Twig beetles, Pityophthorus spp. (Coleoptera: Scolytidae), are vectors of Fusarium circinatum (Fc) , the cause of pitch canker in Monterey pines in California. Pitch canker severity has been shown to be greater in coastal areas than in more inland locations. The present study is being undertaken to test the hypothesis that differences in disease severity between coastal and inland sites are correlated with differences in species composition and activity of Pityophthorus populations. Four inland and four coastal locations are being used in this study. At each location, populations are sampled using baited pheromone traps, inoculated branches and cut branches. Pheromone traps are baited with pityol to attract P. setosus, or with pityol and conophthorin to attract P. carmeli. At each location, one branch on each of ten trees are inoculated with Fc, and ten branches obtained from outside the plots are cut and hung in the canopy. Following infestation of these branches by twig beetles, insects emerged or dissected from both sets of branches are sorted by sex and species for each location. A subset of the beetles from each location are plated on a Fusarium selective medium to provide an estimate of phoresy. Data will be analyzed for significant differences in Pityophthorus species composition between coastal and inland locations. As an independent test for an effect of geographic location on twig beetle species composition, plots are located along transects from coastal to inland areas. Relative activity level of beetle species are determined using baited pheromone traps, as described above. In addition, temperature and relative humidity are recorded in each plot, and trees are rated for severity of pitch canker. Data will be used to test for correlations between disease severity and Pityophthorus activity, and between disease severity and environmental conditions.
Species 1: Coleoptera Scolytidae Pityophthorus (twig beetle)
Keywords: forest pathology
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