Grafton-Cardwell, E.E. 2000a Can reduced-risk pesticides upset biological control of citrus pests?. California Conference on Biological Control II, The Historic Mission Inn Riverside, California, USA, 11-12 July, 2000. Center for Biological Control, College of Natural Resources, University of California Berkeley

Notes: Reduced-risk insecticides have been fast-tracked through the registration process primarily because of their low mammalian toxicity. Only through experience with the insecticides in various growing regions are we beginning to see the costs and benefits for the San Joaquin Valley citrus IPM programme. For citrus, the insect growth regulators and spinosad have greatly relieved problems with OP and carbamate-resistant citrus thrips (Scirtothrips citri) and California red scale (Aonidiella aurantii) thereby reducing overall insecticide use. They have also allowed more parasitoids and some groups of predators to survive and assist with biological control. The problems with reduced-risk and OP replacement pesticides have been 2-fold. First many of the new insecticides are very selective and so are not controlling katydids (Scuddaria furcata [Scudderia furcata]) or citricola scale (Coccus pseudomagnoliarum) which have inadequate biological control. Thus, additional, albeit low rates, of the OP Lorsban [chlorpyrifos] are needed to control these pests. In addition, both the reduced-risk and OP replacement insecticides (pyrethroids and neonicotinoids) are highly toxic to vedalia beetle (Rodolia cardinalis) resulting in sporadic, but highly damaging outbreaks of cottony cushion scale (Icerya purchasi). Thus, we have traded OPs and carbamates that were toxic to Hymenopterous parasitoids with new insecticides that are toxic to predatory beetles and in so doing have traded key pests. Citrus growers are now far more concerned about cottony cushion scale and citricola scale, which can both severely lower fruit yield, than California red scale and citrus thrips. Because of the critical role that predatory beetles play in citrus IPM, reduced-risk insecticides are not fully compatible.