Contents:
Introduction
Chinch bugs are a complex of
three different species within the Lygaeidae family.
They have piercing-sucking mouthparts and they feed on the sap of
grass plants. They reside in the thatch area of the turfgrass
stand and prefer to feed on the lower leaf sheath and crown area
of the plant.
Identification
The three species of chinch bugs
in the U.S. are the hairy chinch bug (Blissus leucopterus hirtus (Montandon), common chinch bug (Blissus leuropterus leucopterus (Say), and the southern chinch bug
(Blissus insularis (Barber). They closely resemble one another and a
key developed by Leonard (1968) can be used to separate out the
different species.
The hairy chinch bug is the major species found in Maryland and its description follows. The adults are small, 1/8"(3 mm) in length, black, and have white wings. The wings rest flat over the back of the insect and there is a black spot in the central area of the wings. Adults may be long-winged or short-winged.
There are five nymphal instars of chinch bugs ranging in size from 1 to 3 mm. The first two nymphal instars are red with a white band across their abdomen while third and fourth instars are orange with wing pads just beginning to appear. The fifth instar is black with wing pads easily visible.
Distribution
Chinch bugs occur throughout the
United States. The southern chinch bug is a pest in the Gulf
states, Georgia, South Carolina, and North Carolina. The hairy
chinch bug is a pest of the more north central and eastern two
thirds of the United States. The common chinch bugs range overlaps
that of the two previous species and is often a pest of corn, rye,
sorghum and millet. It may occasionally be a pest of turfgrasses
if they migrate from infested grain fields.
Hosts
Based on years of field
observations, the hairy chinch bug prefers the following grasses
listed in the order of importance:
Studies conducted at Maryland have shown insect preference in chinch bug feeding trials. Chinch bugs will avoid feeding on endophyte infected grasses.
Life Cycle
Chinch bugs overwinter as adults
in protected areas such as under turfgrass thatch, under litter or
leaves at woodland borders, under hedges, in fence rows, or in
mulched landscape beds. Winter inactivity may be broken by
abnormally warm weather. Generally, migration from winter sites
begins after 1 or 2 sunny days with temperatures of 70°F or
more. Females lay eggs in leaf sheaths, in the crown-area, roots
or on the soil near host plants. Fifteen to 20 eggs per day are
deposited in 2-3 weeks. Eggs hatch in 1-2 weeks, and nymphs begin
sucking juices from host plants. The bugs pass through 5 instars
in 30-90 days, before reaching the adult stage. The eggs produced
by this generation of females become the second generation of
adults in late summer and early fall. From August to October,
these adults gradually migrate to their overwintering sites. In
the South and Southwest, three or more generations may be produced
before hibernation.
Damage
Chinch bugs damage grass plants
by inserting their hollow, needle-like beaks into the stems,
sucking the plant juices, and injecting chemicals into the plant
which clog the vascular system. The area around the feeding
puncture usually turns yellow. Damage
appears as patches of dead or
gradually yellowing grass, especially where heat is radiated into
the grass from sidewalks or roadways. Once the grass turns brown,
the turf will not recover.
Reseeding or renovation is usually necessary after moderate damage. Usually 15-20 chinch bugs per square foot. ft. will require treatment. Chinch bugs prefer warm, sunny, dry locations. Adults rarely fly in the mid-Atlantic region, however in Canada, where the short winged form is limited in numbers adults frequently fly from lawn to lawn.
Biological-Biorational
Control
Natural occurring fungal diseases
such as Beauveria bassiana
regularly control chinch bugs
during cool, wet weather. Another major regulating biological
agent is the big-eyed
bug. These predators may control
chinch bug populations. However, chinch bugs frequently have
caused serious damage before the big-eyed bug populations have
peaked. Also, the wasp Eumicrosoma
benefica may parasitize up to 50%
of the chinch bug eggs in favorable localities.
Commercial parasitic nematodes products haven't been thoroughly tested to date. Some nematode species may be effective under moist to wet thatch conditions but they are generally not recommended.
Cultural Control
Plant resistance has been
reported for a number of turfgrass species and cultivars. Research
conducted at Maryland has demonstrated strong resistance of
endophyte-enhanced turfgrasses to the hairy chinch bug. Currently
endophyte-enhanced turfgrasses are in various cultivars of these
three turfgrass species; perennial ryegrass, tall fescue, and fine
fescues.
Genetic based resistance has also been observed in other turfgrass species and cultivars. In Florida resistant cultivars of St. Augustinegrass to the southern chinch bug have been developed.
Chemical Control
Turfgrass managers usually
control chinch bug populations after major damage has occurred. To
avoid this problem in areas with habitual problems an April to
mid-May insecticide application will control the overwintering
females and subsequent generations during the summer.
Reinfestation may occur from adjacent areas, but this process is
slow and may require an additional year or more. This adult
treatment must be made before egg laying occurs. Some heat unit
models have been developed and indicate that egg hatch of
overwintering adults was completed by 115 degree-days at a
threshold temperature of 59 degrees Fahrenheit. This corresponded
to a time period of early June in New Jersey.
The following insecticides are labeled for control of chinch bugs however, several of the products have restrictive labeling.
Pyrethroids: Talstar, Astro and Tempo
Carbamates: Sevin and Turcam*
*Indicates restrictive labeling
by Dr. Lee Hellman, Department of Entomology and Dr. J. Kevin Mathias, Institute of Applied Agriculture