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Improved Pesticide Rotation Plan to Manage Insecticide/Miticide Resistance
Jim Price, Curtis Nagle and Elzie McCord
Arthropod resistance to pesticides has been a problem in strawberry culture since the early era of synthetic organic
pesticides. A notable example of the problem comes from the twospotted spider mite and the miticides developed for its control.
Since the 1960s, spider mites have become resistant to several miticides, including malathion, dicofol (Kelthane ), fenbutatin-
oxide (Vendex), pyrethroids, and abamectin (Agri-Mek).
Methods to manage resistance have included reducing the selection pressure of pesticides by emphasizing rotations
among pesticides of different chemical classes and limiting repeated applications of pesticides within identical classes. This
method is flawed in that pesticides of multiple chemical classes sometimes disrupt biological processes (mode of action) that are
identical. Rotations between those increase the selection pressure toward a resistant pest population. Traditional rotational
schemes allow rotations between organophosphate and carbamate classes, but both are acetylcholine esterase inhibitors that
interfere with neural transmission at the synaptic cleft.
Some advocate that farmers rotate among pesticides of different modes of action rather than of different chemical
classes. By this plan, rotations would provide for selection of one pesticide from the organophosphates and carbamates (inhibit
acetylcholine esterase) and one pesticide from pyrethroids and organochlorines (cause nerve axons to leak sodium ions).
Adoption of this plan could reduce the selection pressure in a pest population toward pesticides of each mode of action and
should result in an increased period of effectiveness for many of our valuable products.
We have developed a table that presents the insecticides and miticides registered in Florida for strawberry, their modes
of action and related group codes. The table is available at our Web site: http://strawberry.ifas.ufl.edu/prodguide.htm.
Growers should minimize the application of products to the same arthropod species from a single mode of action group in order
to reduce selection pressures toward resistance. Rather, they should make their choices for pesticide rotations among different
modes of action. No code is given to products to which resistance is unlikely. Our plan does not restrict their use beyond those
imposed by product labels.
Table 1. Mode of action codes for strawberry insecticides and miticidesz'y
Active Trade Names Chemical Class" Mode of Action and Notes
1 Metaldehyde Deadline /Trails Acetaldehyde GABA system disrupter.
2 Abamectin AgriMek Macrocyclic Lactone GABA agonist, which opens chloride channels preventing
nerve re-polarization at neuromuscular unction.
3 Carbaryl Sevin Carbamate Acetyl Cholinesterase Inhibitor.
3 Malathion Malathion Carbamate Acetyl Cholinesterase Inhibitor.
3 Methomyl Lannate Carbamate Acetyl Cholinesterase Inhibitor.
3 Azinphos-methyl Guthion Organophosphate Acetyl Cholinesterase Inhibitor.
3 Chlorpyrifos Lorsban Organophosphate Acetyl Cholinesterase Inhibitor.
3 Diazinon Diazinon Organophosphate Acetyl Cholinesterase Inhibitor.
3 Naled DiBrom Organophosphate Acetyl Cholinesterase Inhibitor.
4 Azadirachtin Azatin Tetranortriterpenoid Ecdysone metabolism inhibitor and blocks styloconic
Berry Times 1
5 Bacillus thruingiensis XentariR Unique Biological 6-Endotoxin causes gut paralysis.
aizawai Fermentation Product
6 Endosulfan ThiodanR/Phaser Organochlorine Axonic Poison (Sodium channels leak sodium ions).
6 Dicofol Kelthanee Organochlorine Axonic Poison (Sodium channels leak sodium ions).
6 Methoxychlor MethoxychlorR Organochlorine Axonic Poison (Sodium channels leak sodium ions).
6 Bifenthrin BrigadeR Pyrethroid Axonic Poison (Sodium channels leak sodium ions).
6 Fenpropathrin DanitolR Pyrethroid Axonic Poison (Sodium channels leak sodium ions).
6 Pyrethrum + Piperonyl Pyrenone Pyrethrum Axonic Poison (Sodium channels leak sodium ions).
6 &7 Pyrethrum + Rotenone Pyrellin Pyrethrum Axonic Poison (Sodium channels leak sodium ions) and
Inhibits electron transport.
7 Propargite OmiteR Organosulfur Inhibits ATPase.
7 Fenbutatin-oxide Vendex Organotin Oxidative phosphorylation inhibitor/uncoupler
8 Cinnamaldehyde Cinnamite Unique Specific mode of action unknown.
9 Hexythiazox SaveyR/HexygonR Carboxamide Ovicide/larvacide, specific mode of action unknown.
10 1,3-Dichloropropene Telone IIR Organochlorine Broad Biological toxicant.
11 Beauveria bassiana BotanigardR Unique Biological Unique Fungal Entomopathogen.
Naturalist L Agent
Refined Petroleum Ultra-Fine Oil Refined Petroleum Suffocation. Resistance to oil is unlikely.
Clarified hydrophobic TrilogyR Botanical Oil Suffocation. Resistance to oil is unlikely.
extract of neem oil
Potassium salt of fatty M-PedeR Potassium salt of Pesticidal soap, breaks cuticular surface tension causing
acid fatty acid insect to dehydrate. Resistance to soap is unlikely.
Potassium salt of fatty Insecticidal Soap@ Potassium salt of Pesticidal soap, breaks cuticular surface tension causing
acid fatty acid insect to dehydrate. Resistance to soap is unlikely.
z Minimize repeated use of products possessing identical codes on any arthropod community.
Y Mention of a product does not constitute a recommendation by the University Florida, nor does it warrant or imply warranty of
x Codes only apply to this table.
w Read and follow products labels.
The San Luis Valley and UF/IFAS
Strawberries Jim Sumler
"Perhaps if we go forward in the search we may stumble
upon the thing which we are looking for, but if we stay
where we are, nothing will come to light" Plato
The San Luis Valley in south central Colorado is
120 miles long and 45 miles wide, and an average altitude
of 7,600 feet. The San Juan and Sangre de Cristo
Mountains border three sides of the valley and provide a
natural barrier to some disease and insect problems. The
valley is an agricultural center where potatoes, alfalfa and
barley predominate. Smaller acreages of vegetable crops
mlle Ut/IhAS strawberry seedling program m
Monte Vista, Colorado is progressing.
Berry Times 2
include spinach, head lettuce and carrots. Major soils in the
agricultural areas are a loamy sand with a high water table,
usually at a depth of 2 to 5 feet. The soil is alkaline, around
pH 8, which can cause some minor element deficiencies.
The San Luis Valley Research Center operated by
Colorado State University is currently conducting a
strawberry research project with a Valley grower. This
involves the use of row covers and different planting dates to
establish early plantings for nursery production. So far there
seems to be some success with using row covers for early
The UF/IFAS strawberry seedling program is
progressing along the usual stages. Seeds planted in late
April in a greenhouse near Center, Colorado were subjected
to some rather low temperatures in May, most nights with
temperatures in the 20s (Fahrenheit). Although the
greenhouse was heated, high winds made it difficult to
maintain optimum temperatures. The low temperatures
probably delayed seed germination; however, germination
greatly increased in mid June when greenhouse low
temperatures were in the 50s. Seedlings were transferred
from seed trays to peat pellets beginning on 25 June, and
with the help of Margaret Sanderson a total of 4,498
seedlings were set. Some seed trays were saved after the
seedlings were dug and more seeds are now germinating.
These new seedlings may be dug later if time allows and a
back order of peat pellets arrives in time. This would allow a
later planting of strawberries to determine if this would be
practical there. The seedlings that have been transferred to
peat pellets were planted in the field beginning on 16 July.
In September two daughter plants from each seedling will be
dug and shipped to Florida for evaluation in the fruiting field
Fungicide resistance management: The
nursery challenge Dan Legard
Last month I talked about fungicide resistance and
how fruit growers could minimize the risk of pathogens
developing resistance by carefully managing their use of
fungicides. However, since annual fruit production fields are
typically established with transplants from either high
elevation or Canadian nurseries, fungicide use in nurseries
also can be important in the development of fungicide
resistance in pathogens. For Colletotrichum crown rot (C.
gloeosporioides), if fungicide resistance develops in a
fruiting field, it may be able to over-summer in Florida on
weed hosts around the field. However, the pathogens for
anthracnose fruit rot (C. acutatum) and powdery mildew
(Sphaerotheca macularis) do not appear to over-summer in
Florida, so it is most likely that fungicide resistant strains
would develop only in nurseries.
The proper use of fungicides in nurseries is critical
for the production of disease-free transplants and to prevent
the development of fungicide resistant pathogens. Many
manufactures limit or prohibit the use of pesticides in nursery
situations because of the greater likelihood of fungicide
resistance developing when the same fungicides are used in
both nursery and fruiting fields. However, there is a clear
benefit for using fungicides in nurseries to help prevent the
establishment of pathogens on transplants and reduce the
spread of disease after transplanting. It is also more cost
effective to treat plants in a nursery than after they have been
transplanted in the fruiting field.
I would suggest that nurseries continue to use
fungicides as directed by the label and employ the same
fungicide resistance management strategies we
recommended for fruit production fields (Berry Times July
2002). By using sound disease control programs in both the
nursery and the fruiting field we should be able to control
disease and prevent the development of fungicide resistant
Soil pH management for the 2002 2003
season John Duval
With the 2002-2003 season just two months away it
is time to start thinking about soil fertility. Soil testing
should be conducted now to allow analytical results to be
returned and fertilizer and lime orders to be placed.
pH is the measure of soil acidity and it affects
chemical, physical and biological properties of the soil. The
availability of nutrients in the soil is the main concern for
growers (see figure). While pH affects the availability all
nutrients, micro elements (manganese, boron, copper, and
zinc) are more severely affected than macro nutrients. The
best pH for production of strawberry is between 6.0 and 6.5
with 6.2 being optimum. Soil test results should give a
recommendation for the amount of lime to apply to raise the
pH into this range. Liming materials are also beneficial in
adding calcium and magnesium to fruiting fields. Lime
should be broadcast and thoroughly incorporated prior to bed
pH 40 4b 0 5 f60 65 70
7 S 8n R5 9g
Strongly aid Neutral Stron ly alkaline
| A nl Ir I I* I I I
4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9
4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8-5 9_(
The wide portions of the bands indicate the zones of
greatest nutrient availability. (Mengel and Kirkby 1987)
Berry Times 3
Center Update Christine Manley
After two months of work, our horticulture building is occupied once again by our plant breeding and plant
physiology programs. A new air handling system has been installed, new ceiling panels replaced the old, fresh paint covers
the walls, and a new room especially designed to hold our growth chambers was constructed in the former storage area.
Next will be the installation of our new computerized irrigation system. Bids have been received and the work should
We are pleased to announce that Steve MacKenzie, Biological Scientist in our Plant Pathology Department, has
been accepted to the Ph.D. graduate program at the University of Florida and awarded an Alumni Fellowship. He will be
under the supervision of Dr. Dan Legard and will continue working on strawberry research at our center in between
commutes to Gainesville. As a result of Steve's departure, a new face will be found at GCREC-Dover. Teresa Seijo will
be joining Dr. Legard's program. Teresa worked with Dr. Bob McGovern in the Bradenton plant pathology program, where
she conducted research on various vegetables. With Dr. McGovern accepting a position in Gainesville, Teresa was given
some options, and we are happy she elected to try her hand at strawberries.
We would also like to welcome Camille Esmel who will be working with Dr. John Duval on her MS degree in
strawberry nutrition. Camille has a B.S. degree in Environmental Horticulture from the University of New Hampshire in
Durham and specialized in crop production and nutrition. Her experience and enthusiasm will be welcomed at GCREC
AgriTech 2002 is schedule for August 27 and 28 with IFAS presentations scheduled for Wednesday, August
28. For complete information call the Florida Strawberry Grower's Association at (813) 752-6822 or visit their
website at http://www.straw-berrv.org.
New growth chambers will be
used for a variety of
experiments including a
hydroponic experiment on
The use of trade names in this publication is solelyfor the purpose of providing
specific information. It is not a guarantee or warranty of the products named, 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
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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) 744-6630 SC512-1160
Website http//strawberry ifas ufl edu
Editors Dan Legard (leaardaiufl edu) & Craig Chandler (ckc, ufl edu),
Design, Layout & Distribution Christine Manley (cmanlevaufl edu),
Director lack Rechcinl