sunny front lawn has a big brown patch in it. At first, I thought it
was just the hot, dry weather, but I discovered these insects
scurrying around in the dead grass. Could they be to blame?
writer enclosed a sample of insects with the question. They are
hairy chinch bugs (Blissus leucopterus hirtus), a common pest
of lawn grasses, wheat, sorghum and other cereal grasses.
They are classified as true bugs in the order Hemiptera (not all
insects are “bugs” even though the term is frequently used that
way). They undergo incomplete metamorphosis, which means that nymphs
hatch from eggs, and undergo five instars (growth stages) until they
molt into adult insects. They do not pupate. Nymphs are generally
more susceptible to control than the adults.
CHINCH BUG IDENTIFICATION
Adults are roughly one-eighth of an inch long, with gray-black
bodies and white wing covers sporting a black spot in the middle
front edge. Nymphs start out reddish-orange with a white band across
their abdomens, and darken as they grow. Depending on the instar
stage, nymphs range in size from one-thirty second of an inch to
Chinch bugs are always worst in full sun, and in areas where heat is
reflected from pavement and buildings. They really thrive in hot,
dry weather. When infestations are severe, they can reach
populations of 150 to 200 chinch bugs per square foot; researchers
recommend treatment when populations reach 15 to 20 chinch bugs per
square foot. Being true bugs, chinch bugs feed with piercing-sucking
mouthparts. They inject a toxin into the grass blades as they feed
which causes the grass to die. Injury is particularly severe when
turf is dormant due to drought stress.
Chinch bugs overwinter as adults in thatch, along the edges of
paving and close to buildings. They begin actively feeding when
temperatures reach 70°F. Adult females begin laying eggs roughly
from mid-April until June. The eggs hatch anywhere from one to four
weeks, depending on temperatures. First generation nymphs mature by
mid-July. Their eggs hatch and a second generation matures from the
end of August through September.
Before applying any insecticide, monitor your lawn for their
presence. You can easily see chinch bugs scurrying around in the
turf by getting down on your hands and knees and parting the grass.
You will find the most activity where damaged turf goes into healthy
turf. Another technique for monitoring their presence is to take a
coffee can and remove the top and bottom lids. Push and twist one
end into the ground where you think the chinch bugs are active. Fill
the can with water and count the number of chinch bugs that float to
the surface in 10 to 15 minutes. If the water drains into the soil
before then, refill the can. If you find 20 adults per square foot,
treatment is warranted.
Mother Nature can help keep chinch bugs in check. When we have cool,
wet spring weather, or cool, wet weather in summer, chinch bugs are
often infected with a naturally occurring fungal disease known as
Beauvaria bassiana. Infected chinch bugs appear covered with a
white mold. You can help this process by keeping your lawn irrigated
during hot dry weather. The added moisture favors the spread of
Beauvaria and can help keep chinch bug populations down.
Other cultural controls include replacing susceptible grasses with
endophyte-enhanced varieties. These grasses are infected with a
beneficial fungus that make the grass unpalatable to surface-feeding
insects such as chinch bugs. Avoid using endophyte-enhanced grasses
if there is chance that livestock might graze there.
Another least toxic option recommended by Beyond Pesticides is to
apply diatomaceous earth to the affected area of your lawn.
Diatomaceous earth works by piercing insects’ exoskeletons, causing
them to dehydrate and die. Be sure to use diatomaceous earth labeled
for insect control, rather than that sold for swimming pool filters.
It is important to wear a dust mask when applying this product to
avoid inhaling the particles.
FOR CHINCH BUGS
If chemical control is required, carbaryl (Sevin), cyfluthrin (Bayer
PowerForce Multi-Insect Killer), and imidacloprid (Bayer Advanced
Season Long Grub Control, Spectracide Grub Stop Once & Done and
others) are labeled to control or suppress chinch bugs in home
lawns. Scout for chinch bug activity regularly and apply your
insecticide of choice if they exceed the threshold of 20 per square
foot as soon as possible. If you get good control of the first
generation, you may not need to treat for the second generation.
This is especially true if we are having adequate rain and
Beauvaria helps keep them in check. Conversely, if we are having
a very hot and dry summer, a second application may be necessary
mid- to late August.
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