YOUTH & AGRICULTURE FAMILIES HEALTH ECONOMY ENVIRONMENT ENERGY COMMUNITIES. Session 4: Chemical Weed Control Strategies

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1 YOUTH & AGRICULTURE FAMILIES HEALTH ECONOMY ENVIRONMENT ENERGY COMMUNITIES Session 4: Chemical Weed Control Strategies

2 Chemical Control Is Often Based On A Herbicide s: Selectivity - Placement - Timing Mode of action Spectrum of activity

3 Selectivity Based On Plant Physiology 2,4-D Causes a toxic reaction in some plants (e.g., in broadleaves vs. grasses)

4 Selectivity Based On Plant Physiology 2,4-D Causes a toxic reaction in some plants (e.g., in broadleaves vs. grasses) Herbicide blocks an enzyme used in amino acid or lipid synthesis or photosynthesis

5 Selectivity Based On Plant Structure Leaf shape

6 Selectivity Based On Plant Structure Stomata, wax, hairs, or dust on the leaves all affect herbicide uptake

7 Selectivity Based On Application Timing Preplant incorporated (PPI) Preemergence to crop or weed (PRE) Postemergence (POST)

8 Selectivity Based On Placement Depth in soil Above crop roots Germinating seedlings absorb herbicide Debris on soil surface can reduce herbicide effectiveness

9 Selectivity Based On Placement Keep herbicide from touching desirable vegetation Spot spray Rope wick or wiper Directed sprays Orchard application

10 Herbicide Selectivity Based On Application Rate Rate 1 pt/acre for annual broadleaf weeds 2 qt/acre for perennial broadleaf weeds 4 qts/acre for woody brush and trees Examples Lambsquarters Mustard Dandelion Canada thistle Red alder Black poplar

11 Herbicide Mode Of Action

12 Herbicide Mode Of Action

13 Herbicide Mode Of Action

14 Herbicide Mode Of Action

15 Growth Regulator Herbicides Broadleaf weeds Can injure grass; depend on stage and rate Mimic hormones (auxins) Disrupt hormone balance and protein synthesis Epinasty (abnormal twisting and bending) Affects new growth Uptake through foliage Move in xylem and phloem Soil residual activity

16 Growth Regulator Herbicides Phenoxy Acetic Acids 2,4-D; MCPA Benzoic Acids Dicamba (Banvel) Picolinic Acids Triclopyr (Garlon) Mixes Triclopyr + 2,4-D (Crossbow)

17 Amino Acid Synthesis Inhibitor Herbicides Act on enzyme to prevent amino acid production Protein for normal growth Active on broadleaf and/or grass weeds Some give excellent perennial weed control Foliage and root uptake, move in xylem and/or phloem Injury symptoms slow (1 to 3 weeks) New foliage symptomatic first Stunting, yellowing or purpling

18 Amino Acid Synthesis Inhibitor Herbicides ALS enzyme inhibitors Sulfonylurea Rimsulfuron (Matrix) EPSP enzyme inhibitor Amino Acid Derivative Glyphosate (Roundup, Rodeo, Aquamaster)

19 Lipid Synthesis Inhibitor Herbicides Controls weedy grasses Broadleaf plants tolerant Prevent fatty acid production for lipids Cell membranes and new growth Growth points become rotted and easily removed from rest of plant Injury symptoms slow (1 to 2 weeks) New leaf tissue yellow or dead Foliage uptake, move in phloem

20 Lipid Synthesis Inhibitor Herbicides Aryloxyphenoxypropionate (the fops ) Fluazifop (Fusilade) Cyclohexanedione (the dims ) Sethoxydim (Poast), Clethodim (Select)

21 Seedling Growth Inhibitor Herbicides Soil applied Act on emerging weed seedlings Often die prior to emergence Active on developing roots and shoots Stops cell division, enlargement, and protein synthesis Inhibit shoot elongation and lateral root formation

22 Seedling Growth Inhibitor Herbicides Root Inhibitors Dinitroanilines Trifluralin (Treflan), Oryzalin (Surflan), Pendimethalin (Prowl H2O) Shoot Inhibitors (MOA not completely known) Substituted Amide Napropamide (Devrinol), Pronamide (Kerb)

23 Photosynthesis Inhibitor Herbicides Bind to specific sites in chloroplasts to shut down photosynthetic process Secondary toxic substances likely produced Chlorosis then necrosis Control grass or broadleaf weeds Most are applied preemergence Postemergence causes rapid burning Grape products are mobile, taken up via roots or foliage and move in xylem

24 Photosynthesis Inhibitor Herbicides Phenylureas Diuron (Karmex) Nitriles Dichobenil (Casoron)

25 Glutamine Synthesis Inhibitor Herbicide Inhibits the enzyme GS Glutamine production stops, ammonia builds up in the cells, leads to chlorosis then necrosis For annual weed control; perennials will regrow Absorbed through foliage, no translocation, not selective Organophosphorus Glufosinate (Rely)

26 Cell Membrane Disruptor Herbicides Postemergence, contact Activated by sunlight to form oxygen compounds (hydrogen peroxide) which rupture plant cell membranes Symptoms quick (1 to 2 hours) Rapid burn-down For annual weed control; perennials will regrow Grape products are nonselective

27 Cell Membrane Disruptor Herbicides Bipyridyliums Paraquat (Gramoxone) Diphenylethers Carfentrazone (Aim), Flumioxazin (Chateau), Oxyfluorfen (Goal), Pyraflufen (Venue) Oils and acids Clove oil (Matran), Pine oil (Interceptor), Acetic and Citric Acids (vinegars, Green Match), Pelargonic Acid (Scythe)

28 Pigment Inhibitor Herbicides Prevent formation of chlorophyll Can t photosynthesize White or translucent leaf coloration results Grape product is mobile, taken up via roots or foliage and move in xylem Pyridazinones Norflurazon (Solicam)

29 Herbicide Mode Of Action A foliar-applied, systemic, photosynthesis inhibitor (atrazine). It is applied to a leaf, absorbed through the cuticle, translocated to the chloroplasts (site of action), and then inhibits photosynthesis (mechanism of action).

30 Herbicide Mode Of Action A foliar-applied, systemic, photosynthesis inhibitor (atrazine). It is applied to a leaf, absorbed through the cuticle, translocated to the chloroplasts (site of action), and then inhibits photosynthesis (mechanism of action).

31 Herbicide Mode Of Action A foliar-applied, systemic, photosynthesis inhibitor (atrazine). It is applied to a leaf, absorbed through the cuticle, translocated to the chloroplasts (site of action), and then inhibits photosynthesis (mechanism of action).

32 Herbicide Mode Of Action A foliar-applied, systemic, photosynthesis inhibitor (atrazine). It is applied to a leaf, absorbed through the cuticle, translocated to the chloroplasts (site of action), and then inhibits photosynthesis (mechanism of action).

33 Herbicide Application Foliar-applied Soil-applied - Usually requires incorporation Water: irrigation, sprinkler, rainfall Mechanical: tillage, raking

34 Herbicide Precautions, Drift Close proximity, downwind - Sensitive areas - Wind direction/speed - Product characteristics (vapor pressure) Long distance movement - Volume applied - Wind direction - Surface air stability

35 Herbicide Precautions, Drift All formulations of 2,4-D and other growth regulator herbicides can cause injury to grapes at very low levels Amine and low volatile esters High volatile esters are illegal in WA

36 Herbicide Precautions, Movement in Water Lateral movement to neighboring properties Vertical movement to groundwater - Label has leaching statement - Site vulnerability - Soil type and moisture content - Expected rain or irrigation

37 Herbicide Precautions, Other Factors Soil/Plant Material Residuals - May persist for weeks to years - Root zones of grape plants - Downslope movement of herbicides/soils - Activity in compost or soils

38 Have You Completed The Four Weed Sessions? Session 1: Biology of Weeds Session 2: Weed Reproduction Session 3: Non-chemical Weed Management Session 4: Chemical Weed Management