In This Section | Notes
on Nut Insects |
| Author: | OMAFRA Staff |
|---|---|
| Creation Date: | 17 May 2006 |
| Last Reviewed: | 17 May 2006 |
Codling moth (Laspeyresia pomonella) is a serious pest in English walnuts and less of a problem in other walnut species, although severe infestations may occur in some years. Moths are small, approximately 9 mm long and grey-brown with white lines and dark banding. The larvae are pinkish white with brown heads and reach 10-12 mm at maturity. Mature female moths lay eggs on the surface of foliage, twigs and nuts. When eggs hatch the young larvae crawl to and burrow into nuts at the calyx end or enter where two nuts contact each other. Once inside the nut, larvae bore tunnels and expel frass out the opening on the husk surface. Frass that collects on the surface of the nut husk provides a visual indication of larval -infestation.
Early season infestations that occur before the developing nut shells harden, will allow larvae to burrow into the kernel or 'nut meat'. Later infestations that occur after the developing shell has begun to harden will restrict larval tunnels to the husk and not the inner kernel. Infestation by codling moth can cause premature nut drop and may be severe in some years. Where nuts do not drop prematurely, infested husks can impart off-flavours to the kernel.
Use pheromone traps to detect the earliest emergence of new adults in the spring. See Suppliers of Pest Monitoring Equipment and Biological Control Agents on the OMAFRA website.
Insecticides for codling moth control on walnuts have a similar timing as cover sprays applied on apples for codling moth control.
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