Group Title: Berry/vegetable times.
Title: Berry/vegetable times. December 2004.
Full Citation
Permanent Link:
 Material Information
Title: Berry/vegetable times. December 2004.
Uniform Title: Berry/vegetable times.
Physical Description: Newspaper
Creator: Gulf Coast Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida
Publisher: Gulf Coast Research and Education Center, University of Florida
Gulf Coast Research and Education Center
Publication Date: December 2004
 Record Information
Bibliographic ID: UF00087388
Volume ID: VID00031
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.


This item has the following downloads:

BVT1204 ( PDF )

Full Text


EXTENSION December 2004

1^ IKL-l" h^da-.A-Zla~ 53n-j: ^b l^R SjL-* ^^^f^^~ j,^
ft oef-ce rAf tt rf t^fAf^f-ot^ft ^f-c(^ r i f ^^Bl t ^~~ff^^tp(Bet6f(^^^r^^ t~t(t

In this issue...
Strawberry Freeze Protection Page 2

Early Season Arthropod Pests in
the Strawberry Crop: Cyclamen

Page 2

Early Season Arthropod Pests in Page 3
the Strawberry Crop:
Lepidopterous Larvae, Aphids
Pesticide Registrations and Page 5
Pesticide Potpourri Page 5
GCREC Center Update Page 6

Powdery Mildew of Strawberries

From Your Extension
Blueberry Cold Protection

Now that a couple of cold
Fronts have come through and we see
the cold weather the rest of the
country is having, we are starting to
think about cold protection. An
excellent publication entitled
S"Protecting Blueberries from Freezes
in Florida" by Drs. Paul Lyrene and
Jeff Williamson came out this year
Son EDIS. I will give a brief overview
here, but be sure to read the paper to
learn all the helpful information that
it contains. The paper can be found
at, or
get in touch with me for a copy.
Blueberries enter a dormant
condition in the winter where there is
no growth and this aids in surviving
cold weather. If the blueberry plant
is fully dormant it is very cold hardy,
and in Florida air temperatures
usually do not get low enough to
cause plant damage. Also, blueberry
plants need a certain amount of
chilling to break dormancy and grow
and flower well the next spring.
Each variety has its own
characteristic chilling requirement,
and this is the main reason why some
varieties do better in central Florida
than others. Plants in our area of the
state frequently do not lose all their
leaves and this can affect the amount
of chill time they accumulate. Plants
that retain at least some of their
leaves will not have their chill
requirement satisfied as quickly as
plants that loose all their leaves.
Since the industry in west
central Florida is based on varieties

that produce early fruit, freezes in
February and March are of great
concern. Fruit and open flowers will
freeze at higher temperatures than
flowers that have not opened, and
dormant buds are even more cold
Factors to pay attention to
are temperature, wind speed, and dew
point. The predicted low temperature
plays a part in deciding whether to
cold protect and the method of
protection. Wind speed can
influence the effectiveness of the
sprinkler irrigation method of freeze
protection. And dew point (an
indicator of the amount of water
vapor in the air) affects how quickly
air temperature drops. Moist air
retains more heat than dry air. Also,
when the dew point is low, the rate of
evaporative cooling is high, which is
of concern when sprinkler irrigation
is used for freeze protection.
Site selection can influence
temperatures in the field. For
example, hillsides can be warmer
than bottomland when nights are still.
Also, making sure soil is moist,
compacted, and free of weeds prior to
a freeze can help maximize moisture
in the air, and thereby maximize air
If you use overhead
irrigation for freeze protection you
must be able to pump large volumes
of water to get good protection.
Remember that when the air is dry it
will take even higher volumes of
water to give protection to the plants.
On calm nights, the sprinkler system
can be turned on when the
temperature in the coldest part of the

(Continued on page 2)

IFAS is an Equal Employment Opportunity Affirmative Action Employer authonzedto provide research, educational information and other services onlyto individuals andinstitutions that
function without regardto race, color, sex, age, handicap, or national origin US Departmein of Agnculture, Cooperative Extension Service, University of Flonda, IFAS, Florida A & M
University Cooperative Extension Program, and Bloards of the County Commissioners Cooperating

A monthly newsletter of the University of Florida
IFAS, Gulf Coast Research and Education Center,
and Florida Cooperative Extension Service
Hillsborough County Cooperative Ext Service
5339 CR 579, Seffner, FL 33584
(813) 744-5519 SC 541-5772
Alicia Whidden, Editor Mary Chernesky,
Gulf Coast Research and Education Center
13138 Lewis Gallagher Road, Dover, FL 33527
(813)744-6630 SC 512-1160
Christine Cooley, Layout and Design
Jack Rechcigl, Director

December 2004

Berry/Vegetable Times

Berry/Vegetable Times

field is 32. If there is a low dew
point (i.e., the air is very dry), the
system should be turned on when the
temperature is 34. Turn the system
off when icicles are falling from the
plants, or the wet bulb temperature
has risen above 32. If wind speeds
are high, it may be difficult to
achieve uniform coverage, and
watering may cause more damage
than it prevents. Fortunately, windy
freezes are not common in west
central Florida.
In most situations, watering
the field the afternoon before a
freeze can reduce damage. For pot
culture, water the pots and the
ground around the pots if possible.
Just remember: there are
more factors to consider in a freeze
event than just the expected
minimum temperature. Watering for
cold protection is not always the best
choice. If you do use the sprinkler
irrigation method, make sure the
system 1) applies water uniformly
over your planting, and 2) puts out
the volume of water needed for
adequate freeze protection.
A happy and joyous holiday
season to everyone!
Alicia Whidden
(813) 744-5519 Ext. 134

Strawberry Freeze
Craig Chandler

While strawberry crown
tissue isn't usually injured until it
reaches a temperature of about 20
F, damage to flowers and fruit can
start to occur when tissue
temperature reaches 30 F. Sprinkler
irrigation is the standard method for
protecting strawberry flowers and
fruit from freeze damage. This
method of protection is convenient
and can be highly effective, although
it can also damage fruit (water

soaking and cracking), spread
disease inoculum, and result in the
loss of bed integrity.
Most of the freeze events in
Hillsborough and Manatee County
(where the main strawberry
production area is located) are
radiation freezes (little or no wind),
with air temperature typically
bottoming out in the low 30s or high
20s. In this type of freeze, growers
will generally wait to turn on their
sprinkler irrigation system until the
air temperature just above the plastic
mulch, in an area open to the sky, is
31 F. Standard practice for a
system where sprinklers are spaced
50 ft. x 50 ft. is to use 9/64-inch
nozzles in the sprinkler heads and
run the system so that there is 75
pounds of water pressure to the
heads. Such a system should apply
water uniformly and in sufficient
quantity (about 0.15 inch per hour).
It is important that sprinklers make
at least one revolution per minute for
adequate freeze protection.
When an advective (windy)
freeze is expected, and temperatures
are predicted to drop into the low to
mid 20s, it is common practice to use
11/64-inch nozzles (to provide the
additional water needed for
protection) and turn the sprinkler
system on when the air temperature
reaches 34 F. However, if wind
speeds are 10 mph or greater, at least
some flower and fruit damage is
likely to occur.
Once the sprinkler system
has been turned on, it should remain
on until the wet bulb temperature has
risen above 32 F.

Early Season Arthropod
Pests in the Strawberry
Crop: Cyclamen Mites
James F. Price and Silvia I Rondon

Almost every year from
Thanksgiving into early January
some Hillsborough County

strawberry farmer, and sometimes
many farmers, discover cyclamen
mites in their crops. The problem
needs to be recognized early and
treated immediately to avoid
detrimental effects on yield. This
mite can be a very serious pest in the
area. Infested plants are stunted and
produce a late and reduced crop. The
cyclamen mite is found frequently on
ornamental crops in Florida,
particularly those crops produced in
greenhouses. However, widespread
infestations in Florida strawberry
fields occur only occasionally. In the
northeastern United States,
California and the Pacific Northwest
cyclamen mites in strawberry crops
are common. The following
summarizes points concerning this
pest that are important to Florida
strawberry growers.

Cyclamen mites.

Symptoms of Attack on
Strawberries from Hillsborough
County: When local strawberry
fields are infested we find that
strawberry leaves are small,
chlorotic, highly wrinkled,
thickened, and possess short petioles.
Runners oftentimes have numerous
small "thorns" rather than a smooth
texture. Additional symptoms
include dark brown, dry flowers,
russeted berries and poorly
developed root systems.
Examination of plants under a
stereomicroscope reveal cyclamen
mites in the crevices of leaf wrinkles,
on unopened and opened flowers, on
newly formed fruit and in the plant
bud. Some plants contain as many as
a few hundred of these mites.
(Continued onpage 3)

December 2004

Berry/Vegetable Times

Development of the
Problem on Strawberries:
Problems with the cyclamen mite on
strawberries in Florida develop from
setting infested plants imported from
the north. In more northern climates,
where strawberries are grown for late
spring fruiting, cyclamen mites
overwinter as adult females in the
crowns of infested strawberry plants.
Populations begin to develop in the
early spring and reach peaks in
Cyclamen mites move
along runners from mother plants to
daughter plants. New fields
established from the daughter plants
are rarely heavily infested unless the
daughter plants had been severely
infested earlier. Plants grown for a
second year are much more likely to
be heavily infested, and thus should
not be used as planting stock.
This pest, once introduced
into fields in Florida, can move
along runners to infest neighboring
plants or can be carried by bees,
other insects, birds, field workers or
machinery to infest other fields. The
movement of mites along the soil or
on plastic mulch is not likely since
the mite requires the humid
environment of plant surfaces.
Appearance and
Development of the Mite:All forms
are so small that they are only faintly
visible without optical
magnification. In the field, they can
be seen with a 14X or stronger hand
lens. Eggs, nymphs and adult
females are the forms most
frequently observed. Eggs are about
half as large as adult females, oval
and smooth, opaque white. Several
eggs may be found bunched
together. The adult female is slightly
tan with its hind legs reduced to
thread-like structures. Males are
smaller and with hind legs modified
with claspers to hold onto and
transport adult females and immobile
pupae. Nymphs (larvae) are opaque
white with a triangular enlargement
on their posteriors.
Controlling a Cyclamen

Mite Infestation: Control of an
outbreak of cyclamen mites is
difficult to achieve, so strategies
should be directed toward preventing
an outbreak through the use of plants
certified to be free of the pest. To
control cyclamen mites established
in a fruiting crop in Florida, it is
extremely important to detect the
infestation early before plant growth
has been affected significantly and
before the numbers of mites have
become too large. A regular program
of crop scouting should insure the
earliest detection of this pest.
Thiodan' endosulfann), Kelthane
(dicofol) and diazinon are the
miticides available for cyclamen
mites on strawberries, but none
provides the rapid control of this pest
that is desired. Thiodan' should be
applied at 2 pounds of active
ingredient in 400 gallons of
preparation per acre. This material
cannot be applied more than once in
35 days. There is a 4-day waiting
period between application of the
product and the earliest permissible
Kelthane? should be
applied twice at 1.5-2 pounds of
active ingredient in 400 gallons
preparation per acre at 10 to 20-day
intervals. There is a 3-day waiting
period between application of
Kelthane? and the earliest
permissible harvest.
Diazinon should be applied
at 1 pound of active ingredient in
100 gallons of preparation per acre
and directed to the plant crown and
leaves. A maximum of four
applications can be made, but no
application should be made within 5
days of harvest.
High volumes of spray
preparations are favored for
miticides to contact the mites deep in
the plant bud. At least 150 psi is
required to penetrate the strawberry
canopy and contact mites in crevices.
Application machinery and methods
must be adjusted in order to achieve
proper delivery of Thiodan? or

Kelthane' All pesticide label
restrictions must be observed.
Special predatory mites are sold to
control cyclamen mites, however the
predators cannot control an
infestation sufficiently under our
conditions to avoid excessive losses.
Summary of Precautions
Against Cyclamen Mites:
1. Plant only stock from reputable
nurseries that has been and is
strawberries free of cyclamen mites.
2. Inspect fields regularly for
3. Restrict movements of possibly
contaminated personnel and
machinery into noninfested sites.
4. As the cyclamen mite has few
weed hosts on which to survive the
non-cropped summer, the
elimination of strawberry plants
from the area of an infested farm is
important to prevent reinfestation in
the following year.
5. Kelthane?, Thiodan? or diazinon
should be used to control any
infestations discovered.

Early Season Arthropod
Pests in the Strawberry
Crop: Lepidopterous
Larvae, Aphids
Silvia I. Rondon and James F. Price

After strawberries are
established, growers must pay
attention for the next several weeks
to early -season pests such as
lepidopterous larvae ("worms"),
aphids, cyclamen mites and spider
mites. Scouting should start as soon
as transplant establishment irrigation
ends to determine level of pest
infestations and to be in position to
choose among the best control
methods. This article discusses the
early-season aphid and worm
problems. Another article discusses
cyclamen mites.

(Continued on page 4)

December 2004

Berry/Vegetable Times

Lepidopterous Larvae.
There are two principal species of
worms that cause early losses in the
Plant City production area. These
are the fall armyworm (Fig. 1) and
southern armyworm (Fig. 2). These
worms are the immature stage of the
Lepidoptera family of moths and
develop through a complete
metamorphosis including egg, plant
eating larvae (worm), hidden and
resting pupae and the night flying
adult (moth) stage.

Fig. 1. Larva ofthe fall armyworm (Credit.
J.L.Capmnera, UF). Larva has two
characteristic dark bands along the side of the

Fig. 2. Larva of the southern armyworm
(Credit J.L. Capinera, UF). Larva has
triangular patterns on its upper surface.

Fig. 3. Egg masses ofarmyworms (Credit.
J.K. Clark, UC).

Eggs of both are laid in
masses and covered with the

mother's body scales (Fig. 3). Larvae
feed on young strawberry leaflets
and buds as they develop. Dark,
small fecal pellets on the tops of the
leaves or on the plastic mulch
indicate larval feeding.
Scouting should be
performed once or twice per week
during the early season to check for
young leaves with holes and missing
margins. When larvae are found,
pesticidal interventions are usually
warranted and most insecticides
offer better control when they are
applied at early stages of larval
development. Several products are
available to control these worms.
SpinTor and formulations of
Bacillus thuringiensis ("B.t.") can be
effective and neither of these is very
hazardous to beneficial arthropods,
although, of the two, B.t. is the less
damaging. For instance, in moderate
usage these insecticides are
compatible with Phytoseiulus
persimilis, the predatory mite widely
used to control the twospotted spider
mite. Lannate Brigade and
Danitol can also be effective;
however, they are broad-spectrum
insecticides that have a detrimental
effect on many parasites and
predators. None of the latter three
insecticides should be applied if P.
persimilis predators have been
released. These predators should not
be released within 3 weeks of a
Lannate application or within 6
weeks of a Brigade or Danitol
Aphids. There are two
species of aphids found in Florida
strawberries, the strawberry root
aphid and the cotton aphid (the
cotton aphid has another accepted
name, the melon aphid). Aphids may
be green, black, brown or some other
color depending on the sap color of
the host plant. These slow-moving
insects with pear-shaped bodies
ranged from 1 /16 to 1 /8 inch long
(Fig. 4). Only a few aphids have
wings (Fig. 5), but all have a pair of
cornicles, siphons or "exhaust
pipes", one on each side of the rear

Fig. 4. The cotton aphid (Credit. S.I. Rondon,
UF). Notice the characteristic dark relatively
short corncles.

Fig. 5. The 'winged form' of cotton aphid
(Credit S.I. Rondon, UF).

Aphids are sucking insects that feed
by thrusting their long beaks into the
strawberry plant tissue and can cause
wrinkling of the leaves. They
remove great quantities of sap then
excrete the sugary excess as
"honeydew". The honeydew makes
the plant sticky and the fruits
displeasing. A sooty mold often
develops with the honeydew that can
blacken stems, foliage and fruit.
Aphid damage reduces
photosynthesis when leaves are
distorted. Well established
strawberry plants can tolerate low to
medium levels of aphids. Usually
parasitic wasps, predators and
diseases that contribute greatly to
aphid control can be found in the
field (Fig. 6).

The use of trade names in this pubhcation is
solely for the purpose ofproviding specific
information. It is not a guarantee or war-
ranty of the products names and does not
signify that they are approved to the exclu-
sion of others ofsuitable composition. Use
pesticides safely. I. ,, direc-
tions on the manufacturer's label.

December 2004

Berry/Vegetable Times

Fig. 6. Brown paper-hke texture of a
parasitized aphid (right). (Credit S.I. Rondon,

Among the products
registered in Florida for aphid
control are: Diazinon, malathion,
methomyl, naled, azadirachtin,
Beauveria bassiana, bifenthrin,
endosulfan, oils, and soap.
Good control of early -season worms
and aphids leave the crop in
excellent condition for the high-
value, early-season yields. This
alone is sufficient to give these
problems very special attention at
this time of the year.

Pesticide Registrations
and Actions

?? Based on a request by FMC
Corporation and IR-4, tolerances
are approved for the herbicide
carfentrazone (Aim). This is a
triazolinone herbicide that
controls many broadleaf weeds.
Tolerances of importance to
Florida include all tropical
fruits, herbs and spices (group
19), fig, citrus, okra, peanut,
persimmon, strawberry,
sugarcane, bulb vegetables
(group 6), fruiting vegetables
(group 8), legume foliage
vegetables (group 7), leafy
vegetables (group 4), leaves of
root and tuber vegetables (group
2) and root and tuber vegetables
(group 1). (Federal Register,

?? Based on a request by Bayer
CropScience, tolerances are
approved for fenamidone. This
is an imidazolinone fungicide,
which inhibits respiration in
water molds as well as some
ascomycetes andAlternaria.
Tolerances of importance to
Florida include cucurbits (group
9), tomato, and tuberous and
corm vegetables (group 1C).
(Federal Register, 8/29/04).
?? Based on a request by IR-4,
tolerances are approved for the
fungicide fludioxonil !. .' i .. '
*11.! .1 i. This is a
phenylpyrrole fungicide that is
active against a number of fungi
including Fusarium,
Rhizoctonia, Aspergillus,
Alternaria, Sclerotinia, and
Septoria. Tolerances of
importance to Florida include
snap bean, citrus (group 10),
leafy greens except spinach
(group 4A), melon subgroup 9!,
and yam (Federal Register,
?? On September 1, the FDACS
conditionally registered the
fumigant Profume (sulfuryl
flouoride) for control of
Postharvest pests and rodents.
(FDACS PREC Agenda).
?? On September 1, the FDACS
issued the Special Local Needs
registration SLN FL-040008 to
Syngenta for the use of Bravo
Weatherstik on blueberry plants
after harvest to control rust.
?? Based on a request by Dow
AgroSciences and IR-4,
tolerances are approved for the
insecticide methoxyfenozide
(Intrepid). Tolerances of
importance to Florida include
black sapote, mango, papaya,
pea, and succulent bean
(subgroup 6A & 6B), sapodilla,
star apple, strawberry, legume
foliage vegetables (group 7),
leafy vegetables (group 4),
leaves of root and tuber

vegetables (group 2) and root
and tuber vegetables (group 1).
(Federal Register, 9/29/04).
?? Based on a request by ISK
Biosciences Corporation,
tolerances are approved for the
fungicide cyazofamid. This is a
cyanoimidazole, which inhibits
mitochondrial transport. It is
reportedly efficacious against
water molds and downy mildew.
Tolerances of importance to
Florida include cucurbits (group
9), potato, and tomato. (Federal
Register, 8/30/04).
?? Based on a request by Dow
Agrosciences and IR-4,
tolerances are approved for the
insecticide tebufenozide
(Confirm). Tolerances of
importance to Florida include
citrus (group 10) and tuberous
and corm vegetables except
potato (subgroup ID). (Federal
Register, 9/24/04).
?? ORGANIC--Oro Agri Inc. is
developing a new organic
that contains orange oil, borax,
and surfactants. The use sites
include berries, fruits and nuts,
vegetables, and ornamentals.
(Agricultural Chemical News,
EPA has begun movement on
the methyl bromide critical use
exemption allocation process.
The following are the amounts
(in metric tons) available to
Florida growers of tomato
(2,347), pepper (721),
strawberry (344), and eggplant
(58). (FFVA Presentation of

Pesticide Potpourri
?? The EPA recently released
"Pesticide Industry Sales and
Usages: 2000 and 2001 Market
Estimates." As of 2001,
conventional pesticide use was
(Continued on page 6)

December 2004

Berry/Vegetable Times

nearly one billion pounds per
year. Addition of chlorine and
wood preservatives brought that
figure to nearly 5 billion pounds.
Herbicides were the number one
type of pesticide based on user
expenditures and volume. With
85 to 90 million pounds used in
2001, the herbicide glyphosate
replaced atrazine as the most
widely used pesticide in the
agricultural market. (EPA
Pesticide Program Update,
?? An industry group (RISE)
recently commissioned a poll of
Americans regarding pesticide
and repellent use in light of
West Nile virus. The survey
examined respondent's
knowledge of the virus, their
perceptions of the severity of the
threat and the measures they
have taken to prevent being
bitten by mosquitoes. The
survey found that 73 percent of
respondents have used insect
repellents containing DEET,
while 25 percent have used non-
DEET repellents. Seventy
percent also removed standing
water around their residence.
Sixty-three percent made sure
their family members used a
repellent, and 77 percent said
communities "definitely should"
or "probably should" implement
mosquito control measure such
as fogging or spraying when the
threat of the virus is present.
(Pesticide & Toxic Chemical
News, 8/30/04).
?? A recent comparison between
U.S. Air Force veterans who
sprayed herbicides in Vietnam
with those who served in
Vietnam but did not spray
herbicides revealed little
difference between cancer rates.
However, the comparison did
reveal that incidence of prostate
cancer increased with the
amount of time served in
Vietnam. (Chemical Regulation
Reporter, 9/13/04).

GCREC Center Update
Christine Cooley

Construction will soon be
completed at the new Balm Research
Center and occupancy for the
Bradenton faculty and staff is slated
for January 16th. The Dover faculty
and staff will be relocating to the
new center during the month of April
2005. The address for the center is:
Gulf Coast Research and
Education Center, 14625 Balm
Road, Wimauma, FL 33598.
The Dover research center
will be closed for the holidays on
December 24 and will remain closed
until January 3rd. However, the
faculty and staff will be checking
their voice mail and email messages
throughout the holiday closing.

Congratulations to Dr. Joe
Noling with the Citrus Research
Center in Lake Alfred. Dr. Noling
was recently presented with the
Public Service Award at the
Strawberry Jam held by the Florida
Strawberry Growers Association.
Dr. Noling has worked extensively
with local strawberry growers on
various nematode problems, and his
hard work and dedication is truly
appreciated by the industry.

a Straw&ewy Sawncav

Ctvu tma6

Twas the night before harvest
and all through the farm
not a creature was stirring
till they hear the alarm.

A hard freeze was a'coming,
and all they could do
is get that water going,
sit up, and stew.

With the water's protection
the berries were fine.
The farmers were tired,
but got their pickers in line.

Soon baskets were full
and off to market they went.
To places up north is
where they were sent.

The strawberries of Florida
are a northerner's treat.
During the holiday season
they can't be beat.

So thanks to the farmers
and their hard working hands
for bringing some sweetness
to those cold barren lands.


December 2004

Berry/Vegetable Times

SPECIAL GCREC FACT SHEET leaves in the nursery. Thus, infected the foliar infections helps to prevent

Powdery Mildew of
Natalia Peres and Jim Mertely

Pathogen and Symptoms. Powdery
mildew, caused by Sphaerotheca
macularis, occurs in most areas of
the world where strawberries are
grown. The disease affects leaves,
flowers and fruit. Early foliar
infections are characterized by small
white patches of fungus growing on
the lower leaf surface. On
susceptible cultivars, dense mycelial
growth and numerous chains of
conidia (spores) give these patches a
powdery appearance (Figure
1). Under favorable conditions, the
patches expand and coalesce until
the entire lower surface of the leaf is
covered (Figure 2). At times, round
fruiting structures (cleistothecia) are
produced in the mycelia on the
undersides of leaves (Figure 3).
Cleistothecia are initially white but
turn black as they mature. In some
cultivars, relatively little mycelium is
produced, making it difficult to see
the white patches. Instead, irregular
yellow or reddish brown spots
develop on colonized areas on the
lower leaf surface, and eventually
break through to the upper surface
(Figure 4). The edges of heavily
infected leaves curl upward (Figure
4). The fungus can also infect the
fruit, producing fuzzy mycelia
growth on the achenes (seeds)
(Figure 6). Infection of flowers and
fruit may reduce fruit quality and
marketable yields.

Disease Development and Spread.
Sphaerotheca macularis is an
obligate parasite that only infects
living tissue of wild or cultivated
strawberry. In temperate areas, the
pathogen may survive by producing
cleistothecia, but these structures are
rarely produced in Florida. The
fungus readily infects living, green

transplants are normally the primary
source of inoculum in fruiting fields.
When conditions are favorable,
conidia produced on infected plants
are wind dispersed to infect new
growth. Development and spread of
powdery mildew is favored by
moderate to high humidity and
temperatures (60 to 80 F). Rain, dew
and overhead irrigation inhibit the
fungus. Because dry conditions and
high humidity are common in
greenhouses and plastic tunnels,
powdery mildew is typically more
severe in protected culture. In open
fields in Florida, the disease is
typically most severe in November
and December, usually subsides in
January and early February, but may
reappear in late February and March.

Control. Use of transplants free of
powdery mildew is a good method
for controlling the disease but even
disease free fields can become
infected by conidia blown in from
neighboring fields. Cultivars differ
widely in their resistance to powdery
mildew. Unfortunately, the most
popular cultivars, 'Strawberry
Festival' and 'Camarosa' are fairly
susceptible to the disease. Fields
with susceptible cultivars should be
surveyed regularly for powdery
mildew, especially during the early
season. To control powdery mildew
on susceptible cultivars, fungicides
should be applied at the first sign of
disease. This is especially important
when using protectant fungicides
such as elemental sulfur. Systemic
fungicides like the benzimidazoles
(Topsin M) and the sterol
inhibitors (I i. ,,. and ProcureR
can effectively control powdery
mildew if the pathogen population
has not become resistant to them.
Strobilurin fungicides such as
Abound Cabrio, and Pristine
are also effective in suppressing the
disease, but caution should be taken
not to exceed four to five
applications per season. Controlling

fruit infections.

Fig. 1. Alyceha ofSphaerotheca macularts on
leafsurface. Photo: UF, GCREC

Fig. 2. Lower leaf surface covered with
powdery mildew. Photo: UF, GCREC

Fig. 3. Microscope picture ofcleistothecia on
leafsurface. Photo: UF, GCREC

December 2004

Berry/Vegetable Times

Fig. 4. Necrotic spot reaction caused by
Sphaerotheca macularis in some cultivars.
Photo: UF, GCREC

Fig. 5. Curhng leaves on severely in-
fectedplants. Photo: UF, GCREC

Fig. 6. Sphaerotheca macularis on ache-
nes (seeds). Photo: UF, GCREC


Trade name Active ingredient Type (hours Comments

Do not add silicone surfactants or
Abound azoxystrobin strobilurin 4 Efomlt
mix with EC formulations

Cabrio pyraclostrobin strobilurin 24 No more than two sequential ap-

Nova myclobutanil sterol inhibitor 24 Do not apply more than 40 oz./A/

Pristine boscalid + carboxamide + 24 No more than 115 oz. product per
pyraclostrobin strobilurin season.

Procure triflumizole sterol inhibitor 24 No more than 32 oz./A/season.

Topsin M thiophanate methyl benzimidazole 24 No more than 4 Ibs. product/A/

Ar b, K n potassium bicarbon- p t Do not mix it with highly acidic
Armicarb, Kaligreen ate protectant 4 products.

Wettable sulfurs elemental Supresses mites, including preda-
(numerous trade names) sulfur protectant 24 tory populations in biological con-
trol programs.

December 2004

University of Florida Home Page
© 2004 - 2010 University of Florida George A. Smathers Libraries.
All rights reserved.

Acceptable Use, Copyright, and Disclaimer Statement
Last updated October 10, 2010 - - mvs