The brown stink bug, Euchistus servus (Say), is a polyphagous pest of multiple cultivated hosts in Virginia. It recently emerged as a potentially devastating pest of maize, Zea mays L. (Poaceae), in eastern Virginia where small grain (e.g., wheat, rye) production is common. In order to develop an integrated pest management (IPM) plan, research is needed to determine if brown stink bug feeding causes economic damage in maize at different growth stages and levels of infestations. Experiments were conducted in 2018 and 2019 to determine: 1) effectiveness of seed applied and in-furrow chemical control methods, 2) infestation levels in seedling and reproductive growth stages that cause economic damage, and 3) the effect, if any, of E. servus feeding on grain quality and mycotoxin contamination. Results of these experiments demonstrated that infestation levels (i.e., number of bugs divided by number of plants) of 11% and 15% in seedling and late vegetative maize, respectively, can cause measurable yield reduction at harvest. Seedling damage from E. servus is significantly mitigated by neonicotinoid seed treatments which are applied to nearly all commercial maize seed. Further, experiments indicated that maize quality can be affected by E. servus feeding in late reproductive stages of development. Results of these experiments will help to inform Virginia maize producers of the need to manage E. servus throughout the growing season. / Master of Science in Life Sciences / The brown stink bug, Euschistus servus, has emerged as a potential economic pest of maize (commonly referred to as "corn" or "field corn") in Virginia following reduced broad-spectrum insecticide use and increased adoption of no-tillage or reduced-tillage crop production systems. Stink bug infestations in maize frequently occur at two times in the growing season: following cover crop termination and following small grain harvest. We need to determine the effects of brown stink bug infestations on maize yield and quality, as well as the effectiveness of chemical management options, to help minimize yield losses and input costs for maize producers in our region. Experiments were conducted to determine: 1) the control provided by insecticidal seed treatments and in-furrow insecticide applications, 2) the level of brown stink bug infestations that cause economic damage at different growth stages of maize, and 3) the effect of brown stink bug feeding and a Fusarium fungal pathogen on grain yield and quality. Results of these experiments determined economic injury levels in seedling corn and late vegetative stages. Additionally, we found that universally applied neonicotinoid seed treatments mitigated early damage. Further, stink bug feeding through reproductive stages of development can reduce grain quality. Our results will help Virginia maize producers to make informed pest management decisions throughout the season.

Natural enemies provide critical population regulation of many pest species, though their effects are not commonly incorporated into agricultural management decisions. Conservation biological control is an important tool that can be implemented to minimize pest damage, but applying it requires appropriate understanding of pest and natural enemy relationships. Through experimental cotton field trials, I identified predator: prey ratios based on key arthropod predators as action thresholds of the whitefly pest Bemisia tabaci MEAM1 (Dinsdale et al. 2010; equivalent to Bemisia argentifolii Bellows et al. 1994 [Hemiptera: Aleyrodidae]), validated their efficacy, and promoted them to cotton pest managers. This dissertation begins with a multi-year field trial where whitefly and natural enemy populations were manipulated with a series of insecticidal treatments to identify key arthropod predators. The critical abundance of four key predators necessary to suppress whiteflies was estimated through predator: prey ratios. These ratios were refined for commercial pest management and developed to conform to the current whitefly IPM framework as a simple to use management-decision tool that would be readily adopted and used by pest managers. Predator: prey ratios were then validated in 1) a second field trial, 2) commercial fields in Arizona and northern Mexico and 3) historical field trials conducted from 1997-2010, where whitefly management decisions made with the standard threshold and ratios, were compared with the standard threshold alone. I found no difference in management outcomes when decisions were made with the standard threshold alone, or with predator: prey ratios in the field trial, but analysis of potential decisions on commercial farms and with historical trial data indicated that the majority of sprays could be delayed if control decisions incorporated ratio-based thresholds. Finally, an outreach program was developed and deployed to present ratios as decision-making tools for cotton pest managers that reduce uncertainty in control decisions and optimize spray outcomes. Pest managers indicated positive changes in knowledge and a gradual adoption of ratios for decision-making. The implementation of whitefly control decisions that incorporate predator: prey ratios may reduce pest managers' uncertainty in decision-making, as well as insecticide use and management costs.