I have fruit flies in my garden. How can I get rid of them? I have drained my plant’s soil and changed the water, but that didn’t work. Please advise.
Fruit flies and sand flies are about 1/16 of an inch long, and look like tiny black gnats. They usually hang out toward the lower part of the plant and near the planting medium. Both are vectors for disease. They and their pupae, which live in the planting medium, eat decaying organic matter. In their travels they are likely to pick up pathogens from an infected plant and transfer it to the next one.
These insects are attracted to the color yellow. One way to determine whether the garden is infected is to hang a yellow sticky card. If the garden is infected, some of the pests will stick to it. Pyrethrum, an organic insecticide completely safe to mammals, is effective at eliminating the insects. It can be sprayed or used as a soak. The soak will kill the pupae.
Biological control is an even more effective method of eliminating the pests. Beneficial nematodes are microscopic worms, which attack all kinds of soil-dwelling insects. They are available at many nurseries and by mail order. They are inoculated into the medium by adding them to the irrigation water just before it is to be used. The nematodes search out the pupae and then invade and eat them from the inside out. Then they reproduce and the cycle repeats. Within a week or so the mature flies die, and virtually no pupae emerge from the inoculated medium.
Readers with grow questions (or answers) should send them to Ed at:
Ask Ed, PMB 147, 530 Divisadero St., San Francisco, California 94117, USA
You can also email Ed at [email protected], and send queries via his website at www.quicktrading.com.
All featured questions will be rewarded with a copy of Marijuana Question? Ask Ed.
Sorry, Ed cannot send personal replies to your questions.