Issue 15, September 23, 2014
Oak Sawfly
Oak sawflies are being found on white oak. They are generally most common on pin oak, also occurring on black and scarlet oaks. It is one of the slug sawflies along with pear slug and rose slug that appear as slimy, elongate, slug-like creatures. Oak slug sawfly larvae are yellow and green.
Oak sawfly larvae on white oak.
They feed on the leaf underside, causing window-feeding. They eat through the lower leaf surface or epidermis and eat the inside of the leaf, leaving the upper leaf surface intact. This remaining leaf surface is initially whitish but soon dries and turns brown. As the larvae mature, they lose their slimy coverings and appear more like the sawfly larvae that they are. They will be greenish with three obvious pairs of true legs and more than five pairs of prolegs. These older larvae will skeletonize the leaves, eating holes in the leaves and eating away the leaf margins.
Oak sawfly damage on white oak.
Although slug sawflies are usually not numerous, it is important that correct control measures are used if the population is large enough to warrant treatment. Bacillus thuringiensis kurstaki or slug baits are not effective. However, many other chemical insecticides such as carbaryl (Sevin) or pyrethroids used for caterpillar or beetle control will provide control. (Phil Nixon)
Author:
Phil Nixon