A recent development is the fungus Beauveria bassiana, which kills aphids, caterpillars mites, psyllids, thrips, whiteflies and spider mites. Once inside the host, the fungus rapidly multiplies throughout its body, killing the insect. Naturalis-O, this microbial insecticide is not yet available in California. Approval is pending. Many gardeners think of nematodes as pests, but there are beneficial ones that prey upon detrimental insects.
Nematodes are microscopic roundworms.
The nematode Steinernema carpocapsae is effective in killing root weevils, cucumber beetles, armyworms, beetles, root and seed maggots, fall armyworm, corn earworm and fleas in the yard. When applied to plants and soil, nematodes hunt for their prey, attracted by the carbon dioxide emitted by the doomed host. Carrying insect-pathogenic bacteria within its gut, the nematode penetrates its host and the bacteria multiply, killing the pest. The nematode feeds on the bacteria and insect's body, then mate and reproduce. A week or two later, young nematodes emerge from the insect's carcass and hunt for new hosts.