Spring Weed Management Tips For Almonds: Reduce Herbicide Resistance
April 14, 2015 Properly identifying weeds in the spring is the first step to determining proper control measures, and paying close attention to what you spray — and when you spray it — is critical for ensuring long-term efficacy of herbicides.
Glyphosate resistance is one major area of concern. “We’ve relied so heavily on that one herbicide — that one mode of action — that we’ve gotten into a situation where we have half a dozen or so important weeds that have some level or resistance to glyphosate in California orchards,” says Brad Hanson, University of California-Davis Cooperative Extension weed specialist.
Hanson says management techniques for glyphosate-resistant weeds vary depending on the specific weed problem, but in many cases, the best management is not to rely on post-emergent herbicides only. “I can’t think of any of our glyphosate-resistant weeds that can’t be controlled by some effective pre-emergent herbicide,” he says.
One problem with pre-emergent herbicides, though, is lack of rainfall to incorporate them. “But, if we can know our weed problem and select pre-emergent herbicides that have efficacy on the weeds in your orchard, and you can get it applied well in a timely fashion and incorporated, we can control those weeds,” says Hanson.
The Almond Board of California recently shared some other strategies, courtesy of Hanson, to help prevent herbicide resistance in almond orchards:
- Rotate herbicides with different modes of action and Weed Science Society of America (WSSA) group numbers.
- Monitor for weed survival after an herbicide application.
- Use short-residual herbicides.
- Clean equipment after working in weed-contaminated orchards to prevent the spread of weed seeds.
- If weeds escape treatment, use shovels, hoes and other hand tools to cut the plants below the soil surface to prevent flowering.
Additional information on integrated weed management is available on the UC IPM integrated weed management page.
Read Part 1 to learn about common weed management mistakes and how to avoid them.
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