Group Title: Berry/vegetable times.
Title: Berry/vegetable times. September 2005.
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Title: Berry/vegetable times. September 2005.
Uniform Title: Berry/vegetable times.
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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: September 2005
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Volume ID: VID00037
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September 2005

A monthly newsletter of the University of Florida IFAS
Florida Cooperative ExtensionService,
Hillsborough County
5339 CR 579, Seffner, FL 33584
(813) 744-5519 SC 541-5772
Alicia Whidden, Editor Mary Chernesky, Director
Gulf CoastResearch and Educaon Center
14625 County Road 672, Wimauma, FL 33598
(813) 634-0000 SC514-6890
Christine Cooley, Layout and Design
Craig K. Chandler, Ce Editor
Jack Rechcigl, Center Director

From Your Agent...
Syngenta Products
Doug Wilbanks of
Syngenta notified me of
several changes that have
occurred since last strawberry
season. For Switch, the
plant back restriction has been
reduced to 30 days from the
last application and
anthracnose control has been
added to the label. Previously
Switch only had Botrytis on
the label. Now the insecticide
Actara has a label for
strawberries for aphids.
Thanks Doug for the update!

Mark Your Calendars!
On Dec.8 the first
Cucurbit Production
Workshop will be held by
Phyllis Gilreath, Manatee
County Extension, and me at
GCREC in Balm. There are
thousands of acres of cucurbits
are grown in the south central
Florida region. This important
group includes yellow squash,
zucchini, cucumbers,
cantaloupe and watermelons.
The meeting will be in the
auditorium from 1:30 pm-4:30
pm. It is being held in the
afternoon so growers can
harvest in the morning and
come to the research center in
the afternoon to hear a wide

range of talks on this very
valuable group of crops.
Topics planned are insects and
viruses, diseases, herbicides,
water and fertilization,
nematodes, and varieties.
There will be a "trade show"
area where you can mingle
with industry representatives
and learn about the latest
products and varieties.

Alicia Whidden
Hillsborough County Extension
813-744-5519, ext. 134

Switching to Highly-
Retentive Mulches to
Reduce Methyl
Bromide Rates
James P. Gilreath and Bielinski M.
Santos, GCREC Weed Science
Phyllis R. Gilreath, Manatee County
Extension Service

During the next few
years, it is expected that the
price and availability of methyl
bromide will be serious
limitations to polyethylene-
mulched crop production.
Currently, most growers use a
rate of 350 lb/acre of the 67:33
(w:w) formulation of methyl
bromide + chloropicrin. This
is based on use of methyl
(Continued on page 2)

IFAS is an Equal Employment Opportunity Affirmative Action Employer authored to provide research, educational information and other services only to individuals and institutions that
function without regard to race, color, sex, age, handicap, or national origin U S Department of Agnculture, Cooperative Extension Service, University of Flonda, IFAS, Florida A & M
University Cooperative Extension Program, and Bloards of the County Commissioners Cooperating

September 2005

BerryNegetable Times

Berry/Vegetable Times

bromide with standard low or high density
polyethylene film mulch, which has low
fumigant retention.
Recent research and grower trials have
demonstrated that both virtually impermeable
films (VIF) and metalized mulches greatly
improve fumigant retention and therefore
increase efficacy against soilborne pests. The
main advantage of these films is they allow
reduction in methyl bromide rates up to one-
half of the current recommendations, without
significantly losing efficacy on pests,
especially hard-to-control weeds, such as

S...... ............. I

The days of plastic mulch and methyl bromide
will soon be history.

With regard to VIF, there are two main
concerns: cost and handling characteristics.
Today, all VIF is made in Europe and must be
imported, thus resulting in much higher cost
than standard film. Also, most VIF products
are more difficult to lay than standard films in
that they are prone to linear sheer under too
much tension. Handling characteristics among
VIF materials differ significantly, but all are
based on polyamides, such as nylon, for their
barrier properties and these polyamides do not
stretch well. Also, none are embossed at the
present time.
The barrier properties of metalized
films also have been tested under field
conditions, first with Inline and more recently
with methyl bromide. In each case, application
of Inline or methyl bromide in conjunction
with metalized film greatly increased the
retention of the fumigant. Rate reduction with
methyl bromide works when combined with a

highly retentive mulch film like VIF or Canslit
metalized film.
In addition to the use of the right film,
success requires close monitoring of fumigant
flow, assuring not only the correct rate, but
also uniform delivery in the bed. Non-
uniformity guarantees poor fumigant
performance at any rate, but with reduced rates
of methyl bromide, the results can be even
more dramatic. It would be wise for growers to
start experimenting with highly-retentive films
before the lack of methyl bromide catches
them unprepared.

Whitefly Q Biotype
Phyllis R. Gilreath, Manatee County Extension Service
David Schuster, GCRECEntomology
Paul Stansly, SWFREC Entomology

The whitefly Q biotype is thought to
have originated in the Mediterranean region
where it is now the most prevalent strain of the
sweet potato whitefly Bemisia tabaci. It has
plagued greenhouses in southern Spain for
years, increasing insecticide costs. The Q
biotype was first identified in the U.S. in
March 2005 by scientists at the University of
Arizona and California on poinsettia plants in
Arizona that originated from a nursery in
California. More recently, the Q biotype has
been confirmed in an ornamental greenhouse
in northern Georgia; thus, it may be just a
matter of time before it's found in Florida.

(Continued on page 3)

September 2005

Berry/egetable Times

The Q biotype is visually
indistinguishable from the B biotype (also
called the silverleaf whitefly), currently the
only biotype of B. tabaci in Florida fields. The
two biotypes can only be identified by
analyzing enzymes, or DNA. The B biotype
reproduces and develops more rapidly than the
Q biotype on most host plants in the absence of
insecticides, and both have a wide range of
host plants (more than 500 species from 74
families). However, Q outcompetes B in the
presence of many insecticides, and Q can
transmit TYLCV faster and more efficiently
than the B biotype.
The major problem facing Florida
growers is that Q is resistant or tolerant to
many of our commonly used insecticides for
managing whiteflies, including the nicotinoids
such as imidacloprid (Admire) and the insect
growth regulators Knack and Courier.
Resistance to endosulfan is uncertain, and,
while Oberon still seems to be active, the Q
biotype does have reduced susceptibility to the
nicotinoids Admire, Assail and Platinum. A
new nicotinoid from Valent called Venom has
yet to be tested under commercial field
conditions in Florida, but reportedly is
effective. The level of resistance that we see
in this pest will depend in part on the origin of
the invasion and the history of previous
exposure. Unfortunately, and unlike the B
biotype, resistance in biotype Q is stable, and
does not diminish over time. With the B
biotype, susceptibility to the nicotinoids
returns after 2-3 generations without exposure
to the nicotinoids. This is not the case with the
Q biotype, where tolerance to the nicotinoids
persists for over a year in the lab, even when
the whitefly is not exposed to the nicotinoids.
Fortunately, biotype B appears to out-compete
biotype Q; that is, in the absence of insecticide
use (i.e. organic farm), biotype B
What can growers do? Keep in mind
that if both biotypes are present and we spray
heavily, we are selecting for the Q biotype.

Thus, there is even more pressure to follow
resistance management recommendations,
including rotation of chemicals, proper use of
nicotinoids (i.e. only once per season) and,
especially, the inclusion of a 2-3 month crop-
free period into the production cycle. This
latter permits biotype Q to move into non-crop,
non-sprayed host plants where it will be
displaced by biotype B, and also permits the
dissipation of any nicotinoid tolerance that
may have developed in biotype B. Perimeter
spraying is not recommended, because this will
increase unnecessary exposure of the whitefly
population to insecticides. Additionally,
natural enemies such as parasitic wasps are
killed that can be helpful in controlling
whiteflies, especially the Q biotype. Growers
are also urged to refrain from using nicotinoid
products on crops where they aren't necessary
to further decrease exposure to these important
Early detection will be key to any
attempt to control this pest. Growers should
maintain good scouting activities and good
cultural practices (chemical rotation, rouging
of infected plants, etc.). Unusual whitefly
activity or higher than normal control
difficulty, even under an optimal control
program, should be reported immediately. As
to what the future holds in one
knows for sure. There are varying opinions as
to how big the potential problem could be, but
until we actually have to deal with the pest,
this is all speculative. When the B biotype was
first confirmed back in the late 1980's, the A
biotype was the primary biotype. Biotype A
was not a large problem and not well
established, so the B biotype established
quickly. This time, the B biotype is well
established, so some think Q may have a
harder time getting established. Looking at the
resistance situation, and knowing it can
outcompete the B biotype, we can only hope
this will be the case. Time will tell.
Reference: FDACS-DPI Pest Alert on Bemisia tabaci
(Gennadius) biotypee 'Q'): A potential new biotype for
Florida's vegetable and ornamental crops, 4/21/05.

September 2005

Berry/Vegetable Times

Know the Signs of Heat Stress
Alicia Whidden, Hillsborough County Extension

This summer in North Carolina there
were several reports of farm workers
collapsing in the fields and even dying from
heat stroke when temperatures were in the
mid-90's. At this time of year when we are
preparing fields for the new growing season
the temperatures still feel like the middle of
summer and can be in the 90's. It is important
to know the signs of heat stress and what
emergency treatment to take. Also it is very
important to make sure your workers are
educated about heat stress as part of their WPS
training. Remember WPS training of new
workers should be done before the start of the
sixth day of work.

Heat stress is an illness that occurs
when there is a buildup of body heat that is
more than the body can tolerate. It can occur
from body heat generated by our muscles as
we work or externally by the environment.
Heat leaves our bodies by moving from our
skin to the air, evaporation by perspiration,
exhaling hot air or touching a cool object.
High humidity makes it harder to cool
ourselves. As we age our ability to sweat
decreases so as you get older you need to be
more careful about heat stress. For agricultural
workers heat stress is a major concern as
agricultural workers have more Worker
Compensation claims related to heat illness
than other occupations. Heat illness impairs
our judgment and coordination and can lead to

(Continued on page 5)

Heat Stress Warning Signs and Treatments

Illes cipti Sy tse

Mild heat stress

Results from decreased flow of
blood to the brain; may lead to
heat exhaustion or stroke.

Dizziness, fatigue or irrita-
bility; reduced ability to

Move person to a shaded area for
half hour or more; loosen or
remove clothing; give water to

Heat cramps Painful muscle spasms Heavy sweating; thirst; Move person to shaded area to
(stomach, arm or leg) muscle spasms. rest; loosen clothing; give cool
during or after physical exertion fluids to drink, preferably con-
in heat. training electrolytes.
Heat exhaustion Acute reaction; results from Heavy sweating; pale, Immediately remove person to
decreased flow of blood to the clammy skin; increased cool shaded are and call 911;
brain and within circulatory pulse and breathing; weak- loosen or remove clothing and
system; may lead to heat stroke. ness; dizziness/fainting; splash cold water on body; have
excessive thirst person rest lying down; if con-
scious, give person water to
drink (frequently and in small
amounts) do not give salt.
Heat stroke Life-threatening medical emer- Excessively high body Call 911 immediately; move
agency; results from temperature; confusion; person to a shaded area and
inability of body to cool irrational behavior; slowed remove outer clothing; cover
itself and decreased flow of down or no sweating; rapid with thin wet towels or wrap in
blood to the brain and other breathing and pulse (if con- wet sheet, then pour on water
body organs. scious); possible and fan vigorously; if conscious,
convulsions and/or coma. give water to drink (frequently
and in small amounts), do not
give salt.
Table excerpted from: Mulher, Barbara. "If You Can't Stand the Heat Get Out of the Greenhouse", Ornamental Outlook, May 2005.

September 2005

Berry/Vegetable Times

other accidents and injuries.
In farm work there are several factors
that influence heat stress:
1. Environmental Factors- temperature, humidity,
air movement and sunlight
2. Workload- how difficult the job and the time of
3. PPE- personal protective equipment if required
for the job; choose the coolest possible to get
the job done.
4. Amount of water the person drinks
5. Scheduling- breaks to get out of heat and drink
fluids & gradually increasing work load to give
the body a chance to adjust to the heat.

One thing that is always stressed is to
drink plenty of water. One word of caution
is that there have been instances in extremely
hot conditions where a person drank so much
water they diluted their blood potassium level.
When your potassium levels are too low you
can have muscle weakness, cramping, trouble
breathing and cardiac arrest. It is very
important to maintain your body's mineral
balance so drinking sports drinks can help.
When you are profusely sweating remember to
replace the fluids you have lost but also think
about replacing the minerals as well.
Be sure everyone working in your
operation knows the symptoms of heat stress
and the first aid treatment to take. Do not
delay treatment!

Recent Experiments Yield New
Ideas: Plant Dip Experiments
Jim Mertely and Natalia Peres, GCREC Plant Pathology

At the AgriTech meeting last month,
several growers asked about dipping
strawberry plants in fungicides before planting.
There were two main questions: (1) Should I
dip? (2) What product should I use? Over the
past two seasons, we have tested several pre-
plant dip treatments for their effects on yield,
plant mortality, and anthracnose fruit rot

caused by Colletotrichum acutatum. The
results have not always been consistent, and
seem highly dependent on the condition of the
transplants to be treated.
'Festival' runner plants were used in the
2003-04 dip experiment. Although they
looked vigorous, 2 to 6% of the transplants
showed typical anthracnose lesions on the leaf
stalks or petioles (Fig. 1), and some plants also
had unusually dark roots (Fig. 2). These
symptoms were caused by Colletotrichum
acutatum, the anthracnose fungus responsible
for root necrosis leading to poor establishment,
and for anthracnose fruit rot. Plants from this
shipment were dipped for five minutes in
Abound, Oxidate, or Switch just prior to
planting. Other treatments included planting
without dipping (the dry control), dipping in
water alone (the wet control), washing the
plants before planting, applying extra fertilizer
(Osmocote), or spraying plants and plastic
mulch with white kaolin clay (Surround). The
last two treatments were applied immediately
after the plants were watered in.
In 2003-04, little anthracnose fruit rot
occurred in the experimental plots, and
marketable yields were relatively high. Over
the entire season, the highest marketable yields
were produced by the kaolin clay treatment
(33,800 lb/acre), followed by the Switch dip
(33,300 lb) and the Abound dip (32,000 lb)
treatments, although these yields are not
statistically higher than the comparable wet
control (30,000 lb) or the dry control (30,700
lb). During the December to January period,
the Oxidate dip treatment and the extra
fertilizer treatment produced lower marketable
yields than the controls because more plants
had died in these treatments. During the
February to March period, plants dipped in
Switch (28,600 lb) yielded significantly more
than the wet control (24,500 lb).
'Treasure' runner plants were used in the
2004-05 experiment. In addition to
anthracnose infections, these transplants had
(Continued on page 6)

September 2005

Berry/Vegetable Times

been exposed to unusual conditions in transit,
and showed signs of deterioration caused by
Botrytis and other microorganisms. The same
treatments were applied to these plants, but
with very different results.
Plant mortality was an important factor in
the 2004-05 experiment. By 7 weeks after
planting, 39% of the dry control plants had
died. However, only 25% of the wet controls
died, suggesting that the plants were
dehydrated and benefited from a 5-minute dip
in water before planting. Plant mortalities
were highest in the Oxidate dip (44%) and
extra fertilizer (41%) treatments and lowest in
the Abound dip (6%) and Switch dip (7%)
treatments. Yields over the entire season were
low due to plant mortality and poor growth of
the surviving plants in some treatments.
Dipping in Switch gave the highest marketable
yield of 18,400 lb/A (Fig. 3). The Abound dip
treatment produced the second highest yield
(9,200 lb), which was not significantly better
than the wet control (6,300 lb, Fig 4). The
stress-reducing effect of kaolin clay (4,700 lb)
did not significantly increase yield over the dry
control (3,900 lb).
Although these experiments may not
answer the grower's questions directly, they
may provide some helpful insights.
Considering product expense, labor
requirements, pesticide disposal issues, and
worker safety considerations, strawberry
transplants should not be routinely dipped in
fungicides before planting. However, dipping
may be necessary when susceptible cultivars
have been infected by C. acutatum in the
nursery. 'Camarosa' and 'Treasure' are highly
susceptible to anthracnose, and are more at risk
for infection in the nursery and development of
root necrosis disease following transplant.
Shipments of'Camarosa' and 'Treasure'
containing plants with petiole and root
symptoms shown in Figures 1 and 2 are good
candidates for dip treatment. Aromas, Camino
Real, Gaviota, and Ventana are less popular
cultivars that are also susceptible to C.

acutatum. 'Festival' is less susceptible than
'Camarosa' and 'Treasure'; however,
'Festival' may still become infected in the
nursery and fail to establish properly in the
field. 'Carmine', 'Sweet Charlie', and 'Winter
Dawn' are highly resistant to C. acutatum, and
presumably would not benefit from a dip

Fig. 1. Petiole lesions caused by C.acutatum.

Fig. 2. Root necrosis caused by C. acutatum.

Abound, Oxidate, and Switch are
currently labeled for pre-plant dip treatment of
strawberry transplants. Switch gave the best
results in our experiments. Before dipping, the
main labels and supplementary dip labels
(Continued on page 7)

September 2005

Berry/Vegetable Times

Examine Transplants To Get a Jump
on Insect and Mite Problems
Jim Price, GCREC Entomology

Some of our insect and mite problems
begin entirely or in part with infested trans-
plants. A little time spent examining the stock
on transplanting day can pay dividends in al-
lowing us to react to problems early. Insects
and mites that typically arrive on our trans-
plants include cyclamen mites, spider mites,
and aphids.

Pig. 3. Pre-plant dip in switch

Fig. 4. Wet

should be read carefully. Labels for Abound
and Switch can be found at
The Oxidate label is available at According to the
labels for all three products, plants should be
set in the bed as soon as possible after
treatment. Plants which have been treated the
day before and stored in the shade or in the
cooler may show stunting, burning, root
abnormalities, and other symptoms of

In order to assess the status of insects
and mites on transplants, growers should select
one transplant from as many crates and bun-
dles as practical from each homogenous plant-
ing unit. A homogeneous planting unit is the
area planted from one week of transplanting of
one cultivar from one farm. The fully ex-
panded leaves of the selected transplants
should be examined for spider mites and
aphids with a 5 X hand lens and the still-folded
leaves within the crown should be examined
for cyclamen mites with a 14 X hand lens.
If pests are found then plans should be
developed to treat the plants early or to watch
the pests especially closely for quick reaction
once thresholds are reached.

The use of trade names in this publication is solely for the purpose of providing specific information. It is not a
guarantee or warranty of the products names and does not signify that they are approved to the exclusion of
others of suitable composition. Use pesticides safely. Read andfollow directions on the manufacturer's label.

September 2005

Berry/Vegetable Times

Comparison of UF/IFAS Cultivars Recommended for Commercial
Plantings in West Central Florida
Craig Chandler, GCREC Strawberry Breeding and Alicia Whidden, Hillsborough County Extension Service

Recommended Oct. 10-17 Oct. 1-21 Oct. 1-15 Sept. 24 Oct. 7
planting dates
within row spacing 12-14 14-15 12-14 12-14
Runner production
Runner production moderate high moderate low
in fruiting field
Average fruit wt. < 20 g < 20 g <20 g 18-22 g

primary medium
conic or wedge
- short conic

mostly conic

Primary wedge
Secondary/tertiary -

Primary medium
conic to wedge; sec./
tert. short conic

Fruit color -
rut lr deep red, glossy red orange red deep orange red
Fruit color orange streaked with warm red fading into
internal warm red bright red white white
internal white white
Calyx size medium large large medium

Fruit firmness med.-firm firm soft-medium medium

Flavor intensity medium med.-high medium low-medium

Sweetness low medium high low

Fruit production .
rt pr t early mid early very early
Susceptibility to
y to low moderate high low
Botrytis fruit rot

Resistance/susc. to moderate suscepti-
esistacesus. to low susceptibility rt ti resistant low susceptibility
anthracnose fruit rot ability

Susceptibility to Col-
letotrichum low to moderate high low to moderate low
Crown rot

high antioxidant
levels in fruit

best combination
of fruit quality and
yield when planted
Oct. 10-17
r ...1.

may be more suscep-
tible to Phytophthora
root rot than the other
T ,.TU -1+'. ,-

propagation in
Florida a possibility
because of crown rot

'Sweet Charlie'

Fruit shape


September 2005



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