See Dry Weather Weed Control on Manitoba Agriculture website for more details and complete recommendations and cautions.
Dry weather means both weeds and crops shift gears. Weed spectrums can be different, post-emergent herbicides can be less effective because weeds may have smaller leaves and/or thicker cuticles (waxy layer) that slows the penetration of herbicides.
Some herbicides withstand dry weather better than others so choose your product carefully. Here are some general guidelines on weed control during a dry period.
1. Remove weeds early.
2. Know your crop stage.
3. Review the “Effects of Growing Conditions” section of each product in the Manitoba Agriculture Guide to Field Crop Protection to determine likely outcomes.
4. High Daytime temperatures can trigger crop injury in some herbicides.
5. Use full rates of herbicide.
6. Use higher water volumes.
7. Use split applications of broadleaf and grassy herbicides rather than tank mixing if the Guide to Field Crop Protection warns that antagonism can occur.
8. Check the forecast for rain – shallow, stressed crops roots may be impacted by herbicides moving into the root zone.
9. Compare the risk of crop injury to the risk of yield loss due to weed pressure.