Ambrosia Beetles are a real irritation to growers of young trees. Pecan trees are just one of the victims of this pest. An attack is almost always fatal to the tree. The signs of the attack are not always noticeable so often the sudden death of an otherwise apparently healthy tree remains a mystery. The tell tale sign of attack are the toothpick like sticks of frass that stick out of the entry holes. If it has rained, the signs are there but the entry holes are small and require close inspection to see if the frass has washed away in the rain.
Ambrosia Beetles are hard to kill because the adults don’t actually eat the tree. They bore a hole into the tree to lay their eggs. They also deposit a fungus with the eggs. The fungus kills the tree and feeds the larvae.
The trees that are killed are always under stress but often that stress is not visible or apparent. Stress can be caused by cold injury, too much water from winter floods, drought injury, or other insect or fungal damage. Stressed trees emit ethanol and the ethanol is the homing beacon for the Ambrosia Beetle. It is the randomness of the attacks that is most maddening about this pest. Often the victim tree is in the middle of dozens of otherwise unaffected trees
There are several species of Ambrosia Beetle, some native and some invasive. The invasive ones are the ones causing the trouble here. I could go into descriptions but this is not a scholarly paper on the minutia of tiny insects.
Systemic pesticides are required to kill these little buggers. Because they don’t actually feed on the tree, the pesticide must be present when they take the first bite and be concentrated enough to kill with the first bite. Pesticides only need to be applied to the trunk of the tree. The beetles begin to fly at 70 degrees.