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Pest Control in a Nutshell

In Scott Hunter's almond orchards in Merced County, long patches of grass separate the rows of trees. But they aren't there to entice picnickers. By providing a home for beneficial insects-bugs that eat almond crop-destroying insects like mites, ants, and aphids-the grass is part of Hunter's environmentally friendly pest management strategy.

Like Hunter, most California almond growers use a gentle pest control approach that nurtures beneficial insects, plants, and animals while putting the kibosh on pests. Called integrated pest management (IPM), this method emphasizes surface and groundwater protection. It recommends using only the least-toxic pesticides and only as a last resort.

"The almond industry is a poster child when it comes to environmentally responsible pest control," says the California Almond Board's Chris Heintz, who directs pesticide research. "It's way ahead of other fruit and nut industries."

Almond growing practices haven't always been so kind to the environment. Twenty years ago, diazinon, an organophosphate that kills insects by attacking their nervous systems and also harms fish, birds, and mammals, was applied annually in almond orchards throughout the state. Known as a "dormant" spray because it was used during the winter when trees "sleep," diazinon warded off a broad spectrum of pests before they ever got a toehold. It also ran off into gullies, sloughs, and creeks, and found its way into rivers. According to a 2004 California Department of Pesticide Regulation (CDPR) report, diazinon has turned up in the San Joaquin and Sacramento rivers at levels high enough to kill aquatic life.

Fortunately, almond growers have found that they can usually get along fine without it. Their diazinon use fell from 115,000 pounds in 1997 to 63,000 pounds in 2001, a 45% drop. Credit for this drop goes largely to research and educational efforts by the University of California Cooperative Extension, often funded by the Almond Board.

Now IPM has reached a new level as a result of a five-year study funded by a $500,000 pest management grant from CDPR. Completed in 2004, the study was undertaken by the public-private Pest Management Alliance, composed of the Almond Board, U.C. Cooperative Extension farm advisers, state IPM advisers, and the Almond Hullers and Processors Association. The Alliance conducted demonstration projects in Kern, Stanislaus, and Butte counties. Based on the study's findings, it published The Seasonal Guide to Environmentally Responsible Pest Management in January. "The guide connects the research into an [ecosystems] approach and recommends different pest control activities for each season," says the U.C. Cooperative Extension's Roger Duncan. "It considers the tradeoffs: When you kill damaging insects, you might knock off the beneficial ones too."

"The guide emphasizes that constant orchard monitoring is the key to controlling pests and to being a good orchard steward," says Heintz. In a nutshell, monitoring means trapping insects early in the year to see what insects are there and how many, says Duncan. "If the insect level is low, below the economic damage threshold, nothing needs to be done. The study compared orchards that weren't sprayed with orchards that were. It looked at yields, damage, the environment, and beneficial insects, and the findings for not spraying were encouraging," says Duncan. "They should help get more growers to choose not to spray."

But if traps show that the insect level is high, the grower should use a targeted pesticide, one that wipes out only the peach twig borer or the navel orangeworm, says Duncan. With the help of computer models and detailed temperature data, the grower can pinpoint the two- or three-day period when spraying will work best, so long-lasting sprays aren't necessary.

If spraying is necessary, growers can minimize the amount of pesticide spray used in a host of ways. They can avoid spraying when rain is forecast or when the wind kicks up. Hunter says he uses a machine with a sensor that turns the spray off between tree canopies and at the end of rows. To reduce the amount of pesticides draining into the river, he plants cover crops that absorb the pesticide-laden water.

To prevent insects from over-wintering in the trees, the guide suggests shaking off the "mummy" nuts still clinging stubbornly to the branches after the harvesters have been put away, and then chopping them up, says Blue Diamond Growers' Dave Baker. No more than two nuts should remain on each tree. In the rare cases where a grower needs a preventive dormant spray, the guide recommends an oil spray.

The almond growers are using environmentally safe practices voluntarily, and staying ahead of the regulators in part because of the Almond Board's research and outreach efforts, notes Baker. The research should also help the regulators-as they develop the total maximum daily loads (TMDLs) for pesticides for the state's rivers, they'll have a lot of good science to base them on.

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