Formica perpilosa Wheeler is a serious economic ant pest on table grapes grown in the Coachella Valley, California, and Hermosillo, Sonora, Mexico. This ant aggressively tends hemipteran pests, such as the vine mealybug, Planococcus ficus Signoret, and disrupts natural control by predators and parasitoids. Efforts are underway to develop control measures against F. perpilosa using granular bait, yet little is known about the colony life cycle or foraging characteristics of this ant. We studied the seasonal activity, mating behavior, and density and spatial characteristics of F. perpilosa nests in vineyards as well as its foraging and recruitment behavior. Nests were active from early February to mid-October. Mating flights occurred in early August and again in the first two weeks of September and new colonies were founded by a single queen. F. perpilosa rapidly colonized a new, non-infested vineyard with ca. 9% of the vines infested after 1.5 y. In September the proportions of infested vines at 5, 20, and 30 y old vineyards were 18.6, 21.8, and 16.2%, respectively. This ant is seasonally polydomous and nest density increased ca. two-fold at the 5 and 20-year old vineyards between February and September. Foraging and recruitment primarily occurred up to 6.39 m from a home nest. The implications of these studies for controlling F. perpilosa using low-toxic bait delivery systems are discussed.

Avocado thrips, Scirtothrips perseae Nakahara (Thysanoptera: Thripidae) was discovered in California in July of 1996 and spread rapidly from two initial sites of discovery near Port Hueneme in Ventura County and at the Irvine Ranch in Orange County. Avocado thrips larvae and adults can build to such high densities over the fall through spring period on young leaves on top-worked trees that leaves damaged from feeding can drop. The main source of economic loss attributable to avocado thrips, however, is scarring of immature fruit in spring by feeding thrips. Economic losses attributable to avocado thrips have been calculated using packout records. Economic data for 22 anonymous growers were combined with costs of thrips control incurred by either using biological control agents, Veratran-D (sabadilla), or Agri- Mek (abamectin). An economic model was developed by an agricultural economist at UC Davis to estimate the effects to growers and consumers of rising production costs, retail prices, and decreases in quality. The model indicated an annual short-run loss to avocado growers of between $7.6 and $13.4 million in 1998 from the combined effects of losses in quality and increased production costs associated with avocado thrips management. Economic losses to avocado thrips continue to accrue annually, but the magnitude of decreased revenue will vary yearly depending on the severity of thrips infestations, costs of control (biological or chemical), percentage of crop damaged, severity of damage, and market value for harvested fruit. Our research sponsored by the California Avocado Commission has taken a three pronged approach to investigating potential control strategies to minimize economic losses to avocado thrips. Our thrips management program is based on: (1) an improved understanding of this pest's biology, behavior, ecology, and natural enemies. We intend to use this information for the development of biological and cultural control programs for avocado thrips. (2) Screening and selection of IPM compatible insecticides and monitoring avocado thrips populations for resistance to these insecticides, and (3) investigating cost effective strategies for applying insecticides by air or ground as selected from screening trials.