|skeletonized oak leaf|
You might think, as I did originally, that the insect called Oak Leaf Skeletonizer was the culprit. But a conversation with Penn State entomologist Greg Hoover led to the conclusion that this was another insect, Scarlet Oak Sawfly. Both insects skeletonize leaves but Scarlet Oak Sawfly does not leave tell-tale pupal cases on the leaves as does the Oak Leaf Skeletonizer.
|pin oak injury from sawfly feeding|
So, what will become of oaks infested with Scarlet oak sawfly? PSU’s Greg Hoover thinks that natural predators and parasites will begin to take control and reduce sawfly populations to levels that are almost harmless. Defoliation is the issue here. The question is: “How much foliage can a tree stand to lose?” Answer is: "Some, not too much, not too often." It is not a black and white situation. Many factors such as overall tree condition, amount of foliage loss and site factors come in to play. It is unlikely that partial defoliation in one year will be a life or death situation for an oak.
|sawfly larva feeding|
Personally, I have my bet on Mother Nature to come to the rescue. Sure, She can be unpredictable and is habitually late, but population spikes of one bug eventually result in their enemies coming along to even things out.