Biological controls (the use of natural enemies) and cultural controls (the modification of cropping practices) provide valuable alternatives to organophosphate insecticides (OPs) for the suppression of major arthropod crop pests in California. We discuss the successes and limitations of these two approaches with regard to tree fruits and nuts, vines, and field and row crops. For example, a historic success story is that the cottony cushion scale remains innocuous in citrus production, more than 100 years after its successful suppression by the vedalia beetle. More recently, growers’ use of groundcovers and road maintenance helps keep dust down on orchard roads to limit the buildup of web-spinning mites, and good vineyard management is now synonymous with cultural controls for grape pests. Although such alternatives may not always be as effective and predictable as conventional insecticide programs, recognition that partial suppression can greatly reduce the need for OPs will lead to the more widespread adoption of alternatives.

The results of a mealybug study in Central Valley vineyards, designed to develop sampling guidelines, reveal that mealybug distribution on vines varies greatly through the season and that mealybugs usually prefer concealed locations, such as under bark. This combination makes sampling difficult. A number of sampling techniques were compared. Three- or 5-minute timed counts were most efficient because samplers could follow the mealybugs' movement over the season. Midseason counts were much better predictors of damage at harvest than early season counts. This research confirms past control guidelines and opens new control options. Grape bunches touching vine trunks or spurs will have higher damage. Removing these bunches or using barriers between bunches and mealybug oviposition sites can also reduce damage.

Olive fruit fly commonly infests olives in California’s Central Valley. Field studies indicate that trap counts for olive fruit fly adults in pesticide-free sites decrease in mid- and late summer and then rebound from September to November. Part of this decline is associated with heat stress that the flies experience in mid-July and August. Studies have shown that adult flies will die within a few days if they cannot access adequate amounts of water and carbohydrates. Flight ability is dramatically reduced when resources are unavailable. Olive fruit fly adults may use black scale honeydew as a carbohydrate source to help them survive hot periods. Heat also affects the fly’s reproduction and immature stages within olive fruit. Geographic information system (GIS) maps may be useful for predicting the risk of olive fruit fly infestation.