Relative Toxicity Rating of Insecticides and Miticides to Common Beneficial Mites and Insects*

Beneficial insects and mites provide biological control of several important pests of tree fruits such as European red mite, rust mites, spider mites, aphids, tentiform leafminer, apple mealybug, pear psylla and leafrollers. The preservation of native biological control agents is an essential component of IPM programs designed to keep mites, pear psylla and leafminer below damaging levels. Unfortunately some of the pesticides used in orchards can be harmful to these beneficial organisms, either through direct contact with the sprays or with the moist spray residues. In most cases pesticides are not harmful to beneficials once the residues are dry. Some pesticides will eliminate beneficials while others will reduce their numbers (suppress), allowing their populations to rebound in the absence of further disruptive sprays. To take full advantage of the biological control services provided by these beneficial insects and mites, growers should become familiar with the identity of the beneficials, their life cycles, and know what pesticides are harmful to them.

The table below lists the toxicity (L = low; M = moderate; H = high) of some pesticides to some common beneficial insects and mites. Use this table to select the product(s) least toxic to the beneficials ‘working’ in your orchard. These ratings are a guide only – individual populations of beneficials can vary in their susceptibility due to exposure history to the pesticides.

* This table is compiled from published references and reports from local crop/pest management specialists.

¹ Acute mortality is low, however, new information shows that exposure to this product suppresses the population growth of natural enemies.