Zig Zag Sawfly adults are emerging in Central Ohio.
Tom Macy from Ohio Department of Natural Resources Division of Forestry reported that Elm Zig Zag Sawfly adults were trapped last week in Central Ohio. Zig Zag Sawfly (Aproceros leucopoda Order: HYMENOPTERA ) is a new non-native invasive wasp from Asia whose larva cause defoliation on native and non-native elms (Ulmus spp.). Adult wasps are small (approx. 1/4 inch), black with white legs.
They emerge from overwintering pupa in the soil. Eggs are laid on the serrated margins of leaves.
Eggs hatch within 8 days and larva begin feeding in a distinct zigzag pattern into the leaf. As larva grow through 6 instars, reaching only ½ inch long, the feeding zone increases and larva can fully skeletonize elm leaves. Larva are lime green with brown markings. It has distinct, "T" shaped brown markings on its true legs, and a brown stripe across its head capsule. NOTE: Larva may resemble caterpillars of butterfly and moth species (Order: Lepidoptera), but sawflies are actually wasps (Order: Hymenoptera)! This is important when considering control measures. Products labeled for use against lepidopterans, such as BT products, will not work on wasp pests.
Female ZigZag Sawfly reproduce parthenogenically, meaning females do not need to mate in order to lay viable eggs. These clonal female eggs can lead to high populations and we may see several generations a year. Research still needs to determine how many generations Ohio will see. It takes 24-29 days for the insect to complete its lifecycle from egg to adult. Pupa are protected by a net-like dome and will be found on the underside of leaves or on other nearby surfaces. The final pupa before overwintering is solid (not cage-like) and will be found in soil or leaf litter under the host.
This new pest is currently being researched for control options, phenology, and long-term impacts of its damage. We need your help monitoring for this new pest. If you see the signature zig zag feeding on any elm, please report it to the Ohio Department of Agriculture or your local Extension Office. You can report to ODA online using their Plant Pest Reporter found here.
Reference:
Oten, KLF., Day, E., Dellinger, T., Disque HH., Barringer LE., Cancelliere, J., Somers, L., and Bertone MA. (2023). First Records of Elm ZigZag Sawfly (Hymenoptera: Argidae) in the United States. Journal of Integrated Pest Management. 14(1):12. https://doi.org/10.1093/jipm/pmad009