   Pheromones and Insect Control - December 23, 1998 Jeff Schalau, County Director, Agent, Agriculture & Natural Resources Arizona Cooperative Extension, Yavapai County How do insects communicate? Grasshoppers, crickets and cicadas use sound. Lightning bugs use their flashing lights. Honey bees use a dance to tell others where the foraging is good. Other insects use chemicals called pheromones to communicate their availability for mating, where to find food, and where to gather and rest. Most outdoor enthusiasts have seen a mass of Lady Beetles on a tree stump or rock. They are responding to an aggregation pheromone and do this to overwinter. Ants also use pheromones to trail each other. The next time you see an ant trail in your kitchen, take a damp, soapy sponge, wipe it across the ant trail and observe them as they reestablish their bearings. Entomologists and biochemists have made great strides in identifying chemical structures of these compounds and have succeeded in synthesizing several pheromones. Sex pheromones are commonly used to disrupt insect mating. Under normal circumstances, the female insect releases a sex pheromone from the tip of her abdomen. The chemical is lighter than air and is transported on the slightest breeze. The male has receptors on his antennae that detect the pheromone on the air. In this manner, they follow the chemical trail to seek a mate. Most pheromones are specific for insects of that particular species. Otherwise there would be considerable confusion (and frustration) among the insect species involved. Think of the many ways we can use the natural system to meet human goals. In the old days (the 1970's), pheromone traps were used to monitor insect populations so that optimal times could be determined for insecticide applications. Now, we use this technology to trap insects to directly reduce the male population. Pheromone trapping has been very successful in controlling codling moths in apples. Take this a step farther by putting the pheromone throughout the orchard to disrupt mating and confuse the males so they use all their energy flying around and never find a mate. This is commonly done by putting small coated wire "twist ties" impregnated with the pheromone all over a fruit orchard. A newer technology uses spray cans that are timed to go off at dawn and dusk, the time of peak activity for codling moths. Each puff of spray releases the equivalent of 10,000 female moths. Talk about some confused and frustrated males. Now, pheromone traps are used to trap or disrupt many insect pests. The pheromones are harmless to humans, but are still somewhat expensive. Some reasons for this are: a very small amount of the chemical is needed; extensive research is done before the chemical structure of the pheromone; and, if more growers used these products, the price would likely decrease. Many pheromone products are currently available. Codling moth traps, ties and sprays are very common. Traps are available for monitoring corn ear worm, European corn borer, and beet armyworm. Roach traps are readily available in many stores. Peach twig borer mating disruption pheromones are available commercially. Lady beetle attractants are also available to increase predatory nymph populations for aphid control. The list goes on to include products to control red scale, San Jose scale, leafrollers, stinkbugs, and tomato pinworms. I'll go out on a limb to say if there is a pest that utilizes pheromones to navigate and it is causing economically significant crop damage or threatens human health, then someone is working on developing a pheromone to control it. I'll depart this column with some things to think about. With all of the chemical sprays available, we have never eradicated an insect. To rely on chemical control will only lead to increased insect resistance to pesticides. Instead, we should employ many tools in our approach to insect control. Chemical pesticides can be one of those tools along with bio-controls, such as pheromones and beneficial insects. We should also learn to tolerate low levels of insect damage to our crops. Happy Gardening! The University of Arizona Cooperative Extension has publications and information on pest feeding behavior and control. If you have other gardening questions, call the Master Gardener line in the Cottonwood office at 646-9113 or E-mail us at mgardener@kachina.net and be sure to include your address and phone number. |