Native gray ants, found almost universally in San Joaquin Valley peach and nectarine orchards, may help farmers suppress the peach twig borer, University of California scientists report in the November/December issue of California Agriculture magazine.

"Farmers tend to think of ants exclusively as pests," said UC Berkeley biological control specialist Kent Daane, who is based at the Kearney Agricultural Center near Parlier. "And in most cases they are. But our findings may change some farmers' opinions about the native gray ant."

The native gray ant's new-found status as a beneficial insect does not necessarily transfer to other crops. In citrus, prunes, almonds and other crops it can be a serious pest because it will eat the nut meat and protect aphids and scales from natural enemies. But the article's co-authors, Daane and former UC Berkeley graduate student Jeffrey Dlott, found that it is the most important predator of peach twig borer larvae in peaches and nectarines.

Peach twig borer, in its damaging larval stage, is a tiny worm that feeds on peach, nectarine, almond, plum and prune shoots or fruit . The pest has about 30 natural enemies, which by themselves generally do not reduce peach twig borer populations enough to avoid the damage that costs farmers money. However, native gray ant and other PTB predators may work in concert with other control methods -- such as Bacillus thuringiensis sprays at bloom or synthetic pesticides.

The quarter-inch-long native gray ant is found in California and parts of Nevada and Oregon. Its nests are commonly hidden under the soil or in the decaying wood of tree trunks and roots. It exits the nest through cracks in the soil and forages individually for food on the ground or in the trees.

For these reasons, native gray ants may be less apparent than other ant species that have nests with very noticeable ant hills, such as fire ants, or that forage in large numbers
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Contact: Jeannette Warnert
jwarnert@uckac.edu
559-225-5611
University of California - Division of Agriculture & Natural Resources
22-Dec-1998