Limited nematicide choices for vegetable growers

The phase-out of methyl bromide is having a not-so-unexpected impact on many vegetable producers.

“Nematodes are getting worse,” says Richard Molinar, Fresno County UC farm advisor. “We’re seeing bad problems in many specialty vegetables, and it seems like there are more and more problems in bittermelon. That’s ironic because bittermelon is resistant to almost every other pest except root knot nematodes.”

The problem has grown worse in recent years due to increased regulation, which has limited growers’ choices. “It’s partly due to cost and availability of nematicides,” Molinar says. “And then there’s the phase-out of methyl bromide and restrictions on other materials such as Telone.”

Small vegetable growers are often hit even harder due to fewer cultural control options.

“Limited rotations are a problem for many small farmers because of the limited acreage they have to work with. In some cases, new farmers don’t even know about the problem.”

With dwindling options for fumigation, disease is also a problem for vegetable producers. Much attention has been devoted to the benefits of rotating brassica crops in the Salinas Valley as means of mitigating problems with persistent soil borne pathogens such as verticillium, sclerotinia, and fusarium. However, the feasibility of those rotations, in a lot of situations, is somewhat limited.

In addition, a new threat to Salinas Valley lettuce has shown up in the form of Verticillium dahliae, according to Krishna Subbarao, University of California plant pathologist at Salinas. In the past, the disease has been managed by fumigation, but it often returns after a rotation cycle of two crops of lettuce and one of strawberries, requiring fumigation every other year.

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