Description of the Pest
Peachtree borer eggs are laid during the summer on the bark of trees. Larvae overwinter in the tree trunk. They feed in the crown area and burrow up into the tree. At maturity, a larva is about 1.25 inch long and has a light-colored body and a dark head. In late spring, larvae pupate near the entrance of their burrows or in the soil. Adults emerge from May through September; they are steel-blue to black clearwing moths with a 1-inch wingspan.
Damage
Peachtree borers can girdle and kill young trees. Older trees can withstand the damage unless there are many larvae or the tree is attacked several years in a row.
Management
Look for the presence of frass and gum at the bases of trees when monitoring orchards in spring. Also check trees in the fall for signs of peachtree borer activity. At this time, you can kill larvae by carefully using a knife or wire to probe the trunk. Mark any that you find, and return to treat them the following spring. Treat by spraying the tree trunk from the scaffold to the soil line. Apply the insecticide with a hand-held sprayer to the tree trunk from the juncture of the main scaffold limbs to the soil line. Cover the trunk thoroughly, using enough spray material so it will run off to form a small puddle at the base of the tree. Use from 0.5 to 1.5 gallons per tree, depending upon the size of the trunk. Remove suckers and pull soil away from the base of the tree before treating. Two applications are recommended to protect during the prolonged period when adults are active, one in mid-May when adults are first detected and one in the middle of July. Be careful to observe preharvest intervals and use low-pressure sprays to avoid contaminating fruit.
In other areas of the United States, pheromone mating disruption has worked well for controlling this pest in crops where it is a regular problem. However, this technique has not been studied in California because peachtree borer is only an occasional problem.
Keep tree bases free of vegetation to improve spray coverage when treating for this pest, especially in the Central Valley. Also, heat and dryness reduce the survival of eggs and larvae, and keeping vegetation away from the tree bases provides a drier environment.
| Common name | Amount to use** | REI‡ | PHI‡ | ||
|---|---|---|---|---|---|
| (Example trade name) | (conc.) | (dilute) | (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, 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. | |||||
| A. | ESFENVALERATE* | ||||
| (Asana XL) | 4.8-14.5 fl oz | 2–5.8 fl oz | 12 | 14 | |
| MODE-OF-ACTION GROUP NUMBER1: 3A | |||||
| COMMENTS: Apply as a directed trunk and scaffold limb spray. Thorough coverage required. Highly toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging. | |||||
| ** | For concentrate applications, use the amount given in 80–100 gal water/acre, or lower if the label allows; for dilute applications, amount is per 100 gal water to be applied in 300–400 gal water/acre, according to label. |
| ‡ | 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). |