What to Watch For: Ambrosia Beetles in Perennial Fruit Crops
Damage from a cold winter can take a while to become apparent. During the summer, I often receive several about beetle damage in perennial fruit plants. When images accompany these questions, it is clear who the culprit likely was.
The distinctive “frass toothpick” extending from holes is due to feeding from granulated ambrosia beetles. Typically, these insects are attracted to stressed plants are likely keying in on trees, bushes, or vines that sustained freeze damage this winter. They are also attracted to plants with “wet feet”, so good water management can often reduce attraction. Once beetles are present in plants, there is no effective management tool. Steve Frank, who works on ornamental plants, has done work on timing of preventative treatments, which can be quite effective. However, in most fruit crops, ambrosia beetle attack is a symptom, rather than the cause, of a problem. If the underlying issue is water management, then drainage or irrigation should be improved. If the issue is a freeze damaged plant, then the plant may succumb to its other injuries regardless of preventative treatment for ambrosia beetles. Therefore, growers should consider if the cause of the stress can be managed before undergoing an extensive management program.
Granulated ambrosia beetles – Entomology Pest Note