Weed Control Research in Southwest North Dakota Caleb Dalley Hettinger Research Extension Center

Progress in Establishing a Weed Science Research Program in Southwest North Dakota Progress: Acquired materials and equipment needed to conduct small-plot research Spray equipment: spray booms, tractor-mounted sprayers, nozzles, bottles, etc. Planting equipment: No-till drill, planter units Seed: finding seed sources for wheat, field pea, sunflower, safflower, durum, flax, proso millet Weed seed: finding and collecting weed seed to spread onto research plot fields Need for consistent and adequate populations for conducting evaluation of weed control Need weeds of economic concern for conducting trials Hired new weed science technician, Daniel Abe, to assist in research program Bachelor’s degree from Sao Paulo State University Master’s degree from University of Florida

2015 Research No-till herbicide trials were conducted in spring wheat, durum, field pea, lentil, and safflower. Herbicide carryover study conducted using spring wheat, field pea, lentil, safflower, sunflower, flax, and proso millet.

PRE herbicide options for weed control in Clearfield Lentils Evaluation of newer herbicides for potential use in lentil compared with labelled herbicide options Pyroxasulfone 1.5 and 3 oz/A Saflufencil (Sharpen) + imazethapyr oz/A Saflufencil oz/A Saflufencil + metribuzin oz/A Pendimethalin (Prowl 32 oz/A Sulfentrazone 2.5 oz/A Glyphosate was tank-mixed with all treatments to help control existing weeds Lentil were planted on May 4 Treatments were applied on May 8 Lentil emergence was on May 15 Thanks to Justin Mack for help in putting together trial

Higher than average rainfall in May (4.04 inch) and June (5.17 inch) resulted in leaching of metribuzin into root zone

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Weed Control in No-till Crop Production Increased reliance on POST herbicides for weed control Reduced use of soil applied PRE herbicides Many require tillage to incorporate into soil Preplant burndown prior to planting POST weed control in-crop Increased presence of perennial weeds Canada thistle, perennial sowthistle, yellow toadflax, foxtail barley Shift in annual weed populations Weed seeds not incorporated into soil Winter annual broadleaf weeds often are more common in no-till

Weed Control in No-till Crop Production Integrated Weed Management The control of weeds through a long-term management approach using several weed management techniques such as: Physical control: grazing, mowing, mulching, tilling, hand removal, etc Chemical control: Herbicides Biological control: Using weeds natural enemies for control Flea beetles on leafy spurge Weed seed consumption by insects, birds, or rodents Mice reported to consume 10-20% of barnyardgrass and common lambsquarters seed in no-till corn and soybean fields in Ontario, Canada Field mice reported to consume 99.8% of redroot pigweed and common lambsquarters seed in alfalfa fields. Cultural Control: crop rotation, seed rates, narrow row spacings, soil fertility, planting date selection, rotating herbicide modes of action

Weed Control in No-till Crop Production Integrated Weed Management Cultural Control: crop rotation, seed rates, narrow row spacings, soil fertility, planting date selection, rotating herbicide modes of action. Effective crop rotations can be dynamic- be adapted in response to environment, pest, or economics Diverse rotations to consider: Grassy vs Broadleaf Annual vs Perennial Cool season vs Warm season Seeding date: fall, early spring, late spring Growth habit (tall, short, dense, open) Competitive ability (shouldn’t follow a poor competitive crop with another)

Weed Control in No-till Crop Production Crop Rotation: Monoculture systems (the same or similar crop year after year) promotes certain weed problems Downy brome in continuous wheat for example- can be disrupted by planting a broadleaf crop such as canola Crop rotations can slow development of herbicide resistant weeds Must use different control methods in different crops to be effective Roundup Ready corn followed by Roundup Ready soybean using only glyphosate is not an effective cultural weed management program Stacked rotations: two warm season crops followed by two cool season crops For example: corn-corn-wheat-wheat or better corn-soybean-wheat-canola Has been shown to reduce both cool and warm season weed populations

Weed Control in No-till Crop Production Stacked rotations: Oat-winter wheat-soybean No-till vs Conventional-till No herbicide in either oat or wheat Glyphosate applied after harvest Soybean crop Weedy control (weed-infested) Weed free comparison 25% loss in weed infested conventional till soybean No yield loss in weed-infested no-till soybean ~5% yield loss following cover crop From Anderson (2009) Weed Technology 23:

Weed Control in No-till Crop Production Stacked rotations: Weed density was more than 5 times greater in conventionally tilled soybean than no-till with or without cover crop

Weed Control in No-till Crop Production Stacked rotations: Cool season: Winter wheat Spring wheat Dry pea Warm season: Corn Proso millet Sunflower Chickpea Soybean Lowest weed density with alternating fallow or 2 cool season followed by 2 warm season crops From Anderson (2008) Weed Science 56:

Weed Control in No-till Crop Production Weed seed survival: Most seed emerge in year after being produced After two years, much of the soil seedbank reserve is depleted for many weed species It only takes a few surviving and reproducing weeds to maintain soil seedbank levels Some weed seed can remain dormant in soil for many years Fields should be monitored for late emerging weeds and sprayed to control if weed seed production is likely

Thank You!