The small predatory midge Aphidoletes aphidimyza is commercially available from many sources for aphid control in greenhouses. Do-it-yourselfers might like to try raising their own midges from an initial order.
The midge can be reared on aphid species that do not infest commercial greenhouse crops, such as the grain aphids Sitobion avenae, Metopolophium dirhodum, or Rhopalosiphum padi. Wheat or barley plants grown in open trays or boxes are infested with the aphids, then with the predators.
The midge is introduced to the crop plants from these open rearing units or banker plants placed in the greenhouse. The midges develop on the grain aphids, then the adult midges disperse to lay eggs on aphid-infested crop plants.
The rearing units must be established early in the growing season and maintained for several weeks so that a large midge population has developed by the time pest aphids appear. It may take some experimentation to determine the optimum number and timing of introductions of both aphids and predators to produce a good "crop" of midges.
This does not seem to be a practical method in large commercial greenhouses, and it is difficult to determine what "release rates" are occuring.
- Susan Mahr, University of Wisconsin-Madison
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