Measuring only one-fiftieth of an inch, thrips are hard enough to see with the naked eye, let alone identify as to the individual species.

But a team of Australian and University of California, Riverside, researchers have made the task easier by creating a user-friendly, interactive, computer-driven identification tool.

Available on CD-ROM for $52, the electronic tool summarizes information available on 207 species of native and exotic Californian thrips, including 12 species that are considered potential invaders. Although many thrips are harmless, some—such as Western flower thrips and citrus thrips—can feed on leaves, young fruit and flower pollen. Some species spread viruses, such as tomato spotted wilt virus, which can kill plants.

Users of the tool answer a series of simple questions illustrated with photographs of the external appearance—or morphology—of the thrips in question. Each response narrows the number of choices to determine the identity of the thrip until the user is left with one scientific name.

Once the species is identified, the user clicks on the name to open up a fact sheet on the thrip, photographs and other pertinent information.

"Essentially, we have 1,500 high-quality photographs of several entire museum slide collections of thrips of importance to California on a CD-ROM that is highly portable...," says Mark Hoddle, a UC-Riverside biological control specialist who is leading the project. "Until now, there existed few tools for identifying California thrips, and of available tools many are in excess of 40 years of age."

A free interactive version will be available online at http://www.lucidcentral.com/keys/viewkeydetails.aspx?KeyId=468 beginning Sept. 1.

The CD-ROM can be ordered through UC-Riverside by e-mailing Hoddle at mhoddle@ucr.edu.

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Product helps protect walnuts from sun, boosting meat quality

When Aunt Polly asked Tom Sawyer to whitewash the fence in the Mark Twain novel, she probably wanted to brighten up the structure or protect it from decay.

Walnut growers can borrow that premise and apply a whitewash-like product to their trees to protect them—in this case—from the sun and its associated high temperatures.

Kathy Kelly, a University of California Cooperative Extension farm adviser in Stanislaus County, has conducted tests with Surround WP on mature walnuts for four years.

Surround from Tessenderlo Kerley Inc. of Phoenix, contains kaolin clay, which reflects specific wavelengths of light, reducing sunburn and heat stress in several crops.

Treated walnuts average 4 to 8 degrees cooler than untreated nuts and well below the 122-degree threshold for sunburn, according to research conducted by Bruce Lampinen, a UC integrated orchard management specialist based in Davis.

Even though ambient air temperatures never get that high, nuts can be up to 20 degrees warmer than surrounding air, Kelly says, citing Lampinen's work.

"Surround cools the plant off," she says. "The reason that is important is photosynthesis shuts down at 86 degrees in walnuts. So if the tree is cooler, then you can photosynthesize longer."

Surround also helps protect nuts from sunburn. Nut buyers covet light-colored walnut kernels, and sunburn can darken nutmeats.

Kelly's trials involved applying Surround at 50 pounds in 200 gallons of water per acre. The first application was timed in advance of a high-temperature forecast. The second application was made 10 days to three weeks afterward, depending on conditions. Spray intervals between the second and third applications ranged from three to four weeks.

She also examined whether making applications to only one side of the tree was as effective as a full application to both sides of the tree. The theory was that by making a half application, growers could save money.

Of the four walnut varieties in the trials, Vina showed significant improvements in edible yields each year, whereas Howard and Tulare showed improvements only during some years. Treated Chandler orchards showed no improvement over the untreated control.

Diamond Foods Inc. of Stockton, Calif., graded each sample, using commercial criteria.

Results of the half treatments were not significantly different than the full treatments. If growers reduce the application, Kelly recommends applying it to the south or west sides of the trees that receive the afternoon sun.

Regardless of the rates, she suggests growers change the sprayer direction for each application. So if a grower applied the material beginning on the south end and moving north through the rows, the next time he should start on the north edge and move south.

Thorough, uniform and complete coverage is crucial, Kelly says, and ground sprayers may not be able to adequately deposit the material into the canopies of tall trees. Growers may want to consider an aerial application in that case.

"What's worked well in some orchards is spraying the tops by air," she says.

Three aerial applications at the rate of 30 pounds in 20 gallons of water per acre have given good results under non-trial situations, Kelly says.

One question she's posed the manufacturer is, "how white does the tree have to be for the product to be effective?"

"I know in the whitewash days, you had to get it to the color of paper for it to work," she says.

She applied 200 gallons of water per acre and says some growers may try to reduce it to 100 gallons. But that will produce a larger particle droplet that's less well dispersed throughout the trees.

An added benefit of Surround is it suppresses codling moths and husk flies, Kelly says.

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