UC IPM has completed another tutorial about using the degree-day tools on our Web site to go along with Walt Bentley's presentation about degree-days to time insecticide applications in fruit and nut orchards.
Peach twig borer larvae damage growing shoots and their feeding creates shallow channels and surface grooves in the nutmeat. Accumulating degree-days let's you know the best time to manage peach twig borer—when peach twig borer larvae are young and before they have chewed their way into shoots where they're protected from insecticides.
According to the Almond Pest Management Guidelines, put out pheromone traps to determine the biofix:
- Place one peach twig borer pheromone trap per 20 acres (but never less than two traps in smaller orchards) by March 20 in the southern Central Valley and April 1 in northern areas.
- Monitor twice a week to identify the biofix date (when the first male is trapped in April).
- Start accumulating degree-days on the biofix date.
Monitor trees for shoot strikes in mid-April. Make sure strikes are caused by peach twig borer and not Oriental fruit moth. If several strikes are seen in each tree by late April, a spring insecticide application may be necessary. Time it to kill first-generation larvae before the majority of them chew their way into shoots:
- 300 to 400 degree-days after biofix, if applying insect growth regulators
- 400 to 500 degree-days after biofix, if applying conventional insecticides