Insect
and Disease Fact Sheet Compliments of New Century
1-877-79TREES
Japanese Beetle
Distribution
This
imported pest is generally found east of a line running from Michigan, southern
Wisconsin and Illinois, south to Alabama. Occasional introductions are made
into western states such as California and Oregon when the adult beetles or
larvae are shipped in commerce. The original population was detected in New
Jersey in 1916, having been introduced from Japan. In Ohio, the most damaging
populations are east of a line running from Cleveland to Cincinnati.
Hosts
The
adult beetles are general herbivores and are known to feed on over 400 species
of broad-leaved plants, although j only about 50 species are preferred. The
grubs will also feed on a wide variety of plant roots including ornamental
trees and shrubs, garden and truck crops, and turf grasses. They seem to
especially relish Kentucky bluegrass, perennial ryegrass, tall fescues and bent
grass.
Damage Symptoms
The
adults are skeletonizers, that is, they eat the leaf
tissue between the leaf veins but leave the veins behind. Attacked leaves look
like lace that soon withers and dies. The adults will often attack flower buds
and fruit. The grubs can kill small
seedling plants but most commonly damage turf. The turf first appears off-color
as if under water stress. Irrigating causes a short-lasting response or no
response at all. The turf feels spongy under foot and can be easily pulled back
like old carpet to reveal the grubs.
|
Description of Stages The
life stages of the Japanese beetle are typical of white grubs. Eggs: The white oval eggs are
usually about 1/16 inch (1.5 mm) long and 3/64 inch (1.0 mm) wide. They are
placed in the soil where they absorb moisture and become more roundish. Larvae: The larvae are typical white
grubs that can be separated from other soil dwelling white grubs by the
presence of a V-shaped series of bristles on the raster. First instar larvae are about 1/16 inch (1. 5 mm) long while
the mature third instars are about 1-1/4 inch (32 mm) long. Pupae: The pupae are first cream
colored and become light reddish-brown with age. The average pupa is about
1/2 inch (14 mm) long and 1/4 inch (7 mm) wide. |
Adult (top), Grug (bottom
left), raster pattern (bottom right) |
Adults: The adults are a brilliant,
metallic green color, generally oval in outline, 3/8 inch (10 mm) long and 1/4
inch (7 mm) wide. The wing covers are copper brown and the abdomen has a row of
five tufts of white hairs on each side.
Life Cycle and Habits
Larvae
that have matured by June pupate and the adult beetles emerge from the last
week of June through July. On warm sunny days the new beetles crawl onto low
growing plants and warm for a while before taking flight. The first beetles out
of the ground seek out suitable food plants and begin to feed as soon as
possible. These early arrivals begin to release a congregation pheromone (odor)
which is attractive to adults that emerge later. These odors attract additional
adults to gather in masses on the unfortunate plants first selected.
After
feeding for a day or two, the females leave feeding sites in the afternoon and
burrow into the soil to lay eggs at a depth of 2 to 4 inches. Females may lay 1
to 5 eggs scattered in an area before leaving the soil. These females will
leave the following morning or a day or two later and will return to feed and
mate. This cycle of feeding, mating and egg lying continues until the female
has laid 40 to 60 eggs. About 95% of population is generally laid by mid-August,
though adults may be found until the first frost of fall.
If
the soil is sufficiently moist, eggs will swell in a few days. Egg development
takes only 8 to 9 days at 80 to 90 degrees F or as long as 30 days at 65
degrees F. The first instars larvae dig to the soil surface where they feed on
roots and organic material. If sufficient food and moisture are available, the
first instars can complete development in 17 days at 78 degrees F.
Japanese Beetle Life Cycle
Control Strategies
Option 1: Cultural Control-
Quarantine -
Japanese beetle quarantines are currently operated by the USDA-APHIS and states
involved with shipping materials out of infested areas to uninfested areas.
Though this has not stopped the slow progression of Japanese beetles westward,
it seems to have slowed the process.
Option 2: Cultural Control -
Habitat Modification
- Since the eggs and young grubs are very susceptible to dry soils, do not
irrigate during the time the eggs and first instar
larvae are developing. However, if natural rainfall occurs, this tactic will
not work. Do not plant trees and shrubs that are highly attractive to adult
Japanese beetles near turf. Trees and shrubs most attractive to adults include:
Japanese and Norway maple, birch, pin oak, horse chestnut, rose of sharon, sycamore, ornamental apple, plum, cherry, rose,
mountain ash, willows, lindens, elms and Virginia creeper. Trees and shrubs
rarely attacked include: red and silver maple, holly, boxwood, euonymus,
flowering dogwood, cedar, juniper, arborvitae, red oak, tulip tree, magnolias,
red mulberry, forsythia, ashes, privet, lilac, spruces, hydrangeas and taxus (yew).
Option 3: Mechanical Control -
Trapping -
Several traps have been developed to capture the adults. These traps generally
use a mixture of the aggregation and sex pheromones. Recent data indicate that
these traps do not significantly reduce grub populations and in some cases may
actually contribute to increased foliar plant damage.
Option 4: Chemical Controls -
Insecticides -
When using trapping to monitor adult activity, keep in mind that the females
lay the majority of their eggs within the first 7 to 10 days of their
existence. When applying insecticides it becomes difficult to accomplish
long-term control due to the number of generations produced. Applications may
need to be made several times per season.
Information obtained through the Ohio State Extension FactSheet HYG-2504-91
Insect
and Disease Fact Sheet Compliments of New Century
1-877-79TREES