Peach Twig Borer


General Description

Hosts

Peach, apricot, nectarine, plum, and prune

Damage

In the spring, larvae bore into buds and developing shoots causing them to wilt and die (Fig. 1). Larvae of the summer generations attack the fruit, usually making several entry holes near the stem end (Fig. 2). Damaged fruit and twigs exude gum.

Figure 1. Peach twig larva feeding damage to new growth. (H. Philip) Figure 2. Peaches damaged by peach twig borer larvae. (AA-FC)

 

Identification

Larva - Reddish-brown with pale to white segments giving a ringed appearance; head and thorax dark brown to gray. Mature larvae up to 12 mm long (Fig. 3).

Figure 3. Peach twig borer larva. (H. Philip)

 

Adults - Grayish moths, 11 mm long.

Life History

Overwinter as larvae on host trees and are active March to early May. First brood adults are present in May and June during which time they lay eggs on leaves, fruit or twigs. First generation larvae are present June through early August. Second brood adults appear in late July and lay eggs for the second generation of larvae, which appear in late September to feed for a short time before seeking overwintering sites. There are two generations each year with a partial third in some years.

Monitoring

Use commercially-available pheromone-baited traps to monitor male moths in order to properly time spray applications against spring and summer broods of larvae. Careful examination of developing shoots and buds (spring) and fruit (summer) for presence of larvae will also aid in proper timing of sprays.

Management

Biological Control

Bacillus thuringiensis (Bt) products (Dipel 2X DF, Foray 48BA, Bioprotec CAF, Bioprotec PLUS) are effective if applied when larvae are first noticed and before they tunnel into twigs, buds or fruit.

Chemical Control

If an average of two or more first brood moths are caught per trap per week, apply treatments 10-14 days later to control adults and emerged larvae. To ensure good crop protection, continue monitoring for second brood moths until at least mid-August. Apply a second spray 10-14 days if moth captures exceed an average of five moths per trap. Apply Altacor or Exirel, within 7 days of first trap catch of adult male moths.  Imidan 70WP lasts about 2 weeks and Altacor 7 days.

Imidan is registered for use on peaches only against this pest (maximum four applications/season)

Recommended treatments and timing are:

  • Dormant/delayed dormant: Rimon, Harvanta

  • Pink: Imidan WP, Decis

  • Petal fall - Imidan, Altacor, Exirel, Success/Entrust, Rimon, Harvanta, Decis

  • Petal fall (peach only) - Decis, Imidan

  • Husk fall (apricot) - Spinosad/Entrust

  • Summer – Altacor, Exirel, Rimon, Success/Entrust, Imidan, Harvanta