Description of the Pest
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.
|Common name||Amount to use||REI‡||PHI‡|
|(Example trade name)||(hours)||(days)|
|Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies and honey bees, and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Always read the label of the product being used.|
|(Sevin XLR Plus)||3–4 qt/acre||12||1|
|MODE-OF-ACTION GROUP NUMBER1: 1A|
|COMMENTS: Use a hand-held sprayer. Do not apply more than 14 qt/acre per season. Highly toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging.|
|(Diazinon 50WP)||0.21 lb/gal water||5 days||21|
|MODE-OF-ACTION GROUP NUMBER1: 1B|
|COMMENTS: For in-season use only. Use a hand-held sprayer. Apply 1 pint per tree; do not apply more than 4 lb product/acre per application. Highly toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging.|
|‡||Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.|
|*||Permit required from county agricultural commissioner for purchase or use.|
|1||Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated with chemicals that have a Group number other than 1B. Mode of action Group numbers are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://www.irac-online.org/.|