Don't confuse these nematodes with the harmful ones that infect plant roots. The beneficial nematodes won't harm plants or earthworms. You can spray them in solution on the soil surface or add some to each hole when transplanting. Ladybugs, lacewings, and trichogramma wasps can be purchased from some garden centers and mail order companies. Goldenrod alone has been found to attract more than 75 species of beneficials.
Lacewings are especially fond of fennel, caraway, and dill.
Pathogens You can combat insects with insect diseases as well. Bt is sold as a dust or liquid under such trade names as Dipel and Thuricide. This strain is sold under various trade names, such as Beetle Beater. These remedies can be made up in your kitchen, and modified as you desire. The measurements aren't exact, and sometimes the results aren't either.