We initiated field experiments to determine if twig beetles, Pityophthorus spp., can vector Fusarium circinatum from infected Monterey pines to Bishop, ponderosa, and knobcone pines and Douglas-fir, all of which are hosts of F. circinatum. Seven sites were located in Central and Costal California. Our treatments consisted of healthy branch tips (50-100 cm long) cut from the above tree species and attached them to the lower canopy of these conifer species. For each site, branches cut from each pair of tree species were placed on both heterospecific and conspecific host trees; thus each experiment consisted of 4 treatments. For example, branches taken from Monterey pines were placed on both Monterey and Bishop pines, and likewise branches of Bishop pines were placed on both Bishop and Monterey pines. For each experiment, we used at least 10 branches for each treatment. After about 8-10 weeks, branches were brought to the laboratory, and placed into rearing tubes at room temperature and 24 h light. Emerging insects were collected, sorted, counted, identified to species, and placed on a pitch canker selective medium. Our results suggest that Pityophthorus spp. are highly associated with Monterey and Bishop pines and rarely associated with ponderosa and knobcone pines and Douglas-firs. These results may help explaining the very low incidence of pitch canker on ponderosa and knobcone pines and Douglas-fir in this area. In addition, results of inoculation studies of the above tree species to determine their resistance/susceptibility status will be reported.
Species 1: Hypocreales Hypocreaceae Fusarium circinatum (pitch canker fungus)
Species 2: Coleoptera Scolytidae Pityophthorus (Twig beetles)
Keywords: Insect-pathogen association, Host-tree resistance
Back to Ten-Minute Papers, Section Cc. Insect Vectors in Relation to Plant Disease, Ce. Insect Pathology and Microbial Control, Ca. Biological Control
Back to Ten-Minute Papers, Section Ca, Cb, Cc, Cd, Ce, and Cf
Back to The 2003 ESA Annual Meeting and Exhibition