Plant essential oils as arrestants and repellents for neonate larvae of the codling moth (Lepidoptera : Tortricidae)

Nonhost chemicals may be useful for controlling insect pests of crop plants by interfering with orientation to, and selection of, host plants. Essenti al oils of 27 plant species were tested in 2 different laboratory assays fo r evidence of arrest and repellency of neonate larvae of the codling moth, Cydia pomonella L. In an olfactometer in which larval upwind movement towar d apples was assessed, greatest arrest was achieved with oils of lavender, Lavandula officinalis L.; pennyroyal, Mentha pulegium L.; and cypress, Cupr essus sempervirens L.. Oil of lavender was most effective in preventing lar vae from moving upwind in the olfactometer. In a barrier assay, essential p lant oils were applied to the distal ends of a glass rod (15 cm long) on wh ich larvae were placed. Larvae crossed the barrier to reach apples impaled on each end of the glass rod. The most effective repellents in this barrier assay were rue, Ruta graveolens L.; garlic, Allium sativum L.; patchouly, Pogostemom cablin (Blanco);and tansy Tanacetum vulgare L., oils. These 4 pl ant essential oils were most effective in causing larvae to turn away at th e oil barrier. These materials, or their active ingredients, may be useful in protecting fruit from attack by codling moth larvae by preventing larvae from orienting to and arriving at fruit.