1. Pesticide Mode of Action
Shelley Mills
Valley County Extension Agent

2. What is a pesticide?

3. Pesticides Insecticides Acaricides Herbicides Chemosterilants
Fungicides
Virucides
Rodenticides
Algicides
Miticides
Nematicides
Avicides
Piscicides
Molluscicide
Bactericides

4. Mode of Action
Where and how the pesticide works within the organism.

5. Insecticides IGR – Insect Growth Regulators
Methoprene, NEEM oil, Pyriproxifen

6. Central nervous system disruptors
Neonicitinoids (neonics)
Imidacloprid – Gaucho, Advocate, Admire
Thiamethoxam – Platinum, Cruiser
Clothianidin – Poncho, Dantop
Thiacloprid - Calypso
Organophosphates
Malathion
Parathion
Carbamates
Carbaryl - Sevin

7. Neonicitinoids (neonics)
Acetylcholine is a neurotransmitter – sends signals to other cells
Neonicotinoids (neonics) like imidacloprid irreversibly bind to the nicotinic aceytlcholine receptors and block them in the open position causing constant neuromuscular stimulation. Acytlcholinesterase is an endogenous enzyme that under normal conditions breaks down the acetylcholine and stops the stimulation, but it cannot break down neonics - so the process is irreversible. Insects are much more susceptible than humans and other mammals to this binding.

8. Ogranophosphates and Carbamates
Organophosphates interfere with the production of acetylcholinesterase the enzyme that stops the overstimulation of the nerves.

9. Pyrethroids
Pyrethroids and DDT interact with the sodium pump that is necessary to produce acytelcholine. This in turn stops the firing of the neurons by causing the cell to be unable to repolarize. The membrane becomes permanently depolarized and ultimately leads to paralysis.

10. Pheremones Sex attractants Aggregation pheromones Repellants
Pheromones usually have limited use because their range of influence is much smaller and they are very difficult to reproduce from nature

11. Rodenticides Anticoagulant
Wafarins and coumarins functions as an anitvitamin and competes with vitamin K uptake in the liver. (reversible)

12. Rodenticides Acute single dose products Aluminum phosphide (burrow)
Zinc Phosphide (gut)
Aluminum phosphide and zinc phosphide kill by converting to phosgene gas in the presence of moisture. In the gut or in the burrow.

13. Herbicides Group 1
ACCase inhibitor – fop’s, dim’s and den’s – acetyl CoAcarboxylase inhibitor (membrane synthesis)
Clodinafop-P Discover
Fenoxaprop-P Puma , Tacoma, Parity
Fluazifop-P Fusilade DX
Quizalofop Assure II, Targa
Clethodim Select, Trigger, Volunteer Intensity
Sethoxydim Poast
Pinoxaden Axial XL
Usually used for post emergence grassy weed control BLW have a less sensitive ACCase enzyme
Acetyl co enzyme A carboxylase inhibitor and affects fatty acid that is important in membrane synthesis. Many broadleaved species are more resistant to group 1 because they have a less sensitive ACCase enzyme

14. Symptoms = yellowing of young leaves purpling of older leaves
Symptoms = yellowing of young leaves purpling of older leaves. Affects growing point

15. Herbicides Group 2
ALS inhibitors – Imi’s, SU’s, TPS’s, SACT’s – branched chain amino acid disruption
Imidazolinones - Assert, Beyond, Arsenal Pursuit
Sulfonyl Ureas – Glean, Telar, Escort, Ally Oust, Harmony, Finesse, Matrix
Triazolopyrimidine – First Rate, PowerFlex
Sulfonylamino-carbonyltriasonlinone – Everest, Olympus and Varro
Broad spectrum contol – usually at low rates, soil applied or post-emergent
Acetolactate synthase interupts the formation of branched-chain amino acids
Symptoms are latent – usually chlorosis first with purple underleaves, growing points are affected can cause stunting and shortened internodes.

16. Axillary leaf bud growth and chlorosis of the new growth

17. Herbicides Group 3 Mitotic inhibitor
Dinitroaniline – Sonalan, Prowl and Treflan
Inhibit cell division
Generally applied pre-emergent, absorbed by roots and shoots but don’t translocate much so you will see stubby, shortened roots and thickened, stubby shoots.

18. Stubby roots and thickened and shortened shoots.

19. Herbicides Group 4 Growth Regulators – synthetic auxins
Benzoic Acids - Banvel, Clarity, Rifle
Pyridines - Milestone, Clopyralid (Stinger, transline), Tordon, Starane, Clean Slate
Quinoline – Facet, Quinstar,
Phenoxy’s – 2,4-D amine and ester, MCPA,
Symptoms are leaf twisting and curling (generally upward leaf curl) stem elongation, epinasty, stunting and yellowing.

21. Herbicides group 5, 6 & 7 Photosystem II disruptors
PSI (5) - Atrazine, Princep metribuzen, Sencor
PSII (6) – Bromoxynil, Basagran
PSII (7) – Diuron, Linuron, Spike (soil sterilants)
Disrupt photosynthesis resulting in bleaching of plant. Symptoms appear in the presence of sunlight.
PSI and PSII herbicides are like rapid cancer agents, destroying tissues right and left. Very destructive.

22. Bromoxynil & Traizine

23. Herbicides Group 9 EPSP Synthase Inhibitor Glyphosate
Disrupts aromatic amino acid production (used to make proteins) which are used extensively throughout the plant
Chlorosis after 7 to 10 days – then characteristic orange-yellow color. Symptoms appear much slower in cold weather and lower use rates.
Affects the Shikimate pathway

25. Other herbicides that you may hear about
(14) PPO (Protox) Inhibitor – Sharpen, Vida, Aim
(22) PSI (Photosystem I inhibitor) – Paraquat, Diquat
(31) CHT
PPO –
PSI symptoms appear rapidly within 1 to 2 hours after application
CHT – Cold, Hard, Steel

26. Contact VS Translocated

27. Herbicide Resistance Group 1, Group 2 and Group 9
Kochia – 2, 9, 4, 2+9,
Wild Oats – 1, 2, 8 (2 different sites), 1+2
Russian Thistle – 2
Green Foxtail – 1
Horseweed – 9
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