INTEGRATING CULTURAL MANAGEMENT PRACTICES AND BIOLOGICAL CONTROL TO SUPPRESS CITRUS MEALYBUG

The citrus mealybug, Planococcus citri (Risso) (Hemiptera: Pseudococcidae), is one of the most common and damaging insect pests in greenhouses and protected cultures. Pesticides are frequently used, often unsuccessfully, to control this pest. Our objective was to determine the influence of water and nutrient management practices on mealybug populations and their impact on the efficacy of augmentative releases of Cryptolaemus montrouzieri Mulsant (Coleoptera: Coccinellidae), a mealybug predator. Studies were conducted on Heuchera micrantha ‘Palace Purple’ growing in protected culture. Heuchera plants received 3 rates of nitrogen: low (25 ppm/wk), medium (75 ppm/wk), and high (150 ppm/wk). Within each fertilizer treatment plants were either water stressed or not water stressed. In the absence of predators, citrus mealybug populations increased dramatically on water stressed plants receiving high and low levels of fertilizer. Cryptolaemus montrouzieri reduced mealybug populations and consistently had the greatest impact on mealybugs where mealybugs were the most abundant, regardless of fertilizer or water treatment. In the presence of predators, mealybug populations are regulated by predation rather than mealybug interactions with fertilizer or water. This data suggests plant management practices that avoid high or low rates of fertilization of water stressed plants should reduce the outbreak potential of citrus mealybug. If mealybugs do outbreak, implementing augmentative biological control with C. montrouzieri should be effective regardless of fertilization and irrigation practices.