Southern Chinch bugs, Blissus insularis is an tiny insect pest of St. Augustinegrass, Stenotaphrum secundatum. This blog is excerpts from the University of Florida Featured Creatures publication written by Stacy Woods http://entomology.ifas.ufl.edu/creatures/orn/turf/southern_chinch_bug.htm. In most instances, a population of B. insularis moves from lawn to lawn within a neighborhood by walking from a heavily infested area to a fresh feeding area. An adult female B. insularis deposits eggs for a period of weeks close to where the plant contacts the soil (Wilson 1929). During the summer months, the eggs hatch between six to 13 days, with an average period of 11 days. This process can last a month or more during the winter months. The newly emerged nymphs resemble a smaller, wingless adult form. The first nymphal instar displays a yellow body color. The color will change to red with a pale white band across the abdomen and finally to black with a similar white band as the insect progresses through five nymphal stages. The adult southern chinch bug has a black body measuring about 1/5 inch long (6 mm in length) (Wilson 1929). The wings are white with a black spot on the margins of the forewings.
An infested lawn displays discolored patches, which are usually circular in shape. Injury typically occurs first in water-stressed areas along the edges of the lawn or where the grass is growing in full sunlight (Short and Black 1997; Short, Black and McCarty 1995). St. Augustinegrass cultivated on high, dry, sandy or shell soil is especially vulnerable to southern chinch bug damage (Wilson 1929).
To ensure proper treatment, homeowners must make a proper diagnosis of chinch bug infestation. To test for chinch bug presence, use the flotation method: cut the ends out of a metal coffee can and insert the can into the soil surrounding the discolored grass. Use a knife or shovel to dig the edges of the can down 3 inches into the soil. Fill the can with water continuously for five minutes. The chinch bugs trapped in the can will float to the top of the water. Repeat this method at least four times throughout the discolored area, concentrating on the perimeter of the injured spots, to ensure proper diagnosis (Short and Black 1997). Another way to collect your chinch bugs would be using your dust buster, on the edges of the affected area. Treatment may be necessary if 20 chinch bugs are found per square foot.
Specialists recommend integrated crop management to reduce the potential of chinch bug infestations on turfgrass. This method includes proper fertilization, irrigation, mowing, and pest control of St. Augustinegrass.
Cultural control. Planting resistant St. Augustine varieties: Floratam, Floralawn, and Floratine provide various degrees of resistance to chinch bug feeding. Most chinch bugs cannot complete their development when attempting to feed on Floratam and Floralawn. Cultural practices, including proper mowing, fertilization, and irrigation, can greatly reduce the susceptibility of St. Augustinegrass to chinch bug infestations. St. Augustinegrass should be kept to a height of 3 to 4 inches to ensure a strong root system, which will increase the grass tolerance against chinch bug infestations (Short and Black 1997). Lawns should be mowed frequently enough so that no more than 1/3 of the leaf blade is removed at each mowing. Furthermore, mowing with a sharpened blade will reduce the stress on the grass, thus making the lawn less susceptible to chinch bug outbreaks (McCarty and Cisar 1995).
Large applications of inorganic nitrogen fertilizers can cause rapid grass growth and heightened chinch bug susceptibility (Short and Black 1997). To reduce potential damage after fertilizing, use a water insoluble, time-release or multiple-application fertilizer (Short 1998).
Moisture stress in lawns also encourages chinch bug infestations (Short and Black 1997). To avoid over-watering, irrigate only after wilting begins, when the edges of the grass leaves start to curl. Less than an inch of water is usually sufficient to rewet the top 8 to 12 inches of the root zone (McCarty and Cisar 1995). Excessive water and fertilization can cause a thick layer of thatch to accumulate directly above the soil surface (Short and Black 1997). Thatch, a spongy mat of shoots, stems, and roots, provides a prime habitat for chinch bugs to feed and lay their eggs. If a significant layer of thatch covers a lawn, it may be removed mechanically by vertical mowing or power raking.
Chemical control. Presently, the preferred method of management and control remains the application of insecticides to infected areas. However, isolated populations of B. insularis have developed resistance to insecticides (Nagata and Cherry 1999). Furthermore, popular insecticides such as acephate, chloropyrifos, and lambda-cyhalothrin have varying effects on the different life stages of the southern chinch bug, and all are virtually ineffective in treating the egg stage when sprayed on a lawn of St. Augustinegrass. Therefore, outbreaks require many insecticidal applications before the problem is eradicated, which makes the southern chinch bug an extremely difficult and expensive pest to manage.
Biological control. In response to the development of resistance in B. insularis to chemical insecticides, researchers have focused on alternative methods of management. Reinert (1978) found that a bigeyed bug, Geocoris uliginosus, is the most numerous predator of the southern chinch bug in St. Augustinegrass.
This article was updated in April 2013 to provide a current link.