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Maximize benefits of beneficial insects

The use beneficials to manage of insect pests continues to increase.

“Although some growers use these predatory insects in place of insecticides and miticides, others use them in conjunction with chemicals to control these pests,” says Kim Horton, general manager of Sterling Insectary, Delano, Calif.

Among the natural enemies of vineyard insect pests offered by the company are lacewings, which prey on various soft-body insects or mites and predatory mites, which feed on all life stages of leaf-damaging spider mites.

Horton offers this advice for getting your money’s worth from these and other beneficial insects:

Distinguish good bugs from bad bugs — Effective use of biological controls requires effective scouting, she notes. That includes properly identifying what you find in a vineyard.

“Sometimes growers think the mites they see on their vines are pests, but they might actually be beneficial predatory mites. It’s important to know the specific types of pests you have so you can use the right predators to control them.”

Determine pest thresholds — Unless the population of a particular pest reaches a certain threshold, the use of predatory insects may not be cost-effective. Beneficial suppliers or UC IPM guidelines can identify thresholds, Horton says.

Order beneficials early — Once the pest population reaches the threshold level, order predatory insects or mites. A reputable insectary should be able to ship an order the same day or the next.

Know what you’re getting — Before placing an order, make sure it is up to the job of controlling the pest. That requires getting the right information from your supplier.

“The more information an insectary provides, the better,” Horton says. “For example, the supplier should be willing to tell you where and how the predatory insects were produced and provide a list of chemicals used in vineyards to which they are resistant.

“Ask how they will be shipped to keep them healthy and to arrive on time. The shipment should arrive overnight or within two days at the most. Also, find out exactly what is coming, such as nice, healthy female mites that will start laying eggs right away once they are released.”

Release predators immediately — Pest numbers can increase rapidly and any delay in releasing the predators will reduce their ability to control the pests.

“Many growers don’t realize how quickly insect populations can explode,” Horton says. “Spider mites, for example, can grow from an egg to an adult in just five days when the temperature is 85 degrees or higher. If the predators aren’t released immediately, it can take them a lot of time to catch up to the pest population. In general, the smaller the insect, the faster it can complete its life cycle.”

Place them where they will do the most good — Put predatory insects as close to the pest insect as possible. In the case of her predatory mites, Horton ships them on a bouquet of cut soybean plants. Every 250 of these cut plants contains about 10,000 of the beneficial mites. She recommends spreading the plants out in the vineyard so about 2,500 to 5,000 mites are released in each acre.

Assess the results — Assuming the predatory insects are doing their job, scouting should show numbers of insect pests beginning to drop within a week or two of releasing the predators.

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