Recent advances in agroecological research for increasing scope of areawide pest management of arthropods in cropping systems.

We propose that a growing research base considering pest management as an ecosystem service can be leveraged to expand areawide pest management (AWPM) to an agroecological-oriented framework when addressing pest arthropods in cropping systems. This AWPM framework centers on the innate capacity of the agroecosystem to suppress pests and is supported with strategic insertion of AWPM tactics. Recent studies on agroecological pest management are valuable to identify AWPM candidates. The estimation and predictability of AWPM outcomes may be improved by measuring effects of interactions of pest and pest suppression agents, and mediating factors such as landscape and weather. This knowledge helps formulate selection and strategic insertion of AWPM tactics into the system to support innate pest suppression. Advances in biotechnology and agricultural engineering have increased effectiveness of AWPM tactics, further improving positive AWPM outcomes. Furthermore, multifunctional agricultural, environmental, and economic benefits may be seen when adopting this framework.

A Special Collection: Spodoptera frugiperda (Fall Armyworm): Ecology and Management of its World-Scale Invasion Outside of the Americas.

The Special Collection 'Spodoptera frugiperda (fall armyworm): Ecology and Management of its World-scale Invasion Outside of the Americas' presents reviews and research that address topics of overarching interest and contributes to a better understanding of this pest and its management, now that it has spread outside the Americas. The collection is a combination of invited articles presenting new information published for the first time, invited review papers, and a selection of relevant high-quality articles previously published in Journal of Economic Entomology (JEE). Articles in the Collection, as well as selected citations of articles in other publications, reflect the increase in research on S. frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), which became the most important pest of maize in the world during recent years. This Special Collection addresses a wide range of topics, including pest behavior, host strains, insecticide and Bt protein resistance, biological control, host plant resistance, and yield loss estimates. Topics are presented in context of research primarily conducted in regions outside of the Americas where S. frugiperda has invaded and disrupted crop production to varying degrees. In recognition of further spread, the threat of a S. frugiperda invasion into Europe and potential management options are also presented.

Parasitoids and Predators of the Invasive Aphid Melanaphis sorghi Found in Sorghum and Non-Crop Vegetation of the Sorghum Agroecosystem.

Melanaphis sorghi (Theobald) (sorghum aphid), (=Melanaphis sacchari Zehntner) (Hemiptera: Aphididae), is an invasive pest of Sorghum bicolor (L.) in North America. Over 19 species of predators and parasitoids have been found to prey on M. sorghi. Natural enemies may reside in vegetation such as sorghum in cultivation (in-season) and persist after harvest (off-season), in Johnson grass (Sorghum halepense) (L.) and riparian areas consisting of shrubs and grasses, including Johnson grass. The objective was to assess the ability of these vegetation types to harbor M. sorghi natural enemies during and between annual grain sorghum production. Predator diversity was greatest in riparian vegetation in-season, with twelve species detected across seven families, and four orders of insects. Six lady beetle (Coleoptera: Coccinellidae) species were abundant in-season, and Cycloneda sanguinea (L.) persisted at relatively high abundance off-season. Parasitoid diversity was more limited (two primary parasitoids and one hyperparasitoid detected) with the primary parasitoids commonly detected. Aphelinus nigritus (Howard) (Hymenoptera: Aphelinidae), accounted for 85% and 57% of parasitoids in- and off-season, respectively. Aphelinus nigritus abundance was steady across the annual sorghum season in all vegetation types. Results from this study will inform land-management strategies on how diverse vegetations can play a role in the biological control of M. sorghi.

Landscape Complexity has Mixed Effects on an Invasive Aphid and Its Natural Enemies in Sorghum Agroecosystems.

Landscapes with more complex composition and configuration are generally expected to enhance natural enemy densities and pest suppression. To evaluate this hypothesis for an invasive aphid pest of sorghum, Melanaphis sorghi Theobald (Hemiptera: Aphididae), sampling in sorghum fields for aphids and natural enemies was conducted over two years in a southern U.S. coastal production region. Landscape composition and configuration of crop and noncrop elements were assessed using correlation and multivariate regression modeling to detect relationships with insects at different spatial scales. Significant models found more complex landscape configuration, particularly the amount of habitat edges, was associated with increased aphid and natural enemy abundance. Composition associated with noncrop habitats had the opposite effect. Numerical response of natural enemies was taxa dependent, with parasitism lower as landscape complexity increased, while predator numerical response was not affected by landscape complexity. These results indicate landscape complexity may increase both aphid and natural enemy abundance, but with decreasing parasitism and little association with predator numerical response. These relationships are likely contingent on overall environmental suitability to aphid population increase as results were less evident in the second year when average aphid abundance regularly exceeded the economic threshold. This study supports the importance of configuration, especially habitat borders, as a critical metric for determining pest-natural enemy dynamics within a large-scale cereal agroecosystem.

Evaluation of Areawide Forecasts of Wind-borne Crop Pests: Sugarcane Aphid (Hemiptera: Aphididae) Infestations of Sorghum in the Great Plains of North America.

Airborne pests pose a major challenge in agriculture. Integrated pest management programs have been considered a viable response to this challenge, and pest forecasting can aid in strategic management decisions. Annually recurrent areawide sugarcane aphid [Melanaphis sacchari (Zehntner) (Hemiptera: Aphididae)] infestations of sorghum [Sorghum bicolor (L.) Moench (Poales: Poaceae)] in the Great Plains of North America is one of such challenges. As part of the response, a spatially-explicit individual-based model was developed that simulates sugarcane aphid infestations over the southern-to-central part of the region. In this work, we evaluated model forecasts using 2015-2018 field data. The ranges of forecasted days of first infestation significantly overlapped with those observed in the field. The average days of first infestation observed in the field were approximated by the model with differences of less than 28 days in Texas and southern Oklahoma (2015-2018), and in northern Oklahoma (2016-2017). In half of these cases the difference was less than 14 days. In general, the modeled average day of first infestation was earlier than the observed one. As conceptual modeling decisions may impact model forecasts and as various socio-environmental factors may impact spatio-temporal patterns of field data collection, agreement between the forecasts and the observed estimates may vary between locations and seasons. Predictive modeling has the potential to occupy a central position within areawide integrated pest management programs. More detailed consideration of local agricultural practices and local environmental conditions could improve forecasting accuracy, as could broader participation of producers in field monitoring efforts.

Suppression of the Sugarcane Aphid, Melanaphis sacchari (Hemiptera: Aphididae), by Resident Natural Enemies on Susceptible and Resistant Sorghum Hybrids.

The sugarcane aphid, Melanaphis sacchari (Zehntner) (Hemiptera: Aphididae), is an invasive sorghum pest that has threatened over 90% of North American sorghum production. Resident parasitoids, coccinellids, syrphids, and lacewings prey on this aphid. Our objective was to compare and estimate parasitoid and predator suppression of sugarcane aphids placed on resistant and susceptible hybrids in a field setting using natural enemy exclusion cages. During 2018 and 2019 along the Texas Gulf Coast and Central Oklahoma, three natural enemy exclusion treatments-no exclusion (full access for parasitoids and predators), partial exclusion (access limited to parasitoids), and complete exclusion (excludes parasitoids and predators)-were used. The parasitoid Aphelinus nigritus Howard (Hymenoptera: Aphelinidae) accounted for 90% of recovered natural enemies. In 2018, aphid suppression attributable to A. nigritus was ca. 95% on the resistant hybrids and 80% on the susceptible hybrids when comparing aphid counts from complete and partial exclusion treatments, while few predators were observed. In 2019, aphid suppression was attributed to a combination of predation and parasitism. Relatively more predators were recorded at both sites, accounting for 14% to 33% of specimens recovered in the no exclusion treatment. Aphid suppression attributed to predators and parasitoids ranged from 85% on aphid-resistant hybrids and 27% on susceptible hybrids in south Texas and >95% on both hybrids in Oklahoma when comparing aphid abundance in the complete and no exclusion treatments. Parasitism and predation contributed to aphid regulation on both hybrids, which may accrue multiple benefits leading to a more resilient sugarcane aphid management system.

Natural Enemies, Mediated by Landscape and Weather Conditions, Shape Response of the Sorghum Agroecosystem of North America to the Invasive Aphid Melanaphis sorghi.

The sorghum (Sorghum bicolor [L.]) agroecosystem of North America provided an opportunity to evaluate agroecosystem response to an invading insect herbivore, Melanaphis sorghi (Theobald) (sorghum aphid) (previously published as Melanaphis sacchari Zehntner) (Hemiptera: Aphididae) onto a widely planted crop that experiences a range of agro-landscape and weather conditions. Initial sorghum risk assessments after M. sorghi's invasion in the mid-2010s provided forecasts of range expansion and annual migration, which were based on aphid life history, extent of sorghum cultivation and susceptibility to M. sorghi, and weather (aphid-plant-weather [APW] risk scenario). A more comprehensive risk assessment proposed here brings top-down forces of M. sorghi-natural enemy interactions to the forefront as mediated by agro-landscape and weather conditions (aphid-enemy/landscape-weather mediated [AE/LW] risk scenario). A hypothesis of regional differences in aphids and natural enemies and sensitivity to agro-landscape and weather was tested using empirical data of insect, landscape, and weather data across 5 years and four regions (two in the U.S. Great Plains [South GP and North GP], one farther south (South), and one in the southeast U.S. [South E]). Natural enemies were widespread with two parasitoids and four coccinellid species common across regions, but regional variation in M. sorghi and natural enemy abundance was detected. The AE/LW risk scenario accounted for natural enemy abundance and activity that was highest in the South region, functioned well across agro-landscape and weather conditions, and was accompanied by average low M. sorghi abundance (~23 M. sorghi per leaf). Positive correlations of natural enemy-M. sorghi abundance also occurred in the South GP region where M. sorghi abundance was low (~20 M. sorghi per leaf), and selected natural enemy activity appeared to be mediated by landscape composition. Melanaphis sorghi abundance was highest in the South E region (~136 aphids/leaf) where natural enemy activity was low and influenced by weather. The AE/LW risk scenario appeared suited, and essential in the South region, in assessing risk on a regional scale, and sets the stage for further modeling to generate estimates of the degree of influence of natural enemies under varying agro-landscape and weather conditions considered in the AE/LW risk scenario. Broadly, these findings are relevant in understanding agroecosystem resilience and recommending supportive management inputs in response to insect invasions in context of natural enemy activity and varied environmental conditions.

Crop and Semi-Natural Habitat Configuration Affects Diversity and Abundance of Native Bees (Hymenoptera: Anthophila) in a Large-Field Cotton Agroecosystem.

The cotton agroecosystem is one of the most intensely managed, economically and culturally important fiber crops worldwide, including in the United States of America (U.S.), China, India, Pakistan, and Brazil. The composition and configuration of crop species and semi-natural habitat can have significant effects on ecosystem services such as pollination. Here, we investigated the local-scale effect of crop and semi-natural habitat configuration in a large field (>200 ha in size) cotton agroecosystem on the diversity and abundance of native bees. The interfaces sampled included cotton grown next to cotton, sorghum or semi-natural habitat along with a natural habitat comparator. Collections of native bees across interface types revealed 32 species in 13 genera across 3 families. Average species richness metrics ranged between 20.5 and 30.5, with the highest (30.5) at the interface of cotton and semi-natural habitat. The most abundant species was Melissodes tepaneca Cresson (>4000 individuals, ~75% of bees collected) with a higher number of individuals found in all cotton-crop interfaces compared to the cotton interface with semi-natural habitat or natural habitat alone. It was also found that interface type had a significant effect on the native bee communities. Communities of native bees in the cotton-crop interfaces tended to be more consistent in species richness and abundance. While cotton grown next to semi-natural habitat had higher species richness, the number of bees collected varied. These data suggest that native bee communities persist in large-field cotton agroecosystems. Selected species dominate (i.e., M. tepaneca) and thrive in this large-field cotton system where cotton-crop interfaces are key local landscape features. These data have implications for potential pollination benefits to cotton production. The findings also contribute to a discussion regarding the role of large-field commercial cotton growing systems in conserving native bees.

Field Assessment of Aphid Doubling Time and Yield of Sorghum Susceptible and Partially Resistant to Sugarcane Aphid (Hemiptera: Aphididae).

Since outbreaks were first detected in grain sorghum, Sorghum bicolor (L.) Moench (Cyperales: Poaceae), in 2013, sugarcane aphid, Melanaphis sacchari Zehntner has become a major annual pest in grain sorghum-producing regions of North America. Economic thresholds have been recommended for susceptible hybrids, but these recommendations may not be suitable for grain sorghum hybrids partially resistant to sugarcane aphid. The objectives were to evaluate the grain yield-aphid density relationship and field-based population growth rates of the aphid on sorghum hybrids susceptible and partially resistant to sugarcane aphid across multiple years, locations, and hybrids. These data verified previously established economic injury levels for susceptible hybrids. The observed maximum aphid density ranged from 6 to 451 aphids per leaf for resistant hybrids and from 67 to 1,025 for susceptible hybrids. Across 50 location-year combinations, the maximum aphid density observed on resistant hybrids decreased by 0-99%, compared to a susceptible hybrid at the same location (mean reduction = 80%). Doubling time for sugarcane aphid populations on partially resistant hybrids was up to 6.4-fold higher than on known susceptible hybrids. For 48 of the 50 location-years, yield loss attributable to sugarcane aphid was not detected on the partially resistant hybrids; therefore, an economic injury level was unable to be estimated. If an economic injury level exists for resistant hybrids, it is likely at an aphid population level that exceeds the levels experienced in this study. It remains prudent to monitor resistant hybrids for unusual leaf decay associated with aphid densities that exceed current economic injury levels used for susceptible hybrids.

A Special Collection: Drones to Improve Insect Pest Management.

The Special Collection Drones to Improve Insect Pest Management presents research and development of unmanned (or uncrewed) aircraft system (UAS, or drone) technology to improve insect pest management. The articles bridge from more foundational studies (i.e., evaluating and refining abilities of drones to detect pest concerns or deliver pest management materials) to application-oriented case studies (i.e., evaluating opportunities and challenges of drone use in pest management systems). The collection is composed of a combination of articles presenting information first-time published, and a selection of articles previously published in Journal of Economic Entomology (JEE). Articles in the Collection, as well as selected citations of articles in other publications, reflect the increase in entomology research using drones that has been stimulated by advancement in drone structural and software engineering such as autonomous flight guidance; in- and post-flight data storage and processing; and companion advances in spatial data management and analyses including machine learning and data visualization. The Collection is also intended to stimulate discussion on the role of JEE as a publication venue for future articles on drones as well as other cybernectic-physical systems, big data analyses, and deep learning processes. While these technologies have their genesis in fields arguably afar from the discipline of entomology, we propose that interdisciplinary collaboration is the pathway for applications research and technology transfer leading to an acceleration of research and development of these technologies to improve pest management.

Complete Genome Sequence of Serratia sp. Strain CC119, Associated with Inner Cotton Boll Rot via Insect Vector Transmission.

Serratia species are Gram-negative bacteria that can infect both animals and plants. The annotated genome presented is the first for a Serratia sp. strain (called CC119) that is a cotton boll pathogen. The opportunistic strain is associated with the boll-piercing-sucking insect Creontiades signatus.

Yield, Insect-Derived Ear Injury, and Aflatoxin Among Developmental and Commercial Maize Hybrids Adapted to the North American Subtropics.

The development of maize (Zea mays L.) hybrids that are adapted to subtropical areas of North America should consider yield potential under heat and moisture stress, and reduced susceptibility to insect herbivory and disease. To aid in this process, maize hybrids (43 developmental and seven non-Bt commercial hybrids) were evaluated for severity of ear injury to Helicoverpa zea (Boddie) and Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), susceptibility to Aspergillus flavus (Link) (Deuteromycetes: Moniliales), and yield. In subtropical Corpus Christi and College Station, TX, field experiments conducted over three years revealed significant differences among maize hybrids with the rank of the selected measurements differing across the two locations. When the location by maize hybrid interaction was not significant, variation across the main factors of maize hybrid genetics (in all cases) and location (in some cases) was detected. In 2014, a significant location by maize hybrid interaction in yield but not aflatoxin and ear injury were likely associated with differences in weather between locations. In Corpus Christi in 2015, a location by maize hybrid interaction was detected for ear injury only. Overall, experimental maize hybrids, containing the inbred line Tx777, displayed partial resistance to insect derived ear injury in both locations, and some hybrid testcrosses exhibited low rates of aflatoxin accumulation while maintaining relatively high yields. Tx777 was selected from populations originating in Bolivia and adapted to subtropical climates. The most promising hybrid testcrosses had lower ear injury and aflatoxin accumulation, and good yield under varying heat and moisture stress at the two subtropical maize growing areas in this study.

A Native Bee, Melissodes tepaneca (Hymenoptera: Apidae), Benefits Cotton Production.

The cotton agroecosystem is one of the most intensely managed, economically and culturally important cropping systems worldwide. Native pollinators are essential in providing pollination services to a diverse array of crops, including those which have the ability to self-pollinate. Cotton, which is autogamous, can potentially benefit from insect-mediated pollination services provided by native bees within the agroecosystem. Examined through two replicated experiments over two years, we hypothesized that native bees facilitated cross-pollination, which resulted in increased lint of harvested bolls produced by flowers exposed to bees and overall lint weight yield of the plant. Cotton bolls from flowers that were caged and exposed to bees, flowers that were hand-crossed, and bolls from flowers on uncaged plants exposed to pollinators had higher pre-gin weights and post-gin weights than bolls from flowers of caged plants excluded from pollinators. When cotton plants were caged with the local native bee Melissodes tepaneca, seed cotton weight was 0.8 g higher on average in 2018 and 1.18 g higher on average in 2019 than when cotton plants were excluded from bees. Cotton production gains from flowers exposed to M. tepaneca were similar when measuring lint and seed separately. Cotton flowers exposed over two weeks around the middle of the blooming period resulted in an overall yield gain of 12% to 15% on a whole plant basis and up to 24% from bolls produced from flowers exposed directly to M. tepaneca. This information complements cotton-mediated conservation benefits provided to native pollinators by substantiating native bee-mediated pollination services provided to the cotton agroecosystem.

Field Edge and Field-to-Field Ecotone-Type Influences on Two Cotton Herbivores: Cotton Fleahopper, Pseudatomoscelis seriatus (Hemiptera: Miridae), and Verde Plant Bug, Creontiades signatus.

In the United States, the average field size has roughly doubled from the 1980s to the mid-2000s, while average cropland has stayed the same. This will likely influence how semi-natural habitats and edges affect local patterns and processes such as natural pest control or pest densities. We hypothesized that densities of two cotton pests, cotton fleahopper (Pseudatomoscelis seriatus) and verde plant bug (Creontiades signatus) (Hemiptera: Miridae), and corresponding cotton injury in a cotton agroecosystem were affected by field edge, ecotone type (described by the neighboring habitat), and the influence of ecotone type on edge effects. Studies over 2 yr using transect and random point sampling indicated that densities of both insects declined significantly and in a linear fashion from the cotton field boundary (0 m) to field interior (200-300 m from field edge). The decline was influenced by ecotone type for cotton fleahopper. Pest densities in cotton at the interface with semi-natural habitat were higher but declined at a greater rate into the cotton field interior compared to densities seen at the interfaces with sorghum or another cotton field. These effects were also observed for verde plant bug and the cotton boll injury it causes. Regardless of the pest densities near the field edge and the rate of decline into the field interior, densities beyond 100 m into the field were up to 70% less than field edges for both insect species and for boll injury. Potential for land managers to improve sampling efficiency when scouting is apparent. For example, pest species may be at economic threshold in certain parts of the field but not others, leading to different management decisions in larger fields. Therefore, for cotton fleahopper and verde plant bug, edges should be the focus of initial pest detection and sampling, and interior field sampling may only be required when edges are above the economic threshold.

Development of Binomial Sequential Sampling Plans for Sugarcane Aphid (Hemiptera: Aphididae) in Commercial Grain Sorghum.

The sugarcane aphid (Melanaphis sacchari Zehntner) is a significant economic pest of grain sorghum (Sorghum bicolor (L.) Moench) in the Southern United States. Current nominal and research-based economic thresholds are based on estimates of mean aphids per leaf. Because enumerating aphids per leaf is potentially time consuming, binomial sequential sampling plans for M. sacchari were developed that allow users to quickly classify the economic status of field populations and determine when an economic threshold has been exceeded. During 2016 and 2017, counts of M. sacchari were recorded from 281 sampling events in 140 sorghum fields located in six states (Oklahoma, Kansas, Texas, Arkansas, Louisiana, Mississippi) . Regression analysis was used to describe the relationships between the mean M. sacchari density per two-leaf sample and proportion of plants infested with one or more aphids. Tally thresholds of T50 and T100 aphids per two-leaf sample were selected based on goodness of fit and practicality. Stop lines for both tally thresholds were developed for selected economic thresholds using Wald's sequential probability ratio test. Model validations using an additional 48 fields demonstrated that reliable classification decisions could be made with an average of 11 samples regardless of location. This sampling system, when adopted, can allow users to easily and rapidly determine when M. sacchari infestations need to be treated.

Transmission of Cotton Seed and Boll Rotting Bacteria by the Verde Plant Bug (Hemiptera: Miridae).

Field experiments and supporting laboratory work were conducted to characterize the ability of the verde plant bug, Creontiades signatus (Distant), a boll-feeding sucking bug, to transmit a cotton seed and boll rot bacterial pathogen, Serratia marcescens (Bizio) (Enterobacteriales: Enterobacteriaceae). Serratia marcescens was originally isolated from bolls infested with verde plant bug in south Texas, and a Rifampicin resistant S. marcescens strain was used in transmission and retention experiments. Serratia-exposed and nonexposed adult verde plant bugs from a laboratory colony were placed individually on 5-, 6-, 7-, and 8-d-old bolls (postanthesis). The bacterial acquisition process did not apparently affect insect vigor based on similar average boll injury ratings observed across both exposed and nonexposed bugs. Cotton bolls caged with Serratia-exposed verde plant bugs had significantly greater presence of S. marcescens and cotton boll rot symptoms than bolls caged without bugs (no-insect controls) or nonexposed bugs. Transmission of the disease agent by verde plant bug was confirmed across all boll ages assayed. Incidence of diseased locules on 5- and 6-d-old bolls was the same or greater than on 7- and 8-d-old bolls. Verde plant bug was able to harbor the disease agent from 24- to 96-h postinfection, and transmission efficiency rates ranged from 54 to 62% during initial transmission and retention (transmission across two bolls fed upon consecutively) studies. Along with photographic evidence, the experimental data supported that boll damage associated with verde plant bug infestations was magnified when insects transmitted the cotton pathogen S. marcescens as demonstrated in this 2-yr field experiment.

Association of Insect-Derived Ear Injury With Yield and Aflatoxin of Maize Hybrids Varying in Bt Transgenes.

Environmental factors have been associated with the production of aflatoxin in maize, Zea mays L., and it is inconclusive whether transgenic, Bacillus thuringiensis (Bt), maize has an impact on aflatoxin accumulation. Maize hybrids differing in transgenes were planted in two locations from 2014 to 2017. Yield, aflatoxin, and ear injury caused by corn earworm, Helicoverpa zea (Boddie), and fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), were measured across three groups of hybrids differing in transgenes including near-isogenic hybrids, and water-stressed conditions. The hybrid groups consisted of non-Bt hybrids with no Bt transgenes, a second group with one or more Cry-Bt transgenes, and the third group with vegetative insecticidal Bt protein and Cry-Bt transgenes (Cry/Vip-Bt). Across the six data sets derived from 11 experiments, the Cry-Bt and Cry/Vip-Bt hybrids had less ear injury and aflatoxin on average than non-Bt hybrids. The effects of ear injury on yield and aflatoxin were more prominent and consistent in Corpus Christi, TX, where hybrids experienced more water-limited conditions than in College Station, TX. The trend of increased aflatoxin among hybrids with increased ear injury was further resolved when looking at Cry-Bt and Cry/Vip-Bt isogenic hybrids in Corpus Christi. The results supported that the maize hybrids with the inclusion of Cry-Bt and Cry/Vip-Bt transgenes warrant further investigation in an integrated approach to insect and aflatoxin management in sub-tropical rain-fed maize production regions. Research outcomes may be improved by focusing on areas prone to water-stress and by using hybrids with similar genetic backgrounds.

Photoperiod-Specific Within-Plant Distribution of the Green Stink Bug (Hemiptera: Pentatomidae) on Cotton.

Sampling methods for detecting stink bugs are intensive, time-consuming, and yield variable results. In a 2-yr mark-release-observe experiment, over 500 adult green stink bugs, Chinavia hilaris (Say) (Hemiptera: Pentatomidae), were used to test for variation in nocturnal and diurnal insect distribution patterns on cotton. Field-collected stink bugs were marked or unmarked with nontoxic fluorescent sharpie markers, released, and monitored in cotton fields at peak bloom. Stink bugs were monitored visually during day and night, aided by a handheld blacklight for nighttime observations. Within-cotton distribution insect observations were categorized by plant section (i.e., bottom, middle, and top branches), by fruiting positions and leaf surface, and by concealed or exposed orientation on floral bracts and leaf surfaces. Green stink bugs were primarily distributed on the middle and top branches irrespective of photoperiod, and on bolls in first position from the main stem. Differences in stink bugs observed concealed or exposed on fruiting structures were detected. During daytime, stink bugs were primarily observed inside the bract of bolls, and when detected on leaves concealed on the lower surface. In contrast, stink bugs were primarily outside the bract of bolls at night, and when detected on leaves were exposed on an upper surface. These results support focus on assessing internal boll injury for evaluating stink bug injury to avoid the challenges in stink bug detection observed here, and point to additional study to refine stink bug density estimation when needed.

Development of Economic Thresholds for Sugarcane Aphid (Hemiptera: Aphididae) in Susceptible Grain Sorghum Hybrids.

Sugarcane aphid, Melanaphis sacchari Zehtner (Hemiptera: Aphididae), outbreaks on grain sorghum were first detected in the United States in 2013. The spread of sugarcane aphid across the sorghum-producing regions of North America necessitated increased insecticide use to mitigate economic loss. A field experiment to develop economic thresholds for sugarcane aphid was conducted 15 times across seven locations across the southern United States during 3 yr (2014-2016). Grain sorghum hybrids were evaluated by measuring yield in response to a range of aphid infestations. Yield-aphid population density relationships were described by linear function, which facilitated calculating economic injury levels and economic thresholds. The slopes of the yield-aphid density regressions were significant, negative, and relatively stable across locations, years, and agronomic conditions. The relationships aggregated into two groups, populations that exhibited relatively slow and fast population growth, and common economic injury levels were determined using control costs and market values of grain. Average economic injury levels of 37 and 102 aphids per leaf were most applicable to the two groupings of sorghum/aphid relationships and aphid population growth. Using field-based sugarcane aphid population doubling time estimated from weekly observations of aphid densities, economic thresholds were calculated, ranging from 19 to 132 aphids per leaf across the 15 locations-years. Without site-specific knowledge of a slow-growing aphid population and given cost and market price variability of the system, a 40 aphid per leaf threshold is most prudent to use across the range of hybrid, environmental, and market conditions experienced in this study.

Plant Response and Economic Injury Levels for a Boll-Feeding Sucking Bug Complex on Cotton.

Whole-plant cage field experiments were conducted in 2014, 2015, and 2016 to characterize cotton injury from a species complex of boll-feeding sucking bugs represented by the verde plant bug, Creontiades signatus (Distant) (Hemiptera: Miridae), brown stink bug, Euschistus servus (Say), green stink bug, Acrosternum hilare (Say), and redbanded stink bug, Piezodorus guildinii (Westwood) (Hemiptera: Pentatomidae). Field-collected adult bugs were used to infest cotton plants previously maintained free of insect injury. Plants caged in groups of four were infested at mid-bloom and late-bloom for 7 d with four insect densities: 0 (control), 0.25 bugs per plant, 1 bug per plant, and 2 bugs per plant. Species and water stress conditions varied across years, allowing selective within-year comparisons. Response to feeding resulted in boll injury in the form of lint deterioration and cotton boll rot at mid- and late-bloom stages, and in water limiting and non-water limiting conditions. Although plant injury was apparent across a wide range of conditions, subsequent yield decline attributed to insect feeding was seen primarily under water limiting conditions when plants were infested at mid-bloom. For these conditions, significant yield-insect density relationships were used to calculate economic injury levels (EILs) for each species. EILs expressed as bugs per plant from lowest to highest were the brown stink bug (0.29-0.31 bugs per plant), redbanded stink bug (0.33), verde plant bug (0.49), and green stink bug (0.50). Given the variability observed among species, species-specific EILs may be used where the injurious species is known and combined for stink bugs (a common EIL of 0.34 bugs per plant) where multiple species occur. Verde plant bug was less damaging and can be considered separately, but its EIL was generally within a range of values for the boll-feeders encountered.