No abstract

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).

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.

Eff orts to exclude disease organisms from farms growing irrigated lettuce and leafy vegetables on California's central coast are confl icting with traditionally accepted strategies to protect surface water quality. To begin resolving this dilemma, over 100 offi cials, researchers, and industry representatives gathered in April 2007 to set research priorities that could lead to eff ective co-management of both food safety and water quality. Following the meeting, research priorities were refi ned and ordered by way of a Delphi process completed by 35 meeting participants. Although water quality and food safety experts conceptualized the issues diff erently, there were no deep disagreements with respect to research needs. Top priority was given to investigating the fate of pathogens potentially present on farms. Intermediate priorities included characterizing the infl uence of specifi c farm management practices on food safety and improving our understanding of vector processes. A scientifi c subdiscipline focusing on competing risks is needed to characterize and resolve confl icts between human and environmental health.

Avocado branch canker in California is caused by a complex of fungal species in the families Botryosphaeriaceae and Diaporthaceae. As the popularity of avocado fruit increases, California growers are under pressure to increase their productivity in order to compete with imports. One way to increase production is through high-density planting, which entails intense canopy management, possibly leaving the trees vulnerable to infection through pruning wounds. A spore trap study was undertaken to determine the seasonal spore discharge of Botryosphaeriaceous and Diaporthaceous fungi. Based on colony counts, the highest population of Botryosphaeriaceous fungi (68%) occurred during or soon after precipitation events, which coincided with the winter months of December, January, and February. The spring and fall seasons had lower numbers of spores trapped (at 13 and 17%, respectively), with few spores trapped in the summer season. For members of the Diaporthaceae family, spores trapped were almost evenly split between winter and fall seasons (50 and 49%, respectively), with few to no spores trapped in the spring and summer seasons. A pathogenicity test of six fungi of Botryosphaeriaceae and one fungus of Diaporthaceae was conducted in the greenhouse. Internal plant vascular lesion lengths resulting from inoculation with any of the seven fungal species differed significantly from the noninoculated control. These studies suggest that pruning during the drier parts of the year would minimize infection by fungi in the Botryosphaeriaceae and Diaporthaceae families.