Southern Chinch Bug
- Scientific Name: Blissus insularus Barber. [Phylum Arthropoda: Class Insecta: Order Hemiptera: Family Lygaeidae]
- Common Names: southern chinch bug
- Climatic Zone: tropical and semitropical
- Geographic Distribution: The southern chinch bug is found from southern North Carolina to the Florida Keys, west to central Oklahoma, California and Hawaii. This pest has apparently been spread with sod to other countries.
- Damaging Stage: nymphs and adults
- Hosts: This species occasionally attacks centipedegrass, zoysiagrass, bahiagrass and bermudagrass, but it is a major pest of St. Augustinegrass wherever it is grown.
- Damage Symptoms: Irregular patches of St. Augustinegrass or bermudagrass turn yellow and then brown. These patches may expand or new patches may begin to form in lawns or grounds. As the southern chinch bug populations build up, they may kill extensive areas in a lawn and begin moving in mass across sidewalks and driveways. Populations of over 1,000 chinch bugs ft2 have been recorded in heavily damaged St. Augustinegrass.
- Description of Stages: Chinch bugs are true bugs that have a gradual life cycle with egg, nymphal and adult stages. All the species of Blissus are similar in form and an expert is needed to separate species and subspecies. Generally, any chinch bug found in St. Augustinegrass will most likely be the southern chinch bug. Chinch bugs in bermudagrass or zoysiagrass may also be western or common chinch bugs.
Eggs: The eggs are elongate oval, approximately 1/32 by 1/64 inch (0.75 mm by 0.23 mm), and are squarely cut off at the top. The blunt end has four small tubercles visible through a dissecting microscope. The eggs are first white but change to bright orange before hatching.
Nymphs: There are five to six nymphal instars which change considerably in color and markings during their development. The first instars are bright orange with a cream colored stripe running across the abdomen. The head and thorax become brownish with age. The second through fourth instars continue to have this same general color pattern except that the orange color of the abdomen gradually changes to a dusky gray with small black spots. The fourth instar increases to more than 3/32 inch (2 mm) long. The fifth instars are quite different because the wing pads have expanded and are easily visible. Occasionally an additional instar, the sixth, will be undertaken, especially in cooler weather. The abdomen becomes blue black with some darker black spots and the total body length is about 1/8 inch (3 mm).
Adults: Females are slightly less than 1/8 inch (3.1 mm) long and 1/16 inch (0.85 mm) wide with males being slightly smaller than the females. The head, pronotum and abdomen are gray black in color to dark chestnut brown and covered with fine yellow to white hairs. The wings are white with a black spot located in the middle front edge. The legs are chestnut brown. Individuals in a population, may have short, nonfunctional wings which reach only half way down the abdomen.
- Life Cycle and Habits: In its southern range, adults and individuals of all stages overwinter in St. Augustinegrass and bermudagrass, especially in the thatch. In the northernmost part of the range, only adults overwinter. These insects may become active any time the temperatures rise above 65 F but reproduction generally does not begin until April or May.
Females prefer to deposit their eggs by forcing them between the leaf sheath and stem, and occasionally in thatch. Each female may lay 45 to 100 eggs over several weeks. Eggs hatch in eight to nine days at 83 °F and 24 to 25 days at 70 °F. Newly emerged nymphs immediately begin feeding under the leaf sheaths. Nymphs hatching elsewhere crawl into available spaces under leaf sheaths. Nymphs may feed in aggregations. The nymphs go through five and occasionally six instars in 40 to 50 days during warm weather (above 80 °F). In cool weather, below 70 °F, they may take two to three months to mature. In most areas of the Gulf States, three to five overlapping generations occur each season. However, seven to ten generations occur in south Florida and the Carribean Islands.
The first two generations after overwintering are fairly well defined with first major adult peak occurring in June and the second peak in August. Subsequent peaks often occur in October and December. Most damage occurs during the dry season in the summer.
- Control Approaches: The southern chinch bug is very difficult to control in St. Augustinegrass because of the tendency of this grass to develop thick thatch-like layers. Southern chinch bugs are very adaptable and populations have overcome resistant turfgrasses and other populations have been found to be resistant to organophosphate and carbamate insecticides.
Cultural/Natural Control - Irrigation - Since this pest requires hot dry conditions for optimum survival and reproduction, irrigation and rainfall during the spring and early summer increase the incidence of the fungal pathogen, Beauveria bassiana, the white fungus of insects. Adults can also withstand water droplets because of the protective hairs on the body but small nymphs can be damaged.
Cultural Control - Use Resistant Turfgrasses - Common St. Augustinegrass is highly susceptible to the southern chinch bug while most bermudagrasses are fairly resistant. The St. Augustinegrass variety Floratam™ has been the standard in Florida for resistance but in recent years, this chinch bug has develop the ability to attack this variety. New varieties are under development and Floralawn™ seems to be a good alternative. In the bermudagrasses, Tifton 292™ seems to be a highly resistant variety. Check with suppliers and local county agents for locally adapted turfs with resistance to chinch bugs.
Cultural Control - Modify Agronomic Management - Generally, St. Augustinegrass and bermudagrass can be over fertilized and this leads to rapid growth and build up of thatch. In fact, such turf can be growing in its own thatch layer. This environment is very conducive to southern chinch bug survival. Overly thatched lawns or grounds should be dethatched, verticut or top dressed to improve the general conditions. Reducing fertilizers and increasing irrigation can greatly reduce populations of this pest.
Natural Control - Parasites and Predators - Several egg parasites and an adult parasite, tiny wasps, are known but these do not seem to build up populations rapidly enough to control this pest. Predators, especially the bigeyed bugs, Geocoris spp., kill large numbers of chinch bugs. Bigeyed bugs are often mistaken for chinch bugs because of their similarity in size and shape. Bigeyed bugs usually do not build up large populations until after considerable turf damage from chinch bugs has already occurred.
Biological Control - Beauveria Fungus - Chinch bugs are susceptible to infection by the fungus Beauveria. This fungus is most infectious when the turf has adequate moisture for good growth. Commercial preparations of this fungus are available, but little documented data exists as to their efficacy.
Chemical Control - Insecticides – Southern chinch bugs are notorious for developing resistance to insecticides. Because populations are often subjected to multiple applications of insecticides in a single season, it is recommended that insecticide classes (by mode of action) be rotated if more than one application is needed within a season.
Curative Treatments. Chinch bugs are rather easy to detect in turf and insecticide applications that target extensive infestations readily reduce populations below damaging levels. However, treatment must be applied before significant damage occurs. Sampling to detect developing populations in late spring is recommended.
Preventive Treatments. In turf areas where chinch bugs have been a perennial problem, early insecticide applications have been used successfully to reduce the population of overwintered adults, the source of summer infestations. This works well if applications are made in April or early May after the adults have finished spring migrations. Recent research indicates that new systemic insecticides with extended residual activity (100+ days) applied at this time may suppress the development of damaging summer populations.
Insecticides and Application. Most liquid insecticides applied for chinch bugs should be lightly watered in after treatment in order to maximize residues in the upper layers of thatch. High volume spray equipment can also help accomplish this task. Granular formulations often require some irrigation to activate the insecticide (release it from the granule). Be sure to check the instructions for specific recommendations on posttreatment irrigation.
Several sampling schemes have been developed for determining chinch bug populations in turf. The simplest method is to visually inspect the turf by spreading the turf canopy. Chinch bug nymphs tend to hide in the deeper thatch so careful inspection is necessary. Small chinch bugs are easily missed. A more reliable method is to use the flotation technique. To use the flotation technique, cut the lid out and the bottom lid and rim off a two pound coffee can. Twist the sharp edge of the can through the turf into the underlying soil. Fill the can with water and count the chinch bugs that float to the surface in 10 minutes. Refill if the water soaks into the ground before the 10 minute period ends. Populations of 25 to 30 individuals per square foot warrant control, especially if these numbers are encountered in June and July.