Stink Bugs in Corn

Key Takeaways

• Stink bug damage in corn can reduce yield and grain quality, especially during early vegetative and reproductive growth stages when plants are most vulnerable to feeding injury.
• Early scouting is critical to prevent stink bug injury, with the first two weeks after emergence being the most important timing to detect infestations and protect seedlings.
• Feeding injury can cause plant death, deformed ears, and kernel damage, leading reduced grain quality and yield loss.
• Use economic thresholds to guide stink bug treatment decisions, as insecticide applications should be based on infestation levels, crop stage, and local recommendations.

Stink Bug Damage in Corn and Potential for Yield Loss

Stink bug damage to corn occurs at three main corn growth stages – early vegetative (V1 to V6 - one to six collared leaves), pre-tassel (V14 to VT - 14 collared leaves through tasseling), and reproductive growth stages (R1 to R4 - silking to dough stage).^3,4 Plant injury occurs when the stink bug’s needle like stylet is inserted into plant tissues. The stylet may cause “mechanical” damage depending on where it is inserted.

If the stylet is inserted directly into the seedling corn plant’s growing point during early vegetative stages, deformed seedlings, excessive tillering, or plant death may occur. Injected saliva can cause plant stunting, tillering, and seedling “deadheart”.⁵ These seedling injuries may reduce root mass which can reduce water and nutrient uptake. Seedling feeding can also result in irregular oblong-shaped holes with yellow borders across the corn leaf (Figure 1).^5,6,7 Billbug feeding creates similar holes; therefore, proper investigation is needed to verify the causal insect.^6,7 Research conducted by the University of Kentucky found that early season stunted plants from stink bug feeding can reduce yield potential by about 10%.⁶

Feeding during the pre-tassel stage can result in “banana ears” (Figure 2), while less severe injury can result in missing or deformed kernels.⁸ Other stresses such as drought or lack of nutrients can result in similar symptoms.

Feeding injury can extend into the late milk or early dent stage as well. The damage includes discolored and deformed kernels, some with obvious holes caused by feeding (Figure 3).^2,6 The feeding directly into the kernels may lead to aflatoxin or fumonisin contamination.⁴

Stink Bug Species in Corn

About 24 species and subspecies of native and invasive stink bugs may be found in the corn growing areas of the United States.¹ Species importance may vary within US regions. The brown stink bug (Figure 4), southern green stink bug, and one-spotted stink bug are the most common in the southeastern United States. In the Central Plains, along with the previously mentioned species, the green stink bug (Figure 5) and red shouldered stink bug (Figure 6) have been reported to damage corn. In addition, the brown marmorated stink bug, an invasive Asian species (Figure 7) identified in 1996 is becoming a concern throughout much of the United States.¹

Stink Bug Life Cycle

Though insect coloration and size differ among stink bug species, their general biology is similar. Stink bugs have round or oval shaped bodies, a well-developed and usually triangle-shaped scutellum, mouthparts shaped for piercing and sucking (stylet), and five-segmented antennae.¹ Cylindrical eggs, in masses of 15 to 20, are laid on the leaves of plant hosts (Figure 8). Hatchlings are nymphs that resemble adults in shape but are more colorful compared to adults (Figure 9). The eggs, which hatch in mass, and the hatchlings may be guarded by the female. Feeding by the adults and nymphs can result in crop injury.¹

Stink Bugs and Tillage

Corn produced in no-till systems, particularly fields bordered by woods, appear to be at a higher risk for potential infestation and injury. While conventional-tilled fields can experience stink bug injury, the injury is usually less severe and limited to the border rows.⁶ In the southeastern United States, surveys documented that a soybean-wheat-corn rotation can lead to an increased risk of stink bug injury in corn.⁶ Open seed slots are particularly vulnerable to stink bug feeding on seedling corn.⁷

Stink Bug Scouting Strategies

Scouting during the first two weeks after emergence is the most effective way to help prevent seedling stink bug damage. The base of seedling corn should be examined as adults usually feed attached to the plant with their head in the soil so they can pierce into the seedling growing point.⁶ Scouting should be done cautiously as stink bugs tend to hide under crop residue and deep within leaf attachments to the stalk.

Field margins should be a focus, particularly in those fields which have a history of stink bug injury and whose fields which border wooded areas or wheat fields. Pick at least 5 random field places and look for adults or injuries on 20 consecutive plants at each location (total of 100 plants). For injury to later growth stages, focus on field margins and pay particular attention to the ear nodes as the stink bugs tend to concentrate in the ear zone area. As with scouting seedling plants, choose 5 random locations and count the number of stink bugs on 20 consecutive plants. If stink bugs are found on the edge of the field, walk into the field at least 100 feet to determine if the infestation has spread inward.^3,9

Stink Bug Treatment Guidelines for Corn Plants

Treatment guidelines can vary from state to state; therefore, consult with your local Bayer Crop Science agronomist and extension service agent for local recommendations. A working treatment guideline for the Midwest is one stink bug per four plants (25% infested plants) prior to pollination, and one stink bug per two plants (50% infested plants) after pollination up to early dough stage.² In the southeastern United States, the thresholds are based on a 100-plant sample; if a treatment decision cannot be made, continue to sample until a confident decision can be made (Table 1).^3,4,6

An alternative scouting threshold suggested by North Carolina State University is based on sampling the entire plant. Thresholds are 1 stink bug per 10 plants for V1 to V6 growth stages, 1 stink bug per 4 plants for V14 to VT growth stages, and 1 per 2 plants for R1 to R2 growth stages.⁴

Table 1. Stink bug treatment guidelines for corn in the southeastern United States.*

For additional information on billbug injury please see Billbug Management in Corn.

For additional information on corn growth stages, please see How to Determine Corn Growth Stages.

Sources

¹Koch, R. L., Pezzini, D. T., Michel, A. P., and Hunt, T. E. 2017. Identification, biology, impacts, and management of stink bugs (Hemiptera: Heteroptera: Pentatomidae) of soybean and corn in the Midwestern United States. Journal of Integrated Pest Management Volume. 8:1–14. https://academic.oup.com/jipm/article/8/1/11/3745633/.
²Hunt, T., Wright, B., and Jarvi, K. 2015. Stink bugs reported in corn and soybean. CROPWATCH. Institute of Agriculture and Natural Resources. University of Nebraska-Lincoln. https://cropwatch.unl.edu/stink-bugs-reported-corn-and-soybeans/.
³Reisig, D. 2019. Scout before spraying stink bugs in corn. North Carolina State University Extension. https://corn.ces.ncsu.edu/2019/06/scout-before-spraying-stink-bugs-in-corn/.
⁴Reisig, D. and Heiniger, R. 2023. Stink bug management in corn. North Carolina State University Extension. https://corn.ces.ncsu.edu/corn-insect-management/scouting-and-thresholds/stink-bug-management-in-corn/.
⁵Hardman, W.C., Cook, D.R., Gore, J., Catchot, A.L., and Henry, W.B. 2020. 2020 Beltwide Cotton Conferences, Austin, TX. https://www.cotton.org/beltwide/proceedings/2005-2022/data/conferences/2020/paper/20122.pdf
⁶Bessin, R. 2019. Stink bug damage to corn. ENTFACT-305. Cooperative Extension Service. University of Kentucky. https://entomology.ca.uky.edu/ef305/.
⁷Obermeyer, J. 2019. Stink bug damage in corn. Pest&Crop Newsletter. Extension Entomology. Purdue University. https://extension.entm.purdue.edu/newsletters/pestandcrop/article/stink-bug-damage-in-corn/
⁸Bryant, T. 2020. Brown stink bug as a pest of corn in the southeastern United States. LGP 1082. Land-Grant Press® by Clemson® Extension https://lgpress.clemson.edu/publication/brown-stink-bug-as-a-pest-of-corn-in-the-southeastern-united-states/.
⁹Reisig, D. and Reay-Jones, F. 2023. Stink bug scouting guide for field corn in the southeastern US. NC State Extension. North Carolina State University. https://content.ces.ncsu.edu/stink-bug-scouting-guide-for-field-corn-in-the-southeastern-us

Additional Source
Koch, R. 2018. Stink bugs as an emerging threat to crop production: Overview of their biology, impacts and management. University of Minnesota. https://extension.soils.wisc.edu/wp-content/uploads/sites/68/2018/06/2-Koch_2018_WI-Ag-Classic_Stink-Bugs.pdf
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