What are the top ten weeds almond growers fight to control?

“This is so subjective,” said Kurt Hembree, Weed Science Advisor, UCCE Fresno County, addressing a crowd of growers in Fresno. “I can talk to any one of you and your ten list is going to be different than my ten.”

Nevertheless, Hembree counted off his Top 10 and told growers what they should do to control the common weeds. For a look at his full presentation described below, click on this link to see it on the University of California website.

“If you want to control fleabane and horseweed, that is the time to do it,” Hembree said.

Another weed that Hembree highlighted was junglerice, which he warned is resistant to glyphosate.

Likewise, he said sprangletop is starting to emerge as a problem in almonds--it moves in irrigation ditches, and is herbicide tolerant but not resistant.

Glyphosate resistance is a big deal beyond almonds, and Hembree focused on the species that are resistant, and beyond that, the increasing speed with which new species are becoming resistant, as seen in the chart above.

“As we think about our herbicide programs in almonds and pistachios, think about the mode of action, and think about the herbicide longevity,” Hembree said. “How do we keep these things working for us?”

For growers to maintain the effectiveness of herbicide products, he said, sprays should be timed to be early instead of late.

Hembree pointed to the last decade when he said resistance to glyphosate has spiked.

“How long has glyphosate been in California? Since ‘72,” he said. “This has all happened in the last 10 years...it's been pretty rapid.”

Besides spraying early, Hembree said growers should do anything they can do so that “we don't have the same herbicide program year after year after year.”

That can be costly, but it’s better than losing herbicides to resistance, he said.

“Don't let any herbicide sprays go out with less than two modes of action in the tank,” Hembree said. “If you want to maintain those products, you have to have at least two, or continually rotate.”

Besides changing up spray programs, growers should make sure to get as much coverage as possible when they spray--50% exposure on the weed is not enough to kill a plant, he said.

For more details on tank mixing, see the full presentation at the link above.

“If you have a sprangletop problem, this is the time to treat it,” Hembree told growers. “Don't let this stuff start producing seeds and getting out of control. It's not that resistant, but it acts like it.”

On the other hand, when it comes to field bindweed, he said just because growers see a patch doesn’t mean it’s time to treat. If the plant is no bigger than your hand, growers should hold off, he said. Sprays should be reserved for when the plant growers bigger runners.

Russian thistle requires a different strategy: growers should hit it before the runners are big, when the plant is less than softball size.

Equipment readiness is important regardless of the specific weeds a grower faces, according to Hembree.

When a weed is at the right stage for a spray, if equipment is dusty, it’s hard to get everything ready in a timely fashion, he said.

“It's a lot of things to think about in a short period of time, if you haven't prepared.”

Industry trends Pest and disease Almonds

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