Effects of selected Larix laricina terpenoids on Lymantria dispar (Lepidoptera: Lymantriidae) development and behavior

The effects of selected terpenoids of tamarack, Larix laricina (Du Roil K. Koch, on the growth and development of gypsy moth, Lymantria dispar (L.). w ere studied in laboratory trials. Second instars were fed standard artifici al diet disks supplemented with a known amount of diterpene acid, monoterpe ne, or control. Diterpene acids had strong, dose-dependent antifeedant effe cts on gypsy moth larvae. Monoterpenes had less pronounced and more varied effects on gypsy moth larval performance. High concentrations of monoterpen es did not affect gypsy moth growth. However, low concentrations of some mo noterpenes that are present in tamarack in small amounts (<10% total monote rpenes) appeared to increase gypsy moth growth. Some monoterpenes caused sl ightly longer development time.