Erin W. Hodgson

European corn borer, Ostrinia nubilalis (Lepidoptera: Crambidae), remains an important pest of corn and several other vegetable and field crops across North America despite substantial population declines following widespread adoption of Bacillus thuringiensis (Bt) plant-incorporated protectant (PIP) corn. Recent reports of field resistance to multiple Bt proteins in Canada and the United States highlight the need to reassess current management practices and reestablish active monitoring for this historically destructive species. This manuscript provides an updated synthesis of European corn borer biology, ecology, host range, injury patterns, and movement behavior, emphasizing traits that influence risk and management outcomes in modern production systems. We summarize current detection approaches, including pheromone trapping, degree-day models, and targeted scouting strategies. Management recommendations integrate cultural practices, abiotic mortality factors, biological control, chemical control, and PIP stewardship, with particular attention to resistance monitoring and refuge compliance. Collectively, these updates underscore the continued importance of European corn borer as a dynamic pest whose management requires coordinated surveillance, adherence to integrated pest management principles, and sustained trait stewardship to preserve the long-term efficacy of Bt technologies across North America.

Dectes stem borer, Dectes texanus LeConte, is native to North America and is an economically important pest of sunflower and soybean across the US Dectes stem borer reached the status of an economical pest of sunflower and soybean during the 1970s. But this impact was often isolated and did not affect the entire production acres of these crops. In recent years, some states, including Iowa, Kansas, Minnesota, and South Dakota have observed an increase in Dectes stem borer pressure in soybean. Although the sunflower acreage varies by state, infestations of Dectes stem borer are common and may affect a large proportion of plants. In most soybean-producing states, severe Dectes stem borer infestations are sporadic but infestations that are not economical are common. The larvae feed on the central pith core of the host plant stem, and their girdling behavior can cause pre-harvest lodging that results in yield loss. Stem feeding can also cause 0% to 17% yield loss in soybean but causes negligible yield loss in sunflower. This document reviews the existing knowledge on Dectes stem borer ecology, biology, and management in soybean and sunflower. Emerging issues of this insect pest are discussed. It specifically focuses on developing integrated management tools to reduce insecticide selection pressure and promote economic management.

Corn and soybeans account for most of the agricultural land use in Iowa. Farmers must manage insect pests feeding on these crops throughout the growing season. Western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), and soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), are currently considered the most important pests of corn and soybean, respectively, in Iowa. We explore the rates at which genetic resistance has developed in these pests, tactics to delay resistance evolution, and the relative success of these methods. The documented occurrence of Bt-resistant (Bacillus thuringiensis Berliner) western corn rootworm in Iowa is greater than for pyrethroid-resistant aphids. The perceived risk of resistance and adoption of insect resistance management strategies by farmers for each pest may be more critical than which pest has evolved resistance faster. While farmers are required to practice insect resistance management when using Bt corn for western corn rootworm, similar requirements do not exist for using insecticides for soybean aphid. We suggest that more robust insect resistance management strategies along with integrated pest management practices need to be adopted for both species. Specifically, for soybean aphid, scouting and monitoring soybean fields throughout the summer and following the economic threshold to decide on the need for foliar insecticide applications is strongly recommended. For western corn rootworm, insect resistance management strategies, such as crop rotation and the mandatory use of refuge when planting Bt corn are recommended. Farmers’ compliance to insect resistance management and integrated pest management practices impacts the rates of resistance evolution to management tactics for these pests.

Corn is one of the major commodities in the United States, and is grown for fuel, feed, and food around the world. Much of the production is centered in the Midwest, but corn is grown throughout the country and has a national production value of $91.7 billion. Because of the substantial national economic impact of corn production, as well as the profitability of individual farming operations, crop protection from pests is critical. Corn is most vulnerable during ear and kernel formation, and pest infestations during this time can have a substantial impact on grain quality and yield. Detecting pests is one of the most important components of integrated pest management, and regular scouting can allow farmers to make timely management decisions for pests in corn. However, farmers and crop consultants sometimes do not notice ear-feeding pests of corn until the fall, or near harvest, when pests are nearly done feeding or have vacated the ear. When this happens, it can be difficult to diagnose the problem, which can be important for assessing management tactics that were used in the field during the current growing season or making decisions for the following growing season based on pest activity in the field. This article provides profiles of common ear-feeding pests, with written descriptions and photographs of typical injury to corn ears for those pests.

Twenty years after the arrival of soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), in the United States, it remains the most economically important arthropod pest of soybean in the Upper Midwest Region. After years of repeated and sustained insecticidal pressures placed on the aphid, resistance to the pyrethroid class of insecticides has been documented in multiple years over a large geographic area. In this study, the fitness of aphid isolates displaying resistant and susceptible phenotypes to λ-cyhalothrin were compared within several experiments over three soybean-growing seasons. Rates of population increase were evaluated on whole plants in the greenhouse, intrinsic rates of increase were calculated from leaf discs in the laboratory, and aphid size and asymmetry were compared through tibial measurements. No evidence of a fitness cost associated with the resistant phenotype was seen in any of our experiments. In contrast, individual resistant isolates occasionally supported significantly higher fitness values than some susceptible isolates. Additionally, a pooled analysis comparing resistant and susceptible phenotypes across years and isolates revealed that, on average, the resistant phenotype had significantly higher fitness values than the susceptible phenotype in most experiments. The lack of reproductive fitness costs associated with the pyrethroid-resistant phenotype raises concerns for longevity of pyrethroid use in soybean aphid management.

Spectral remote sensing has the potential to improve scouting and management of soybean aphid (Aphis glycines Matsumura), which can cause yield losses of over 40% in the North Central Region of the United States. We used linear support vector machines (SVMs) to determine 1) whether hyperspectral samples could be classified into treat/no-treat classes based on the economic threshold (250 aphids per plant) and 2) how many wavelengths or features are needed to generate an accurate model without overfitting the data. A range of aphid infestation levels on soybean was created using caged field plots in 2013, 2014, 2017, and 2018 in Minnesota and in 2017 and 2018 in Iowa. Hyperspectral measurements of soybean canopies in each plot were recorded with a spectroradiometer. SVM training and testing were performed using 15 combinations of normalized canopy reflectance at wavelengths of 720, 750, 780, and 1,010 nm. Pairwise Bonferroni-adjusted t-tests of Cohen’s kappa values showed four wavelength combinations were optimal, namely model 1 (780 nm), model 2 (780 and 1,010 nm), model 3 (780, 1,010, and 720 nm), and model 4 (780, 1,010, 720, and 750 nm). Model 2 showed the best overall performance, with an accuracy of 89.4%, a sensitivity of 81.2%, and a specificity of 91.6%. The findings from this experiment provide the first documentation of successful classification of remotely sensed spectral data of soybean aphid-induced stress into threshold-based classes.

Soybean gall midge, Resseliella maxima Gagné (Diptera: Cecidomyiidae), is a newly identified pest confirmed on soybean, Glycine max (L.) Merr. (Fabales: Fabaceae). To date, soybean gall midge has been found in Nebraska, Iowa, South Dakota, Minnesota, and Missouri, and has caused severe economic loss to commercial fields since 2018. Much is still unknown about this pest, so research efforts have been focused on biology and management. Larvae feed on the inside of the stem just above the soil line and are difficult to access and time-consuming to sample. In order to accelerate nondestructive sampling efforts, we developed an injury rating system to quantify the severity of plant injury from soybean gall midge larvae. Research plots from 2019 and 2020 in Iowa and Nebraska were evaluated for injury throughout the growing season and yield was measured. Our objective was to describe the relationship between injury severity and yield loss caused from soybean gall midge. A nonlinear regression model was developed to validate our injury rating system and to express the relationship between season long injury severity and yield loss. Results from our analysis indicate the injury rating system we developed correlates well with yield loss caused by larvae and may be an important tool for understanding the economic impact of this emergent pest of soybeans.

The north central state of Iowa is heavily dominated by agriculture, with limited nesting and foraging habitat for wild and managed pollinators. This region has been identified as critical for pollinator conservation for bees and non-bee species (e.g., monarch butterfly [Danaus plexippus]). Pollinator sustainability (i.e., wild bee conservation and sustainable beekeeping) relies upon management decisions by beekeepers, farmers, and landowners, but it is unclear if these stakeholders are aware of and use best practices. We present results of surveys administered to Iowan beekeepers, farmers, and landowners after extension programming on best management practices for sustaining honey bees (Apis mellifera) and other pollinators. Results show beekeepers, farmers, and landowners believe implementing pollinator-friendly practices is important. However, knowledge of tools to implement these practices, such as registering apiaries to avoid pesticide drift or cost-share programs for establishing habitat on their land, was very low. These results suggest opportunities exist for connecting beekeepers seeking higher quality apiaries with landowners that have established habitat with added floral resources. Further, we reviewed practices that reconstruct tallgrass prairie with support of federal cost-share funds, specifically CP42 and CP43 of the USDA’s conservation reserve program. Overall, we document strong support and enthusiasm for pollinator-friendly practices in Iowa but note gaps in knowledge of practices that are most effective and what tools are available to implement them. These results suggest a way for pollinator extension programs to address these knowledge gaps in a receptive group of beekeepers, farmers, and landowners.

Corn, Zea mays L. (Cyperales: Poaceae), production is essential to Iowa’s economy and provides food, feed, and fuel beyond the state. Farmers face a number of challenges in corn production, including insect pests, and understanding farmers’ perceptions and concerns is critical for extension personnel to provide adequate and relevant programming. The Iowa State University Agriculture and Natural Resources Crops Team conducted a survey of Iowa farmers and agribusiness professionals during the 2019–2020 extension season. The goal was to understand farmer perceptions of corn pests and whether farmers experienced challenges with resistance to Bt traits or insecticides. Additionally, we aimed to realize farmers’ confidence in developing resistance management plans and discussing those needs with their input suppliers and advisors. Our survey revealed that northern corn rootworm, Diabrotica barberi Smith & Lawrence (Coleoptera: Chrysomelidae), was the pest of greatest concern across the state. People were generally more concerned about belowground Bt trait performance than aboveground traits, though only 12% of respondents reported Bt trait failure for corn rootworms. In general, people were not concerned about the performance of seed treatments or soil- or foliar-applied insecticides. Farmers generally felt very confident in developing a resistance management plan and discussing their needs with their advisors. The results of this survey will be used to target extension programming throughout the state and increase confidence for farmers and agribusiness employees to discuss resistance management plans together.

Soybean is an established crop with a high production value in the United States. The insects that utilize soybean as a food source have changed drastically over the last 20 yr. Much of the extension literature summarizing pest species distribution and abundance is out of date. This article provides profiles for five common soybean caterpillars, including description, life cycle, and injury to plants.