New nematicide, techniques hold promise for walnut orchards, other crops

University of California researchers are trying to perfect a treatment for nematodes, a ubiquitous pest that can damage walnut trees and other crops.

UC Cooperative Extension scientists have been working with a foliar applied systemic nematicide called Movento, a new product from Bayer CropScience that replaced the abandoned Nemacur.

A team led by Michael McKenry, a specialist at the UC's Kearney Agricultural Center in Parlier, achieved a 50 percent reduction in lesion nematode populations in walnut orchards over about a six-month period using variations in applications and timing.

Before figuring out how best to apply the treatment, the scientists had been seeing only a 10 percent to 15 percent reduction, McKenry said.

"It was just a tease," he said. "Then finally we began to see that there were some tricks, and the tricks later became part of the guidelines."

For instance, growers are advised not to irrigate for nine days after applying the spray and not to apply the treatment more than once a year.

The guidelines could provide some hope for growers in battling nematodes, which are responsible for causing as much as $100 billion in damage to turf and agricultural crops each year, according to a golf industry website.

In walnut orchards, nematodes are a serious pest even when measures are taken to limit their impact with sanitation and fumigation before planting, noted a report on the research written by UC farm advisor Carolyn DeBuse.

The pests live in or feed off tree roots, causing a lack of new growth and depleting yields. Lesion nematodes are the worst culprit, migrating, procreating and feeding inside the root, according to DeBuse.

Lots of lesion nematodes have been found in soil samples taken in the Dairyville area in the northern Sacramento Valley, said Rick Buchner, a UCCE farm advisor in Red Bluff.

"We need more information" about Movento, Buchner said. "It's kind of a new deal, but I think it's kind of an exciting tool to get control of systemic nematodes feeding on walnut roots."

One advantage for Movento is that it appears to be less harsh than past treatments, Buchner said.

Scientists have spent four decades looking for a material that can be sprayed on and will achieve nematode control under the soil surface, McKenry said. In 2006, the researchers started working with Movento, seeing lots of potential but limited results at first.

"It was there but it wasn't there," McKenry said. "It was never really working more than say 10 or 15 percent. We could always see it, but we couldn't bank on it."

Among its guidelines, the UC advises growers that the best time to apply Movento is in late May, although other times in the season are possible. Growers should irrigate the orchard well four days before the application, and not again until at least nine days afterward.

Protection with Movento lasts for about six months, McKenry said. For areas that need longer protection, researchers are looking for other materials that could be "lesser agents that we could couple with Movento" to stretch nematode reductions out to eight or nine months, he said.

Source: Capital Press