Feeding Preferences of Dogwood Sawfly Larvae Indicate Resistance in Cornus

Abstract

Abstract Dogwood sawfly (Macremphytus tarsatus Say) is a native, phytophagous insect that relies on Cornus sp. host plants for larval development. Feeding injury by dogwood sawflies is primarily aesthetic and seldom results in host plant death. Still, native and non-native dogwoods have not been evaluated for susceptibility to larval feeding by this aesthetically damaging wasp. Ten species or cultivars of dogwoods that are either naturalized native plants or economically significant landscape plants were assayed for host suitability to dogwood sawfly larvae in no-choice and choice experiments. Flowering, kousa and corneliancherry dogwoods were consistently ranked among the least susceptible host plants while ‘Sibirica’ tatarian, gray, and ‘Flaviramea’ golden-twig dogwoods were highly preferred hosts. Preliminary GC/MS comparisons of foliar metabolite extracts from all 10 species have identified five peaks of interest that varied between resistant and susceptible hosts. These results suggest that certain chemical constituents in foliage of dogwood species may be important predictors of host palatability. More research is needed to confirm this hypothesis before crossbreeding for sawfly resistance can proceed.