The primary visible symptoms of borer damage caused by larvae of the giant palm borer, Dinapate wrighii, are the large (2-3 cm) holes in the upper portion of the trunk (Fig. 1). Inside this region, extensive galleries may be found. In severe cases, the palm trunk is weakened and the crown may fall off. The bud or meristem may also be destroyed by the feeding larvae.
Holes caused by acorn woodpeckers (Melanerpes formicivorus) are similar, but smaller in diameter and are typically plugged with stashed acorns.
Larvae of Dinapate wrightii burrow into the upper trunk of palms, causing extensive structural damage and potentially death of the palm. The visible holes are the exit holes of the adult borers.
Dinapate wrightii infests only California fan palms (Washingtonia filifera) and date palms (Phoenix dactylifera) in the states of California, Nevada, and Arizona.