Japanese Beetle Biocontrol
Tiphia larva attached to a white grub, Michael Reding, USDA Agricultural Research Service, Bugwood.org
JULIE VAN METER, NEBRASKA DEPARTMENT OF AGRICULTURE
The Nebraska Department of Agriculture (NDA) is partnering with the Oregon Department of Agriculture and Japanese beetle (JB) researchers on a biocontrol project to release two parasitoid insects in the state that could help reduce JB populations.
Biocontrol uses natural enemies to suppress the populations of a target pest. NDA is identifying suitable locations for release of Spring tiphia (Tiphia vernalis) and the winsome fly (Istocheta aldrichi) in eastern Nebraska. These biocontrol agents have a long and well documented history of use in the United States. The first releases occurred in the 1920s, in New Jersey and Pennsylvania. Since that time, they have become established in several other states. Importantly, these organisms have not been found parasitizing any other insects – they only go after the Japanese beetle.
Spring tiphia are small wasps, around ½” in length. Adults emerge in the spring, and after mating, the female locates a JB grub in the soil, and burrows down to it, stinging the grub and causing temporary paralysis. She then attaches an egg to the grub. After the egg hatches, the larva slowly consumes the grub alive. After the grub dies, the larva spins a cocoon and overwinters in the soil, to emerge the next spring.
Winsome fly is a small fly, and adult emergence occurs mid-spring through mid- summer. Female flies attach a single egg to an adult JB’s pronotum. The egg hatches and the larva burrows into the beetle, consuming it from the inside, leaving only the exoskeleton. The feeding irritates the beetle, which responds by burrowing into the soil, to die within a few days. The larva overwinters underground inside the beetle’s exoskeleton, and will pupate and emerge as an adult the next year.
The tiphia parasitism rate can be 60-100% in areas where they become well established. Winsome fly parasitism rates are lower, but in combination with tiphia may still be effective.
NDA will conduct surveys for appropriate release sites in spring and summer 2019. A good site will have high JB numbers, minimal to no pesticide use, and suitable plants for parasitoid feeding and resting. Spring tiphia were released at one site in Lancaster County in May, and NDA staff is scouting for additional sites in eastern Nebraska.