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APHID PREDATORS FACT SHEET & Release Instructions
(Aphidoletes aphidimyza, the predatory gall midge)
Aphid predators arrive as cocoons ready to "hatch" into adult predators - a few adults may already be flying inside the container(s). Spread the contents evenly throughout the greenhouse, either on plant leaves (in the shade) or among the soil debris. Adult predators, rarely seen, emerge within a week or so as very tiny, frail-looking creatures, looking much like very small mosquitoes. They fly off to lay eggs near aphid colonies, each female laying some 250 eggs, and living about 10 days. Aphid predator activity is mostly at night.
Aphid predator larvae soon hatch, and begin feeding on aphids. This is the stage most often seen, as each orange colored larvae grows to 1/10" long. To reach full development, each aphid predator larvae has to eat about 10 aphids, However, when aphid densities are high, they'll destroy a far greater number. Watching predators feed is not for the squeamish: predator larvae bite the knee joint of the aphid and inject a paralyzing toxin. After the aphid stops struggling, the predator bites into the thorax and sucks out the body contents. Killed aphids remain attached to the plant leaves, and eventually dry up (proving that predators are doing their job). Aphid predators continue reproducing all season long in greenhouses and other confined areas, often from a single release.
After reaching full size as larvae, aphid predators then drop off the plant and require soil or humid leaf debris for a pupation stage, For this reason, aphid predators don't reproduce well in most hydroponic (soil-less) growing media. Also, predatory nematodes should be avoided when using aphid predators. At 68� F., the total aphid predator life cycle takes about 3 weeks. Optimum conditions would be temperatures from 68�-81�, at high relative humidity.
Typical field release rates have been 3000-4000 aphid predators per acre, repeated weekly during the aphid season until control. For greenhouse use or house plants indoors, one release, early in the season, is often enough to keep predators going all season. For small home greenhouses start with at least 250 predators, or 1000 to get a population going in larger greenhouses. They should reproduce from there, but making repeat releases at 2 week intervals will get them going faster. As a preventative control, smaller numbers of aphid predators can be released occasionally during the aphid season.
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