also used in a bait made from a feed base containing mostly wheat products, to which enough chlordane is added to 100 pounds of bait to make a 2 percent product. To make your own bait, use 4 pounds of a 50 percent chlordane or 5 pounds of 40 percent chlordane in 100 pounds of wheat feed. Apply the bait only to soil that has been moistened. Bait should be fresh and used at once. Apply bait in the late afternoon. If mole-crickets are a problem after the berries have set, use 5 percent granular chlordane. FLORIDA FLOWER THRIPS This sucking insect, Frankliniella cephalica (Crawford), is minute, soft-bodied, yellowish and quite active. The insects sometimes are found in considerable numbers in blossoms, where Fig. 15.-Mole-cricket "runs" on newly graded yard.



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24 Florida Agricultural Experiment Stations control has been practiced, little damage should result from the lesser cornstalk borer. At least 2 applications of chlordane at the same rate as for wireworms should be made from the time the plants are set until the berries first set. The spray boom should be within 12 to 18 inches of the ground and the spray rig driven so that a sufficient amount of coarse spray is directed toward the ground where it will do the most good and wet the ground with the spray. Pressure should not exceed 200 pounds. Fig. 12.-Larva of lesser cornstalk borer and its damage to strawberry fruit. Fertilizer mixtures containing insecticides are of little benefit against this pest because the material is normally placed in the soil too deep to be effective against surface insects. After



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Insects and Diseases Affecting Strawberries 31 Control.-Apply 5 percent chlordane dust or 5 percent granular chlordane. ROOT APHIDS Aphis forbesi Weed, the strawberry root aphid, damages strawberry plants by sucking the plant juice from the roots. They are a very minor pest. Control.-Same as for ants. Fig. 18.-Snails, Polygyra septemvolva Say (natural size). WHITE GRUBS White grubs are the larvae of May beetles. They are thickbodied, dirty-white, approximately 1 to 11/2 inch long when full grown. They are always in a curved position. Larvae damage the plant by cutting off the roots, frequently below the crown (Fig. 16). Damage usually is most severe on new ground recently cleared of a heavy stand of saw palmetto, Serenoa repens.



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Insects and Diseases Affecting Strawberries 21 1. Chlordane Treatment.-Apply 5 pounds of active chlordane either emulsion concentrate, wettable powder or granules. Chlordane as an emulsion has 72 to 78 percent active chlordane or 8 pounds active ingredient per gallon. Each pint contains 1 pound, so 5 pints per acre sprayed broadcast or in the row should be applied. Granules are formulated at 5 or 10 percent, and 100 pounds of the 5 percent is equivalent to 5 pounds active ingredient. Wettable powder is usually formulated as a 40 percent product, so 121/2 pounds are required for 5 pounds of active ingredient. Chlordane may be applied with the fertilizer. Regardless of formulation, these materials are applied to the soil surface and disked in as deeply as possible. Setting may commence at once, but a short wait of 2 or 3 days between treatment and setting is preferred because insect activity, stirred up by the chlordane, will have ceased by this time. This same application controls mole-crickets, earwigs, ants, grubs, cutworms and armyworms that might be in the soil. Fig. 10.-Damage to strawberry fruits by wireworm and lesser cornstalk borer. *~^^~



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Insects and Diseases Affecting Strawberries 33 Grub damage seldom, if ever, occurs on land that has been in cultivation except with certain home gardens that are near electric lights. The beetles or adults of the white grub are attracted to lights and heavy infestation occurs in the vicinity of the lights. Control.-Chlordane applied at the same rate as for wireworm control is effective against this pest. SLUGS AND SNAILS Home gardeners are especially plagued with these pests that attack the strawberry fruit and eat out large portions (Figs. 17, 18). Heavy mulching makes a favorite hiding place for these pests. They feed late in the afternoon or in the evening. Control.-Chemicals that control slugs and snails are too poisonous to humans to be used on strawberries, so hand picking and sanitation are the only methods recommended. Fig. 21.-Adult of citrus root weevil (X2). CITRUS ROOT WEEVIL The larvae of the citrus root weevil, Pachnaeus litus (Germar), severely damage strawberry plantings in Dade County. First observed in 1926 (Figs. 19, 20), it was then called the crown borer. The adult is a greenish-blue snout beetle from 1/3 to 1/2 inch long (Fig. 21). The larvae are large, white, fat grubs. The chief damage is caused by the larvae which tunnel through the strawberry crown and kill or stunt the plants (Fig.



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Insects and Diseases Affecting Strawberries 7 and if extremely numerous cause death of the leaflet. If many leaflets die, the plant itself may be killed. Florida Ninety is susceptible to this disease, Missionary is resistant. LEAF SCORCH This leaf spot is caused by the fungus Diplocarpon earliana (Ell. and Ev.) Wolf. The young spots appear on the upper surfaces of the leaves as small purplish discolorations which rapidly enlarge into irregular p u r p 1 i s h blotches from 1/16 to 3/16 inch in diameter. In Fig. 3.-Common leaf spot on strawberries. these spots are very small black, glistening bodies which are the fruiting structures of the fungus (Fig. 4). The spots on each leaflet may become so numerous that they coalesce and give a dark reddish cast to the entire leaflet. In severe cases of infection t h e edges of the leaflets curl upward and the leaf tissue dies and dries to a tan color, progressively from edge to midrib, giving the plant a scorched appearance. LEAF BLIGHT This leaf spot is caused by the fungus Dendrophoma obscurans (Ell. and ras (E. and Fig. 4.-Leaf-scorch. Ev.) Anderson. The young spots of this disease are larger than the mature spots of either common leaf spot or leaf scorch. From 1 to 5



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Insects and Diseases Affecting Strawberries 5 BUD ROT The fungus which causes this disease, Rhizoctonia solani Kuhn, is quite prevalent in the soils of Florida and causes diseases in many species of plant. It can attack any part of the strawberry plant in contact with the surface of the soil, or it can grow superficially over the plant surface and attack leaf buds and flower buds. It is this latter phase that will be described here. As yet, it has not been found attacking roots. When strawberry plants with single-bud crowns are attacked by the fungus, the bud is killed by dry-rot and may be pulled easily from the remainder of the plant. The older leaves may or may not be attacked. If attacked, they become dry-rotted at the bases of the leaf stems, weakening the support of the leaves and causing them to lie flat on the soil. In this position the leaves may continue to grow and live out their normal span of life. Death of the main bud results in death to the plant unless lateral buds subsequently develop and are not themselves attacked by the fungus. When large plants with many buds in the crown are attacked, the disease may go unnoticed for some time because diseased buds are hidden by abundant foliage. Later, the disease will be noticed when the lack of new vegetative growth and lack of fruit production become apparent. The fungus attacks not only leaf buds but also flower buds. It attacks the buds in any stage of development from the early forms to open blossoms. When the early forms are attacked, the buds develop dry-rot and die. When open or nearly opened blossoms are attacked, the petals remain white but the centers become black, similar in appearance to frosted blossoms. Bud rot is usually more prevalent during the winter months, when air temperature is below 75 degrees and humidity is high. The disease is favored by foggy weather and heavy dews, which may keep the plants covered with moisture for long periods. Large plants and plants set too closely together on the bed tend to hold a moist atmosphere around the buds and thus favor the disease. Moist soil surfaces favor the growth of the fungus from plant to plant. This is especially true where the beds are covered with mulch of any kind, such as straw, shavings or plastic film. Control.-To control the disease it is necessary to make the environment as unfavorable as possible for the development



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;., .:: , -. T.. .. , e,.. .4£ i 1... i..: -.-.> .'.i:?r~i~:.,. -.I. ..-"-.. .. , A ' ..m,, ,I w,L,, , -. ---·...,4C W "-.i..i,. ._.,A -.k .AN ,., . ' -r4 -~s~ -9k : ' .-..k Fig. 19.-A strawberry field heavily damaged by citrus root weevil. Fig. 20.-Close-up view of plants damaged by citrus root weevil. '~~~~~~ , " '..",, ' .* ,,. ,,. I 'V ' ..., -.1 .;.' 47 ..' ,.4 ', , -., '



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16 Florida Agricultural Experiment Stations land can be bedded 2 weeks from treating time and strawberry plants set. Each grower can treat his land himself by the row method or bed method. Costs for this method are quite low. Full details concerning this method can be obtained from County Agricultural Agents, Florida Agricultural Experiment Stations or several of the agricultural supply companies. INSECTS AND SPIDER MITES Insects and spider mites cause considerable damage to those fields set to strawberry plants for fruit production. Insects are of less importance in strawberry nurseries. The pests are listed in the order of their importance. The first 7 should always be considered as an annual menace to the strawberry grower. PESTS OF MAJOR IMPORTANCE SPIDER MITES The problem of identifying infested plants in the field is of primary importance. Symptoms of mite infestation become so pronounced that it is hard to believe that so few mites present could be responsible for the condition of the plant. Severe injury consists of dwarfing and stunting of the plants. Medium injury is characterized by wrinkled leaves and reduced plant growth and yield. Slight injury causes a slight wrinkling of the leaves and irregular folds of the leaf margins. Plants in the field may turn brown or brownish red, but this condition cannot be entirely attributed to mites because other factors could cause these same symptoms. Of the plant-feeding mites, the Tetranychidae or spider mites are most widespread and most important economically. There is hardly a plant that is not attacked by at least 1 species, and all species apepar to be pests. Mites are distributed by birds, wind and man. They may be carried on clothing from 1 plant to another. Strawberry varieties differ in their susceptibility. Missionary is quite susceptible to mite attack and Florida Ninety to a lesser degree. None are immune. The degree of susceptibility seems to be associated with the plant's growth habit. An upright variety, as Florida Ninety, with a fairly smooth lower leaf surface is more resistant to mites than low-growing varieties having leaves flat on the



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Insects and Diseases Affecting Strawberries 17 ground. Missionary, for example, is a prostrate variety with lower leaves lying against the soil, making an ideal place for mite infestation and making it very difficult for control measures to be effective. The Northern or green 2-spotted mite, Tetranychus telarius (L.), and the Southern lobed mite, T. lobosus Boudreaux, are 2 common species. T. lobosus is referred to as the red spider mite. These mites are found on many weeds, so infestation is simple. The 2-spotted mite is found on nightshade, pokeweed, hairy indigo, gladiolus and many other plants. Plants shipped in from Maryland, Tennessee, Arkansas and other localities in the North, even though arriving in a defoliated condition, may possibly harbor mites or eggs in the crown of the plant. These plants are set in the nurseries for next year's runners. T. lobosus has been seen on strawberries in the Plant City area for over 30 years. This species is readily controlled with dusting sulfur and, as a result of the rigorous control measures used against another species of mite, is difficult to find in any large populations. The green 2-spotted mite, first noticed in 1950 on eggplants and later on strawberries, is difficult to control with those measures successful against the red spider mite. Control.-Most strawberries are set in the field by the middle of October and, depending upon market and weather conditions, are plowed under some time in March or April. The plants are growing during the cooler portion of the year, and this makes an ideal condition for mite development. Growers who think that weather conditions are unfavorable for mites sometimes neglect to keep up their control program during cold weather, which allows the mites to increase in numbers to the point that every effort must be used to combat the pests. Plants injured by mites suffer a lasting damage and seldom recover their former vigorThe low soil temperature and cool nights that are ideal for mites make it difficult to obtain adequate control. The presence of 2 or more mite species may account for the failure of miticides to control all infestations. Dusting sulfur, for example, has always been effective against the red spider mite, but the appearance of another species may necessitate the use of other materials. Parathion 15W applied at 2 pounds to 100 gallons of water has been as effective under the same conditions as 2 percent dust. However, parathion failed to control heavy, established infestations. Parathion, too, is poisonous and should not be handled



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KEEP INFORMED ABOUT Florida's Agricultural Research 0 For You It Can Mean Better Yields of Crops and Animal Products, Improved Practices, Less Cost, More Income, Help in Fighting Plant and Animal Pests. * Read Sunshine State Agricultural RESEARCH REPORT Issued January, April, July and October It's Free-Just Write AGRICULTURAL EXPERIMENT STATION UNIVERSITY OF FLORIDA GAINESVILLE, FLORIDA



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Bulletin 629 UNIVERSITY OF FLORIDA AGRICULTURAL EXPERIMENT STATIONS J. R. BECKENBACH, Director GAINESVILLE, FLORIDA Insects and Diseases Affecting Strawberries A. N. BROOKS AND E. G. KELSHEIMER Fig. 1.-Strawberry leaf blight, showi ario t of lesi The leaflet at the top shows a typical fansh e dead ar, m Agr. Exp. Sta. Bul. 229.) I Single copies free to Florida resi t AGRICULTURAL EXPERIME O GAINESVILLE, FLORIDA



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30 Florida Agricultural Experiment Stations Fig. 16.-Severe injury to strawberry plant caused by white grub. ig. .-Slugs (natural sie). Fig. 17.-Slugs (natural size).



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12 Florida Agricultural Experiment Stations the size of strawberry seed, are most easily seen on diseased leaf-stems. The fungus can attack most of the cultivated crops and weeds in central Florida. However, infection is seldom widespread. Even in individual fields it is quite localized. Control of this disease has been accomplished by the use of pentachloronitrobenzene 3 as a spray at the rate of 10 pounds per 100 gallons. Only the diseased areas in the field are sprayed to kill the fungus, since this fungicide is quite toxic to strawberry plants if it remains in contact with the aboveground parts of the plants. NEMATODES Three species of nematodes attack strawberry plants. The root-knot nematode and sting nematode attack the roots. The bud nematode infects buds and produces the disease known as crimp or Frenchbud. BUD NEMATODE This nematode, Aphelenchoides besseyi (Ritzena Bos) Christie, does not actually get into the bud tissue. Instead it inhabits the air spaces in the leaf buds and runner buds. It feeds by puncturing the young tissues and sucking out the plant juices by means of a stylet or tube. The saliva which it injects into these young growing parts causes them to develop abnormally. The young leaves are crimped, crinkled, darker green in color, with reddish coloration on edges and veins (Fig. 6). The leaf area may be greatly reduced; in some cases not much more than mid-ribs develop. Plants infested with this nematode are practically worthless for fruit production. The nematodes are most active during late spring to early fall, when temperatures are well above 75 degrees. At the lower temperatures occurring during late fall and winter the nematodes are so sluggish that infested plants put on some normal growth. Bud nematodes have been and still are spread from state to state in shipments of nursery plants. The same thing happens from field to field in local areas. Spread in individual fields is accomplished by the nematodes swimming in the soil moisture or being transported longer distances by heavy rains and flood waters. The nematodes can live in the soil for long periods. They feed on 1 or more species of fungi which are present in the soil. " Terraclor.



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18 Florida Agricultural Experiment Stations carelessly. However, it is a good insecticide and miticide and should be used where recommended. Malathion applied as a 5 percent dust or a spray of 1 pound active ingredient (4 pounds of 25 percent) per 100 gallons of water has proven effective under some conditions. There is a short residual, so a follow-up treatment must be made to kill newly hatched crawlers and adults missed in previous treatment. The most satisfactory control for mites has been 1,1-bis(4chlorophenyl) 2,2,2-trichloroethanol 5, a non-phosphatic material. This is formulated as an emulsion concentrate, an 18.5 percent wettable powder and in dusts. The wettable powder is used at 2 pounds to 100 gallons of water and as a 2 percent dust and to date has proven effective against all species of mites. Kelthane kills mites in the adult, larval and egg stages. Kelthane is relatively safe for workers. Control.-Once the plants are set in the seedbed area and leaf out, spray thoroughly with Kelthane wettable powder at the rate of 2 pounds to 100 gallons of water. Since varieties vary in susceptibility to mite injury, susceptible varieties should be separated from the others in the seedbed and receive frequent thorough sprayings. Repeat applications every week or 10 days until ready for planting in the field. If a grower does not spray as suggested above, he may try this procedure. Prior to setting plants in the seedbed, dip them in a Kelthane suspension made from the emulsion concentrate at 11/2 gallons to 100 gallons of water or 10 pounds of the wettable powder to 100 gallons of water. Captan 50W may be included at the rate of 2 pounds per 100 gallons to prevent the spread of disease fungi. Completely immerse and shake the plants in the liquid, remove and allow to drain into the same vat in which they were dipped. As soon as they have drained, set out in the field. Discard the liquid at the end of each day because of the accumulation of soil and debris from the immersed plants. After the plants are set in the field and have leafed out, they should be sprayed with Kelthane at the rate of 2 pounds to 100 gallons of water to control any mites not killed by dipping. Remember, 1 mite infested plant set in the field can cause much unnecessary spraying. If dusting is preferred, use a 2 percent Kelthane dust. Apply either dust or spray every 3 weeks. As soon as the buttons appear on the plants, cease spraying with Kelthane and use parathion wettable powder at 11/2 pounds S Kelthane.



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Insects and Diseases Affecting Strawberries 29 STRAWBERRY LEAF ROLLER The strawberry leaf roller, Ancylis comptana fragariae (W. & R.), is more prevalent in nursery plantings than in the field. The gradual change in color of the leaves from green to silver in a nursery may be the first indication that this pest is present. A heavy infestation results in many folded leaves with the color changing from green to silver because the lower sides of the leaves are exposed due to being webbed together. Later, as feeding continues, the leaves have a scorched appearance. The moth is about 1/4 inch long and 1/ inch wide, including wingspan. The adult is a light brown or rusty brown. The larvae are pale green at first, changing to grayish brown as they reach maturity, when they are approximately 1/ inch in length. The larvae pupate inside a folded leaf or leaves. A newly hatched larva feeds on either side of the leaf, eventually feeding on the upper surface after pulling the leaf or leaves together with silver threads to form an enclosure. The larvae feed upon the surface of the leaves, which causes the entire leaflet to turn brown and die. Newly formed leaves are often webbed together. Control.-Insects within a leaf enclosure are difficult to kill, but parathion applied for other insects often effectively controls many new infestations. Sometimes the parathion will drive the pests out of the folded leaves where they may be more easily controlled. DDT spray or dust is very effective if used when the insects first appear. The pest is seldom seen in commercial plantings, but may occur in home gardens when plants are set. ROOT WORMS The adult, Paria canella (Fab.), acts as a leaf beetle in the fall on early set plants. Nothing is known of its larval habits. Control.-Apply 10 percent DDT dust. GRASSHOPPERS The young nymphs are usually the most destructive. Control.-Apply 5 percent chlordane dust or 2 percent chlordane bait. ANTS Several species of ants damage plants by building mounds over the buds, causing them to rot. Ants carry aphids from plant to plant.



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6 Florida Agricultural Experiment Stations of the fungus. Frequent shallow cultivations around the plants will keep the soil surface dry. Wider spacing of plants on beds will give better air circulation and allow foliage and buds to dry more rapidly. Most fungicidal sprays are of little value in controlling rhizoctonia. One material is quite specific against the fungus, but is toxic to strawberry plants if allowed to remain on the plant. This material, pentachloronitrobenzene, can be used as a soil treatment to kill the fungus. Bud rot disease practically disappears when the weather changes from high humidity and relative calm to low humidity and more air movement. ROOT ROT This disease is caused by another species of Rhizoctonia and occurs in the summer in nursery fields. It attacks the roots but not the crowns of plants. WEB BLIGHT In this case the fungus, another species of Rhizoctonia, grows superficially over the lower surface of leaves and may cause death of some leaves. VEIN INFECTION The species of Rhizoctonia involved here infects the lower surfaces of main veins. This retards or stops growth in the infected area and causes the leaflets to curl downward. LEAF SPOT DISEASES There are 3 different leaf spot diseases of strawberry: common leaf spot, leaf scorch and leaf blight, the first being the most important. Copper spray applications at 7to 10-day intervals will control these diseases in the nursery field. The captan spray program to be outlined later for Botrytis rot control in the fruiting field will also control leaf spot diseases. COMMON LEAF SPOT This leaf spot is caused by the fungus Mycosphaerella fragariae (Tul.) Lindau. The spots are at first small, less than 1/8 inch in diameter and purplish red. They increase to a diameter of approximately 3/16 inch. The centers become white or gray (Fig. 3). The spots may number from 1 to many on each leaflet



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14 Florida Agricultural Experiment Stations vances. This increase in size is due not to migration of nematodes from plant to plant but rather to the build-up in population around each individual plant. The initial density of population of nematodes in these infested areas depends upon the type of cover crop growing there prior to preparation of land for strawberries. If crab-grass is the cover, the population of sting nematodes will be quite dense. Crabgrass roots favor the rapid multiplication of the nematode and are capable of supporting large populations, without having the grass show any signs of the nematodes being present. Sesbania also is favorable for the nematode but becomes stunted if too many are present on the roots. Velvet bean and hairy indigo are not good host plants for the nematode and should be used as cover crops for strawberry land. In the fruiting fields satisfactory control of the nematode can be obtained by in-the-row injection with D-D or ethylene dibromide at the rate of 1 pint to 150 lineal feet. This must be done at least 2 weeks before plants are set, as these materials are toxic to plants. For the nursery fields nematode control is best accomplished with 1,2-dibromo-3-chloropropane 4.Plants are set out and soil is treated after plants are well established. The entire bed is drenched with Nemagon at the rate of 2 gallons technical per acre. ROOT-KNOT NEMATODE The type of root injury caused by this nematode occurs on roots of many of the vegetable crops in the South grown during warm weather. On strawberries the disease is less severe. Fruiting plants are not much affected, mainly because during the fruiting season temperatures are comparatively low and the rootknot nematode somewhat dormant. The disease can become severe and cause considerable root injury and even death of plants during prolonged periods of drought and high temperature, especially if the plants are being grown on light, sandy soil. The microscopic eelworm or nematode, Meloidogyne sp., which causes root-knot is quite common in the soils of Southern states. It enters strawberry roots and causes galls 1/16 to 1/8 inch in diameter, much smaller than those formed on roots of vegetable crops (Fig. 7). These galls interfere with normal root function, such as absorption of nutrient solutions from the soil. Plants thus attacked become unthrifty and may eventually die. " Nemagon.



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4 Florida Agricultural Experiment Stations small black bristles which are part of the fungus, and which are readily distinguished from the lighter colored, large hairy structures of the strawberry runner. Control.-Since the disease occurs during the rainy season, it is most difficult to control and keep from spreading throughout the nursery. It is readily spread by wind-blown spores and also quite easily spread from nursery to nursery by man or "animal walking through a dis"eased nursery and then walking into a disease-free nursery. If the disease is noticed early, some benefit can be achieved by carefully removing the diseased plants and runners from the nursery and burning them. Careful removal and complete destruction are necessary so that the fungous spores attached to the diseased part of the plants may not be scattered to healthy plants. A spray program will, to a certain extent, keep the disease from spreading, except during prolonged rainy periods. Copper spray materials, if used with some good spreading and sticking agent, may be applied at weekly intervals or more Soften if necessary. All plant Sparts, especially runners, Fg. 2 r , s g should be covered by the spray. Fig. 2.-Anthracnose, showing typical lesions on runners. T h e fungicidal residue will stick to the plants and remain effective if it thoroughly dries before rain falls. RHIZOCTONIA DISEASES There are 4 distinct diseases caused by different species of the fungus Rhizoctonia. One disease, bud rot, occurs during the winter months. The other 3, root rot, web blight and vein infection, occur during late spring and summer.



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28 Florida Agricultural Experiment Stations they feed on stamens, pistils and young berries. When numerous they can cause blossom drop or the young berry may remain hard and brown and fail to grow. They usually are found in the field in the late spring after the picking season, but may infest blossoms. Control.-Nicotine is the most effective control for flower thrips. Dusts are very effective but the mixture must be fresh. Nicotine dusts should be applied when it is warm (above 600 F.) and quiet. These conditions are rarely present where needed, so nicotine sulfate applied as a spray at 1 pint of the 40 percent emulsion per 100 gallons of water is more satisfactory. In those areas where parathion is used, apply 1 pound of the 15 percent wettable per 100 gallons of water or else a 1.5 percent dust. Generally, 1 or at most 2 applications are all that is required after flowering has begun. CUTWORMS AND ARMYWORMS Several species of cutworms and armyworms attack strawberries but no attempt is made here to separate the species. Damage is caused by the larvae cutting off the young plants or leaves. They also feed on the berries, sometimes cutting the fruits from the plants. They are found in the field and in the nursery, especially in early fall. Control.-The control measures used against wireworms are effective against cutworms and armyworms. Again, if these pests appear when the fruit is set, use granular 5 percent chlordane. INSECTS OF LESSER IMPORTANCE CRICKETS Field crickets, Gryllus sp., in the past have been destructive but now are seldom seen since the new organic insecticides have been in use. Control.-Apply 5 percent chlordane, 10 percent DDT dust or 2 percent chlordane bait. STRAWBERRY FLEA BEETLE This flea beetle, Altica ignita (Illiger), is a bronze-colored insect about 1/5 inch long that damages strawberry leaves by eating round holes in them. They are most frequently found in the fall on early set plants. Control.-Apply 10 percent DDT dust as for others.



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Insects and Diseases Affecting Strawberries 35 PRECAUTIONS All insecticides are poisonous. Handle them with care and follow the directions and precautions on the container label. Always work on the windward side of the crop. Do not chew tobacco or smoke while handling parathion. Do not eat food without washing hands carefully with soap and water after handling parathion. Children and adult workers should not enter a parathion-treated field for 24 hours after application. Children working on hands and knees are in closer contact with the treated plants than adults who stoop or bend over to pick the fruit. After 24 hours there is no danger to the pickers. Store insecticides in closed containers out of reach of children and irresponsible persons. Use only fresh materials. Buy only amounts needed for 3 or 4 weeks. If you accidentally swallow an insecticide, induce vomiting by taking 1 tablespoonful of salt in a glass of warm water. Never give oil. Repeat if necessary. Call a doctor and be sure to show him or tell him the antidote printed on the label. Identify the poison; then the doctor can act accordingly. COMPATIBILITY All materials mentioned herein are compatible with fungicides and nutrients commonly used on strawberries. Do not use with any alkaline materials such as hydrated lime. INTERVAL BETWEEN INSECTICIDE APPLICATION AND HARVEST Wait 3 days after parathion application and 1 day after malathion before harvesting again, and wash the berries before packing. Wait 2 days after applying Kelthane before harvesting fruit. The safe intervals between application and harvest for the other materials have not yet been established. ACKNOWLEDGMENT Figs. 13, 21, 22 courtesy Lewis Maxwell.