We had a report last week from the Wichita area that a number of ash trees have ash sawfly larvae feeding on the leaves.
These sawfly larvae are a light green color with a broad, whitish stripe on the top side. In the middle of the whitish stripe there appears to be a darker green stripe that is actually the digestive tract of the insect. Though sawfly larvae resemble caterpillars, they have at least six pairs of “stublike” prolegs behind the three pairs of true legs on their abdomen. Caterpillars never have more than five pairs of prolegs.
There are usually no detrimental effects to the health of the tree if nature is allowed to run its course. Even if all the leaves are eaten, it is early enough in the growing season for trees to put out a complete new set of leaves with enough time to make all the food reserves needed to survive the coming winter. However, if control is desired, a number of insecticides may be used for control including cyfluthrin (Bayer Lawn and Garden Multi-Insect Killer), malathion, esfenvalerate (Monterey Bug Buster II) and carbaryl (Sevin). An effective organic product is spinosad (Captain Jack’s Deadbug Brew; Monterey Garden Insect Spray). Horticultural oils and insecticidal soaps are also effective because of the soft skin of sawfly larvae. (Ward Upham)