A useful tool for controlling gnats and shore flies, that transmit Pythium and other pathogens into hydroponics systems is Diatomaceous Earth. It is a chalky white to cream powder obtained from the natural fossilized remains of diatoms, a type of small hard-shelled ocean organism. These diatom particles are very small and sharp but only harmful to the small exoskeletons of insects. Insects cannot become immune to their action since it is a mechanical killer. Because it is a light dust, it clings to the bodies of all stages of the insects. Maggots may also ingest the powder. The tiny diatom particles then cut through the waxy coating or lining of the insects gut and they eventually dry out and die.
Seed beds, especially those that use capillary matting, composted bark, rock wool or vermiculite, can be liberally dusted with diatomaceous earth. Use a “pepper pot” technique to liberally coat the media as seedlings are about to emerge. If washed into media during irrigation it will eliminate maggots as they hatch from eggs and will maintain its activity when plants are transferred into hydroponics systems. Also spread about any areas near the houses where gnat adults, larvae (maggots) or pupae may be present.
Diatomaceous earth is available from Pure Hydroponics. Some lines of diatomaceous earth, used for insulation in walls etc, have been heat treated to reduce abrasive
properties. Do not use products that have been heated since they do not abrade the insects? exoskeleton
Diatomaceous earth contains a variety of elements and usefully contribute to the supply of silica, that is used in plant roots and leaves. Supplies of this element can be low in
1kg Bags for $8.50 + GST