Description

Corn thrips are minute insects found on the leaf surfaces of field corn. Adults are black and about 1/16 in. long (Photo 5-5). Two pairs of wings are present and long hairs occur on the edges of the wings. Immature thrips are smaller and lighter in color.

Distribution, damage and impact

Thrips occur throughout Arkansas and may be abundant on seedling corn adjacent to maturing wheat. Adults and immature stages “rasp” the leaf surface with their mouthparts and feed on the exuding plant sap. The impact of thrips on field corn is not well documented but large populations of thrips can cause yellowing of foliage and stunting of seedling field corn.

Life History

Overwintering adult thrips migrate from maturing weeds and wheat into field corn in spring and early summer. Mating occurs and females insert eggs into the corn tissue. Larvae emerge and feed by scraping the plant surface and ingesting plant sap. Maturity is reached in less than one week and pupation occurs in soil. Adults emerge in about four days and the cycle is repeated. Several generations occur annually in Arkansas.

Management

Because the impact of thrips on field corn is not fully understood and the sporadic occurrence of thrips on field corn, management decisions are difficult. Foliar insecticides directed at the top of corn seedlings and applied in large volumes of water can be used to reduce the number of thrips. Economic benefits of these applications are not well established, however. Field location may play a major role in thrips management as large thrips populations may move from maturing wheat into adjacent crops.

Insecticide recommendations for corn thrips on field corn

See Table 5-2 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.