Group Title: Berry/vegetable times.
Title: Berry/vegetable times. November 2002.
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 Material Information
Title: Berry/vegetable times. November 2002.
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: November 2002
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Bibliographic ID: UF00087388
Volume ID: VID00011
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.


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Berry Times

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Sources and Considerations for Predatory Mites
James F. Price

Those who choose to use predatory mites for
twospotted spider mite management this season should have
selected suppliers and initiated discussions about the events to
come. In case this has not occurred, this article lists points to
consider in selecting a supplier of Phytoseiulus persimilis
predators. Some elements are especially important in selecting
suppliers and are presented below. The suppliers should be
recognized in the area for providing high-quality predators in a
timely manner.
The Phytoseiuluspersimilis predators should be from a
strain selected for tolerance to organophosphorus insecticides.
The suppliers should be prepared to send a replacement
shipment immediately if the original shipment is of insufficient
quality or is damaged. The suppliers should be knowledgeable
about their products, our strawberry cultural system (pests and
diseases encountered; insecticides, miticides, fungicides, and
bactericides used; plant spacing; planting, growth, irrigation,
harvest and termination schedules, frost protection methods,
temperatures, humidities, etc.), and how the predators can be
managed successfully here. Suppliers, and growers alike, should
insist that predators be used only in conjunction with weekly
scouting by a professional contractor or a well-trained employee
whose primary responsibility is to scout.
The author knows of two firms that regularly supply
predators to Plant City area strawberry growers, Agri-Tech
Services (Gordon DeCou, Home: 941-756-2981, Cell: 941-
745-4416, email: and EcoSolutions (Jim
Cashion, 727-787-3669, email:
Others may exist in the area.
There are many suppliers available through Suppliers
of Beneficial Organisms in North America, an electronic
publication by the California Department of Pesticide
Regulation and available on-line at
hlII. i". pl.r .. c. v/docs/ipminov/ben supp/contents.htm
Only a small portion of the suppliers from this list possess the
understanding of our system of culture to provide the support
growers need.

WEDNESDAY NOVEMBER 13th 10 am- 4 pm
John R. Duval

Do you want to make the most efficient use of your
water, fertilizer, and chemical resources? Then come to the
Drip Irrigation School taking place Wednesday November 13th
from 10 AM to 4 PM at the GCREC -Dover and find out how.
Topics to be covered include injection of fertilizers and
chemicals, irrigation scheduling, drip system trouble shooting,
soil water monitoring, and irrigation BMPs.

Lunch is provided and 1 1 CEU credits (of which 1
will be CORE) and 2 2 CCA credits will be available. If you
are interested in attending please call Christine Manley at
813-744-6630 ext 60 to reserve your space. For more
information and the program please go to

Strawberry Culture under Protective Structures
I. Production Systems
Dr. Daniel Cantliffe, Dr. Silvia I. Rondon, and Ashwin

The loss of methyl bromide in the year 2005, the
regulations on water-use for frost protection and transplant
establishment, regulations on pesticide usage, reduced number
of farms due to rapid urbanization, increasing labor cost, and
low productivity during winter (November to February), are
some of the major concerns for the Florida strawberry
industry. Growing strawberries in passive-ventilated
greenhouses using soil-less substrates, and integrating
biological control in the pest management practices may offer
a viable alternative for strawberry growers.

Figure 1.
The Protected
Agriculture Project,
Gainesville, FL

The Florida/Israeli Protected Agriculture Project
(Figure 1). il, '. 'i I. j .ill .. d '!i '.Ic d... headed by
Dr. Dan Cantliffe of the Horticultural Sciences Department,
University of Florida, has been conducting various
experiments to generate practical and location-specific
information for greenhouse production of cucumbers,
peppers, Galia melons, and strawberries in north-central
Florida. Researchers are studying various growing systems
(containers), soil-less substrates, plant densities, new
varieties, and methods of biological control for producing off-
season vegetables under passive-ventilated greenhouses. This
article specifically deals with some of our production systems
research. In next month's Berry Times, a follow-up article
will discuss our work on the biological control of strawberry
pests. Information about the research done with other crops
can be accessed at the previously listed website.
During Fall 2000 and 2001, a study was conducted
to compare the quality and yield of 'Sweet Charlie'

Berry Times 1


strawberry grown in polyethylene bags placed on the ground,
polyethylene bagsplaced on elevated gutter sections, or in a
specially designed 'Hanging Bed-Pack' trough system (Figure 2)
(Polygal Plastic Industries, Ramat Hashofet, Israel), elevated 1.8 m
above the ground level. Soil-less substrates like perlite, peat, and
pine bark were also evaluated for their performance in protected
strawberry culture. When plants were grown in polyethylene bags
placed on a gutter, yields were slightly higher than when plants
were grown in elevated troughs or in bags placed on the ground.
Yields were not affected by the type of soil-less substrate. These
studies provided us with some basic information on how the
various growing systems and soil-less substrates perform under
protected strawberry culture.

Figure 2. 'Hanging Bed-Pack' trough system

For the profitability of a protected strawberry operation,
maximum space utilization is critical. A study was conducted
during Fall 2001 to determine the effect of high plant densiies on
yield and quality of'Sweet Charlie' strawberry grown in a
passive-ventilated greenhouse (Figure 3). Plug transplants were
planted in a 'Hanging Bed-Pack' trough system filled with locally
available 1-inch sieved pine bark (Elixson Wood Products Inc.,
Starke, FL). The troughs were spaced 25.5, 23.5, 21.6, and 19.6
inches apart (center-to-center), resulting in four between-row
spacings. Plugs were either transplanted in every hole (7-inch
within-row spacing), or every other hole (14-inch within-row
spacing). The combinations of four between-row spacings and two
within-row spacings resulted in eight plant densities ranging from
36,120 plants to 73,578 plants per acre. Early yield (Nov 28 Jan
28) and total yield (Nov 28 Mar 22) per acre increased linearly
as plant density increased. The early yield per plant
(approximately 200 grams) was similar at all plant densities
whereas the total yield per plant was higher at 14-inch within -row
spacing than at the 7-inch within-row spacing (425 grams vs. 411
grams). The average fruit weight was 19.9 grams and more than 90
percent of the yield was marketable.

Figure 3. 'Sweet
Charlie '
growing in
'Hanging Bed-Pack'
trough system filled
with pine bark

Since plant density in protected strawberry
cultivation can be five times greater than the plant density
in the field, and higher air temperatures can be maintained
inside the passive-ventilated greenhouses during winter,
early yield from greenhouse-grown strawberries (3,192
12-lb flats/acre) can surp ass the total yield (2,226 12-lb
flats/acre; Florida Agricultural Statistics,
( of field-grown strawberries. The
total yield obtained from our greenhouse trials (6,605 12-
lb flats/acre) was almost three times that of field-grown
strawberries. The use of locally available and relatively
inexpensive soil-less substrate like pine bark ($6.50 /yd3)
eliminates the need for methyl bromide and offers a cost-
effective alternative to more expensive and commonly
used soil-less substrates like perlite ($31 / yd3) and peat
($53 /yd3). Thus, protected strawberry culture at high
plant densities can enhance early fruit production, which,
at higher off-season market prices, can translate into
higher income. This fall, we are conducting a variety trial
to test the performance of 'Sweet Charlie', 'Festival',
'Earlibrite', 'Treasure', 'Carmine', FL 97-39, and
'Camarosa' under protected culture.

Irrigating New Plantings
John R. Duval

Fruiting fields have been established and the fruit
will soon begin arriving, time for a breather. Think again!
As soon as over head irrigation is stopped, it is time to
start scheduling drip irrigation and fertigation. This is
perhaps the most critical time to pay attention to these
details. Plants are actively growing now and need
fertilization and adequate water. Most pre-plant fertilizer
has been leached out of the root zones of plants and needs
to be replenished, and while beds may seem to contain
adequate moisture this may not be the case. Young plants
have limited root systems and can only mine water from a
small volume of soil.

Calcium deficiency
induced top-burn

Frequently we see calcium deficiencies on
young leaves during November, not due to lack of calcium
in the soil but due to fluctuating soil moisture. Calcium
movement in the soil and plant occurs by mass flow. This
means that calcium moves only in the water stream.
Applications of calcium as a foliar spray have limited use
because calcium is not very mobile from one plant part to
another. The best means to avoid this is to maintain
proper soil moisture in the beds (soil water tension
between 8 and 15 centibars). IFAS recommendations for
fertilization are 0.3 lbs nitrogen and potassium per acre per
day for the first two weeks after establishment and 0.6 lbs
nitrogen and potassium per acre per day until February.

Berry Times 2

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plastic sheet with 5 cm
dia holes 20 cm apart



PVC guter section

These recommendations are a guide and can be adjusted due to
weather, variety or other factors that may alter the crop's
requirement for fertilizer.

Spotlight on Diagnosis
Jim Mertely and Dan Legard

Samples began arriving at the UF i !. i'cny.
Diagnostic Lab about three weeks ago. Some arrived in the box,
while others had already been planted. This season appears to
be repeating what occurred last year. Nearly all the samples
have been diagnosed with anthracnose disease caused by
Colletotrichum acutatum. Many were showing sunken dark
spots on the petioles, which is typical of this fungus. The plants
also showed a mixture of tan living and dark dying roots, which
probably account for establishment problems reported by the
A total of eight samples have been diagnosed with
anthracnose to date. 'Treasure' was the most seriously affected
cultivar. Samples of cultivar 'Camarosa', 'Gaviota', and
'Festival' were also positive for this disease. 'Camarosa' may
account for more samples in the future, since several
nurserymen have reported problems with this cultivar.
Hopefully, the late arrival of 'Camarosa' from northern
nurseries will allow these plants to become established under
cooler conditions, and reduce stress-related losses toC.

Plant Sanitation: Is it worth doing?
Jim Mertely

Most strawberry fields have already been planted and
watered in. At this point, many growers will consider trimming
old leaves off of their established plants. This form of pruning
or plant sanitation hastraditionally been carried out to suppress
disease and improve the appearance of the plant. When these
old leaves are removed, as the theory goes, pathogens are
removed with them, and a source of inoculum for newly
emerging leaves is eliminated.
We tested this theory in a series of field experiments to
determine the effects of plant sanitation on Botrytis fruit rot
(gray mold). Trimming old leaves after plant establishment
slightly reduced Botrytis fruit rot during the 1996-97
experiment, but was only partly effective in 1998-99, when
disease pressure was higher. In addition, the yields of trimmed
plants were no higher than those of plants that had not been
trimmed. During both seasons, a standard fungicide control
program based on captain provided better control of Botrytis
fruit rot, and higher yields than plant sanitation. While this was
not surprising, there were several unexpected results. For
example, combining plant sanitation and fungicide applications
did not improve disease control over fungicides alone. In
addition, the combined treatment yielded less than the fungicide
treatment alone. This suggests that cutting old leaves that have
not completely died may weaken the plant and decrease yield.
Based on these results, we do not recommend that growers use
plant sanitation to control Botrytis in Florida, although it may
prove useful in special situations. An organic or home grower
may obtain some control by selecting a cultivar with resistance
to Botrytis fruit rot (e.g., 'Camarosa' or 'Carmine'), and
periodically removing old dead leaves.

The effect of plant sanitation on anthracnose
diseases caused by Colletotrichum acutatum has not been
investigated. However, the biology of this fungus
suggests that trimming old leaves would not be very
effective. During the establishment period, mild weather
and overhead irrigation are favorable to the sporulation
and spread of this fungus. Young tissues are highly
susceptible to infection. Therefore, new leaves emerging
during establishment would likely be infected before the
old leaves are removed. These new leaves and petioles
may not show symptoms immediately, but maintain the
pathogen until February or March, when favorable weather
and an abundance of susceptible flowers and fruit lead to
epidemics of anthracnose fruit rot.

To trim or not
to trim

There is another form of plant sanitation that
may be essential to good disease management. This is the
practice of picking and throwing diseased fruit into the
alleyways during each harvest operation. Based on
theoretical considerations and our own observations, fruit
sanitation should be carried out.

Control of Powdery Mildew
Dan Legard

Powdery mildew is caused by the fungus
Sphaerotheca macularis. The disease typically begins as
small white patches of web-like growth on the bottom of
leaves. Tiny, semi-transparent conidia give the patches a
powdery appearance. As the disease progresses, it can
spread until it covers most of the underside of the leaflet.
On many cultivars, the fungus doesn't grow as much and it
may be hard to see white patches on the leaves. Instead
irregular-shaped yellow or black necrotic spots up to 3/8
inch (8.5 mm) develop on the lower surface of the leaf
which eventually spread through to the upper surfaces.
The edges of heavily infected leaflets may curl, and
flowers and fruit can also be infected. The fungus
colonizes achenes of the fruit and produce aerial mycelia
that make the seeds appear fuzzy.
The fungus only infects strawberry and does not
survive in the absence of living host tissue in Florida. In
nursery areas, it can over-winter in infected leaves (as
cleistothecia) and the most likely source of primary
inoculum in Florida is transplants. Spores are produced on
infected plants and air dispersed throughout the field and
to neighboring fields. The development and spread of
powdery mildew is favored by moderate to high humidity
and temperatures of 60 to 80 F (15 to 27 C). Interestingly,
rain or dew inhibits the fungus. Typically, powdery
mildew is only a problem in west central Florida from late
October to mid-December. However, when winter
temperatures are mild, the disease can continue to cause

Berry Times 3

Evidence ofpowdery mildew on leaves
and fruit

Cultivars differ in their susceptibility to powdery mildew. To control powdery mildew on susceptible cultivars, apply
fungicides at the first sign of disease. This is especially important when using protectants such as sulfur. Systemic fungicides like
Topsin M and other fungicides such as Nova can effectively control powdery mildew if the pathogen population has not developed
resistance to them. Survey the field looking for leaf distortion and discoloration that is indicative of powdery mildew, especially
during the early and late season. Controlling the foliar infections helps to prevent fruit infections. Once disease is found we
recommend that growers alternate applications of sulfur and Nova or Topsin M on a weekly schedule. Alternating fungicides
reduces the chance that pathogens resistant to the fungicides will develop.

Dan Legard accepts position with California Strawberry Commission
Craig Chandler

Dr. Dan Legard recently accepted the position of Director of Research for the California i !.i i-. ny Commission. Dan
began working at the University of Florida's Dover research center as an Assistant Professor of Plant Pathology in 1995, and was
promoted to Associate Professor in 2001. Dan's research program has focused on Botrytis and anthracnose fruit rot and
Colletotrichum crown rot- making significant contributions to our understandings of these serious diseases. In 1998, using grant and
gift money, Dan hired Dr. Jim Mertely to assist with field and laboratory work and to manage the center's diagnostic clinic. Dan has
run an active fungicide-testing program, which has been well supported by the agro -chemical industry. Several valuable fungicides
have been registered and labeled for use in Florida as a result of this program. In addition to developing an internationally recognized
research program, Dan has been very instrumental in the overall modernization of the Dover center, and deserves much credit for lab,
field, and computer upgrades at the center over the past seven years. Finally I must mention that the center's popular web site and
newsletter are primarily the result of Dan's vision (along with a lot of hard work and creativity from our very capable office
coordinator, Christine Manley).
Dan will be moving to the Monterey Bay area of California in mid December. His efforts on behalf of the University of
Florida and the Florida strawberry industry will be missed, but we are pleased his focus will remain on strawberries. Good luck Dan!
Jim Mertely will continue to manage the disease diagnostic clinic and handle other essential dutiesof the strawberry
p.,ii. l. '. program. A national search for a plant pathologist to fill Dan Legard's tenure-track position will be conducted over the
next several months.

The use of trade names n this publication is solely for the purpose ofproviding
specific information. It is not a guarantee or warranty of the products named, and
does not signify that they are approved to the exclusion ofothers ofsuitable
composition. Use pesticides safely. Read andfollow directions on the manufacturer's

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A monthly newsletter of the University of Florida Institute of Food and
Agricultural Sciences, Gulf Coast Research and Education Center, and
Florida Cooperative Extension Service
Gulf Coast Research and Education Center
13138 Lewis Gallagher Road, Dover, FL 33527
(813) 7446630 SC512-1160
Website http//strawberry ifas ufl edu
Editors Dan Legard (legard@ufl edu) & Craig Chandler (ckc@ ufl edu),
Design, Layout & Distribution Christine Manley (cmanlevyufl edu),
Director Jack Rechclgl

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