Stink bug pests across the southeastern cotton belt consist of three main species: the brown stink bug, Euschistus servus (Say); the green stink bug, Acrosternum hilare (Say); and the southern green stink bug, Nezara viridula (L.).
Due to the diverse environmental conditions across this production region, population levels of these species vary widely across seasons, states, and fields.
In North Carolina and Virginia, green and brown stink bugs are the primary species, while southern green and brown stink bugs predominate in Georgia, and all three species are commonly observed in South Carolina.
Stink bugs primarily feed on a wide range of developing fruit and seed hosts, including – but not limited to – cotton, corn, soybeans, peanuts, fruits, grains, vegetables, grasses, shrubs, and trees.
Adult stink bugs overwinter in protected areas such as leaf litter, straw, under tree bark, and at the base of native grasses.
As the season progresses, adults move (fly) to find a sequence of host plants with overlapping reproductive (seed and fruit-producing) stages. In temperate climates, some stink bug species will feed on succulent plants like mustards and wild radish on mild winter days.
In those areas where the insects diapause (a period of low activity), exposure to longer day lengths and warm temperatures breaks the reproductive diapause. Adults then fly to early blooming hosts (weeds, clover, small grains, and early spring vegetables) or to trees (elderberry, locust, and peach) to deposit eggs.
As these hosts age, the surviving offspring and adults seek midseason hosts such as leguminous weeds, corn, vegetables, sorghum, alfalfa, and fruit crops. Populations continue to build before moving into late-season crops like cotton, peanuts, soybeans, fall vegetables, and pecans.
The largest populations are generally observed in the late summer and fall. Depending on the stink bug species and location (latitude), one to five generations develop annually. Stink bugs are serious cotton pests in the Southeast.
A recent increase in stink bug pest status in this region has been attributed to the reduced use of broad-spectrum insecticides, primarily due to the adoption of Bt (Bacillus thuringiensis) cotton varieties (for caterpillar control), and the eradication of the boll weevil, Anthonomous grandis grandis Boheman (Figure 3).
Although stink bugs may infest cotton in most U.S. cotton-production regions, the majority of crop losses and costs associated with control occur in the southeastern region. In cotton, stink bugs prefer to feed on medium-sized bolls (approximately the diameter of a quarter), but are capable of feeding on bolls of any size (hereafter referred to as “stink bug damage”).
Although stink bugs may feed on bolls 25 days of age and older, bolls of this maturity are relatively safe from yield loss. Direct yield losses occur due to shedding of young bolls (fewer than 10 days of age) and damage to seeds; indirectly, the transmission of pathogens that cause boll rot affects the yield and fiber quality.
For example, excessive stink bug feeding on cotton results in stained lint, poor color grades, and reductions in physical fiber quality. Although sweep-netting and drop-cloth techniques can be used to sample for stink bugs in cotton, most Extension programs have adopted stink bug action or treatment thresholds based on the percentage of bolls with evidence of internal damage (callus growths/warts or stained lint associated with feeding puncture).
Recent work by entomologists at the University of Georgia and Clemson University confirmed this approach by comparing stink bug numbers using different sampling methods (sweep net, drop cloth) to boll samples in commercial cotton fields. While almost 90 percent of the boll samples (20 bolls evaluated per sample) had some internal damage, stink bugs were recovered in less than 10 percent of sweep-net samples and less than 5 percent of drop-cloth samples.
Results from this and many other studies have contributed to more effective management of stink bugs. However, a number of questions about the biology, ecology, damage relationships, and scouting procedures persist:
- Do regional differences in patterns of stink bug damage exist?
- What are the relationships between stink bug damage, yield, and fiber quality?
- What is the relationship between cotton- crop stage and damage potential?
- How does the agricultural landscape impact stink bug movement?
- What sampling methods and sample sizes are most efficient for stink bug damage detection?
- With this information in mind, Cotton Incorporated,
along with the state cotton support committees from Alabama, Florida, Georgia, North Carolina, South Carolina, and Virginia, and the Southern Region Integrated Pest Management Center supported a three-year regional project from 2005 to 2007, titled Identifying Practical Knowledge and Solutions for Managing the Sucking- Bug Complex in Cotton: Research in the Southeast Region. The main objectives of this research were to:
- Investigate the impact of stink bug feeding on cotton yield and fiber quality.
- Develop practical treatment thresholds for stink bugs in cotton.
- Develop efficient detection methods for stink bugs or their damage in cotton.
- Investigate the spatial and temporal dynamics of stink bugs within farm scapes to determine whether there are predictable patterns of crop and noncrop utilization.
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