The red gum lerp psyllid is an insect native to Australia, where it feeds upon eucalyptus species. Since 1998 this psyllid has spread throughout California, resulting in millions of dollars in damage and control costs. To help suppress the red gum lerp psyllid, a biological control program was initiated and a psyllid-specific parasitic wasp was imported from Australia in 1999 and released in 2000. In most coastal regions this biological control agent has provided substantial control, but in some interior regions the psyllid still remains a problem. Researchers are continuing their investigations to determine if full statewide suppression will be realized eventually, or if further importation of new parasitoid species is needed. Fig. 4. Percentage of large lerps with parasitoid emergence exit holes during fall survey, 2003 (Roltsch et al. 2004). California county borders demark the four regional sampling zones (except for the Central Valley).

Many natural enemies of bark beetles are attracted to bark beetle pheromones, and substantial numbers of them are removed along with the target pests in mass trap-out programs. Thus, additional information on bark beetle and predator behavior is needed to maximize trap-out of target pests while decreasing trapping of beneÞcial insects. Ips pini (Say) is the most widespread bark beetle associated with pine trees in the United States and Canada. Geographically distant populations vary considerably in their production of, and response to, different stereoisomers of their principal pheromone component, ipsdienol, and an additional pheromone component, lanierone. California populations of I. pini are attracted to 99.9%(Ð)-ipsdienol, and the presence of lanierone has no effect on attraction. We simulated trap-outs by conducting no-choice assays using three different ratios of (ϩ)/(Ϫ) enantiomers of ipsdienol with or without lanierone in the Þeld. Experiments were performed in mixed pine forests in northern California in 1997 and 1998. Experiments were performed twice each year to sample the two major ßight periods of I. pini. Ips pini and its predators showed temporal and behavioral differences in their attraction to lures. Lures that are preferred by I. pini, 3(ϩ)/97(Ϫ) ipsdienol with or without lanierone, selectively removed up to 5Ð7 times more pests than predators during early summer. Moreover, the ratios of pest to predators were much higher in the late than early summer, and pest numbers were as much as 282 times higher than predators. In contrast, lures most attractive to predators removed as much as 10 predators for each I. pini trapped. These results suggest that timely applications of carefully selected synthetic lures, in combination with other complementary forest management practices, can greatly improve trap-out programs for bark beetles and natural enemy conservation. In addition, behavioral differences in attraction suggest the potential for augmentation of natural enemies.

High densities of the blue gum psyllid can inhibit new shoot formation, distort the shape of new foliage and despoil foliage with white flocculate secretions produced by the immature stages and black sooty molds that grow on the honeydew. 4 The blue gum psyllid was first found in a plantation of baby blue gum in Monterey County.

Effective management of bark beetles (Coleoptera: Curculionidae, Scolytinae) relies on accurate assessments of pest and predator populations. Semiochemicals provide a powerful tool for attracting bark beetles and associated predators, but the extent to which trap catches reßect actual population densities are poorly understood. We conducted Þeld experiments in California during 2 consecutive yr to determine how attraction of Ips pini (Say) and its major predators to synthetic pheromones vary from each other and from attraction to natural volatiles emitted from colonized hosts. Synthetic lures consisted of different ratios of the (ϩ) and (Ð) enantiomers of ipsdienol, the primary pheromone component of I. pini, with or without lanierone, an additional component that synergizes attraction in some populations. I. pini was consistently attracted to either 3(ϩ)/97(Ϫ) ipsdienol or infested host plant material. Lanierone had no effect on the attraction of I. pini. Coleopteran predators showed a range of responses, more of which coincided with I. pini. Temnochila chlorodia (Mannerheim) (Trogositidae) was attracted to infested host materials and all synthetic lures. Enoclerus lecontei (Wolcott) (Cleridae) preferentially responded to higher ratios of (ϩ)-ipsdienol, and its attraction was strongly enhanced by lanierone. Enoclerus sphegeus F. was most attracted to infested hosts and exhibited a preference for (Ϫ)-over (ϩ)-ipsdienol. Our results suggest that preferences of bark beetles and predators for bark beetle pheromones at the regional scale should be considered before deploying semiochemicals. These results are also consistent with a model of co-evolving responses to pheromones by predators and their prey. The roles of plant volatiles should be further investigated, both to improve monitoring programs and from an ecological perspective.