Northern Plains Integrated Pest Management GuideIPM

Authors: Buyung Hadi, Robert Wright, R. Jeff Whitworth, Holly Davis, and J.P. Michaud

Identification

Adult chinch bugs (Blissus leucopterus leucopterus) are small (3/16 in or about 5 mm), with black bodies and white bands across the folded wings. The newly hatched bugs are red with no wings. In the last nymphal stages, the body turns black and wings start to develop.

Chinch bug nymph

Life Cycle and Seasonal History

Chinch bugs survive the winter as adults. Clumps of native warm-season bunchgrasses such as little bluestem, big bluestem and switchgrass serve as the preferred overwintering sites. Adult chinch bugs may also overwinter in cool-season pasture grasses, other grassy areas in field margins and under crop residue in corn or sorghum fields.

In the spring when temperatures rise above 70°F (21.1°C) for several consecutive days, adult chinch bugs start to move out of their overwintering sites and migrate to nearby small grains such as wheat, barley, oats and rye. Areas with the poorest stands of wheat seemed to be more attractive for chinch bug migration. The bugs mate and lay eggs on these crops, usually behind the lower leaf sheaths or just below the soil surface. Females may lay several hundred eggs in two to four weeks. The resulting nymphs feed by sucking plant saps at the root zone or behind the leaf sheath.

When the small grains start to mature, chinch bugs begin to migrate in large numbers to corn. The nymphs migrate by walking while the adults fly to the adjacent corn fields. The bugs begin to feed at the crowns and on plant parts below the soil surface. Seedling corn less than 12 inches tall are very susceptible to injuries inflicted by sustained feeding of chinch bugs. Later, the bugs move to above-ground plant parts and start to feed on stems and lower leaves. Chinch bug infestation start at the field margin and may move deeper into the field.

Adult cinch bugs mate and lay eggs within the corn field, producing the second generation of the year. When the temperatures begin to fall below 70°F (21.1°C) in the fall, the chinch bugs begin to migrate to bunchgrasses.

Plant Injury and Damage

Depending on the population levels, injury caused by chinch bugs may range from slight to severe. Chinch bug deprives the plant of nutrients by sucking the plant sap. Severely infested plants are stunted, the leaves wilted and the plant may eventually die. Chinch bug is considered a sporadic pest of corn but it can be a major problem in situations where late planting is followed by dry weather. .

Management Approaches

Scouting and Threshold

Cultural Methods

Early planting helps to avoid chinch bug infestation during susceptible seedling stages. Since chinch bugs migrate from small grains to corn in the spring, planting corn near wheat, oat, barley or rye is not advisable.

Chemical Control

Soil insecticides applied at planting time and insecticidal seed treatments are effective against chinch bug. Usage of these insecticides maybe warranted in areas with history of chinch bug infestation.

Foliar insecticide sprays are recommended in dry conditions where injuries due to chinch bug are evident and 5 or more chinch bugs are present on 20 percent of seedlings less than 6 in (15 cm) tall. Foliar insecticides registered for chinch bug management are typically contact insecticides (they need to come in contact with the bugs to be efficacious) with short field activity (two to three days). Thus, applications of foliar insecticides are most efficacious when the bugs are out in the open, which usually occurs when the temperature is cool (before 10 a.m or after 6 pm) or after a rain. Broadcast applications may not be effective in reaching the bugs hidden in the soil or behind leaf sheaths. Drop and sqivel nozzle teps are necessary to spray the lower portion of the plant and the surrounding soil.

Trap crops have been found to prevent damage from migrating chinch bugs. Forage sorghum or sorghum sudangrass hybrids can be used as trap crop, when planted between maturing small grain and corn fields. The width of the trap crop should be at least 25 to 30 feet (7.6 - 9.1 m). Trap crops should be planted two to three weeks prior to the corn. When chinch bugs begin to move from small grains to trap crops, apply insecticides at regular interval (follow the limitation on frequency and number of applications on the insecticide's individual label) to the trap crop for as long as migration period lasts. It is important to monitor the chinch bug migration to time the insecticide application on the trap crop.