Chinch Bug, Blissus leucopterus leucopterus, Heteroptera: Lygaeidae.

Description

Chinch bug adults are true bugs, i.e., the front half of the fore wing is hardened while the rear portion is membraneous. Color is generally black but the light colored wings give the appearance of a white band across the midsection (Photo 2). Adults are only about 3/16 in long. Immatures vary greatly in appearance. Newly hatched nymphs appear as minute reddish/orange specs on sorghum stalks and foliage (Photo 3). As nymphs develop, color changes from orange to dark gray or black. All nymphs are wingless.

Distribution, damage and impact

In Arkansas, chinch bug populations have varied greatly during the past four years. Few were detected during 1999 and 2000 except for Lafayette County in extreme southwest Arkansas. Surveys during the last two years, however, have detected chinch bugs throughout the state. Outside of Arkansas, chinch bug occurs in all states east of the Rocky Mountains and into southern Canada. On seedling grain sorghum adult chinch bugs can be found either on the ground or on stems near the ground, often under leaf sheaths. Here they insert their stylet mouth parts into the plant and remove plant fluids. Infested plants often become yellow and distortion of seedlings is common.

Life History

Generally adult chinch bugs migrate from overwintering sites including grasses into seedling grain sorghum where they mate and begin egg laying. The orange nymphs emerge and by peeling back the lower leaves on seedlings, large numbers of nymphs can often be detected. Nymphs develop for a few weeks and form the winged adult form. This process continues throughout the growing season. In Arkansas about three generations of chinch bug can develop each season.

Management

Chinch bug damage is generally greater under hot, dry conditions. Plants with sufficient moisture are more able to out grow the damage. Thus, irrigation during periods of drought may reduce the impact of chinch bugs on grain sorghum. Irrigation also may aid the uptake of insecticides applied to the seed or soil. In areas with a history of chinch bug problems, it may be beneficial to use seed treated with insecticide or to apply a soil insecticide at planting. However, chinch bug populations may experience great fluctuations between years and preventative soil or seed insecticides may not always be justified. In areas with a history of chinch bug problems and where treated seed or soil insecticides are used, it is suggested that a small portion of the field be left untreated and periodically checked for chinch bug. The final approach at chinch bug management is with the use of insecticide sprays applied to the foliage of seedling grain sorghum. The chinch bug threshold is variable and depends on the rate of plant growth and size. Slow growing smaller plants are most susceptible to severe damage. A general threshold for chinch bug has been established on seedlings less than 6 in. in height. Foliar treatments should be justified when 20% or more of the sampled plants harbor a minimum of 2 chinch bugs per plant. Fields should be sampled in several areas due to the variability in chinch bug distribution. Because the chinch bug is often found between the leaf sheath and stem, spray coverage is critical. Foliar insecticides must be applied in a minimum of 20 gpa and directed at the top of the seedling. Also, surfactants will likely increase effectiveness.

Insecticide recommendations for chinch bug on grain sorghum

See Tables 1 and 2 for insecticide recommendations current at time of publishing. Current updated recommendations can be found in the Cooperative Extension Service publication MP-144 and on the world wide web at WWW.cdms.net/manuf/default.asp. Always follow instructions on pesticide labels.