Suggestions for Managing Insecticide Resistance in the Greenhouse

J.P. Sanderson, Dept. of Entomology, Cornell University, Ithaca, NY

 

            Insecticide resistance is a major concern for chemical control of almost all of the important greenhouse insect and mite pests.  A combination of the biology of the pests, the intensity of chemical use in the past and present, and several aspects of the greenhouse environment and commercial production practices, has led to insecticide resistance problems.  The following suggestions should be considered as a part of any chemical control program.

 

            1.  Minimize Insecticide Use.  If pest control relies exclusively on synthetic insecticides, then resistance can only be delayed, not avoided.  Therefore, the use of non-chemical control tactics (sanitation, eliminate weeds, soil sterilization, screening vents, natural enemies, etc.) should be maximized.  The decision to apply insecticides should primarily be based on pest scouting reports, not a calendar schedule.

            2.  Avoid persistent applications.  Ideally, an effective insecticide should be applied at a concentration high enough (within legal limits) to kill all individuals in a population, then quickly disappear from the environment, so that the insecticide residues do not degrade over time to a concentration that will kill only susceptible individuals.  For example, aerosol formulations that apply a short "burst" of a high insecticide concentration and do not leave much residue may select for resistance more slowly than full-coverage or systemic applications of the same insecticide, as long as resistance to the insecticide has not already developed in the population.

            3.  Avoid "Tank Mixes."  A mixture of two insecticides may provide superior short-term control than either insecticide used alone, but there is a danger in the long-term use of insecticide mixtures.  The assumption behind the use of tank mixes is that if individuals which are resistant to one or the other pesticide in the tank mix are rare in the population, there is little chance that resistance mechanisms to both pesticides would occur together in any one individual.   However, if by chance individuals do exist with resistance mechanisms to both chemicals, then continued use of the tank mix will begin to select for these multiply resistant pests.  Chemical control would then become much more difficult, because the pests would be resistant to multiple classes of insecticides.    

            4.  Use Long-term Insecticide Rotations.  The pesticides used in a rotation scheme should have different modes of action against the pest (see Table 1), and resistance to the chemicals should be at a low (undetectable) level at the start.  Organophosphate and carbamate insecticides have similar modes of action and should not be alternated in an insecticide rotation scheme.  Use each effective insecticide for at least the duration of one generation of the pest before rotating to a different insecticide.  If two insecticides are used within the same pest generation, the selection effect will be essentially the same as using a tank mix.  This is because the same individuals would be contacted with both insecticides, although at slightly different times.  To minimize the problems of overlapping generations and persistent insecticide residues, it might be wise to use the same insecticide for two or even three generations prior to rotating.  

            5.  Use Pesticides with Non-specific Modes of Action.  Insecticidal soaps and horticultural oils both have broad modes of action, and it is therefore unlikely that resistance will occur to either of these.  In addition, tank mixes of these materials with effective synthetic organic insecticides might delay resistance to the synthetic insecticide, because the soap or oil will kill many individuals that are resistant.  However, some tank mixes that include oil or soap may be toxic to certain plants.

            6.  Integrate Chemical and Biological Control.  Many of the newer insecticides are compatible with the use of many kinds of natural enemies.  The effective use of natural enemies can add an additional mortality factor that does not select for resistance, and may conserve the effectiveness of insecticides. Effective natural enemies may include predators, parasitoids, and/or insect pathogens.  Many extension entomologists and commercial insectaries have information on pesticides that are compatible with various natural enemies.  The searchable Koppert Side Effects List can be found at http://www.koppert.nl/e0110.html.

 

 

Table 1. Mode of Action Classification of Insecticides and Miticides Used in Greenhouses

 

Most insecticides and miticides affect insects and mites in specific ways.  These ways may be called the pesticide╣s │mode of action▓.  The Insecticide Resistance Action Committee (IRAC) is an organization of chemical companies and researchers that has classified insecticides and miticides into one of 28 (currently) different modes of action.  The following chart identifies those insecticides and miticides used in greenhouses by their modes of action.  This chart may be used to identify the mode of action of a pesticide and to determine other pesticides with different modes of action that may be used in a pesticide rotation plan. Rotate among pesticides from different major groups, but not within the same major group.  For example, it is OK to rotate a pesticide from Group 1 with another from Group 3, but do not rotate a Group 1A pesticide with a Group 1B pesticide.

Note: As of 2/2006, some pesticides listed below have not been registered in New York State.  Check registration status of all pesticides before use.

 

 

Group

Primary Site of Action

Chemical Class

 Trade Name

(Active Ingredient)

1A

 

Acetylcholine

esterase inhibitors

 

Carbamates

Sevin (carbaryl)

Measurol (methiocarb)

1B

Organophosphates

Orthene (acephate)

Dursban (chlorpyrifos)

2A, 2B

GABA-gated chloride channel antagonists

None used on ornamentals

--

3

Sodium channel modulators

Pyrethroids

Talstar (bifenthrin)

Decathalon (cyfluthrin)

Discus (cyfluthrin+imidacloprid)

Scimitar (lambda-cyhalothrin)

Tame (fenpropathrin)

Astro (permethrin)

Pyrethrins

Pyreth-It (pyrethrins)

4A

Nicotine acetylcholine receptor agonists/antagonists

Neonicotinoids

TriStar (acetamiprid)

Celero (clothianidin)

Discus (cyfluthrin+ imidacloprid)

Marathon (imidacloprid)

Flagship (thiomethoxam)

Safari (dinotefuran)

4B

None used on ornamentals

--

4C

None used on ornamentals

--

5

Nicotine acetylcholine receptor agonists/antagonists

(not Group 4)

Spinosyns

Conserve (spinosad)

6

Chloride channel activators

Avermectins

Avid (abamectin)

7A

Juvenile hormone mimics

Juvenile hormone analogues

Enstar II (kinoprene)

7B

None used on ornamentals

--

7C

pyriproxyfen

Distance (pyriproxyfen)

8A

Compounds of unknown or non-specific mode of action

(fumigants)

Methyl bromide

Methyl bromide

8B

None used on ornamentals

--

8C

None used on ornamentals

--

9A

Compounds of unknown or non-specific mode of action

(selective feeding blockers)

None used on ornamentals

--

9B

Pymetrozine

Endeavor (pymetrozine)

9C

Flonicamid

Aria (flonicamid)

10A

 

Compounds of unknown or non-specific mode of action

(mite growth inhibitors)

Clofentazine

Ovation (clofentazine)

Hexythiazox

Hexygon (hexythiazox)

10B

Etoxazole

TetraSan (etoxazole)

11A1

Microbial disruptors of insect midgut membranes

(including transgenic plants expressing Bacillus thuringiensis toxins)

B.t. var israelensis

Gnatrol (B.t. var israelensis)

11A2

None used on ornamentals

--

11B1

None used on ornamentals

--

11B2

B.t. var kurstaki

Dipel (B.t. var kurstaki)

11C

None used on ornamentals

 

12A

Inhibitors of oxidative phosphorylation, disruptors of ATP formation

None used on ornamentals

--

12B

Organotin miticides

 

13

Uncoupler of oxidative phosphorylation via disruption of H proton gradient

Chlorfenapyr

Pylon (chlorfenapyr)

14

Inhibition of magnesium-stimulated ATPase

None used on ornamentals

--

15

Inhibitors of chitin biosynthesis, type 0, Lepidopteran

Benzoylureas

Adept (diflubenzuron)

Pedestal (novaluron)

16

Inhibitors of chitin biosynthesis, type 1, Homopteran

Buprofezin

Talus (buprofezin)

17

Inhibitors of chitin biosynthesis, type 2, Dipteran

Cyromazine

Citation (cyromazine)

18A

Ecdysone agonist/moulting disruptor

Diacylhydrazines

Confirm (tebufenozide)

18B

Azadiractin

Azatin, Ornazin (azadiractin)

19

Octopaminergic agonist

None used on ornamentals

--

20A

Site II electron transport inhibitors

None used on ornamentals

--

20B

Acequinocyl

Shuttle (acequinocyl)

20C

None used on ornamentals

 

21

Site 1 electron transport inhibitors

Mitochondrial electron transport inhibitors,

acaricides

Akari (fenpyroximate)

Sanmite (pyridaben)

Shuttle (napthoquinone derivative)

22

Voltage-dependent sodium channel blocker

None used on ornamentals

--

23

Inhibitors of lipid synthesis

Tetronic acid derivatives

Judo (spiromesifen)

24

Site III electron transport inhibitors

None used on ornamentals

--

25

Neuroactive (unknown mode of action)

Bifenazate

Floramite (bifenazate)

26

Aconitase inhibitors

None used on ornamentals

--

27A

Synergists

P450 monooxygenase inhibitors

Piperonyl butoxide

27B

None used on ornamentals

--

28

Ryanodine receptor modulator

None used on ornamentals

--

UNA

Compounds with unknown modes of action

None used on ornamentals

--

UNB

--

UNC

Dicofol

Kelthane (dicofol)

UND

paridalyl

Overture (paridalyl)

NS

Miscellaneous non-specific, multi-site action

 

Tartar emetic