Species Composition and Abundance of Stink Bugs (Hemiptera: Heteroptera: Pentatomidae) in Minnesota Field Corn

Natural Enemies and Biological Control of Stink Bugs (Hemiptera: Heteroptera) in North America

Stink bugs comprise a significant and costly pest complex for numerous crops in the US, including row crops, vegetables, and tree fruits and nuts. Most management relies on the use of broad-spectrum and disruptive insecticides with high human and environmental risks associated with them. Growing concerns about pesticide resistance in stink bugs are forcing pest managers to explore safer and more sustainable options. Here, we review the diverse suite of natural enemies of stink bugs in the US, noting that the egg and the late nymphal and adult stages of stink bugs are the most commonly attacked by parasitoids, whereas eggs and young nymphs are the stages most commonly attacked by predators. The effectiveness of stink bugs' natural enemies varies widely with stink bug species and habitats, influencing the biological control of stink bugs across crops. Historically, biological control of stink bugs has focused on introduction of exotic natural enemies against exotic stink bugs. Conservation and augmentation methods of biological control have received less attention in the US, although there may be good opportunities to utilize these approaches. We identify some considerations for the current and future use of biological control for stink bugs, including the potential for area-wide management approaches.

Development of Dichelops furcatus (Hemiptera: Heteroptera: Pentatomidae) Reared on Spring Cereals Versus Soybean

The performance and preferences of the stink bug, Dichelops furcatus (F.), for spring cereals (wheat, rye, triticale, oat, and barley) were compared in the laboratory to their preferred host crop, soybean pods. Nymphs took significantly less time to reach adulthood on soybean pods compared to those fed seed heads of the five spring cereals tested. Wheat and rye yielded the longest developmental times, while nymphs fed triticale, oat, or barley developed faster, but still not as fast as those reared on soybean pods. On all foods ≥78% of nymphs reached adulthood. Adult body weight was significantly greater on soybean pods than on any of the spring cereals, and adults increased in body weight on all food sources tested. Fecundity was significantly greater for females fed soybean pods than those reared on the cereals. Egg viability was ≥66.9% except for bugs fed triticale (31.4%). In general, adult D. furcatus preferred soybean pods to seed heads of spring cereals, with wheat being preferred over the other spring cereals.

Developing a Sampling Plan for Brown Stink Bug (Hemiptera: Pentatomidae) in Field Corn

Brown stink bug, Euschistus servus (Say), is a damaging pest of corn, Zea mays (L.), in the southeastern United States. Developing a reliable and practical sampling plan for population monitoring of this pest is essential for implementing integrated pest management measures. E. servus was sampled from commercial corn fields (n = 14) in North Carolina in 2016 and 2017. Both the adults and nymphs had a predominantly aggregated spatial distribution, estimated using the variance to mean ratio and Taylor's power law constant (b). Using the Taylor's power law constants, the optimum sample size required to estimate population density with a given level of reliability was calculated. For early vegetative stage corn (V4-V6), using whole plant visual sampling and an economic threshold density of 2 adult stink bugs per 20 plants, 27 sample units were required to estimate population density within 30% of the mean. At the same growth stage, using partial plant sampling and an economic threshold density of 1.73 adult stink bugs per 20 plants, 28 sample units were required to estimate population density with the same level of reliability. Reproductive stage corn (R1-R4) required eight sample units for whole plant sampling and nine sample units for partial plant sampling (Dx = 0.3). For E. servus adults, the partial plant sampling method was equally or more cost-reliable than the whole-plant sampling method for pest management in all corn growth stages tested.

Landscape Effects on Reproduction of Euschistus servus (Hemiptera: Pentatomidae), a Mobile, Polyphagous, Multivoltine Arthropod Herbivore

Landscape factors can significantly influence arthropod populations. The economically important brown stink bug, Euschistus servus (Say) (Hemiptera: Pentatomidae), is a native mobile, polyphagous and multivoltine pest of many crops in southeastern United States and understanding the relative influence of local and landscape factors on their reproduction may facilitate population management. Finite rate of population increase (λ) was estimated in four major crop hosts-maize, peanut, cotton, and soybean-over 3 yr in 16 landscapes of southern Georgia. A geographic information system (GIS) was used to characterize the surrounding landscape structure. LASSO regression was used to identify the subset of local and landscape characteristics and predator densities that account for variation in λ. The percentage area of maize, peanut and woodland and pasture in the landscape and the connectivity of cropland had no influence on E. servus λ. The best model for explaining variation in λ included only four predictor variables: whether or not the sampled field was a soybean field, mean natural enemy density in the field, percentage area of cotton in the landscape and the percentage area of soybean in the landscape. Soybean was the single most important variable for determining E. servus λ, with much greater reproduction in soybean fields than in other crop species. Penalized regression and post-selection inference provide conservative estimates of the landscape-scale determinants of E. servus reproduction and indicate that a relatively simple set of in-field and landscape variables influences reproduction in this species.

Stink Bug (Hemiptera: Heteroptera: Pentatomidae) Feeding and Phenology on Early-Maturing Soybean in Minnesota

The invasion by Halyomorpha halys (Stål) and an increasing abundance of native Pentatomidae pose a threat to soybean, Glycine max (L.) Merrill, production in northern states. A risk assessment framework was used to provide an initial assessment of the risk of Pentatomidae affecting soybean production in northern states. A caged field study was performed over two years to assess the response of soybean to H. halys feeding. Cages placed over R4 soybean were infested with 0, 1, 2, 4, or 8 fourth-instar H. halys nymphs per 0.3 row-m, and the insects were allowed to feed for 15 to 16 days. Feeding by H. halys on soybean affected yield components, maturity, and quality (i.e., seed injury). Season-long monitoring of soybean fields was performed via sweep net sampling to assess the likelihood of herbivorous Pentatomidae occurring on soybean during plant growth stages susceptible to feeding injury. Adults of herbivorous species were collected at low densities in fields in mid- to late July before collection of herbivorous nymphs. Herbivorous nymphs were first collected in the R3 and R4 soybean growth stages and their abundance peaked during the R6 soybean growth stage. This preliminary assessment indicates that if populations of exotic and native herbivorous Pentatomidae continue to increase in abundance, they will pose a threat to northern soybean production.