Unseasonable Rains Contribute to Weed Control Issues

Brian German Industry

weed control issues

The series of recent storms that swept through California could create increased weed control issues.  The cooler than average temperatures and significant rainfall through Memorial Day weekend will likely require added diligence in weed management approaches.

“I think it’s definitely going to impact weeds.  It’s probably going to stimulate germination that we might not normally see, particularly in systems that are using buried drip,” said Lynn Sosnoskie, UC Cooperative Extension Weed Science Advisor in Merced County.  “The cool temperatures and the wet soil are probably also going to impact crop growth. So, you’re not going to see that ability of some crops that like warmer environments to outpace weeds that they might normally be competitive with.”

Increased germination, especially in areas that do not normally experience significant surface soil moisture, could also be compounded with lowered efficacy of preemergent herbicides in creating weed control issues.  While water is required to activation, Sosnoskie noted that too much water could result in leaching and facilitate microbial degradation resulting in multiple concerns.  “We won’t see the level of control that we’re used to and where we have doses that become reduced due to dilution, we’re increasing the selection pressure on the weeds that do persist in that environment to find individuals that might be resistant to those herbicides,” said Sosnoskie.

Controlling weeds with a foliar application could also be more difficult as a result of the unseasonable weather.  The multiple rain events could have stimulated multiple flushes of weeds, with growers now having to battle weeds of different sizes.  “If we can’t get a foliar herbicide application or some sort of cultivation event in, these weeds are going to get larger and they’re going to grow to sizes where they just become more difficult to control regardless of the strategy that we’re using,” Sosnoskie noted.  “We’ve got different growth stages and weeds that might be shielding smaller weeds from control measures and thus creating problems.”

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Brian German

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Ag News Director, AgNet West