Joshua Temple, Jeffrey A. Davis, Jarrod Hardke, Paul Price, Steve Micinski, Colleen Cookson, Arthur Richter and B. Rogers Leonard

The most yield-limiting and economically important soybean pest across the southern United States is a complex of stink bugs. Historically, the most common species in this complex had been the green stink bug, southern green stink bug and the brown stink bug. However, during the past decade, a new species, the redbanded stink bug, has become more common across Louisiana. This species was first reported in south Louisiana during 2000 by crop consultants and LSU AgCenter extension agents. By 2002, the redbanded stink bug exceeded the stink bug action thresholds and justified using insecticide sprays on a single pest in this complex across many areas of south Louisiana.

It is not clear how or when the redbanded stinkbug became established in Louisiana. This is a neotropical species that ranges from Argentina to the southern United States. This pest has been recognized as a serious soybean pest in South America and was first reported in the United States in the 1960s.

Comprehensive surveys of stink bug pests in Louisiana soybeans have previously reported four common species – the southern green stink bug, green stink bug, brown stink bug and dusky stink bug. Southern green stink bugs have historically represented the highest proportion of the total stink bug complex. Because the redbanded stink bug has become more common and has become established across Louisiana, LSU AgCenter scientists conducted a study to determine the abundance and seasonal occurrence of the redbanded stink bug compared with other common stink bug pests in soybeans.

Surveys of stink bug pests were conducted across Louisiana soybean production regions (Figure 1) from 2008-2010. Soybeans were planted in quarter-acre to half-acre blocks at five locations, representing the state’s soybean production areas. Soybeans representing three maturity groups were planted at recommended planting dates in fields on five AgCenter research stations – Ben Hur at Baton Rouge, Dean Lee at Alexandria, Red River at Bossier City, Macon Ridge at Winnsboro and Iberia at Jeanerette. Soybeans were sampled for insects weekly from first flower through physiological maturity using a sweep net to take six replications of 25 sweeps within each maturity group. Each set of sweep-net samples was evaluated for stink bug species and life stage (adult or nymph). Data were summarized by location and year to determine stink bug abundance and occurrence for maturity group and plant growth stage.

More than 13,000 stink bugs were collected and identified during 2008-2010. The predominant species in the complex were redbanded, southern green, green and brown stink bugs. The most common species of the stink bug collected during this survey was the redbanded stink bug (Figure 2). Previous surveys in the late 1970s and early 1990s did not report redbanded stink bugs in Louisiana soybeans. These new results represent a dramatic shift in species composition of stink bugs. The highest percentage of redbanded stink bugs was collected at the southernmost survey site at the Iberia Research Station in 2010. In contrast, the lowest frequencies of redbanded stink bugs were at the northernmost survey site, the Red River Research Station, in 2010. At the Red River location, the southern green stink bug and the brown stink bug were the most abundant species in 2009 and 2010, respectively.

Redbanded stink bugs prefer to feed on seed and migrate into soybeans during reproductive stages of plant development. Redbanded stink bugs were highest during the R4-R7 soybean growth stages with peak infestations occurring during R6 in all maturity groups (Figure 4). Generally, this pest reached higher peak numbers in early-maturing soybean maturity groups compared with later-maturing maturity groups. The total proportion of redbanded stink bugs relative to other stink bugs ranged from 50 percent to 83 percent (Figure 3) across all matu rity groups. The percentage of redbanded stink bugs in the total species composition decreased in the later-maturing varieties compared with the early-maturing varieties.

Redbanded stink bugs have been found at action threshold levels (six replications of 25 sweeps) in all soybean-producing parishes (Figure 1). The expansion of this insect’s range has not been limited to Louisiana’s borders. Redbanded stink bugs are at pest status in soybeans in all states bordering Louisiana and have been reported as far north as Missouri and Tennessee. The redbanded stink bug has been a significant pest only in soybeans. It has been found in other crops at low levels and only when soybeans are not available in adjacent fields. This differs from other stink bugs typically associated with soybeans. The southern green, green and brown stink bugs are more general feeders that reach damaging levels in other Louisiana crops, including corn and cotton. With limited alternative hosts available during the summer, economic levels of redbanded stink bugs can quickly build in soybeans.

In 2010, total stink bugs collected at five samples sites decreased by 60 percent compared to 2009. The reduction in total stink bug numbers has been attributed to lower temperatures during the winter of 2009-10 and drought conditions during the spring of 2010, which reduced the quality of alternative, noncrop hosts. Because the redbanded stink bug has become more prevalent in Louisiana soybeans, the average number of insecticide applications has increased from one or two per season during the late 1990s to three to five per season, with the bulk of those targeting redbanded stink bugs.

Although the redbanded stink bug has become a significant portion of the overall stink bug complex in Louisiana soybeans, it does not appear to be displacing any of the other common pest species. In spite of low numbers of this pest in 2010, other stink bug species exceeded action threshold levels in Louisiana soybeans and required insecticide sprays for management.

Joshua Temple, Research Associate; Jeffrey A. Davis, Assistant Professor; Jarrod Hardke, Graduate Assistant, Department of Entomology, LSU AgCenter, Baton Rouge, La.; Paul Price, Research Associate, Macon Ridge Research Station, Winnsboro, La.; Steve Micinski, Associate Professor, and Colleen Cookson, Research Associate, Red River Research Station, Bossier City, La.; Arthur Richter, Research Associate, and B. Rogers Leonard, Professor and Jack Hamilton Chair in Cotton Production, Department of Entomology, LSU AgCenter, Baton Rouge, La.

(This article was published in the spring 2011 issue of Louisiana Agriculture magazine.)