Scarlet oak sawfly

These pin oaks are shedding leaves, and large parts of some of them have leaves that look white from the ground.  The culprit is scarlet oak sawfly larvae.

I have never seen damage quite like this from this insect.  It’s unusual for it to reach such a high population that it defoliates the tree like this, and there ARE natural predators that usually keep it in check.  But in this case it could impact the tree’s health, so control would be justified.  Control, by whatever method, would need to be done soon.  Otherwise the larvae will pupate, and later in the year the adult wasps will emerge and lay eggs and there will be another generation!

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