Effects of induced resistance in sand-dune willow (Salix cordata) on larval growth and movement of a willow flea beetle (Altica subplicata).

This study investigated the possible existence of induced resistance in sand dune willow, Salix cordata. Larval growth rates and behavior of a willow flea beetle, Altica subplicata, were compared when larvae were raised on undamaged, manually damaged and naturally damaged plants. Survival did not differ among treatments, though a tendency for higher survival on undamaged plants is indicated. Larval mortality was very high (92.5%). Average weight showed no difference among treatments. There was no difference in the number of larvae found on the plant as opposed to off of it (i.e., on the confining bag). However, comparison of the number of larve found on newer leaves vs. older leaves shows that larvae on the naturally damaged plants were found more frequently on older leaves than larvae on the undamaged plants. This indicates that induced resistance may reduce the quality of newer leaves on damaged plants.