Effects of New Insecticides on Adult Codling Moth

There are many new insecticides available to manage codling moth. Researchers continue to learn how these products work in the field, and how they can be best used in an IPM program. Many of the new insecticides registered for use on codling moth are potent ovicides (active against eggs) and/or larvicides (active against larvae). They also have sublethal activity on adults that may contribute to the overall reduction of pest pressure (and damage) in the orchard over the course of the season.

Rimon (novaluron), a chitin synthesis inhibitor (insect growth regulator), is considered an ovicide. The timing for application of this product is considerably earlier than conventional products such as OPs, before eggs are laid or shortly thereafter. Eggs laid on treated leaves/fruit are affected by the insecticide residues. Rimon will also kill eggs when it is applied directly to the eggs.

Rimon also has significant sublethal activity on the adults of codling moth. Treatment of adults with Rimon, either through contact with treated surfaces, ingestion or direct topical applications, does not affect the number of eggs laid by a female (fecundity), but it does reduce her egg’s viability (hatch) quite significantly. Fruit protection results from a combination of direct ovicidal activity and indirect sublethal effects on female reproduction. Rimon can provide excellent control of internal fruit feeders and leafroller neonates for up to 17 days.

Intrepid (methoxyfenozide), a moult accelerating compound (insect growth regulator), is highly toxic to larvae through ingestion and also has ovicidal properties. The timing of application for an internal feeder such as codling moth is just prior to egg hatch. Unlike OPs that kill larvae as they crawl over treated surfaces, Intrepid works against codling moth larvae through ingestion. When larvae hatch, they chew their way through the eggshell and receive a lethal dose.

Adult codling moths exposed to Intrepid have reduced fecundity and fertility (proportion of eggs that hatch). Sexual behaviours are also affected. Males exposed to treated surfaces are less responsive to sex pheromones, thus affecting the moth’s communication system. If males cannot find females in the field, the females will not lay fertilized eggs.

Altacor (chlorantraniliprole) belongs to a new class of insecticides that disrupt muscle action, affecting the insect heart muscles as well as those required for locomotion. It is toxic to codling moth larvae primarily through ingestion, but also has ovicidal properties. When exposed to surfaces treated with Altacor, female codling moths are less likely to mate. Prolonged exposure to Altacor reduces behaviours related to mating, such as male response to sex pheromone and female “calling”. However, of the females that do mate, fecundity and fertility are not affected. Longevity of adults is not affected.

Applying this information on the sublethal impacts of insecticides to the timing of insecticide applications for codling moth can help us to improve the effectiveness of insecticide treatments. By applying the products at the optimal time, growers can get the best bang for their buck using these new products. For more information on the timing of products for codling moth refer to Publication 310 Apple IPM Manual, and Publication 360 Fruit Production Recommendations and supplement.