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. Essential oils of 27 plant species were tested in 2 different laboratory assays for evidence of arrest and repellency of neonate larvae of the codling moth, Cydia pomonella L. In an olfactometer in which larval upwind movement toward apples was assessed, greatest arrest was achieved with oils of lavender, Lavandula officinalis L.; pennyroyal, Mentha pulegium L.; and cypress, Cupressus sempervirens L.. Oil of lavender was most effective in preventing larvae from moving upwind in the olfactometer. In a barrier assay, essential plant oils were applied to the distal ends of a glass rod (15 cm long) on which 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 plant essential oils were most effective in causing larvae to turn away at the 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.