Title: Strawberry diseases and insects
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 Material Information
Title: Strawberry diseases and insects
Alternate Title: Bulletin 98 ; Florida Agricultural Extension Service
Physical Description: Book
Language: English
Creator: Brooks, A. N.
Watson, J. R.
Publisher: Agricultural Extension Service, University of Florida
Publication Date: 1938
Copyright Date: 1938
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Bibliographic ID: UF00026367
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
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HISTORIC NOTE


The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
(EDIS)

site maintained by the Florida
Cooperative Extension Service.






Copyright 2005, Board of Trustees, University
of Florida








Bulletin 98


May, 1938


(A revision of Bulletin 63 in part)


COOPERATIVE EXTENSION WORK IN
AGRICULTURE AND HOME ECONOMICS
(Acts of May 8 and June 30, 1914)
Agricultural Extension Service, University of Florida
Florida State College for Women
And United States Department of Agriculture
Cooperating
Wilmon Newell, Director


Rerision of
o. (p3

MMf4'195a


STRAWBERRY DISEASES



AND INSECTS


By

A. N. BROOKS, Plant Pathologist

and

J. R. WATSON, Entomologist
Florida Agricultural Experiment Station


CONTENTS


Strawberry Diseases ...................... ....
Anthracnose ............................
Crim p ...................................... ..... .........
Root Troubles ......................... .......
Soil Injury ...... .............................
Fertilizer Burn ..................................
Root-Knot ............ ..........................
Leaf-Spot Diseases -..............................
Fruit Rots .......................................
Injurious Insects and Spiders ..................
Red Spiders .................................
Florida Flower Thrips ...........................


Pameras ........


Page
Cutworms .................................................... 24
Webworms ................................................ 25
The Leaf Roller ..................................... 26
Crown Borer .................... .................. 26
Mole-Crickets ........................................ 27
Crickets ............................................ .. 27
White Grubs ............................................ 28
Grasshoppers ....................................... ......... 28
Earwigs ....................................................... 28
Flea Beetles ................................................ 29
Cowpea Pod Weevil ............................... 29
Aphids .................................................... 29


................................ 23 Negro Bugs ...................................... ...... .. 30


Bulletins will be sent free to Florida residents upon request to
AGRICULTURAL EXTENSION SERVICE
GAINESVILLE, FLORIDA







BOARD OF CONTROL
R. P. TERRY, Acting Chairman, Miami
THOMAS W. BRYANT, Lakeland
W. M. PALMER, Ocala
H. P. ADAIR, Jacksonville
C. P. HELFENSTEIN, Like Oak
J. T. DIAMOND, Secretary, Tallahassee

STAFF, AGRICULTURAL EXTENSION SERVICE
JOHN J. TIGERT, M.A., LL.D., President of the University
WILMON NEWELL, D.Sc., Director
A. P. SPENCER, M.S., Vice-Director and County Agent Leader
J. FRANCIS COOPER, M.S.A., Editor
JEFFERSON THOMAS, Assistant Editor
CLYDE BEALE, A.B., Assistant Editor
E. F. STANTON, Supervisor, Egg-Laying Contest
RUBY NEWHALL, Administrative Manager

COOPERATIVE AGRICULTURAL DEMONSTRATION WORK
W. T. NETTLES, B.S., District Agent
H. G. CLAYTON, M.S.A., District Agent, Organization and Outlook Specialist
J. LEE SMITH, District Agent and Agronomist
R. S. DENNIS, B.S.A., Assistant District Agent
A. E. DUNSCOMBE, M.S., Assistant District Agent
R. W. BLACKLOCK, A.B., Boys' Club Agent
E. F. DEBUSK, B.S., Citriculturist
A. L. SHEALY, D.V.M., Animal Industrialist'
HAMLIN L. BROWN, B.S., Dairyman
N. R. MEHRHOF, M.AGR., Poultrymanl
D. F. SOWELL, M.S., Assistant Poultryman
WALTER J. SHEELY, B.S., Animal Husbandman
C. V. NOBLE, PH.D., Agricultural Economist'
D. E. TIMMONS, M.S.A., Agricultural Economist, Marketing
CHARLES M. HAMPSON, M.S., Agricultural Economist, Farm Management
R. H. HOWARD, M.S.A., Asst. Agr. Economist, Farm Management
GRAY MILEY, B.S.A., Asst. Agr. Economist, Farm Management
R. V. ALLISON, PH.D., Soil Conservationistl

COOPERATIVE HOME DEMONSTRATION WORK
MARY E. KEOWN, M.S., State Agent
LUCY BELLE SETTLE, M.A., District Agent
RUBY MCDAVID, District Agent
ETHYL HOLLOWAY, B.S.H.E., District Agent
ANNA MAE SIKES, B.S., Nutritionist
VIRGINIA P. MOORE, Home Improvement Agent
ISABELLE S. THURSBY, Economist in Food Conservation
CLARINE BELCHER, M.S., Clothing Specialist

NEGRO EXTENSION WORK
A. A. TURNER, Local District Agent
BEULAH SHUTE, Local District Agent

IPart-time.










STRAWBERRY DISEASES

AND INSECTS

A. N. BROOKS and J. R. WATSON
A discussion of strawberry culture is presented in Bulletin 97.
This bulletin deals with diseases and insects affecting straw-
berries in Florida.

STRAWBERRY DISEASES
Various plant diseases are present to a greater or lesser
extent in all strawberry-growing areas of Florida. Sometimes
the loss of plants incurred in individual fields may range as
high as 75 percent. Under favorable environmental conditions
it is possible that any one of the diseases now present in the
state may become widespread and cause considerable loss to
the strawberry industry. A means of minimizing this possi-
bility is for each grower to become familiar with the different
strawberry diseases and the known methods of combating
them.
ANTHRACNOSE
This disease is caused by a fungus, Colletotrichum fragariae,
which apparently is confined to Florida; at least it has not been
reported elsewhere. The common name anthracnose has been
applied because of its characteristic symptoms.
Parts attacked by anthracnose are runners, petioles or leaf
stems, and rhizomes or crowns, attacks being most common
upon runners. Greatest loss due to anthracnose is caused by
the disease girdling the runners and killing young runner plants
before they have rooted and become self-supporting. In some
cases it may even penetrate rhizomes of rooted plants and
cause them to wilt.
Anthracnose may appear to a limited extent during the spring
months, but is more destructive after the first part of August
and up to the time when all runner plants are removed from
the beds. The disease is more severe during warm, moist
weather and in the moister areas of the strawberry fields.
Symptoms:-A typical anthracnose spot as it appears upon
the runner is a small, oval, light brown, sunken area about 1/3
inch long when first noticeable, later gradually increasing in







Florida Cooperative Extension


size until it may extend the entire length of the runner and
girdle it (Fig. 1). The older portion of the spot becomes
shriveled and dark brown to black in color, and over its surface
are scattered groups of setae of the fungus which can be seen


under a strong hand lens as



i/






i

















Fig. 1.-Anthracnose, showing
typical lesions on runners.

"dwarf" disease in Louisiana


small bristle-like tufts. Spores,
by means of which the disease
is spread, are produced in great
abundance in acervuli which de-
velop in these spots.
Control:-Applications of 4-4-
50 bordeaux mixture spray at
10-day intervals during the lat-
ter part of July, August, and
September have been found to
keep anthracnose in check so
that healthy plants will be pro-
duced for fall setting.
CRIMP
This malady is the most wide-
spread of any of the major dis-
eases of strawberries in Florida,
being found in all of the areas
of the state where strawberries
are grown commercially.* It is
known to Florida growers as
French bud, white bud, brier
bud, red bud or crimp. The first-
two terms are misnomers be-
cause the diseased buds are not
white or chlorotic, while the
other three are descriptive of
the symptoms of the disease.
Crimp is identical with the
and may be the same as "red


plant" disease in Great Britain.
The loss of plants due to crimp is 0-75 percent in individual
fields and about 2 percent for the entire state.
The disease may appear at any time of the year when the
plants are actively putting on new growth, in the nursery beds

*Crimp-a nematode disease of strawberry. Fla. Agr. Exp. Sta. Bul.
235. 1931.







Strawberry Diseases and Insects


during spring and summer and in the fields set for fruit pro-
duction in the fall. Cold weather checks the progress of the
disease and sometimes causes a masking of the symptoms, but
as yet no case of true recovery from crimp has been observed.
Crimped plants are worthless as fruit producers, because what
fruit they do put on is late and of inferior quality.
Symptoms:-Crimp is fundamentally a bud disease, affecting
the young leaves as they develop. Affected plants, with but one
bud to the crown, have a flat, spread out, spider-like appearance,
due to a few normal leaves having developed before the disease
appeared. The de-
velopment of sub-
sequent leaves is
materially re-
duced. These
leaves are de-
formed and range
in size from mere
rudiments to al-
most normal.
The leaflets are
crimped or crin-
kled, cupped, and
narrow, with a
reddish cast to
the serrations,
main veins, and
petioles (Fig. 2).
In some cases the
petioles are less Fig. 2.-French bud, showing crimping of young
pubescent than leaves.
normal, in fact, almost smooth. The older diseased leaves have
a darker green color than normal, and both old and young leaves
are more brittle.
The disease may kill the main bud, with the subsequent death
of the plant unless lateral buds chance to develop. The latter,
in most cases, produce small, normal-shaped leaves on long,
spindly petioles. Plants with multi-bud crowns may have both
diseased and healthy buds, and also produce both healthy and
diseased runner plants. The usual thing, however, is for all
the runner plants of a diseased mother plant to show the
disease.






Florida Cooperative Extension


Causal Agent:-Examination of diseased and healthy plants
shows that a microscopic eelworm or nematode (Aphelenchoides
fragariae) is present in large numbers in diseased buds, from
50-1,300 per bud, but is not present in healthy buds. They occur
in protected spaces at the bases of young leaves and in the
fold of leaves in the bud. These nematodes are from 1/42 to
1/25 inch long and are colorless, and hence can be observed
only under a microscope. Experiments have proved that crimp
may be artificially produced by placing some of the nematodes
in the buds of healthy plants. The time required for the symp-
toms to appear varies from 11 to 120 days, depending upon
temperature, moisture, and whether or not the plant is putting
on new foliage.
Dissemination:-The nematodes live over from year to year
in the soil. Infestation is accomplished by rains or irrigation
water washing the nematodes into the plant buds. In moist
fields which are inundated this spread of the eelworm is more
rapid.
This disease has been rather generally distributed through-
out the South by means of infested nursery plants. In most
cases this has been done unknowingly because plants which have
been recently infested with crimp nematodes do not display
the symptoms of the disease and hence are passed on as healthy
plants.
During the propagation of plants in the spring and summer
the runners formed by crimped plants usually become infested
as they push through the infested areas at the bases of the
leaves. This results in circular areas of diseased plants in the
nursery beds.
Control:-Due to the protected position of the nematodes in
the buds, it would be rather difficult to find a spray material
which would kill the nematodes without injuring the plants.
Adequate drainage seems to be the most important part of a
control program. If the land is well drained so that water does
not pond over the beds, the nematodes will not be spread so
rapidly from plant to plant and good control of crimp can be
secured by roguing out the diseased plants as they appear.
These plants should be pulled up and removed from the field,
so that the nematodes do not escape from the buds and re-
infest the soil.
Plants should not be used from nurseries in which crimp is
present, because even plants which appear to be healthy may







Strawberry Diseases and Insects


be in the initial stages of infestation, so that the disease symp-
toms do not appear until after the plants have been set. Ade-
quate inspection of nurseries will prevent crimp from being
disseminated in this manner.
Crop rotation may also be a means of control by reducing
the numbers of this specific nematode in the soil.

ROOT TROUBLES
During seasons favorable for the causal agents, considerable
loss may be caused by the various root troubles affecting the
strawberry. This loss is generally due to the failure of newly
set plants to live or to the checking of growth during the fruit-
ing season, materially reducing yields. Under extremely favor-
able conditions for the development of these troubles death
may occur.
These troubles may be classified as follows: black root, root
rot, Sclerotium rot, soil injury, fertilizer burn and root-knot.

BLACK ROOT
During the latter part of the summer and winter plants are
often found with a dark brown or black root system. This con-
dition is found on plants with either small or large root systems,
and is known to the grower as black root.
Symptoms:-Black-rooted plants generally appear to be nor-
mal, although if present for any length of time the plants may
not appear to be as vigorous as white-rooted plants. The root
system is black or dark brown and in many cases the outer
portion or cortex readily peels off, leaving the white central
cylinder or stele. Under both greenhouse and field conditions
such plants have been found to be capable of putting on new
lateral roots.
Cause:-The exact cause of black root is unknown, although
several workers believe it to be a natural condition due to age.
Control:-There is no known method of control. In the
nursery, however, by loosening the soil about old black-rooted
plants with a potato fork they can often be made to send out
new roots. If this is done a few weeks before setting a better
"live" of the set plants should result. Whenever possible it is
preferable to use white-rooted plants for setting.
ROOT ROT
Root rot may be severe during both cold, wet weather or hot,
dry weather, depending upon the causal organisms involved.







Florida Cooperative Extension


Symptoms:-Plants affected by root rot may appear to be
normal or may show a slight burning at the edge of the older
leaves. This burning gradually progresses inward, killing the
leaves progressively from older to younger. Some forms of
root rot cause a bronzing or purpling of the leaves similar to
that caused by cold weather. Unlike the plants colored by cold,
the root-rotted plants gradually grow smaller, the top becomes
yellow and death finally occurs. All forms of root rot now
known may cause death of the plants under favorable conditions
for the causal organism. The root system in the earlier stages
shows a spotting of the roots in local areas. These spots are
usually brown and may or may not be involved by a soft rot.
They occur at various places along the root from the tip to the
rhizome. Later stages show a complete killing of the older
root system. This is in the form of either a soft rot, in which
case the roots are generally brown, or a dry rot, in which case
the roots are dried and black. Unlike roots affected with black
root, the central cylinder or stele is not white but discolored and
often rotten, and does not produce laterals below the diseased
portion.
Before death occurs the season may become extremely favor-
able for the growth of the plant. In this case the plant resumes
growth, throwing out new roots above the older ones and is
able to live, sometimes becoming quite vigorous and bearing a
good crop. However, if the weather again becomes unfavorable
for plant growth, the rot infects the new roots and may kill
the plant before growth is again resumed.
Cause:-Several organisms, both fungi and bacteria, which
have under certain conditions caused root rot, have been isolated
from diseased roots. However, at present not enough is known
about them to give details.
Control:-No method of controlling or preventing root rot
is known. Care should be taken to use only healthy plants for
setting. Since these troubles seem to be worse on poorly or
excessively drained soils, the use of well but not excessively
drained soils may help to keep these conditions in check.

SCLEROTIUM ROT
Sclerotium rot is not extremely common in strawberry fields
at the present time, but because of the widespread presence
of the causal organism in strawberry land, as indicated by its






Strawberry Diseases and Insects


attacks on other crops, and the possibility of it becoming com-
mon on strawberries, it is described.
Symptoms:-Affected plants may not be noticed until dead,
in which case a white mat of mycelium or fungal threads will
be found around the base of the plant and along the petioles
or leaf stems. Small, brown, round bodies called sclerotia, ap-
pearing quite similar to strawberry seed, will be found scat-
tered on and near this mat. In some cases the white mat and
sclerotia will be found before death occurs. The root system
of infected plants is entirely rotted and the disease may be
recognized on the roots before it appears above ground by
the heavy white mat of mycelium around them and their light
brown color. Even in this stage they are often in a state of
soft rot.
Cause:-This disease is caused by Sclerotium rolfsii Sacc.,
a fungus extremely common in the South, where it causes
Southern blight or wilt of many cultivated plants. Among
plants most commonly attacked and found growing on straw-
berry land are: tomatoes, peppers, eggplants, sweet potatoes
and several of the most common cover crops, such as cowpeas,
velvet beans and crotalaria.
Control:-No satisfactory method of control is known. How-
ever, in the case of small acreages its spread may be checked
by the removal and destruction of diseased plants, care being
taken not to spread the sclerotia.
SOIL INJURY
Areas varying in size from a few plants to a half-acre or
more are occasionally found in which the plants fail to make
satisfactory growth. This condition is often caused by the
presence of some soil factor detrimental to-the strawberry.
Symptoms:-When first set the plants start off normally,
but in a few weeks as new leaves appear they are seen to have
yellow or white areas between the veins and still later, as the
injury progresses, the mottling increases until only yellow or
white leaves are produced. The plants become dwarfed, growth
ceases, and in severe cases death occurs. This is most apt to
be a sign of soil insufficiently acid for the growth of the straw-
berry.
In the case of the presence of soil toxins or too much acid,
the yellowing of the leaves may be absent but the stunting and
killing generally occurs.






Florida Cooperative Extension


Under any of these conditions the root system becomes
stunted, is dark brown or black and is quite often rotten. Death
is caused by the complete destruction of the root system.
Cause:-This condition is generally caused by the presence
of soil toxins, insufficient acid in the soil, which is often caused
by an excessive addition of lime or other base to the soil, or
by an extremely acid soil.
Control:-At the present time not much is known about soil
toxins and the method of eliminating them.
The acidity of a soil is measured by determining its hydrogen-
ion concentration or pH by means of a hydrogen-ion apparatus.
Strawberries grow well in soils ranging in hydrogen-ion concen-
tration from pH 5.00 to 6.00 with the optimum around pH 5.50.
Soils too acid for strawberries may be sweetened by the use
of hardwood ashes or lime, although their use is not advised
when the hydrogen-ion concentration of the soil is unknown.
Soils too alkaline may be made to grow strawberries by applica-
tions of manganese sulfate or iron sulfate at the rate of 50
to 100 pounds per acre, or by using a mixture of both at the
same rate. See Fla. Agr. Exp. Sta. Press Bulletin 513.

FERTILIZER BURN
Symptoms:-Plants burned by fertilizer first show a burn-
ing along the edge of the lower leaves
(Fig. 3) and later this condition
may spread over the entire leaf.
The root system will show a spot-
ting or burning similar to that
caused by root rot, except that
it will be more severe
on the side next to
the fertilizer.
Cause:-A s the
name implies, this is
caused by poorly dis-
tributed fertilizer.
Control:-Fertiliz-
er burn can be pre-
Fig. 3.-Fertilizer vented by using care
burn of a straw-
berry leaf straw- in distributing the
fertilizer to get it
well mixed in the soil. Two applications should not be made







Strawberry Diseases and Insects


consecutively without sufficient rain falling in between to in-
sure their going into solution.

ROOT-KNOT
Root-knot occurs on so many crops in the South that all
farmers should be able to recognize it. Although not as severe
on strawberries as on some other crops, it does at times become
severe enough to cause injury and even death, especially dur-
ing drought.
Symptoms:-There are often no symptoms of the trouble
above ground, but in the case of badly infested plants there
is a dying off of the leaves. It is easily recognized on the
roots by the presence of the small galls or knots at various
points on the roots, most frequently at the tips. These enlarge-
ments vary from 1/16 to 1/8 inch in diameter, which is much
smaller than those found on many truck crops.
Cause:-Root-knot is caused by a small eelworm or nematode,
Heterodera marioni, which is common in most lands in the
South. This nematode enters the root and causes the swelling
which interferes with the absorption of water and nutrient
materials from the soil.
Under favorable environmental conditions such as are found
in warm, well drained, sandy soils containing roots of suitable
host plants, nematodes are in the active or eelworm stage, but
when unfavorable conditions prevail, they are in an encysted
stage and are able to survive an adverse environment for a long
period of time, hatching out into worms when suitable condi-
tions again surround them. The main crop of strawberries
grown during the winter is not so much affected by nematodes,
because the worms are rather inactive during that time. In
fact, strawberries can be successfully grown on heavily in-
fested land, but during the spring and summer the attacks
of the nematodes on the plants in the nursery are more serious
(Fig. 4).
Control:-Root-knot can be kept in check by growing a cover
crop of some resistant plant such as velvet beans, Brabham or
Iron cowpeas or crotalaria and keeping the ground free of all
weeds. Small areas can be cleaned up by steaming or by using
a double treatment of sodium cyanide and ammonium sulfate.
The latter method is expensive but can be used on small areas.
For directions write the Experiment Station at Gainesville.






Florida Cooperative Extension


Fig. 4.-Root-knot as it appears on strawberries.
LEAF-SPOT DISEASES
In Florida leaf-spots make their appearance on the straw-
berry plants chiefly during late spring, summer and early fall
(April to October). Ordinarily they are of minor importance,
but in some instances spotting is so severe that some means
of control is necessary. Following are some of the factors
which tend to check the development of leaf-spot in Florida:
1. The practice of renewing the strawberry beds annually
and obtaining new plants from the North each year, instead
of carrying Florida-grown plants over from year to year.
2. The fair degree of resistance of the Missionary variety to
leaf-spot, as has been demonstrated by variety tests in Florida.
3. The growing of fruiting plants under the hill system, in-
stead of the matted row system, thus giving a freer circulation
of air about the plants which somewhat lessens the accumula-
tion of moisture.
4. The comparatively low temperatures prevailing during the
fruiting season.
Three distinct leaf-spot diseases are described.


ad~







Strawberry Diseases and Insects


COMMON LEAF SPOT
This leaf-spot, which is caused by the fungus Mycosphaerella
fragariae (Tul.) Lindau, is found in most of the strawberry
growing areas of the world. In Florida it appears to be the
least common of the three leaf troubles.
Symptoms:-The spots are at first small, less than 1/8 inch
large, and dark reddish or dark purplish in color. They increase
in size up to a maximum diameter of 1/8
to 3/16 inch, the centers become white
or gray and the border is of the same
color as the immature spots (Fig. 5).
The spots may number from one to
many on each leaflet and
i f extremely numerous
cause the death of the
leaflet. Although a severe
infection may result in
the death of the plant,
under Florida conditions
this rarely occurs. Leaf
spot has been frequently
observed to be present
upon plants shipped in Fig. 5-Common leaf spot
on strawberries.
from Northern nurseries,
and has been found to spread to a limited extent to the younger
leaves after the plants have been set. Later, however, the new
leaves do not become infected and the disease gradually dis-
appears.
Control:-Since this leaf spot does not seriously affect the
Missionary variety as grown under Florida conditions, spraying
should be unnecessary. However, should it ever become serious,
frequent applications of 4-4-50 bordeaux spray will control the
disease.
LEAF-SCORCH
The geographical distribution of leaf-scorch, which is caused
by the fungus Diplocarpon earliana (E. & E.) Wolf, is about
identical with that of common leaf-spot. In Florida it is more
abundant and much more destructive than is the common leaf-
spot.
Although the disease is capable of attacking any of the green
parts of the plant, here it is confined mainly to the leaves and
is most important in the nursery beds during the summer







Florida Cooperative Extension


months. Ordinarily the frequent rains which occur during the
summer tend to keep this disease in check, but during the sum-
mer drought of 1927 in central Florida many plants were killed
by this disease.
Symptoms:-The young lesions of leaf-scorch appear on the
upper surfaces of the leaves as small purplish discolorations
which rapidly enlarge into irregular
purplish blotches from 1/16 to 3/16
inch in diameter with minute dark
glistening bodies (the pycnidia of
the fungus) present on the upper
surface (Fig. 6). The spots on each
leaflet may become so numerous
that they coalesce
and give a reddish
cast to the entire
leaflet. In severe
cases of infection
the edges of the
leaf curl upward
and the leaf dries
out progressively
Fig. 6.-Leaf-scorch. from the edge in
toward the midrib.
The resulting dried or scorched appearance has given rise to
the common name of this disease.
Control:-Spraying plants on the nursery beds with 4-4-50
bordeaux mixture at two weeks' intervals during the summer
months will control leaf scorch. On fall-set plants it is some-
times necessary to make two applications of the above spray,
one shortly after setting and the other about a month later,
to prevent leaf scorch from becoming serious before it is nat-
urally controlled by the advent of cool weather.
LEAF BLIGHT
This disease, which is caused by the fungus Dendrophoma
obscurans (E. & E.) Anderson, has not been reported from so
wide a range as have the two leaf-spots just described. It
occurs in Florida and has caused some damage to strawberry
plants, especially those set early in the fall.
Symptoms:-Even in the early stages the spots caused by this
fungus are larger than the mature spots of common leaf-spot







Strawberry Diseases and Insects


and leaf-scorch. From one to five spots may occur on a leaflet.
The young spots are circular and reddish-purple in color. 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. In advanced stages of the disease the spots increase in
size until a V-shaped area is formed extending from one of the
large veins to the edge of the leaf (Fig. 7). The area remains
alive for a while after displaying the purplish discoloration, but
finally dies. Small black dots, the pycnidia or fruiting bodies


Fig. 7.-Strawberry leaf blight, showing various types of lesions.
The leaflet at the top shows a typical fanshaped dead area. (From
Ill. Agr. Exp. Sta. Bul. 229.)







Florida Cooperative Extension


of the causal fungus, appear in the central dark brown areas
of the older spots.
Control:-Same as for leaf-scorch.
FRUIT ROTS
At present there are four different rots known to attack straw-
berry fruit in Florida. Three of these appear in the field and
ordinarily are not important from an economical standpoint.
One appears only during the shipping and marketing of fruit
and is often highly destructive.
LEAKS OR WHISKERS
This rot is of most importance in the shipping and marketing
of strawberries, although it may rarely be found in the field.


Fig. 8.-"Whiskers" or "Leaks".






Strawberry Diseases and Insects


It is caused by the fungus Rhizopus nigricans, which rapidly
develops in fruit held above 500F. and in a moist atmosphere.
According to Neil E. Stevens in Circular 219, U. S. Department
of Agriculture, a survey of market inspection reports of Florida
strawberries showed that during 1926, 1927 and 1931 Rhizopus
rot was present in 4.3 to 10.7 percent of the shipments inspected,
whereas all other rots were present in only 1.6 to 2.6 percent.
Symptoms:-The fungus readily attacks fruit that has been
injured and causes a collapse of the tissues and rapid extraction
of the fruit juice which accumulates in the bottom of the con-
tainer and drips out, thus giving rise to the common name
"leaks". The fruit settles down until it fills only about one-half
the container. A loose cottony growth of mycelium of the
fungus appears over the surface of the fruit. This is the
"whisker" stage (Fig. 8). Later, black dots appear scattered
amongst the cottony mass. These dots are the spore-bearing
cases of the fungus.
Control:-Fruit should be handled carefully so as to avoid
bruising. Frequent changing of the water used for washing
fruit will greatly reduce the source of infectious material. Fruit
picked early in the morning and protected from the sun during
the trip to the shipping point will have a lower temperature
than that picked later in the day. High temperatures favor
the development of Rhizopus rot. Hence the fruit should be
cooled as quickly as possible after picking. Rapid pre-cooling
of fruit to 350F. before shipment will completely prevent de-
velopment of this rot.
BROWN ROT OR GRAY MOLD
This rot, caused by the fungus Botrytis cinerea, occurs both
in the field and during shipping of fruit. It develops less rapidly
than Rhizopus rot and is of minor importance during trans-
portation, but often causes considerable loss in the field.
Symptoms:-Fruit attacked by this fungus never becomes
"leaky" as is the case with Rhizopus. The spots attacked are
at first light brown, later dark brown in color, the flesh being
somewhat soft at first, then becoming hard and dry. There is
no distinct line of demarcation between diseased and healthy
tissue. Under moist conditions the infected fruit is covered
with "gray mold", the fruiting stage of the causal fungus.
Control:-At present no means of controlling this disease
have been worked out. Infected fruit can readily be identified






Florida Cooperative Extension


and discarded during the packing process, thus preventing
further development of the rot during the transportation period.
LIGHT TAN ROT
This rot, caused by Pezizella lythri (Desm.) Shear and Dodge,
is as important in Florida as that caused by Botrytis. It is
easily distinguished from the other rots.
Symptoms:-The spots produced by this fungus are small,
sunken, and tan in color. They increase but slowly in size. The
infected tissue is a cone shaped core which, due to its corky
texture and to the disintegration of the cells adjoining, can be
removed intact from the sound tissues. This is the distin-
guishing characteristic of the disease.
Control:-Same as for Botrytis rot.
HARD BROWN ROT
This rot, which is caused by a fungus Rhizoctonia sp., is pres-
ent rather generally over the strawberry-growing area of the
State, but does not cause any appreciable loss to the strawberry
industry.
Symptoms:-The fungus causing the disease is present in
the soil. Thus initial infection of the fruit is on the side in
contact with the soil. Fruit in all stages of maturity may be
attacked. The spots are light tan in color unless soil has become
enmeshed in the fungal growth and is adhering to them, in
which case the spots are black or dark gray on the surface. A
section cut through the infected fruit shows that there is a
dark colored band on the surface of the infected area and a
lighter tan colored area adjacent to and sharply separated from
the healthy tissue. In fact, this line of demarcation is so sharp
that the diseased tissue can be cut away and the remainder of
the fruit will be perfectly edible.
Control:-Same as for Botrytis rot.
RULES FOR MAKING SMALL QUANTITIES OF
BORDEAUX MIXTURE SPRAY
Since the average strawberry patch is from 1 to 3 acres in
extent, the quantity of spray mixture necessary for each applica-
tion is comparatively small. A method for making small quanti-
ties of bordeaux mixture, which is the most important-fungicide
used in the control of the diseases of strawberries, is as follows:
Materials: (1) Rock lime or hydrated lime.
(2) Bluestone (blue vitriol or copper sulfate).







Strawberry Diseases and Insects


Equipment: (1) Knapsack sprayer.
(2) Scales for weighing the materials.
(3) One 50-gallon wooden barrel. (Coca Cola
barrel generally used.)
(4) Either another barrel as above or a 10- to
20-gallon tub or keg (not metal).
(5) One strong paddle for stirring mixture.
(6) One burlap sack.
Formula:-The mixture recommended for spraying straw-
berry plants is a 4-4-50, meaning 4 pounds of bluestone and
4 pounds of rock or hydrated lime to 50 gallons of water.
Procedure:-(1) Dissolving the bluestone: Fill the small
tub or keg with water, or if two 50-gallon barrels are to be used,
put 10 to 20 gallons of water in one. Place 4 pounds of blue-
stone in a sack and suspend it in the water near the top surface.
This hastens the dissolving of the bluestone, which would take
days to dissolve if placed in the bottom of the container. Allow
all of the bluestone to dissolve.
(2) Slaking the rock or preparing the hydrated lime: Place
4 pounds of rock lime in the 50-gallon barrel, add just enough
water to moisten the lime thoroughly. As the lime begins to
slake, continue to add water slowly so that the lime does not
dry out, but not too much water to stop the slaking. The lime
should gradually crumble, boil with the evolution of consider-
able heat, and finally form a thick paste. When all action has
stopped, add enough water to bring the contents of the barrel
up to 25 gallons. Stir well, thus thinning the lime-paste to a
milk-of-lime.
If hydrated lime is to be used, add to 25 gallons of water
and mix thoroughly.
(3) Making the mixture: Slowly pour the dissolved bluestone
into the milk-of-lime, at the same time having someone con-
stantly and vigorously stirring the mixture. When all the blue-
stone solution has been added, bring the contents of the barrel
up to 50 gallons by adding water.
Test for Proper Mixture:-A clean knife blade (not stainless
steel) when dipped into the mixture and allowed to stay for a
minute or two should not show any copper deposited upon it.
If the blade turns dark, the mixture does not contain enough
milk-of-lime and more should be added until the mixture is
correct.






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Precautions:-(1) In preparing bordeaux mixture do not use
containers in which the solutions will be in direct contact with
a metal surface.
(2) Use the mixture immediately after preparation, as it
deteriorates upon standing.
(3) Stir mixture well each time before filling the sprayer.
(4) Cover the surfaces of the leaves well. Insecticides may
be added to this spray mixture; for leaf-eating insects 1 to 11/2
pounds of lead arsenate to 50 gallons of mixture; for sucking
insects 2/% pint of "Black Leaf 40" to 50 gallons of mixture.
Many new types of copper sprays are now on the market,
some of which may replace bordeaux mixture as a fungicide.
Most of the materials are insoluble copper compounds, easily
mixed with water and quite efficient when used with the proper
spreading and sticking agents. Their costs compare favorably
with that of bordeaux, especially when ease of mixing is con-
sidered.
INJURIOUS INSECTS AND SPIDERS
Insects are of prime importance in the economy of the straw-
berry industry. It is, therefore, essential that the individual
grower become well informed concerning the various pests, the
seasons during which they appear, the plant parts attacked
and damage done, together with the known methods of con-
trolling each. On the following pages is given information
concerning the more injurious insects now known to attack
strawberries in Florida.
RED SPIDERS, Tetranychus telarius
Red spiders frequently become very prevalent upon straw-
berry plants in spring when the weather is dry and warm.
They breed less rapidly in cool weather and the heavy rains
of summer usually very quickly bring them under control. They
attack both leaves and fruit. The leaves turn a pale ashen
color and, if the infestation is heavy, become dry and shrivel
up and die. The young unripe berries take on a brown color
and also become hard and dry and fail to develop. The injury
is caused by the red spiders sucking the sap out of the foliage
and fruit. The mites themselves are reddish or yellowish in
color and, although small, are plainly visible to the naked eye.
They spin strands of silk which web up both surfaces of the
leaves. They use this web as a road over which to travel and
also to hold the eggs to the leaves, and doubtless also it lessens







Strawberry Diseases and Insects


the danger of the mites being washed off by heavy, dashing
rains. They spread mostly by crawling from one plant to an-
other but may also be carried by the wind.
Like all members of the spider class, they are best controlled
by sulfur. If the weather is reasonably warm, one can ordin-
arily get satisfactory control by simply dusting the plants with
flowers of sulfur. This is easily the quickest and most econom-
ical way of combating red spiders. Sulfur is best spread with
a dust gun but may be applied by hand. To make it go through
a dust gun more readily sulfur is often mixed with 5 to 10
percent of hydrated lime, but the lime is not necessary to kill
the spiders. This dust can be applied any time during the day
when there is not a heavy wind blowing, but better distribution
is obtained when the plants are dry.
During cold weather better control will be obtained by spray-
ing the plants with lime-sulfur. One gallon of lime-sulfur and
10 pounds of wettable sulfur to 100 gallons of water is used.
However, this spray will taint the berries and should not be
used during the picking season, although there will be no danger
to the consumer. Nicotine sulfate, pyrethrum and derris com-
pounds (see below) are also good insecticides for red spiders,
but nicotine compounds also would be objectionable during the
picking season.
In small dooryard patches which can be reached with the hose
or in a field provided with irrigation, a liberal sprinkling with
water will check these pests. The water should be applied with
as great pressure as the plants will stand.
Life History:-The eggs hatch out in some three to five days
and the young mites require about 10 days for growth-more
when the weather is cool. About four days after they become
adults they begin to lay eggs. A generation usually requires
from two to three weeks; although it has been observed to be
as short as 10 days and as long as 35.

FLORIDA FLOWER THRIPS, Frankliniella cephalica
This orange-yellow insect, about 1/25 inch long, is often very
injurious to strawberries in the spring. Its attacks are con-
fined mostly to blossoms where it feeds on stamens, pistils and
young berries. These are sucking insects but their punctures
are very shallow and numerous. The action on the berries re-
sembles much that of the red spider but is more largely con-







Florida Cooperative Extension


fined to very young berries. As a result of their feeding, the
blossoms drop off or the young berry may remain hard and
brown, failing to grow. In cases of less severe infestation the
berry may be deformed as a result of injury on one side and
not on the other. These insects frequently seriously shorten
the bearing season of the vines as they are usually more abund-
ant in the later blossoms.



















Fig. 9.-Adult female Florida flower thrips. Highly magnified.
(Drawing by Dozier.)

Control:-One of the best sprays for thrips is nicotine sulfate
(one part of nicotine sulfate to 600 parts of water). To make
the solution spread better, a little soap should be added to the
solution (2 or 3 pounds to 50 gallons, more if the water is
hard). The soap should be alkaline, such as common laundry
soap. Fish-oil soap is commonly used. Better spreaders are
some of the pine oil soaps. The use of some of these better
spreaders, or an oxidized oil derivative (penetrol), will enable
one to greatly reduce the amount of nicotine in the solution
and make a better insecticide at an appreciably lower cost.
By the use of this spreader or "activator", the nicotine sulfate
can be reduced to 1 part in 3,000. These nicotine sprays should
be applied in the heat of the day, as their strength is soon
dissipated and the kill is much better when the weather is
warm. In fact, at a temperature below 60 degrees it is apt






Strawberry Diseases and Insects


to be unsatisfactory. The spray should be applied with as
much force as possible as the thrips have a tendency to hide
among the stamens and other parts of the flower and will not
be reached by the spray unless good pressure is employed.
As this solution will taint the berries it should be applied
immediately after picking. After 48 hours odor and taste will
have disappeared from the berries.
A satisfactory dust for controlling this insect can be made by
mixing a very finely ground tobacco dust, such as snuff No. 2,
with an equal quantity of sulfur. This is not likely to taint the
fruit, as the dust will be knocked off in picking, and it will also
control red spiders.
Preventive Measures:-Weeds and other plants in bloom about
the strawberry patch should be destroyed as the thrips will
spread from these to the strawberry blossoms. This destruction
should take place some weeks or a month before the straw-
berries bloom. The white-blossomed Spanish needle (Bidens
leucantha), a common plant about strawberry patches in the
southern part of the state, is a favorite host plant of thrips,
as are also roses.
Life History:-The life history of this insect is very short-
two or three weeks when the weather is warm. The eggs are
laid in shallow slits in the stem just below the blossom. They
hatch in three days into a light yellow wingless nymph which
continues to feed on the young berry and other tender parts
of the plant.
PAMERAS
Other very destructive insects liable to attack strawberries
in the spring are the pameras. Usually these pameras do not
make their appearance until late in the season, often not until
picking is over, but during a very warm winter they may appear
much earlier. Indeed, during some winters they are destructive
all winter long, starting as early as December in central Florida
and are very destructive in March and April in northern Florida.
Growers who attempt to carry their vines through the summer
almost invariably have trouble with these insects. They breed
so rapidly and are so inconspicuous in color, size and habits
that they often become very abundant before they are noticed.
The young, in size and color, resemble small yellow ants but
are much more rapid in their movements and the presence of
the darker, winged adults will readily identify them.






Florida Cooperative Extension


This insect causes "buttons"-berries that in some early stage
of development cease to grow and become hard, dry and brown.
A very young berry will turn brown and dry up. Later the
insects attack the crown of the plant which withers rapidly and
dies if the bugs are numerous. The outer leaves of the plant
die first and dry up, turning a brownish color. If these leaves
are disturbed the pameras will scatter in all directions.
There are three species. The smallest, Orthaea vincta, is
black with yellow markings and about 1/5 inch long. 0. bilobata
and 0. longulus are much longer. These bugs belong to the
same family as chinch bugs, the most destructive enemy of
St. Augustine grass in Florida, and have the same "buggy" odor.
Control:-The pyrethrum sprays, of which several brands
are commonly on the market in Florida, are the only effective
control of pameras, particularly if the weather is a little cool.
Because of the position underneath the leaves of the plant these
bugs will not be reached by the spray unless great care is taken.
It is best for two men to work together in spraying for the
pamera. One gathers up the leaves in his hand and holds them
off the ground while the man with the spray machine quickly
sprays around the plant; the man holding the leaves then lets
go and the sprayer wets the center of the crown. In small
garden patches, particularly after the picking season, these
insects usually can be brought under control by allowing young
chickens to have the run of the strawberry patch. Like red
spiders and thrips, these insects tend to disappear as the rainy
season comes on. They are found on many weeds growing in
and around strawberry patches, some of the more important
being spurge (Euphorbia sp.), evening primrose (Onagra sp.),
and cudweed (Gnaphalium sp.).

CUTWORMS
Following their usual habit of severing succulent stems, these
caterpillars often cut off the petioles of the leaves of strawberry
plants or the stems of the young fruit. They also inflict another
type of injury by attacking the green but well grown fruit from
below, often hollowing it out until nothing but the shell of the
berry is left or they may make only a small hollow in it. This
is done without severing the berry from the vine.
Control:-One of the best and cheapest insecticides for cut-
worms is a poisoned bran bait, made by mixing thoroughly 25







Strawberry Diseases and Insects


pounds of bran and 1 pound of Paris green or 11/2 pounds of
calcium arsenate. The bran and poison should be mixed very
thoroughly. Not less than 10 minutes should be occupied in
this mixing. This dry mixture is then moistened with enough
water to make it moist but not sloppy, so that when sown it
will fall in small flakes. This will require about 21 gallons
of water for the 25 pounds of bran. This bait should be put
out in the evening after the sun has set so that it will not dry
out and a few flakes should be distributed around each plant.
The 25 pounds should suffice to cover four or five acres.
Many growers prefer, instead of 25 pounds of bran, a mixture
of 12 pounds of bran and 121/ pounds of cottonseed meal.
This mixture is a little more sticky than the bran alone.
If cutworms are not sufficiently numerous to make this worth
while, they can be dug up and destroyed. If one will go through
the patch early in the morning and dig down an inch or so
under all severed leaves or berries he sees, he will usually dis-
cover the culprits without much trouble.
Preventive Measures:-Cutworms are always worse in beds
made up on ground which was occupied by heavy sod. If such
land is to be used for making the strawberry beds, it should
be plowed two or three weeks before the berries are set. Then,
10 days or two weeks after plowing, the poisoned bran bait
recommended above should be sown broadcast over the land
in the evening. The cutworms, rendered very hungry by their
long fast caused by the destruction of the grass, will eat this
poisoned bait eagerly and a thorough clean-up should result.
Instead of the poisoned bran mash one may scatter over the
ground leaves of mustard or collards or even grass which have
been dipped in a strong solution of lead arsenate, using an ounce
to two or three gallons of water.
WEBWORMS
Webworms (Crambus sp.) often attack strawberry plants and
cause considerable damage. These worms get their name from
the fact that they produce a silk web connecting the outlet of
their burrow in the plant with the soil. This web usually has
particles of soil adhering to it. Like cutworms, they are worse
on land which supported a heavy sod before the strawberries
were put out. The species found most commonly in central
Florida is about as thick as the lead in a pencil and about 1/2
inch long with alternate gray and reddish-brown bars. When







Florida Cooperative Extension


held in the hand and disturbed, the worms wiggle and jump
about quite actively.
The greatest damage caused by these worms is due to their
killing off the runner plants in the nursery. The worm either
burrows into the runner and thus kills the plant at the tip or
burrows into the plant itself. After the plant or runner has
been thus attacked it wilts and dies.
Among other plants attacked by these worms are beans, peas,
corn, and most of the cover crop plants.
Preventive Measures:-These measures will be the same as
those for cutworms.
THE LEAF ROLLER, Ancylis comptana
This is a small caterpillar only about 1/ inch long which folds
over the strawberry leaf along the midrib and lives in this
folded portion, eating the surface of the leaf. In order to fold
the leaf more easily it eats away the surface of the leaf along
the midrib, causing great injury. It lives about a month in
this folded leaf, feeding on its surface, after which it pupates
in the leaf. From this pupa comes out a small moth measuring
only about 1/2 inch across the expanded wings. The wings are
reddish-brown in color with black and white markings.
Control:-The leaf roller can be controlled by spraying or
dusting with lead arsenate before the picking season begins.
The lead arsenate can be placed in bordeaux if one is spraying
with bordeaux for other purposes. After the picking season
begins the use of lead arsenate will have to be discontinued.
At that time one of the rotenone compounds can be substituted
for lead arsenate. Although not as quick in its action as lead
arsenate, it will kill the worms in a few days. This insect also
feeds on blackberries. It would be an excellent idea to cut any
wild blackberry bushes in the neighborhood of the strawberry
patch.
CROWN BORER, Tyloderma fragariae
This is a weevil about 1/8 inch long; dark brown with black
spots. As its name indicates, it feeds in the crown of the plant.
This insect has been observed in Florida only in the region
about Miami. The eggs are laid in hollows near the crown and
here the larvae develop. The insect is pretty well out of reach
of insecticides, but the beetle is incapable of flight and if only
clean plants are used in setting the bed and the bed is placed
some distance from any previously infested bed, the beetles will






Strawberry Diseases and Insects


ordinarily not find the plants in time to be seriously destructive
before the picking season is over. Infested beds should be
thoroughly cleaned up at the end of the picking season and
all old plants destroyed.

MOLE-CRICKETS
These dirty white or yellowish insects make burrows just
below the surface of the ground by means of their enlarged
front legs. These burrows resemble much the runways of moles
but are very much smaller, only about an inch in diameter.
During the day the insects live deep in the ground but at night
they come out to feed and are very destructive to vegetation.
There are three species commonly met with in Florida. Two
of them, Gryllotalpa borealis and Scaperiscus abbreviatus, are
native insects and are confined mostly to low ground. The third
species has been introduced from the West Indies where it is
known as the "Changa". This one works in well drained land
and is very common and destructive where it has been colonized.
Control:-The best means of control yet found is a modifica-
tion of the poisoned bran bait recommended for grasshoppers.
Commercial egg mash is used instead of the bran. (Use 25
pounds egg mash and 1 pound Paris green or 11/2 pounds cal-
cium arsenate. See page 24.) Any commercial egg mash con-
taining dried milk seems to be effective. A cheaper bait which
has been found to give control in some situations (according to
C. F. Stahl of the U. S. Bureau of Entomology working at
Sanford) is made by substituting cottonseed meal for half the
bran in the poisoned bran bait; in other words, 121/2 pounds of
shorts or bran and 121/2 pounds of cottonseed meal.
During March and April large numbers may be caught in light
traps. Suspend a lantern in the field and under it place a pan
containing water with a little kerosene on the surface.

CRICKETS
Crickets are often numerous underneath the mulch of straw-
berry beds. From these hiding places they come out, particu-
larly at night, and feed on the ripening berries. They usually
eat small pits in the berries which soon decay. The poisoned
bran bait used for cutworms (page 24) is about the best poison
for crickets. It should be put out in the evening as for cut-
worms.






Florida Cooperative Extension


WHITE GRUBS
Sometimes the roots of strawberry plants are eaten off by
large white grubs, the larvae of June bugs or May beetles.
This type of injury will be found most frequently where heavy
sod land has been plowed up for strawberry beds. If many
of these grubs are found in the soil when the beds are being
made, the grubs should be exterminated before the plants are
set. This can be done by allowing hogs to run in the field for
a few weeks or the ground may be treated with calcium cyanide.
This should be spread in front of the plow when the bed is being
plowed, at the rate of about 300 pounds per acre. It should
be laid down in the bottom of the furrow, immediately in front
of the plow which will promptly cover it.
GRASSHOPPERS
These well-known pests of practically all garden and field
crops occasionally attack strawberry plants, eating large holes
out of the leaves. They are best controlled by poisoned bran
bait. This is made by mixing thoroughly 25 pounds of bran
and a pound of Paris green. It must be mixed very thoroughly
while still dry, as recommended for cutworms. When thor-
oughly mixed, moisten the poisoned bran with a solution made
by adding a quart of cane syrup and a half dozen lemons or
other citrus fruit to 21/2 gallons of water. The citrus fruits
should be grated or chopped up fine, rind, pulp and all, and the
bran should be moistened with this solution until it is damp
but not sloppy, so that when sown broadcast over the soil it
will fall in small flakes. Instead of Paris green one may use
a pound of white arsenic or 1/ pounds of calcium arsenate,
but not lead arsenate. Sodium arsenate also may be used, and
may be added to the solution instead of being mixed dry with
the bran. This will reduce the amount of labor necessary to
make up the poisoned bran bait and will usually give a more
even distribution of the poison than when the bran and poison
are mixed dry. Poisoned bran bait should be put out early in
the morning as grasshoppers do not feed much at night.
EARWIGS
These dark colored insects with a pair of pincher-like organs
on the end of the body are often very abundant in low grounds.
They feed on the roots of the plants and often come out at
night and feed on the foliage and berries. The poisoned bran







Strawberry Diseases and Insects


bait recommended for grasshoppers is perhaps the best means
of control.
FLEA BEETLES
Several species of flea beetles, especially the strawberry flea
beetle, Haltica ignita, a yellow-bronze insect about 1/5 inch
long, attack strawberry leaves, eating round holes in them.
Control:-Best control is obtained by spraying the plants with
bordeaux, to each 50 gallons of which a pound of lead arsenate
has been added. If the attack occurs during the picking season,
the use of arsenic in any form should be avoided. A good in-
secticide to use under those circumstances would be one of the
pyrethrum or rotenone compounds.
One of the favorite food plants of this beetle is the orna-
mental, crape myrtle. This plant should not be grown in close
proximity to a strawberry bed, or it should be watched closely
during spring and sprayed with lead arsenate in case the beetles
appear on it.
COWPEA POD WEEVIL, Chalcodermus aeneus
This black weevil, about the size of a boll weevil, is a very
general feeder and sometimes in the early spring attacks straw-
berry plants. If the attack does not occur during the picking
season, a spray with lead arsenate will afford protection. If
the attack does occur during the picking season, the best plan
is to go through the patch in the early morning when the
weevils are sluggish and, with the hand or a stick, knock the
beetles off into a flat dish containing a little kerosene in the
bottom.
APHIDS
The strawberry root aphid, Aphis forbesi Weed, sometimes
attacks strawberry plants, sucking the sap from the roots. It
can be controlled by punching holes slantingly under the plants
and pouring in a tablespoonful or so of carbon bisulphide. The
hole should be several inches from the plant, but both the
distance from the plant and amount of carbon bisulphide to
use will vary with the character of the soil. In heavy, dense
soils more of the material will be needed and the distance from
the plant will need to be shortened as the gas does not pene-
trate heavy soils as well as it does light, open, sandy ones.
Other species of aphids will attack the part of the plant
above ground, the crown, etc. They are best controlled by
tobacco extracts, such as nicotine sulfate. This may be applied






Florida Cooperative Extension


either as a dust mixed with lime or as a liquid spray. Dusting
will be much quicker but will take more material. A good
dust is made by thoroughly mixing 3% pounds of nicotine
sulfate with 50 pounds of hydrated lime. The mixing must
be thorough. It should be done in a barrel rigged up for this
purpose (see Bulletin 88). This dust should be applied in the
heat of a good, warm day and when the wind is not blowing.
A somewhat cheaper dust can be made by using free nicotine
instead of nicotine sulfate. In this case use only 2 pounds of
free nicotine in 50 pounds of dust.
If the spray is used, 1 part of nicotine sulfate should be
used to 600 parts of water and to every 50 gallons, 3 or 4
pounds of soap should be added to make it spread and stick
better, or the nicotine sulfate may be added to bordeaux mix-
ture. A cheaper spray can be made by using some of the better
spreaders on the market. By the use of penetrol one can cut
down the nicotine sulfate to as low as 1 part in 3,000. Derris
or pyrethrum compounds may be used instead of nicotine sul-
fate, or pyrethrum.
NEGRO BUGS OR BURROW BUGS
These are small, roundish, shiny black bugs which are some-
times found damaging the roots of strawberries or they may
attack the berries, whose juices they suck. They have a very
nauseous odor, suggesting that of bedbugs. The adult bugs
are about 1/8 inch long. The middle piece of the back is en-
larged so that it covers the entire abdomen, which makes the
insect look more like a beetle than a bug; the sucking mouth
parts, however, readily distinguish it as a bug.
Control:-A spray of crude carbolic acid, a tablespoonful to
two gallons of water, is very effective in driving these bugs
away; during the picking season it should be applied just after
the berries have been picked.




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