Results and Discussion No. 14, Fla. Dept. of Agr. & Consumer Ser., Div. of Plant Industry, Talla- hassee, FL. The disease symptoms first appeared as water soaked spots Chupp, C. and A. F. Sherf. 1960. Vegetable diseases and their control. Ronald 10 mm in diameter. After 20 d, necrotic lesions became visible Press, New York. 692 p. Dwivedi, R. P. and S. C. Dubey. 1987. Web blight of Eupatorium cannabinum on the inoculated plants. The spots enlarged to 25 mm or more L. caused by Thanatephorus cucumeris. Indian Jour. Mycology and Plant and then turned dark brown. A whitish mycelium grew rapidly Pathol. 161:309. over the leaves, killing them (Fig. 5), and spread a mycelial web McMillan, R. T., Jr., H. Vande Hei, and W. R. Graves. 1994. First report of web from leaf to leaf. Many small brown sclerotia and web-like blight caused by Thanatephorus cucumeris on Cupaniopsis anacardiopsis in the United States. Plant Dis. 78:317. mycelia were found on the leaves (Fig. 6), typical of the disease McMillan, R. T., Jr., H. Vande Hei, and W. R. Graves. 1994. First report of web symptoms found on the infected nursery plants. Rhizoctonia blight caused by Thanatephorus cucumeris on Sophora tomentosa in the Unit- solani was consistently re-isolated from all the inoculated plants ed States. Plant Dis. 78:317. while no symptoms were observed on the uninoculated plants McMillan, R. T., Jr., M. Borek, and W. R. Graves. 1997. Web blight of dwarf (Fig. 7). Thus Koch’s postulates were thereby fulfilled. Hawaiian snowbush. Proc. Fla. State Hort. Soc. 110:370. Pirone, P. P. 1970. Diseases and Pests of Ornamental Plants. Ronald Press, New York. 546 p. Literature Cited Preston, D. A. 1968. Host index of Oklahoma plant diseases supplement, 1948. Plant Dis. Reptr. 32:398-401. Alfieri, S. A., Jr., K. R. Langdon, J. W. Kimbrough, N. E. El-Gholl, and C. Sharma, J. K. and K. V. Sankaran. 1984. Rhizoctonia web blight of Albizia fal- Whelburg. 1991. Disease and Disorders and Plants in Florida. Bulletin cataria in India. European J. of Forest Pathol. 14:261-264.

Proc. Fla. State Hort. Soc. 115:130-133. 2002. PESTICIDE MODE OF ACTION CODES TO AID ORNAMENTAL GROWERS IN DEVELOPING CONTROL PROGRAMS TO MANAGE PEST RESISTANCE

ELZIE MCCORD, JR.1 Arthropod resistance to pesticides has been a problem in New College of Florida ornamental crop culture since the early era of synthetic organic Natural Science Division pesticides. A notable example of the problem comes from the 5700 North Tamiami Trail leafminer, Liriomyza trifolii (Burgess) outbreaks of the 1970s. Sarasota, FL 34243-2197 Leafminers were causing losses in chrysanthemum, other annu- al ornamentals (gerbera, aster, gypsophila, and many bedding JAMES F. PRICE AND CURTIS A. NAGLE plants) (Price, pers. comm.) and some vegetables (Parrella et University of Florida, IFAS al., 1981). Several effective pesticides including early organo- Gulf Coast Research and Education Center phosphates (methyl ), (), pyre- 5007 60th Street throids () (Robb and Parrella, 1984), and triazines Bradenton, FL 34203 (cyromazine) (Price, 1984), were identified for leafminer con- trol during the outbreak period, but pesticide efficacy was lost Additional index words. ornamentals, , pesticides, due to resistance by the leafminer (Mason et al., 1987). insects, IPM Methods to manage arthropods have included reducing the Abstract. The development of resistance to pesticides has selection pressure of pesticides by emphasizing rotations caused problems in producing high quality, economically among pesticides of different chemical classes and limiting re- competitive ornamental plants in Florida. Presently, there are peated applications of pesticides within identical ones. This approximately 65 pesticide active ingredients involving at method is flawed in that pesticides of multiple chemical classes least 25 different modes of action available for arthropod con- sometimes compromise biological processes (mode of action) trol on ornamental crops in Florida. Resistance management that are identical. Rotation between different chemical classes requires growers to consider product mode of action as a ma- with the same mode of action increases the selection pressure jor factor in rotational schedules. Mode of action information is and can result in more rapid resistance. For example, tradition- not usually found on product labels or in informational fact sheets, thus preventing many growers from developing indi- al rotational schemes could allow rotations between organo- vidualized control programs with emphases on arthropod re- phosphate and classes, but both are acetyl sistance management. A coding system has been developed cholinesterase inhibitors that interfere with neural transmis- to identify pesticide modes of action. Pesticides of different sion. Additionally, some pesticides within a single chemical class modes of action should be selected to apply in a rotation to a possess different modes of action and rotation between those single arthropod community, thus avoiding selection within should not increase the selection pressure to either. For exam- that community for resistant individuals. ple, and are carbamates, but the mode of action of carbaryl is to inhibit acetyl cholinesterase at the synap- tic cleft and fenoxycarb mimics juvenile hormone. Use of one 1Corresponding author. should not necessarily affect the selection pressure of the other.

130 Proc. Fla. State Hort. Soc. 115: 2002.

We propose that Florida ornamental growers alter their plan would provide for applications of the carbamates, car- rotational schemes to follow a plan that provides for rotation baryl (acetyl cholinesterase inhibitor) and fenoxycarb (juve- among pesticides of different modes of action rather than nile hormone mimic) in rotation. chemical class (Bethke, 2002). This rotational plan would se- Adoption of this plan could reduce the selection pressure lect one pesticide between the organophosphates and car- toward pesticides of each mode of action and should result in bamates (acetyl cholinesterase inhibitors) and one among an increased period of usefulness for many pesticides. aminohydrazones, organosulfurs, organotins, pyrazoles, py- Table 1 shows codes, active ingredients, trade names, use, ridazinones, pyrroles, and the rotenoids due to their related chemical class and mode of action of pesticides registered for effects on oxidative phosphorylation. On the other hand, the use in Florida ornamentals. We assigned simple code num-

Table 1. Mode of action codes for ornamental insecticides and miticides.zy

Codex Active ingredient Trade names Use Chemical classw Mode of action and notes 1 Methyl Bromide Methyl Bromide Biocide Alkyl Bromide Broad biological toxicant. Resistance to fumigants unlikely 2 1,3-Dichloropropene Telone II® Biocide Organochlorine Broad biological toxicant. Resistance to fumi- gants unlikely 3 Metam Sodium Metam®/Metam Sodium® Nematocide Thiocarbamate Broad biological toxicant. Resistance to fumi- gants unlikely 4 Probait®/Amdro® IGR Aminohydrazone Blocks ATP synthesis 4 Propargite Ornamite®/Omite® Miticide Organosulfur Inhibits ATPas 4 Fenbutatin-oxide Vendex® Miticide Organotin Oxidative phosphorylation inhibitor/ uncoupler 4 Fenpyroximate Akari® Miticide Pyrazole Electron transport inhibitor 4 Pyridaben Sanmite® Miticide Pyridazinone Electron transport inhibitor 4 Chlorfenapyr Pylon® Pyrrole Oxidative phosphorylation inhibitor/ uncoupler 4 Rotenone Rotenone 5% Dust® Insecticide Rotenoid Electron transport inhibitor 5 Fenoxycarb Precision®/Preclude® IGRv Carbamate Juvenile hormone mimic 5 Distance®/Pyrigro® IGR Pyridine Juvenile hormone mimic 6 Halofenozide Mach 2® IGR Diacylhydrazine Ecdysteroid antagonist causing premature lethal molting 6Tebufenozide Confirm® IGR Hydrazide Ecdysteroid antagonist causing premature lethal molting 6 Azadirachtin Azatin®/Ornazin® Insecticide Tetranortriterpenoid Ecdysone metabolism inhibitor and blocks sty- loconic receptors 7 Diflubenzuron Adept®/Dimilin® IGR Substituted Chitin synthesis inhibitor 8 Hexythiazox Savey®/Hexygon® Miticide Carboxamide Ovicide/larvacide, specific mode of action unknown 8 Clofentezine Ovation® Miticide Tetrazine Ovicide/larvacide, specific mode of action unknown 9 Carbaryl Sevin® Insecticide Carbamate Acetyl cholinesterase inhibitor 9 Turcam®/Closure® Insecticide Carbamate Acetyl cholinesterase inhibitor 9 Furadan® Insecticide Carbamate Acetyl cholinesterase inhibitor 9 Pinpoint®/Orthene® Insecticide Organophosphate Acetyl cholinesterase inhibitor Brackett®/Address® Sedagri® 9 Azinphos-methyl Guthion®/Sniper® Insecticide Organophosphate Acetyl cholinesterase inhibitor 9 Dursban®/Duraguard® Insecticide Organophosphate Acetyl cholinesterase inhibitor 9 Diazinon®/Knoxout® Insecticide Organophosphate Acetyl cholinesterase inhibitor 9 Dimethoate® Insecticide Organophosphate Acetyl cholinesterase inhibitor 9 Di-Syston® Insecticide Organophosphate Acetyl cholinesterase inhibitor 9 Ethoprop Mocap® Insecticide Organophosphate Acetyl cholinesterase inhibitor 9 Malathion®/Atrapa® Insecticide Organophosphate Acetyl cholinesterase inhibitor Prozap® 9 Supracide® Insecticide Organophosphate Acetyl cholinesterase inhibitor 9 Dibrom® Insecticide Organophosphate Acetyl cholinesterase inhibitor 9 Oxydemeton methyl Metasystox-R ® Insecticide Organophosphate Acetyl cholinesterase inhibitor 9 Imidan® Insecticide Organophosphate Acetyl cholinesterase inhibitor 9 Sulfotepp Plantfume 103® Insecticide Organophosphate Acetyl cholinesterase inhibitor

zMinimize repeated use of products possessing identical codes on any arthropod community. yMention of a product does not constitute a recommendation by New College of Florida or the University of Florida, nor does it warrant or imply warranty of activity. xCodes only apply to this table. wRead and follow product labels. vIGR = . uNo Code. Plan does not restrict use.

Proc. Fla. State Hort. Soc. 115: 2002. 131

Table 1. (Continued) Mode of action codes for ornamental insecticides and miticides.zy

Codex Active ingredient Trade names Use Chemical classw Mode of action and notes 9Trichlorfon Dylox®/Proxol® Insecticide Organophosphate Acetyl cholinesterase inhibitor 9 & 10 Chlorpyrifos + Duraplex® Insecticide Organophosphate Acetyl cholinesterase inhibitor and axonic poi- cyfluthrin and son (Sodium channels leak sodium ions) 10 Thiodan®/Phaser® Insecticide Organochlorine Axonic poison (Sodium channels leak sodium ions) 10 Kelthane® Miticide Organochlorine Axonic poison (Sodium channels leak sodium ions) 10 Talstar®/Attain® Insecticide Pyrethroid Axonic poison (Sodium channels leak sodium ions) 10 Cyfluthrin Decathlon®/Tempo® Insecticide Pyrethroid Axonic poison (Sodium channels leak sodium ions) 10 Demon® Insecticide Pyrethroid Axonic poison (Sodium channels leak sodium ions) 10 Deltaguard® Insecticide Pyrethroid Axonic poison (Sodium channels leak sodium ions) 10 Tame® Insecticide Pyrethroid Axonic poison (Sodium channels leak sodium ions) 10 Lambda- Scimitar®/Battle® Insecticide Pyrethroid Axonic poison (Sodium channels leak sodium Demand® ions) 10 Permethrin Permup®, Astro®/Pounce® Insecticide Pyrethroid Axonic poison (Sodium channels leak sodium Dragnet®/Ambush® ions) 10 Tau-fluvalinate Mavrik®/Yardex® Insecticide Pyrethroid Axonic poison (Sodium channels leak sodium ions) 11 Tefluthrin Fireban® (Bait) Insecticide Pyrethroid Axonic poison (Sodium channels leak sodium ions) Bait unlikely to interact with other pyre- throids; therefore, gets new number. 12 Diatect®/1600, X-clude®/ Insecticide Axonic poison (Sodium channels leak sodium 1100 Pyrethrum®/Pyrellin® ions) Pyreth-It®/Pyrenone® 12 Bifenazate Floramite® Miticide Carbazate GABA antagonist (blocks/closes chloride chan- nels) 12 Chipco® Insecticide Fiprole GABA antagonist (blocks/closes chloride chan- nels) 12 Abamectin Avid® Miticide Macrocyclic Lactone GABA antagonist (blocks/closes chloride chan- nels) 13 Cyromazine Citation® IGR Triazine Affects nervous system of immature insects, spe- cific mode of action unknown 13 Merit®/Marathon® Insecticide Nicotinoids Nicotinic receptor antagonist Provado® 13 Spinosad Conserve® Insecticide Spinosyn Blocks nicotinergic receptors 14 Bacillus thuringiensis Javelin®/Dipel® Insecticide Unique biological fer- δ-Endotoxin causes gut paralysis Kurstaki Foray®/Crymax® Thuri- mentation product cide®/Troy-BT® Biobit® 14 Bacillus thuringiensis Xentari® Insecticide Unique biological fer- δ-Endotoxin causes gut paralysis Azawai mentation product 14 Bacillus thuringiensis Gnatrol® Insecticide Unique biological fer- δ-Endotoxin causes gut paralysis Israeliensis mentation product 14 Bacillus thuringiensis Novodor® Insecticide Unique biological fer- δ-Endotoxin causes gut paralysis Tenebrionis mentation product 15 Beauveria bassiana Naturalis®/Botanigard® Insecticide Unique biological Fungal entomopathogen agent 16 Capsaicin Hot pepper Wax Repellent Unique Repellent 17 Cinnamaldehyde Cinnamite® Insecticide Unique Specific mode of action unknown Miticide 18 Polyhedral occlusion Spod-X®/Gemstar® Insecticide Virus Nuclear polyhedrosis viruses incorporates into Bodies of NPV host’s DNA controlling cells 19 Pymetrozine Endeavor® Insecticide Pyridine azomethines Neural inhibition of feeding behavior 20 Cryolite Prokil® Insecticide Halide Mode of action unknown 21 Sulfur Microthiol® Insecticide Inorganic sulfur Mode of action unknown

zMinimize repeated use of products possessing identical codes on any arthropod community. yMention of a product does not constitute a recommendation by New College of Florida or the University of Florida, nor does it warrant or imply warranty of activity. xCodes only apply to this table. wRead and follow product labels. vIGR = Insect Growth Regulator. uNo Code. Plan does not restrict use.

132 Proc. Fla. State Hort. Soc. 115: 2002.

Table 1. (Continued) Mode of action codes for ornamental insecticides and miticides.zy

Codex Active ingredient Trade names Use Chemical classw Mode of action and notes 22 Metaldehyde Deadline® Molluscicide Acetaldehyde polymer GABA system disrupter. Formulated as a bait, it Trails End®/Durham® is unlikely to affect the same arthropod community as GABA antagonists 23 Fenoxycarb Award® (Bait) IGR Carbamate Juvenile hormone mimic 24 S- Extinguish® (Bait) IGR Isoprenoid Juvenile hormone mimic 25 Abamectin Varsity® Miticide Macrocyclic Lactone GABA antagonist (blocks/closes chloride chan- nels) NCu Potassium salt of fatty Insecticidal Soap® Insecticide Potassium salt of fatty Pesticidal soap, disrupts cuticular wax causing acid M-Pede® acid dehydration. Resistance to soap is unlikely NC Petroleum distillates Citrus oil/ultra fine oil Insecticide Refined Petroleum Suffocation. Resistance to oil is unlikely paraffinic oil, horticultural Distillate oil, Safe-T-Side® NC Clarified hydrophobic Triact® Insecticide Botanical oil Suffocation. Resistance to oil is unlikely extract of neem oil NC Heterorhabditis megidis Nemasys® Insect parasite Unique biological Pathogenic nematode that introduces bacteria Steinernema feltiae agent into insect circulatory system causing septice- mia. Resistance to nematode is unlikely NC Steinernema carpocapsae Millenium® Insect parasite Unique biological Pathogenic nematode that introduces bacteria agent into insect circulatory system causing septice- mia. Resistance to nematode is unlikely

zMinimize repeated use of products possessing identical codes on any arthropod community. yMention of a product does not constitute a recommendation by New College of Florida or the University of Florida, nor does it warrant or imply warranty of activity. xCodes only apply to this table. wRead and follow product labels. vIGR = Insect Growth Regulator. uNo Code. Plan does not restrict use. bers to a list of products so that growers could select among many factors involved in making decisions that are not con- products of interest, those in their chemical sheds, and com- sidered here. If growers use the information in Table 1, we pare modes of action. We encourage growers to limit the use should see an increase in integrated pest management in of products with the same code during a growing season and Florida ornamentals and a possible reduction in insecticide to rotate among products with different codes. resistance. It is difficult to predict resistance to a particular chemical class or insect species. Therefore, we conservatively assigned Literature Cited the same code to active ingredients with similar modes of ac- Bethke, J. 2002. A new mode of resistance management. Greenhouse Prod- tion. We also assigned the same code number to insecticide uct News 12:34-37. classes where cross-resistance has been observed. Bolin et al Bolin, P. C., W. D. Hutchison, and A. D. Andow. 1999. Long-term selection (1999) observed cross-resistance in the European corn borer for resistance to Bacillus thuringiensis Cry1Ac endotoxin in a Minnesota to Bacillus thuringiensis Berliner (Bt) toxin, Cry1Ac, in labora- population of European corn borer (Lepidoptera: Crambidae). J. Econ. tory selections and Iqbal et al. (1996) found evidence of field Entomol. 92:1021-1030. Iqbal, M., R. H. J. Verkerk, M. J. Furlong, P. C. Ong, S. A. Rahman, and D. J. cross-resistance in the diamondback moth to both Bt subspe- Wright. 1996. Evidence for resistance to Bacillus thuringiensis (Bt) subsp. cies, Azaiwa and Kurstaki and abamectin. kurstaki HD-1, Bt subsp. aizawai and abamectin in field populations of 1,3-Dichloropropene (code 2), an organochlorine, was Plutella xylostella from Malaysia. Pestic. Sci. 48:89-97. given a separate code from other organochlorines (code 10) Mason, G. A., M. W. Johnson, and B. E. Tabashnik. 1987. Susceptibility of Li- riomyza sativae and L. trifolii (Diptera: Agromyzidae) to permethrin and because it is a soil fumigant that will have dissipated prior to . J. Econ. Entomol. 80:1262-1266. the arrival of phytophagous insects and mites in ornamentals. Parrella, M. P., K. L. Robb, and P. Morishita. 1981. Response of age-specific Metaldehyde bait (code 22) was also separated from the larvae of Liriomyza trifolii (Diptera: Agromyzidae) to various insecticides GABA system disrupters (code 11) because its target organ- with notes on efficacy testing, p. 206-215. In D. J. Schuster [ed.]. Proceed- isms and delivery system apply minimal selection pressure to ing of IFAS-Industry Conference on Biology and Control of Liriomyza Leafminers. Lake Buena Vista, Florida, November 3-4, 1981. foliar pests. Price, James F. 1984. Results of recent field experiments with Trigard, Avid Nematodes, neem oil, paraffinic oil, and insecticidal soaps and other pesticides on flower crops in Florida, p. 139-150. In S. L. Poe were given the code NC because it is unlikely that insects and [ed.]. Proceedings of the 4th Annual Industry Conference on the Leaf- mites would develop resistance to their modes of action; miner. Sarasota, Florida, January 16-18, 1984. Robb, K. L. and M. P. Parrella. 1984. Efficacy of selected new insecticides therefore, our plan does not restrict their use. against Liriomyza trifolii (Burgess), p. 157-164. In S. L. Poe [ed.]. Proceed- We view Table 1 as a tool to assist growers in their pest ings of the 4th Annual Industry Conference on the Leafminer. Sarasota, management decisions; however, we realize that there are Florida, January 16-18, 1984.

Proc. Fla. State Hort. Soc. 115: 2002. 133