Farmers Take Aim At Troublesome Insects
"FLYING saucers" and thermos flasks full of pest-busters will soon be helping farmers to control insects that devastate their crops.
Researchers working for the US Department of Agriculture in Shafter, California, are developing two fast, cheap ways to get biological control agents such as wasps and mites where they need to be. One is a clay pigeon or skeet catapult that fires parasitic wasps and other predators into position, and the other is an insulated dispenser that keeps tiny mites immobile while they are being dispersed.
Lyle Carter, the USDA engineer who invented the two devices, says farmers keen to use biological controls find that spreading the insects by hand is expensive and time-consuming. To help them, Carter has developed the Aerodynamic Transport Body, which looks like a clay pigeon and can be launched from a catapult mounted on a pickup truck.
The ATB is a "flying saucer" about 10 centimetres wide and 2 centimetres high. It is made of limestone, hollowed out to hold hundreds of Aphelinus wasps or big-eyed bugs (Geocoris punctipes) which attack cotton aphids and other pests. According to Carter, tests show that such predators don't mind being launched at 177 kilometres per hour, and easily cope with forces of up to 175 g from rotation of the ATB in flight.
He adds, "They are flung about 20 to 50 metres, which is ideal for getting them into the edges of fields, where pests first land when they invade a farm." The ATBs, which split open on impact, will eventually be made from biodegradable oatmeal or peat moss.
Carter has also developed the Mite Meter, an insulated container with a capacity of between 3 and 4 litres that distributes the tiny mites into high-value crops like strawberries.
"Getting mites like Galendromus occidentalis onto crops is hard," Carter says. "If they are warm, they crawl to the top of the container. Shaking it so they tumble to the bottom can kill up to half of the mites."
So the Mite Meter, like a huge thermos flask, keeps the mites and corn grits they are packaged with at a stable temperature, near freezing. This keeps them immobile until they hit the ground. The device can be towed behind a tractor or pushed by hand through the field.
A motorised belt running under the outlet at the bottom of the meter determines the application speed. This precisely controls the number of mites that are released in each metre of each row.
Author: Jonathan Beard
New Scientist issue 22nd August 1998, page 17
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