Weed Management Components. Crop Health Rapid canopy cover will reduce weed growth. Tips for Successful Weed Control. Steve Weller Purdue University

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1 Weed Management Components Steve Weller Purdue University Prevention Cultural (rows for cultivation, rotations, fertilizer placement, seeding rate, stale seedbeds, competitive variety, mulches give the crop the advantage by minimizing early season competition) Mechanical (plow, rotary hoe, row cultivation, hoe, others) Chemical (herbicides) Biological (mycoherbicides, traditional biocontrol) Site specific (precision agriculture, in field heterogeneity, macro and micro scale) Integration of tactics Purdue University is an Equal Opportunity/Equal Access institution. Tips for Successful Weed Control 1. Know what weed species you have and choose control methods to match 2. Control weeds when they are small 3. Minimize i i soil compaction 4. Calibrate sprayer 5. Read and follow labels 6. Maintain and adjust cultivation equipment 7. Educate, monitor, encourage weeding crew 8. Have a back-up plan 9. Don t let weeds go to seed Crop Health Rapid canopy cover will reduce weed growth Plant when temperature is above 60 Apply nutrients based on soil test and past field history Use disease-resistant cultivars Manage insects and diseases Maximize Crop Competitiveness Rapid canopy cover will reduce weed growth Good growth conditions Vigorous varieties Narrower rows, more space between plants in the row Start from transplants Maximize Crop Competitiveness Supply water and nutrients near crop Drip irrigation Band dry fertilizer, or supply in drip irrigation Nutrients in sync with crop needs Sidedressing, periodic fertigation 1

2 Mulch Plastic mulch Black Infra-red red transmitting (IRT) Cover crop residue Fall-planted Spring-planted Cultivation Blind cultivation Rotary hoe Row-middles Sweeps Rolling cultivator Plastic edge Cultivation can damage roots - so use shallow cultivation tools Apply Herbicides Correctly Rate Timing Weed size or age Crop size or age Weather conditions Cultivation Incorporation Adjuvants Crop oil Concentrate, UAN, Nonionic surfactant Organic Stale seedbed No-till into mow-killed or crimped winter annual cover crop (rye, hairy vetch) Rotary hoe for direct-seeded crops Mulch in row Cultivation seeded on bare ground no herbicides Stale seedbed prepare p field 2-4 weeks in advance kill emerged weeds prior to or just after seeding (very shallow tillage, flaming) Rotary hoe, others Cultivate Handweed and hoe seeded into killed cover no herbicides Choose planting arrangement and cultivar for rapid canopy closure Kill cover at least 2 wks before seeding Mow Roll and crimp Minimize residue disturbance at planting Handweed as needed 2

3 Preemergence Herbicides Registered for Cucurbits Trade name Dacthal Command Curbit Sinbar Prefar Sandea Strategy Treflan Brawl Common name DCPA clomazone ethalfluralin Terbacil (WM ONLY) bensulide halosulfuron clomazone + ethalfluralin Trifluralin S-metolachlor Soil Applied Herbicides Applied before or just after planting crop Kill weeds soon after they germinate Must be present in the soil where seeds are germinating Ex: Curbit, Command, Brawl, Treflan Curbit 3EC ethalfluralin Weeds: annual grasses, lambsquarters, nightshade, pigweed, purslane Crops: pumpkin, squash, muskmelon, watermelon, cucumber c Rate: 3-4 pt./a Pkg: 5-6 A Cost: $18-24/A Use: apply after seeding before crop emergence, or use directed spray between rows; rain required to move into soil Notes: do not incorporate, do not use under plastic mulch or row covers, low margin of safety Command 3ME clomazone Weeds: annual grasses, velvetleaf, other BL but not pigweeds Crops: squash, muskmelon, watermelon, cucumber. NOT Jack-o-Lantern pumpkin Rate for melons: pt./A Pkg: A Cost: $5-9/A Use: apply before seeding or transplanting or after seeding before crop emergence Notes: 45-day PHI cucumbers and squash Strategy ethalfluralin + clomazone Weeds: annual grasses, lambsquarters, velvetleaf, pigweed, Crops: pumpkin, squash, muskmelon, watermelon, cucumber Rate: 2-6 pt./a Pkg: 3-10 A Cost: $21-64/A Use: apply after seeding before crop emergence, or use directed spray between rows; rain required to move into soil Notes: do not incorporate, do not use under plastic mulch or row covers, low margin of safety Treflan 4EC trifluralin Weeds: annual grasses, lambsquarters, pigweed, purslane Crops: pumpkin, squash, muskmelon, watermelon, cucumber Rate: 1-2 pt./a Pkg: A Cost: $3-5/A Use: apply as directed spray between rows; incorporate immediately Notes: do not use under plastic mulch; 30-day PHI; 60-day PHI for watermelon; granular formulations available 3

4 Sandea halosulfuron Weeds: pigweed, ragweed, velvetleaf, nutsedge, lambsquarters (pre), morningglory (suppression) Crops: pumpkin, winter squash, muskmelon, watermelon, cucumber Rate: oz./a Pkg: A Cost: $21-42/A Use: apply after seeding before crop emergence; apply before transplanting and wait 7 days; for selected crops only apply post after crop has 3 to 5 leaves and before female flowers; apply as directed spray to row middles Notes: low margin of safety; 57-day PHI for melons; 30- day PHI for others Treflan 4EC trifluralin Weeds: annual grasses, lambsquarters, pigweed, purslane Crops: pumpkin, squash, muskmelon, watermelon, cucumber Rate: 1-2 pt./a Pkg: A Cost: $3-5/A Use: apply as directed spray between rows; incorporate immediately Notes: do not use under plastic mulch; 30-day PHI; 60-day PHI for watermelon; granular formulations available Brawl (metolachlor)- Weeds: annual grasses, nightshade, pigweed, and nutsedge Crops: pumpkin ONLY Rate: pt./a Pkg: A Cost: $15-20/A Use: apply as directed spray to row middles, leave 1 ft area over crop untreated, allow minimum of 6 from seed or plant leaves Crop Injury from Command - clomazone Foliar Applied Herbicides Kill weeds after they have emerged May be taken up by leaves and in some cases roots of weeds Some may also be applied to the soil Adjuvants often used to promote absorption by leaves Ex: Sandea, glyphosate, Poast Postemergence Herbicides Registered for Cucurbits Trade name Roundup Gramoxone Poast Select Max Sandea Aim Common name glyphosate paraquat sethoxydim clethodim halosulfuron carfentrazone 4

5 Poast 1.5E sethoxydim Weeds: grasses Rate: pt./a Pkg: 5-8 A Cost: $9-14/A Use: apply to actively growing grass, include 1 qt. COC per acre Notes: 14 day PHI; maximum 3 pt./a per season Select clethodim Weeds: grasses Rate (2EC): 6-8 fl. oz./a Pkg: A Cost: $8-12/A Use: apply to actively growing grass, include 1 qt. COC per acre Notes: 14 day PHI; maximum 1 qt./a per season Herbicides - Postemergence but not over top of crop Gramoxone Roundup Aim Scythe paraquat glyphosate carfentrazone pelargonic acid Gramoxone Inteon paraquat Weeds: emerged annuals Rate (2L): 2-4 pt./a Use: apply before seeding or transplanting or after seeding before crop emergence Notes: restricted use pesticide; contact activity only Roundup glyphosate Weeds: emerged annuals and perennials Rate (4 lb. ai/gal): 1-5qt/A qt./a Use: apply at least 3 days before seeding or transplanting, or apply between rows with hooded or shielded sprayer Notes: 14-day PHI; remove residue from plastic mulch before transplanting Aim EC carfentrazone Weeds: lambsquarters, morningglory, nightshade, velvetleaf, pigweed Rate: fl. oz./a Use: apply before transplanting, or apply between rows with hooded sprayer Notes: use COC or NIS. Do not apply before direct seeding. 5

6 Scythe pelargonic acid Weeds: emerged annuals Rate: 2-10 gal./a Use: apply before planting, or after seeding before crop emergence, or as a directed spray between rows Notes: use 75 to 100 gals. total spray solution per acre; good coverage essential for control; contact activity only; only small weeds are killed Scythe on lambsquarter 1 DAT 10%, 100 gpa 2 WAT Transplant, Plastic Mulch Pre-emergence herbicide Under mulch Row middles only Non-selective herbicide for row middles, hooded or shielded sprayer Cultivation and handweeding Post-emergence broadleaf and/or grass herbicide Weed Control for Pumpkin (C. pepo) Brawl at pts/a between hills or rows only Strategy 3-5 pt/a PRE Curbit 3 pt/a PRE Sandea oz + Poast or Select as directed spray Other treatments include choices of paraquat, glyphosate, Aim, Scythe for pre plant, preemergence and row middles seeded on bare ground Stale seedbed prepare field 2-4 weeks in advance kill weeds prior to or just after seeding (very shallow tillage or nonselective herbicide) Preemergence herbicide after seeding Strategy seeded on bare ground, cont. Depending on weed species and pressure Sandea or Non-selective and/or Poast Cultivation Row-middle application of Curbit or Treflan Handweeding 6

7 No-till, Direct Seed Burndown before seeding Pre-emergence herbicide Non-selective herbicide for row middles, hooded or shielded sprayer Post-emergence broadleaf and/or grass herbicide Handweeding seeded into killed cover Kill cover at least 2 wks before seeding After seeding apply preemergence herbicide and if needed non-selective herbicide for emerged weeds Strategy, glyphosate seeded into killed cover Depending on weed pressure Sandea and/or Poast Row-middle hooded sprayer application of glyphosate or Aim Row-middle application of Curbit Handweeding Sandea on Pumpkin and Squash Pumpkin is more tolerant than squash to Sandea PRE and POST Maxima squash appear to be most sensitive Do not apply more than 0.5 oz Sandea PRE or POST Do not use NIS POST Use directed spray POST Heavy rain will increase injury Preemergence Weed Control In Pumpkin 3WAT Postemergence Weed Control in Pumpkin 3 Weeks after Post Weedy Check Weedy Ck Strategy + Sandea Sandea Sandea 4 pts + 1/2 oz 1/2 oz 2/3 oz Sandea Pre 1 oz Sandea 1/2 oz Post Sandea 2/3 oz Post 7

8 Weed Control for Seeded Melons and Cucumber Bareground (no plastic) Curbit 2 pt + Command 0.67 pt PRE after seeding. Apply water to incorporate; follow with Sandea 0.5 oz + Poast 1 pt (or Select) broadcast at 2-5 leaf stage (before vining) or Strategy 4-6 pt broadcast after seeding; follow with Sandea 0.5 oz + Poast 1 pt (or Select) just before vining or PPI Prefar 6 qt before seeding; follow with Sandea 0.5 oz + Poast 1 pt (or Select) just before vining Weed Control for Transplanted Melons on Plastic Mulch (Option 1) Sandea 0.5 oz to soil before laying plastic mulch; wait 7 days to plant melons; Sandea 0.5 oz + Poast 1 pt to soil between plastic before vines grow beyond plastic Prefar 3 qt, incorporate before laying plastic; Sandea 0.5oz + Poast 1 pt (or Select) broadcast just before vining Weed Control for Transplanted Melons on Plastic Mulch (Option 2) Lay plastic and plant melons; apply Curbit 2 pt + Command 0.67 pt to soil between plastic after TP Lay plastic and plant melons; Treflan 1 qt between rows of plastic water in; followed by Sandea 0.5 oz + Poast 1 pt (or Select) directed between rows of plastic before vining Watermelon Weed Control All treatments labeled for muskmelon are labeled for watermelon Sinbar is labeled for watermelon; 2-4 oz/ac PRE after seeding or before TP; it may be applied under plastic or to row middles. Do not apply over the top of plants. 70 day PHI Important Considerations about Weed Control in Cucurbits Weed control is essential for effective disease control and for high yields Cucurbits are sensitive to many of the herbicides registered Command is not registered on jack-olantern pumpkins ALS-inhibitors (e.g., Sandea) accumulate in the soil and can be toxic to cucurbits Important Considerations Plant crops so that you can cultivate or disk between rows Leave spray aisles for driving in the field Use drop nozzles to keep Sandea off crop leaves Refer to ID-56 for crop production and weed management recommendations 8