Frequently Asked Questions - Pest Management Weed Control

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Weed Control

How long do I need to wait after I apply glyphosate (AKA – Roundup(s), Touchdown, Vantage(s), Maverick, Factor, Credit, Renegade, Glyfos) before working or seeding with high disturbance implements (air seeders with wide shanks or spoons)?

For annual weeds – one day; For perennial weeds (quackgrass, thistles, foxtail barley) – 3 days if weather is warm and sunny (highs >20 and lows > 8) and 5 days if cool and cloudy. Warm days need to be consecutive. Perennial plant needs to be actively moving sugars around the plant to get good distribution of glyphosate. This happens more quickly under warm sunny days than cool cloudy ones.

Zero-Tillage qualifier – If seeding with very low disturbance equipment (discs or knives), a few of the rhizomes and some roots may escape to recover, but most will remain intact so that 3 days should be enough. Farmers have to make that decision for themselves as to whether they want to risk that occasional failure. Guidance on this decision can be obtained by phoning the manufacturer of the glyphosate product.

Can 2,4-D be used either alone or as a tank mix for a preseeding burnoff prior to peas or lentils?

No. Research has shown that peas and lentils can be negatively effected by 2,4-D soil residues when the herbicide is applied in the spring as a pre-seeding burnoff. Peas and lentils can be seeded on fields that received a fall treatment of 2,4-D for the control of winter annual broadleaf weeds.