SUSCEPTIBILITY OF TWO STRAWBERRY VARIETIES TO THE LEAF BEETLE GALERUCELLA SAGITTARIAE

We compared susceptibility of two strawberry cultivars (Jonsok and Honeoye) to the leaf beetle Galerucella sagittariae Gyll. (Coleoptera, Chrysomelidae), which is known to damage strawberry leaves both in larval and adult stage. Larvae and adult leaf beetles were fed on leaves of both strawberry varieties for susceptibility tests. Leaf quality was determined by analysing total phenolic concentrations of plants grown in two localities (Jokioinen and Kuopio). In 1998 the concentration of total phenolics in the foliage was significantly higher in cv. Honeoye than in cv. Jonsok in both localities. In 1999 total phenolics were significantly higher in cv. Honeoye in Jokioinen, but not in Kuopio. Larval mortality was not significantly affected in 1998. However, larval mortality was significantly increased and mean relative growth rate (MRGR) of larvae was significantly reduced on cv. Honeoye in 1999. The results suggest that cv. Honeoye offers higher resistance against G. sagittariae than cv. Jonsok.