The preferred treatment for peach twig borer populations is bloomtime sprays of Bacillus thuringiensis (Bt); these treatments are usually sufficient to keep peach twig borer below damaging levels in orchards where migration from external sources is not a concern.
Bloomtime Bt treatments target overwintering larvae, which feed on exposed shoots and buds before boring into the shoot. The larvae must consume the Bt; once larvae begin feeding inside shoots, Bt treatments are ineffective. For better control, make two applications timed to larval emergence from the overwintering hibernacula.
Bt applications can be timed according to bloom, but this approach is less precise than monitoring emergence. Make the first treatment at popcorn to full bloom. Make the second treatment 7 to 10 days later.
Later in the post-bloom season, you will need to follow up by putting out pheromone traps.