Damage by stink bugs observed in seedling corn Source: Dr. Raul Villanueva; UK Extension Entomologist With corn planting in full swing and starting to wrap up, some issues have been arising at crop emergence. One of those is damage caused by stink bugs on seedling corn. In a small replicate corn field test where seedlings were not more than seven days old, emerged showed more than 45 plants with elongated transversal holes in expanding corn leaves. These holes run perpendicular to the length of the leaf and can be different sizes. Around the hole edges, leaves have a yellowish shade; and this is a sign of damage by stink bugs. While plants continue growing, these holes will expand. Also, corn plants damaged by stink bugs may produce suckers (tillering) and present irregular growth, or be stunted. All these changes are caused by the insertion of stink bug piercing and sucking (needlelike) mouthparts into stems, leaves or apical meristems of corn plants. During this process, stink bugs inject enzymes into plants to aid digestion and fluid removal. Laboratory and field studies conducted at the University of Kentucky by the end of the 1980s showed that the brown stink bug (Euschistus servus) and the one-spotted stink bug (E. variolarius) can reduce plant densities, cause stunted plants with reduced root systems, result in suckers, and cause these plants to yield small or no ears. Stink bugs causing the damage described above are most certainly the brown stink bug and the one-spotted stink bug. Both are native to Kentucky and overwinter in non-tilled corn or wheat fields. Little is known about the impact or management of this insect on corn seedlings. This early occurrence of stink bugs in corn coincides with information from previous studies that suggested wheat could be an early spring host for these insects that move to cornfields when corn emerges. The abundances in corn may be related to the presences of stink bugs in soybeans near the harvest time in this field and many areas of central and western Kentucky in 2018. While conducting aphid tallies in research wheat plots, I found that brown stink bug has been present a little earlier this year. Management actions to control stink bugs at earlier stages of corn development have not been completely studied. However, scouting for pests that affect earlier stages of corn, such as cutworms, apple maggot, or slugs, is an effective and preventive way to manage damage caused by stink bugs. In the publication Insecticide Recommendations for Field Corn-2019, the insecticides recommended for cutworm “rescue treatments” might be used if a problem with stink bugs is found. Many of these insecticides include Brigade, Mustang Maxx, Warrior II, Sevin, Baythroid, and Permethrin. Consult the product label for use rates.
Agriculture & Natural Resources
