Aphid Predatory Midge
by Applied BioNomics
PO Box 1555, Ventura, CA 93002
800-248-2847 * 805-643-5407 * fax 805-643-6267
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Aphids, all types, to some extent potato (tomato, pepper) psyllid
‘Aphidoletes’ larvae are voracious native predators of over 60 species of aphids.
· Larvae are orange, legless maggots, up to 3 mm (1/16 inch) long.
· Adults are small, delicate midges (flies) 2-3 mm (1/16 inch) long, with long legs. Adults are rarely seen as they are mostly active in the evening.
· Rincon-Vitova’s Max Line of Aphidoletes are collected and shipped with minimum time in transit and no holding under refrigeration to assure adults with the ability to fly long distances to find aphids.
Use in Biological Control
· Aphidoletes are used to control aphids indoors in commercial greenhouses and interior plantscapes as well as outdoors in orchards, shade trees, roses and home gardens.
· Optimum conditions are 21-25º C (70-77º F) and high relative humidity (over 70%), particularly for the pupal stage, which must not dry out.
· If aphids are present in outdoor plants in late summer, a release of Aphidoletes at this time helps reduce the overwintering aphid population, while establishing an overwintering predator population that will be active early the following spring.
· A feature of Aphidoletes in production greenhouses is its habit of flicking the aphid off the foliage or flowers leaving no sign on the plant.
Using 10-15 X hand lens, full grown larvae are relatively easy to see among the aphids because of their characteristic orange color. Younger larvae are much smaller and pale in color, difficult to see.
A complete life cycle takes 21 days at 21º C (70º F). Development rate depends on temperature and availability of prey.
· Sex ratio in populations vary, but there are usually somewhat more females (60% females).
· Female midges lay their eggs on leaves beside aphids. Each females lays 150-200 eggs during her lifespan of 1-2 weeks. The eggs are shiny orange ovals, less than 0.3 mm (1/50 inch) long.
· At 21ºC, eggs hatch in 2-3 days and the tiny, legless larvae crawl along the leaf in search of aphids.
· Larvae feed by biting aphids and paralyzing them with a toxin before sucking out the aphid body fluids. They feed for 7-10 days and can kill 3-50 aphids per day. Where aphid populations are high, larvae kill many more aphids than they can consume.
· To pupate, larvae drop to the ground and burrow into the top 1-2 cm (1/2 inch) of soil or organic material to spin a cocoon. Adults emerge in 2-3 weeks.
· Outdoors, the last generation of Aphidoletes in the fall overwinters in the cocoons in the soil. They are very hardy and survive outside throughout the growing regions of Canada.
Aphidoletes is sent as pupae (cocoons) in moist vermiculite or sand. The predators may be released in either of two ways:
· Immediately upon receipt, gently sprinkle the vermiculite carrying the cocoons onto the surface of the soil or growth media, in the shade; keep the vermiculite moist (not wet) until adults have emerged.
· Hold containers at 22ºC (70ºF) temperature checking daily for emergence until adults are seen flying in the container, then place the container with the corner cut open in the shade, greenhouse or garden, ideally at dusk.
· Adults should begin to emerge within 7-10 days and all should emerge within 14 days of receipt.
Note: Aphidoletes larvae respond to cool temperatures and shortening day lengths (less than 16 hrs) by entering diapause (like a hibernation state). There has been hesitation in the past to use them between September and mid-March. However new observations suggest a great value from low year-round releases in greenhouses to keep the pressure on low levels of aphids (see below).
Generally, Aphidoletes should be released in the spring, 2 or 3 times at 7-10 day intervals to establish the predator.
· Tomato – 1 Aphidoletes/6 plants, weekly for 2 weeks
· Pepper – 1 Aphidoletes/plant, weekly or until established
· Cucumber – 10 Aphidoletes/plant, weekly in infested areas only until established
· Gardens – 250 Aphidoletes/aphid hot spot, weekly for 2 weeks
· Orchards – 5-10 Aphidoletes/tree, weekly for 3 weeks
· Shade trees/5-10 Aphidoletes/tree, weekly for 3 weeks
· Roses – 3-5 Aphidoletes/plant, weekly for 3 weeks
For large areas, such as apple orchards, use 2,000-8,000 Aphidoletes/ha (1,000-4,000/acre), repeated 1-3 times, 1-2 weeks apart, or until established.
For outdoor use, release during the evening on the upwind side of the planting so that the prevailing winds will help to disperse the midges throughout the plot.
For Best Results
For effects of specific pesticides on Aphidoletes.
For additional control of aphids, pirimicarb (i.e., Pirliss®) may be used. It is slightly toxic to Aphidoletes, but the repellent effect of the pesticide disperses the aphids and has been found to repel Aphidoletes females from laying eggs on leaves with pirimicarb residues therefore avoid frequent use. Insecticidal soaps are harmful to all stages of Aphidoletes, but have no residual effect.