The overall impression is that of a "shiny green insect." Green June
beetle grubs are cream-colored with brown heads. They range in size from
three-eighths of an inch to an inch-and-a-half long, depending on
maturity, and have three pairs of stubby legs. They have the unusual
characteristic of crawling on their backs to move since those tiny
legs cannot support their large bodies adequately.
Life Cycle of Grubs
have one generation a year in our area. They overwinter as mature
grubs deep in the soil. As temperatures warm in spring, they migrate
back to the soil surface where they feed briefly on thatch, soil,
and grass roots before pupating. Pupation takes 16 - 18 days, and
then they hatch out as adult beetles. That occurred the week of July
9 in the Pittsburgh area, if I can judge by the calls made to our
office. Scarab beetles typically hatch in groups, and they come up
out of the soil in a mass of wriggling beetles that looks like
something out of a sci-fi movie!
What Scarab Beetles
Adults often feed on ripening fruit, and females are attracted to
piles of bark, grass clippings, manure and compost as ideal places
to lay their eggs. Lawn areas that are fertilized with organic
fertilizers, sewage sludge and/or compost are more attractive to
egg-laying females than those treated with conventional fertilizers.
They may also be attracted to lawns with heavy thatch layers. Grubs
hatch in 10 -15 days.
Green June Beetle
beetle grubs feed primarily on decaying organic matter (thatch),
although they can destroy enough grass roots to damage lawns. Mature
larvae burrow to the soil surface at night and often graze on the
grass. The burrowing activity can be the most damaging, as they
build mounds two to three inches in diameter, and the burrows can be
six to twelve inches deep.
controls such as Bayer Advanced Season Long Grub Control (imidacloprid)
or Spectracide Grub Stop Once & Done (halofenozide) should be
applied before green June beetle eggs hatch. Once you see the damage
- and the grubs - Bayer Advanced 24-hour Grub Killer Plus (Dylox) is
a better choice. Overwintered, mature grubs that are active in
spring are more difficult to control.
If the adults
are active in your yard, monitor your lawn for signs of damage.
Where you see thinning or browning, dig up a square foot to check
for grubs. Five or more green June beetle grubs per square foot
warrants treatment. An otherwise healthy lawn can tolerate fewer.