Transcript PowerPoint
Herbicide Modes of Action Eric P. Prostko Extension Weed Specialist Department of Crop & Soil Sciences The University of Georgia April 2008 Some things to remember…. photosynthesis (food) respiration (energy) amino acids (proteins/growth) lipids (cell membranes) pigments (energy/light capture) • chlorophyll, carotenoids mitosis (cell division) Mode of Action the sequence of events that leads to plant death or growth interruption 2 phases * movement to target site * interaction at target site Mechanism of Action (Site) Location at which a herbicide exerts its toxicity at the cellular level more specific ACCase Inhibitors Inhibit acetyl-CoA-carboxylase (ACCase) enzyme Enzyme needed for fatty acid synthesis Dim’s and Fop’s Achieve, Assure, Axial, Fusilade, Poast, Select “rotted” meristem ALS Inhibitors Inhibit acetolactate synthase (ALS) enzyme enzyme needed to produce certain amino acids (isoleucine, leucine, valine) Commonly Used ALS Herbicides Accent Glean Ally/Cimarron Beacon Beyond Cadre Classic Envoke Exceed Express Finesse FirstRate Harmony Extra Maverick Pro Osprey Peak Permit Pursuit Python Scepter Staple Strongarm Cadre “yellow flash” Staple+ on Sorghum Resolve 25WG (rimsulfuron) Injury to Field Corn Pictures @ 18 DAT 1.0 oz/A Applied PRE Photosystem II Inhibitors Inhibit photosynthesis by binding to QB-binding niche on D1 protein Evik, Caparol, Atrazine, Basagran, Buctril, Direx, Cotoron, Lorox, Sencor, Simazine Bladex Cotoran Photosystem I Inhibitors Accept electrons from PSI to form radicals Super radicals formed to create peroxides Diquat, paraquat Paraquat Source: Purdue University PPO Inhibiting Herbicides PPO or Protox • Protoporphyrinogen oxidase • Enzyme found in chloroplast and mitochondria needed for formation of chlorophyll • Cell membrane destruction Many common herbicides have this mode of action!! • Ultra Blazer, Cobra, Goal, Reflex, Ronstar, Resource, Aim, Valor, Storm, Spartan, ET Blazer Injury on Peanut Valor Injury on Peanut Cobra on Soybeans Carotenoid Biosynthesis Inhibitors Inhibit phytoene desaturase (PDS) or hydroxyphenyl pyruvate dioxygenase (HPPD) Command, Callisto, Laudis, Solicam/Zorial, Impact Command Zorial Laudis EPSP Synthase Inhibitor EPSP synthase needed for production of certain amino acids (tryptophan, tyrosine, and phenylalanine) glyphosate Source: Purdue University Weed Science Source: MSU Weed Science Glutamine Synthetase Inhibitors Glutamine synthetase converts glutamate and ammonia to glutamine Causes ammonia accumulation in plants Liberty, Ignite Source: University of Missouri Weed Science Mitosis Inhibitors Microtubule inhibition • Treflan, Prowl, Sonalan, Surflan, Dacthal Inhibition of very long-chain fatty acids • Dual Magnum, Outlook, Intrro Prowl Injury on Corn Dual Injury Source: University of Wisconsin Weed Science Fatty Acid and Lipid Biosynthesis Inhibitors Inhibition of lipid synthesis (not ACCase) • Prefar, Sutan, Eptam, Eradicane, Ordram, Tillam, Bolero Source: Purdue University Weed Science Source: UC-Davis Weed Science Synthetic Auxins Disrupt hormonal balance 2,4-D, Banvel, Clarity, Status, Stinger, MCPA, Facet, Remedy, Grazon P+D Source: Purdue University Weed Science Source: Purdue University Weed Science Unknown MOA DSMA, MSMA Cell membrane destruction??? MSMA on Peanut MSMA on Zoysia UGA Weed Science www.gaweed.com