How to Manage Pests
UC Pest Management Guidelines
Prune limb borer and American plum borer are sporadic pests in young stone fruit orchards from Tehama County to Kern County. Young larvae are white with a large, dark brown head; when mature, larvae are about 1 inch long with a dull white or pinkish body. The larva overwinters in a cocoon within the tree. Adult moths emerge in April and May. Females lay eggs on callus tissue near pruning wounds, in scaffold crotches of young trees, near graft unions, or on crown galls. The forewings of the moth are gray with brown and black marks and have a wingspan of about 0.75 inch.
Larvae bore into the tree leaving reddish orange frass and gum pockets. The boring is most damaging to the scaffold crotches or graft unions of young trees. Vigorous trees will heal over, but with heavy, prolonged infestations, scaffolds may break with wind or a heavy crop.
Monitor young orchards in spring and summer for frass and gum pockets which tend to be very visible if present. If larvae are present, spray trees from 1 foot above the scaffold crotch to 1 foot below, two to three times during the growing season. Make the first application from mid- to late April and subsequent applications at 6-week intervals.
UC IPM Pest Management Guidelines: Nectarine