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Joseph F. Boggs, Ohio State University Extension, Hamilton County/Southwest District; Curtis E. Young, David J. Shetlar, James A. Chatfield, Erik A. Draper, Pamela J. Bennett, Gary Y. Gao, |
Leafminers
As with previous seasons, adults of three leafmining sawflies in the genus Fenusa were on the wing in northeastern Ohio in late April (6, 7, 8). These were the elm leafminer (F. ulmi), European alder leafminer (F. dohrnii), and birch leafminer (F.pusilla). Larvae of these sawflies mine the leaf parenchyma, producing large blister-like, reddish-brown blotch-mines, which usually extend from the leaf margin toward the midvein. The elm leafminer has one generation per year, and the alder and birch leafminers both have three generations.
Damage caused by the oak shothole leafminer (Agromyza viridula) was once again very evident this season on red and white oaks, particularly in the southern and western parts of the state. Damage is caused by the piercing-sucking feeding activity of the adult fly and by spot-mines produced by the larvae. There is one generation per year and all activity is concentrated on newly expanding leaves. Adult feeding holes and abandoned larval leaf mines enlarge along with the expanding leaf tissue. Consequently, small holes become large and may be mistaken for damage caused by a general defoliating insect or by "oak tatters." All reports of damage this season referenced 1/8- to 1/2-inch diameter holes that seemed to "appear" on leaves in June.
The annual ravaging of black locust leaves by locust leafminer (Odontota dorsalis) occurred this season throughout much of Ohio (3, 5, 6, 7, 8). The digitate blotch-mines produced by the larvae coupled with the skeletonized leaves produced by the adult beetles caused many trees to become completely brown by late summer, particularly in the southern part of the state.