Conservation and promotion of natural enemies makes good sense. Can we integrate chemical and biological controls? The impact of conventional pesticides on natural enemies is termed selectivity. Most broad spectrum insecticides are toxic (not selective) to arthropod natural enemies, and fungicides are toxic to entomopathogens. Families, species, and different life stages of the same species may respond differently to pesticides. Acaricides are usually safe to insect natural enemies, but most are harmful to predatory mites. Formulations of the bacteria or endotoxins of Bacillus thuringiensis (B.t.) and fungicides are selective of arthropod natural enemies. Pyrethroids are selective of most lacewing species, but show mixed results versus other predators and parasitoids. Pyrethroids are toxic to predatory mites. Organophosphate pesticides are toxic to most arthropod natural enemies, but chlorinated hydrocarbons are more selective. Botanicals show mixed results with most being selective. Growth regulators are more host specific and usually are selective.
Modification of application methods, such as using reduced rates, spot treatment and better timing, can be used to help conserve natural enemies. Granulars, systemics, or baits can better target the pests so that natural enemies are not exposed to harmful pesticides.
Be cautious about systemic insecticides as they may harm natural enemies in several ways. They may contaminate nectar or plant sap which natural enemies feed upon. They may also be transferred through the food chain. The prey feed on the plant and sequester the systemic poison, but are not affected by it. The poison kills the predator when the contaminated prey are eaten by the predator.
For additional information visit the Florida IPM and Biocontrol Web site at http://biocontrol.ifas.ufl.edu/.