Battling heat and dryness this past summer was challenge enough for New York's backyard gardeners and vegetable farmers, but the overall lack of rain and high temperatures has created another headache: A bumper crop of aphids, spider mites and thrips -- along with some harmful viruses that aphids can spread. Such insect pests thrive in hot weather, where they feed on the liquids inside plants.

"In hotter, drier years, we've seen more problems with aphids," said Brian Nault, assistant professor of entomology at Cornell University's New York State Agricultural Experiment Station in Geneva. "In some crops, aphids can be a problem by just directly feeding on the plants -- but even more serious is their ability to transmit viruses. This year, in particular, viruses that have been transmitted by aphids have been bad."

Among the more common -- and damaging -- viruses are "mosaic" viruses, which cause leaves to pucker or fold under themselves and occasionally stunt the growth of the entire plant. These viruses are a serious problem because infected plants can have significantly reduced crop yields. Some of the more common aphid-borne mosaic viruses afflicting New York vegetables are the cucumber mosaic virus, the watermelon mosaic virus and zucchini yellow mosaic virus. "We have seen the percentage of infected plants with cucumber mosaic virus reach 100 percent in many snap bean fields in western and central New York," Nault said.

Other pests that are surging in the summer heat this year are soybean aphids, which are indigenous to Asia, along with native spider mites and thrips. "New York farmers who have been growing onions all their lives have never seen onion thrips as bad as they are this year," Nault said.

What's a gardener to do? Aphids are susceptible to several control methods, such as pesticides, but many gardeners shy away from using chemical pest controls. In addition, natural predators such as lacewings and ladybird beetles can help control the aphid population. Unfortunately, not much can be done to prevent aphids from transmitting viruses. The best control measure, Nault said, is to hope that heavy rains, such as those that fell this last week of August in the wake of Hurricane Katrina, will reduce the size of these insect populations by washing the insects from leaves and creating better conditions for naturally occurring biological control organisms. One common type of natural biological controls is the fungi from the Entomophthorales group, which can create widespread mortality in aphid populations.

The availability of natural controls and information about pesticide use is available at county Cornell Cooperative Extension offices. A list of county extension offices is available at <http://www.cce.cornell.edu/local_offices.cfm >.