By Dr. Rogerio Lira and Dr. Felipe C. Batista et.al
We have been observing high numbers of thrips in both corn and soybean fields during our monitoring surveys from western to central Kentucky. As double-crop soybean fields emerge and corn enters the ear formation stage, these are critical growth stages when thrips may deserve closer attention in both crops.
Thrips feeding on corn seedlings usually has little direct impact on corn growth or grain yield. However, their greatest impact is often indirect because feeding may increase plant susceptibility to pathogen infections, particularly during ear formation. In soybean, thrips can also vector Soybean Vein Necrosis Virus.
Although thrips can sometimes cause severe leaf injury when combined with other stressful conditions, such as drought or herbicide injury, they are generally considered occasional pests in both corn and soybean and rarely require an insecticide application.
How to recognize thrips in corn and soybean fields?
Thrips are small insects (about 1/16 inch long) with piercing-sucking mouthparts. Immature stages are wingless and yellow, while adults are yellow or dark (depending on the species) and have two fringed wings.
Because of their small size, thrips can be difficult to find in the field. The easiest way to identify their presence is by the silver-gray discoloration and black specks (fecal spots) on leaves. Damaged leaves may also roll and twist.
Thrips are more common during drought periods because dry conditions and high temperatures favor their development, allowing populations to increase. In corn, thrips can be found in whorls, tassels, ears, or between undeveloped leaves. In soybeans, they are usually found on young leaves.
Source : uky.edu