Spiny oak sawflies are one of the many things that will feed on oak leaves. Sawflies look like caterpillars but they aren’t, so the caterpillar-specific pesticide, Bt, will not be effective on them. Spiny oak sawflies feed between the veins of the leaves, leaving a lacy appearance to the leaves. They have forked spines all along their bodies which turn black as they get older. I’m not aware of this ever being much of a real problem but at one site in Price County the damage to understory oaks was significant.
Written by: Linda Williams, forest health specialist, Woodruff, (Linda.Williams@wisconsin.gov), 715-356-5211 x232.