| Four Scotch pine (Pinus sylvestris L.) Christmas tree varieties were tested for resistance to Zimmerman pine moth (Lepidoptera: Pyralidae), European pine sawfly (Hymenoptera: Diprionidae) and pine needle scale (Homoptera: Diaspididae). Insects were reared in 1994 and 1995 on trees at the Michigan State University Kellogg Experimental Forest, Kalamazoo County. Differences among tree varieties in sawfly and scale survival and fecundity were detected, but Zimmerman survival was too low to determine varietal differences. Multiple regressions predicted Zimmerman pupal weight, sawfly development and pupal weight, and scale survival and fecundity. In another study, trees at Kellogg Forest and a field in Montcalm County were monitored twice a month during each summer. Natural feeding guild infestations under observation differed in abundance and phenology, but sap-feeders were dominant. Inconsistent results of guild abundance among varieties implicated factors other than resistance affecting community structure. Alternatives to resistance acting on reared species and guilds are discussed. |
