Friday, February 23, 2024

New Resource: Stink Bug Scouting Guide

Stink bugs are the top insect pest of corn in the Southeastern United States. They tend to follow a predictable pattern of colonization in corn, typically arriving during the late-vegetative stages and reaching their highest population around the tasseling stage. However, even though this pattern is somewhat predictable, it’s not realistic to efficiently control stink bugs using fixed, calendar-based insecticide applications or at the entire farm level.

Because of this, and thanks to the support of the Corn Growers Association of North Carolina and the U.S. Department of Agriculture Crop Protection and Pest Management program, North Carolina Cooperative Extension has created a new scouting guide for stink bugs in corn.

Dominic Reisig, North Carolina Cooperative Extension entomology and plant pathology specialist, says the guide contains recently revised thresholds.

“We have learned a lot about how to manage stink bugs in corn and have a good handle on how to manage them with insecticides.

“Throughout this work, we have also learned how to scout for stink bugs in corn and have created this resource as an aid to proper scouting,” he says.

Treat Each Individual Field

Misshapen ears from stink bug feeding during the late-vegetative stages.

Scouting for stink bugs is necessary because corn maturity varies across the farm due to differences in hybrid types and planting dates. Additionally, stink bug infestations are not evenly spread, as they move into corn from neighboring areas with both non-crop and crop hosts in the surrounding landscape. Infestation levels can vary considerably among fields, even on the same farm. Furthermore, early season damage to corn seedlings can also occur, although this is less common than damage later in the season. As a result, the most effective way to manage stink bugs in corn is to regularly inspect individual fields and apply treatments when the pest population reaches the economic threshold within each specific field on the farm.

The most common stink bugs infesting corn in the Southeastern U.S. are brown stink bug, Euschistus servus, and southern green stink bug, Nezara viridula. Brown marmorated stink bug, Halyomorpha halys, will also infest corn, but it is not common in the Coastal Plain, where most of the field corn is grown in North Carolina. Brown marmorated stink bug has different preferences and infestation patterns than other stink bugs. Green stink bug, Chinavia hilare, can also infest corn, but it is not as common. This scouting guide is focused on the brown stink bug, southern green stink bug and green stink bug.

Scout Seedlings For Early Damage

On seedlings, adult stink bugs feed with their head in the soil, attempting to reach the growing point that is still below the surface. Scouting should be directed to the base of the plant on the stalk beneath the lowest leaf.

Stink bugs can cause significant damage to young corn plants. Most seedlings are protected from light-to-moderate levels of stink bug infestation because all field corn seeds are sold with an insecticidal  treatment that provides a base level of control. However, heavy stink bug populations or environmental conditions that interfere with plant growth or seed treatment uptake can overwhelm the seedling, especially when coupled with lower rates of insecticidal seed treatment.

Stink bug damage to seedlings can range from mild stunting or the development of additional tillers, to the most severe outcome, which is the death of the seedling. The extent of the damage depends on both the growth stage of the plant and how long the stink bugs feed on it. Generally, when stink bugs feed on the corn plant at an early stage of growth and for an extended period, the damage tends to be more severe.

For instance, in a 2019 trial, stink bugs were enclosed in cages and placed on corn plants at the V2 growth stage. When just one stink bug per plant fed on a single plant for a week, there was an average yield loss of 5.9 bushels per acre.

Adult stink bugs that feed on seedling corn during the spring are from the generation produced the previous fall that survived the winter. They feed with their head facing into the soil, attempting to access the growing point that is under the soil, until V5. Because of this, scouting should be directed to the base of the plant on the stalk beneath the lowest leaf. Finding stink bugs on seedling corn can be particularly challenging in fields with heavy crop residue.

For the complete guide, go to the N.C. State Extension website, click on “Field Crops” and then on the “corn” information portal. The guide can also be found at http://go.ncsu.edu/readext?971813. CS

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