Evaluating invasion risk and population dynamics of the brown marmorated stink bug across the contiguous United States.

BACKGROUND: Invasive species threaten the productivity and stability of natural and managed ecosystems. Predicting the spread of invaders, which can aid in early mitigation efforts, is a major challenge, especially in the face of climate change. While ecological niche models are effective tools to assess habitat suitability for invaders, such models have rarely been created for invasive pest species with rapidly expanding ranges. Here, we leveraged a national monitoring effort from 543 sites over 3 years to assess factors mediating the occurrence and abundance of brown marmorated stink bug (BMSB, Halyomorpha halys), an invasive insect pest that has readily established throughout much of the United States. RESULTS: We used maximum entropy models to estimate the suitable habitat of BMSB under several climate scenarios, and generalized boosted models to assess environmental factors that regulated BMSB abundance. Our models captured BMSB distribution and abundance with high accuracy, and predicted a 70% increase in suitable habitat under future climate scenarios. However, environmental factors that mediated the geographical distribution of BMSB were different from those driving abundance. While BMSB occurrence was most affected by winter precipitation and proximity to populated areas, BMSB abundance was influenced most strongly by evapotranspiration and solar photoperiod. CONCLUSION: Our results suggest that linking models of establishment (occurrence) and population dynamics (abundance) offers a more effective way to forecast the spread and impact of BMSB and other invasive species than simply occurrence-based models, allowing for targeted mitigation efforts. Implications of distribution shifts under climate change are discussed. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Altering Planting Date to Manage Melanaphis sacchari (Hemiptera: Aphididae) Populations in Sweet Sorghum.

Melanaphis sacchari Zehntner is a new pest of sweet sorghum in the United States, with the potential to cause complete crop failure. In Kentucky, sweet sorghum is normally planted in early May and harvested in late August or September. Planting sweet sorghum earlier in the season may avoid damaging levels of M. sacchari that develop in late summer. In a 2-yr field study, three different planting dates separated by a month (April, May, and June) were tested for their effect on M. sacchari densities and sweet sorghum yield. April (early) planted sweet sorghum was grown in greenhouses and transplanted to the field. May (mid) and June (late) planted sweet sorghum were direct seeded in the field. Melanaphis sacchari population densities were evaluated weekly starting in June. Sweet sorghum was harvested at the onset of the hard dough stage. Plots were split into two subplots, insecticide or noninsecticide, in the second year to control for planting date effect on yield. Early-planted sweet sorghum had lower aphid densities, but had lower yield relative to mid-planting date, which had the highest yield. Insecticide drenches in 2019 reduced cumulative aphid days in mid-plantings and late plantings, but did not significantly affect yield within planting dates. Seeding sweet sorghum earlier can reduce M. sacchari densities; however, this method alone may not provide the highest yields. We documented that the recommended planting date (May) for Kentucky produced the highest yield.

Supplemental Foods Affect Energetic Reserves, Survival, and Spring Reproduction in Overwintering Adult Hippodamia convergens (Coleoptera: Coccinellidae).

For insects that overwinter as adults, winter food resources may affect subsequent spring reproduction and abundance. We tested if provision of food supplements to overwintering adult Hippodamia convergens (Guerin) increased energy reserves, winter survival, and spring reproduction. During 2015-2016, H. convergens adults were placed in field cages in December; adults in each cage received water, Acyrthosiphon pisum (Harris) (Hemiptera: Aphididae), Ephestia kuehniella (Zeller) (Lepidoptera: Pyralidae) eggs, bee pollen, wheast protein, sugar, honey, or no food (control). In 2016-2017, treatments were reduced to sugar, bee pollen, A. pisum with E. kuehniella eggs, and no food (control). Adults were sampled to quantify weight, lipid, carbohydrate, and protein content. In 2015-2016, A. pisum and E. kuehniella eggs increased adult weight and protein content, but adult carbohydrate content was reduced by A. pisum and wheast protein treatments. Adults receiving honey and sugar supplementation had higher lipid and carbohydrate content relative to controls. The number of live individuals at the end of the experiment in March 2016 did not differ among treatments. In 2016-2017, winter prey supplements had the greatest effect on protein content, weight, and number of live adults recovered, whereas sugar supplementation increased lipid and carbohydrate content, and number of live adults recovered. Spring reproduction of surviving pairs was evaluated among treatments in March 2017. Prey supplementation in 2016-2017 increased the number of eggs laid and decreased preoviposition period, and food treatment did not affect fertility. Our results indicate that prey and sugar resources improve the overwintering success and spring reproduction of H. convergens.

Preference of Peponapis pruinosa (Hymenoptera: Apoidea) for Tilled Soils Regardless of Soil Management System.

Concerns about global pollinator declines have placed a growing focus on understanding the impact of agriculture practices on valuable native pollinators in these systems. Cultivation practices such as tillage disturb agroecosystems and can have negative impacts on ground-nesting pollinators. The squash bee, Peponapis pruinosa (Say), is a ground-nesting specialist pollinator of Cucurbita (Cucurbitaceae) crops (i.e., pumpkins and squash) that often nests in agricultural fields and thus may be vulnerable to these practices. We investigated the impact of tillage on nesting behavior of P. pruinosa in plasticulture and strip-tilled squash systems. We used choice experiments to test nesting substrate preference and nesting success of caged P. pruinosa in two soil tillage systems: strip tillage and plasticulture. The strip tillage system comprised two tillage zones (strip-tilled row with no-till edges), and the plasticulture system comprised two tillage zones (plastic bed and conventional tillage edge). The results of our study indicate that P. pruinosa nesting density did not significantly differ between the strip tillage and plasticulture systems. Within each system, P. pruinosa preferred excavating nests in the most disturbed soil zones (strip-tilled row and conventionally tilled edge). In the strip tillage system, the strip-tilled row had significantly more nests than the no-till edge. Results of these studies suggest that soil tillage practices can influence P. pruinosa nesting choice and production practices should be considered when developing a pollinator protection plan.

Evaluation of native bees as pollinators of cucurbit crops under floating row covers.

Production of cucurbit crops presents growers with numerous challenges. Several severe pests and diseases can be managed through the use of rotation, trap cropping, mechanical barriers, such as row covers, and chemical applications. However, considerations must also be made for pollinating insects, as adequate pollination affects the quantity and quality of fruit. Insecticides may negatively affect pollinators; a concern enhanced in recent years due to losses in managed Apis melifera L. colonies. Row covers can be used in place of chemical control before pollination, but when removed, pests have access to fields along with the pollinators. If pollination services of native bees could be harnessed for use under continuous row covers, both concerns could be balanced for growers. The potential of two bee species which specialize on cucurbit flowers, Peponapis pruinosa Say and Xenoglossa strenua Cresson, were assessed under continuous row covers, employed over acorn squash. Experimental treatments included plots with either naturally or artificially introduced bees under row covers and control plots with row covers either permanently removed at crop flowering, or employed continuously with no added pollinating insects. Pests in plots with permanently removed row covers were managed using standard practices used in certified organic production. Marketable yields from plots inoculated with bees were indistinguishable from those produced under standard practices, indicating this system would provide adequate yields to growers without time and monetary inputs of insecticide applications. Additionally, application of this technique was investigated for muskmelon production and discussed along with considerations for farm management.

Predator-prey trophic relationships in response to organic management practices.

A broad range of environmental conditions likely regulate predator-prey population dynamics and impact the structure of these communities. Central to understanding the interplay between predator and prey populations and their importance is characterizing the corresponding trophic interactions. Here, we use a well-documented molecular approach to examine the structure of the community of natural enemies preying upon the squash bug, Anasa tristis, a herbivorous cucurbit pest that severely hinders organic squash and pumpkin production in the United States. Primer pairs were designed to examine the effects of organic management practices on the strength of these trophic connections and link this metric to measures of the arthropod predator complex density and diversity within an experimental open-field context. Replicated plots of butternut squash were randomly assigned to three treatments and were sampled throughout a growing season. Row-cover treatments had significant negative effects on squash bug and predator communities. In total, 640 predators were tested for squash bug molecular gut-content, of which 11% were found to have preyed on squash bugs, but predation varied over the season between predator groups (coccinellids, geocorids, nabids, web-building spiders and hunting spiders). Through the linking of molecular gut-content analysis to changes in diversity and abundance, these data delineate the complexity of interaction pathways on a pest that limits the profitability of organic squash production.