Brownheaded Ash Sawfly
The brownheaded ash sawfly spends the winter as a full-grown larva within a cocoon in soil around the base of previously infested ash trees. Pupation occurs in early spring. Adults are small, black, nonstinging wasps that typically emerge by late April.
Redheaded Ash Sawfly
Adult redheaded ash sawflies emerge in June. They feed, mate, and lay eggs in the cracks and crevices of the bark. These eggs hatch and the young larvae bore into the bark and feed between the bark and sapwood 4-6 weeks. They then enter the sap and heart wood and completely destroy it. At maturity they construct a pupal cell near the surface of the wood and pupate in early spring.
D I S E A S E S
Anthracnose diseases occur on many landscape trees, though they tend to be most severe on ash, dogwood, maple, oak, and sycamore. In ash trees, buds, leaves, and sometimes twigs can become infected. In early spring, infection of buds or expanding leaves results in irregular brown blotches and distortion of leaflets.
Ash yellows is a recently discovered disease that causes slow growth and decline of ash species. Ash yellows went undetected until the 1980's because its symptoms were not differentiated from those of decline caused by adverse environmental factors such as drought, shallow soils, flooding, or parasitism by opportunistic fungi. Current knowledge supports the theory that ash decline can result from various causes, and ash yellows can be, but is not always, a causal factor.