University of Illinois Extension Horticulture Educator, Kelly Allsup says managing pests organically is easily achieved with biological pesticides.
Becoming organic does not mean that gardeners are without tools to manage garden pests; biological chemicals are commonly available in garden centers and derived from naturally occurring sources. These biological chemicals are safer for the environment because they are more selective in their activity, therefore most are safer to use around pets, wildlife, butterflies, bees and beneficial insects. Here are some examples:
To control cabbage worms, tomato hornworm, bagworm, and tent caterpillars, use Bacillus thuringiensis(Bt), a naturally occurring bacterial disease of insects found in soils. Bt sprayed on leaves must be eaten by the insects. Once infected with Bt, the insects will stop feeding within hours, taking several days to starve to death. Bt is safe to use around pollinators; natural predators (good bugs aren't bothered because they don't eat the plant); humans; mammals; birds; and fish. Sunlight breaks down the bacteria, so spray at dusk.
For control of spider mites, lace bugs, beetles, caterpillars, whitefly, aphids and squash bugs, use Neem Oil or Azadirachtin.
Neem oil is found in the seeds of the neem tree from Southeast Asia and India. Neem oil must be ingested by the insects to become effective. It interferes with insects' hormones, making it hard for insects to grow and lay eggs. There is some slight toxicity to fish. Neem oil has fungicidal properties so it can be used to prevent black spot on roses or powdery mildew on your garden favorites.
For control of whiteflies, aphids, grasshoppers, Colorado potato beetle, Mexican bean beetle, flea beetle, Japanese beetle, boll weevil, bark beetles, fire ants, European corn borer and codling moth, use Beauvaria bassiana.
Beauveria bassiana is a common soilborne fungus found worldwide. The spores infect and germinate directly to the outside of the insect's skin (cuticle). The fungus growing from the spore secretes enzymes that attack and dissolve the cuticle, allowing it to penetrate the skin and grow into the insect body. Once inside it weakens the insect's immune system. Eventually the entire body cavity is filled with fungal mass.
Opting to use compost to amend the soil instead of liquid chemical fertilizers, native plants instead of highly managed plants, and refraining from using chemicals like carbaryl and organophosphate are steps gardeners take to become organic.