64 Nebraskaland • July 2019
MIXED BAG
Japanese beetles (Popillia japonica) are exotic, invasive insects,
established in over 30 Nebraska counties. Japanese beetle
grubs and adults feed on hundreds of types of plants, including
roses and lindens, and even soybeans and corn. The Nebraska
Department of Agriculture is partnering with the Oregon
Department of Agriculture and Japanese beetle researchers on
a biocontrol project to release two parasitoid insects in the state
that could help reduce Japanese beetle populations.
Biocontrol uses natural enemies to suppress the
populations of a target pest. Spring tiphia (Tiphia vernalis)
and winsome fly (Istocheta aldrichi) are two Japanese beetle
biocontrol agents with 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,
these organisms have become established in several other
states. Importantly, they have not been found parasitizing
any other insects – they only go after the Japanese beetle.
Spring tiphia are small wasps, around one-half-inch
in length. Adults emerge in the spring, and after mating,
the female locates a Japanese beetle 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 Japanese beetle
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 Japanese beetle'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 department will conduct
surveys for appropriate release
sites in the spring and summer
of 2019. A good site will have
high Japanese beetle numbers,
minimal-to-no pesticide use and
suitable plants for parasitoid
feeding and resting. If appropriate
sites are found, releases could
begin this summer.
THE INVASIVE JAPANESE BEETLE
By Julie Van Meter, State Entomologist, Nebraska
Department of Agriculture
TIPHIALARVAEFEEDINGONJBGRUB5171060-PPT
