Russian thistle control gets high priority

The California Department of Food and Agriculture's Integrated Pest Control Branch is poised to help solve problems with Russian thistle and other pests but is calling for input from growers to set its priorities.

Branch chief Nathan Dechoretz was on hand at a recent meeting of sugar beet growers in Mendota to describe his program and its multiple services.

Russian thistle, or tumble weed, a pest throughout the western United States for more than a century, is of current, intense interest because it is a host of the beet leafhopper, which vectors curly top virus, deadly to sugar beets, tomatoes, and many other crops. Prospects of additional fallowed acreage in the coming year make the weed a greater threat.

The collapse of the Soviet Union affected how CDFA scientists are able to approach searching for a biological control for the noxious weed, Dechoretz told growers assembled at the Spreckels Sugar Co. refinery.

More open relations between the U.S. authorities and the political entities that once comprised the Soviet Union mean our entomologists have access there to potential natural enemies of Russian thistle, which originated in that part of the world.

Seek control agents

“Russian thistle is a huge problem all over the state, and we have allocated about $200,000 to federal researchers to go to countries we previously could not enter and look for biological control agents specifically for Russian thistle,” said Dechoretz.

Through a contract with USDA, the branch came up with eight insect species considered potential natural enemies for the weed. Among them are root borers, stem feeders and seed-head feeders now under quarantine abroad in anticipation of bringing them into the U.S.

“It's a long process and we expect it will continue to be funded, so we hope to have something to work with in a few years,” he said.

“But we want to make sure the testing is thorough. The last thing we need is to bring in something we think is a bio control agent and have it turn out to be another pest.”

Dechoretz said one peculiar obstacle with biological controls of weeds is they take a long time to become established by natural, classical techniques rather than mass-rearing that might be used for biological control agents for insects.

The amount of the target weed has to be adequate to support a population of natural enemies, but an overwhelming blow-up of the weed can be too much for the agents to control.

Grower finds

At the same time, he said, it may be possible, if a weed pest, such as puncture vine, emerges, for agricultural commissioner officials to move predators or parasites from one location to the problem site.

The branch, he said, is working out details for another new dimension, identification of viruses found by growers in the field and submitted to the branch.

The State Curly Top Virus Program regularly submits samples to the branch laboratory in Sacramento for identification. Many other viruses, however, attack California crops.

“If your sample is not curly top but some other virus, the lab will tell you which virus it is, free of charge. Then you can talk with your pest control advisors to determine what the control for it is.”

To maintain registrations of vertebrate pest control materials CDFA has to perform research, which is supported by surcharges on the materials, on new products and methods. “The process can be long and expensive and we are working diligently to make sure those materials are available to you.”

Research resources are channel via scoping meetings in the field and other efforts gather information on growers' pest control problems. One example is designs of bait stations successful against target pest species yet inaccessible to endangered species in the treated area.

Dechoretz said the county agricultural commissioner's offices work closely with the branch and can answer questions on the branch's pest control projects.

“We are here to help you as best we can, but we need to know the issues, whether vertebrate, insect, or weed pests. When you tell us what your problems are, it helps us set our priorities without working in a vacuum.”

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