Agroecosystems Entomology Lab Research Summary 2020 West Central Research Extension and Education Center North Platte, Nebraska Contents Introduction: Agroecosystems Entomology Lab . 3 Project # 1: Chemigation efficacy and spray deposition on corn for the control of western bean cutworm . 4 Project #2: Insecticide application on western bean cutworm eggs and response of predators to treated eggs . 6 Project #3: Investigating the Role of Spiders in Integrated Pest Management for Biological Control of Nebraska Crop Pests . 9 Project #4: Modeling the potential global geographic distribution of Striacosta albicosta using MaxEnt . 12 Project #5: Diversity and abundance of arthropods in industrial hemp fields of Nebraska . .14 2 Agroecosystems Entomology Lab The Agroecosystems Entomology Lab, located at the West Central Research & Extension Center, pursues research questions addressing the ecology and management of agricultural pests with an emphasis on practical applications for integrated pest management in field crops. Research projects may address a variety of themes, such as food web dynamics, insect behavior, compatibility of pest control strategies (including biological control by natural enemies), and resistance management. Research will support extension programming to develop proactive educational programs in IPM of arthropod pests of field crops grown in west central Nebraska. Julie A. Peterson, Ph.D. Associate Professor & Extension Specialist University of Nebraska–Lincoln Department of Entomology West Central Research & Extension Center 402 West State Farm Road North Platte, NE 69101 Office Phone: 308-696-6704 Twitter: @PetersonInsects Agroecosystems Entomology Lab & Western Bean Cutworm Central Webpage 3 Project #1: Chemigation efficacy and spray deposition on corn for the control of western bean cutworm Authors: Andrea Rilaković, Poliana S. Pereira, Samantha R. Daniel, Bruno C. Vieira, Jeffrey A. Golus, Greg R. Kruger, Brian Krienke, Turner Dorr, Daran R. Rudnick, and Julie A. Peterson The western bean cutworm, (Striacosta albicosta Smith) (Lepidoptera: Noctuidae) is a critical pest in corn that can cause significant yield loss by feeding on the developing ears. In Nebraska, one of the main practices used against this pest is aerial insecticide application, although some producers apply insecticides through the irrigation system, known as chemigation. However, application failures have been reported with both methods, and there are limited data available to support recommendations for chemigation targeting western bean cutworm (WBC). Therefore, field studies were conducted at the Brule South Water Resources Lab under center pivot irrigation, to determine the efficacy of chemigation using different insecticides and application methods on the control of WBC and determine spray deposition. ❖ The main goal of this study was to determine spray deposition and efficacy of chemigation on control of western bean cutworm in corn. Results • PTSA application results As expected, jars treated with 0.75 ac-in of water and PTSA (a tracer dye added to the water), had about 3 times more PTSA deposition compared to 0.25 ac-in. However, the same trend was not observed for leaf deposition. Leaves can hold a certain application volume, everything above that will end up going to the soil. This result indicated that 0.25 ac-in carrier volume provided greater deposition efficiency compared to 0.75 ac-in. Table 1. PTSA deposition on jars and leaves 4 • Insecticide application study Table 2. Insecticide study treatment list Average feeding damage to ears from WBC was measured 28 days after insecticide application. The control treatments were the only ones that were significantly different when comparing the 0.25 to 0.75 acre-inches. Reason for this is unknown, but it could be due to the increased amount of water benefitting the western bean cutworm. Within the 0.25 ac-in carrier volume, Prevathon 14 fl. oz/ac and Brigade 6.4 did the best at reducing ear feeding injury. However, Brigade 2.1 compare to 6.4 did not differ after statistical analysis but numerical differences here presented are still important to consider for a yield loss and recommendations to growers. Within the 0.75 ac-in carrier volume, a similar pattern was observed, with Prevathon performing the best and the higher rate of Brigade numerically but not statistically reducing injury. Figure 1. Results for ear assessment 5 Project #2: Insecticide application on western bean cutworm eggs and response of predators to treated eggs Authors: Rachel Abbott (undergraduate student), Samantha Daniel (technician/MS student), Andrea Rilaković (MS student), Bruno Vieira (post-doctoral scholar), Greg Kruger (associate professor), and Julie Peterson (associate professor) Study Outline: Larvae of Striacosta albicosta, commonly known as western bean cutworm, feed on corn and dry beans. Treatment of this pest relies heavily on insecticide application. There is a short window of time recommended for chemical application between when eggs are about to hatch and when larvae move into the protection of the plant. The presence of multiple stages of larvae at a time also increases the difficulty of choosing when to treat. Even though these insecticides are intended to target larvae, word of mouth among farmers said that some insecticides possibly displayed ovicidal properties. If true, this could be a serious advantage. The objective of this research was to determine if insecticides commonly used on larvae also possess ovicidal properties and the effects of those insecticides on predators of western bean cutworm eggs. A total of 240 S. albicosta egg masses, half younger and white in color with the other half a few days older and tan in color (Fig. 1), were randomly assigned to a control group or one of five insecticides at both high and low labeled rates (Table 1). A spray chamber was used to replicate aerial application (Fig. 2). Eggs in each mass were individually counted before treatment and every 4-5 days after application for two weeks to record the number of dead eggs, hatched larvae, and dead larvae. Another experiment was also done to determine the effects of offering seven spotted and convergent ladybird beetles a choice between both treated and untreated egg masses. Each ladybird beetle was placed in a petri dish with two egg masses, one of which was treated with insecticide and the other with water only, a piece of cotton moistened with water, and a line drawn in the center between the two egg masses (Fig. 5). Behaviors such as activity level, contact with egg masses, and apparent disorientation were recorded using a camera system for 24 hours as well as counting the number of eggs eaten after by each ladybird beetle. Figure 1: Western bean cutworm egg Figure 2: Spray chamber for application of masses at various ages. insecticides to egg masses (Souza et al. 2019, Scientific Reports). 6 Results: Insecticides did not impact the total number of eggs hatched. However, results suggest residual larvicidal effects after hatching such as seen in the white eggs eight days after treatment (Fig. 3) where the control groups had the highest proportion of larvae alive while Mustang Maxx, Brigade, Prevathon, Steward 6.0, and Hero had significantly more dead larvae. There was also no evidence suggesting that ladybird beetles were able to detect or avoid egg masses treated with insecticide. Sublethal behavioral effects were observed depending on the type of insecticide treatment and ladybird beetle species with ladybird beetles given egg masses treated with Mustang Maxx spending significantly more time disoriented and grooming excessively than those with Prevathon (Fig. 4-5). While there was no evidence of ovicidal effects in any of the insecticides tested, residual insecticide still present when eggs hatched impacted survival rates of the larvae. It is useful to consider effectiveness of residual insecticide for controlling hatched larvae when determining which treatment to use and to minimize harm to natural predators of S. albicosta, such as ladybird beetles (Fig. 6). Table 1: Insecticide assigned to each treatment number, its active ingredient/s, and the rate applied (fluid ounces per acre). Figure 3: White eggs eight days after treatment with control groups showing the highest proportion of larvae alive while Mustang Maxx, Brigade, Prevathon, Steward 6.0, and Hero had significantly more dead larvae5 7 Figure 4: Ladybird beetle video results of time spent disoriented and grooming for seven spotted and convergent ladybird beetles offered Mustang Maxx and Prevathon-treated eggs. More time was spent disoriented and grooming in trials with Mustang Maxx compared to Prevathon. In each trial, seven spotted ladybird beetles spent more time disoriented and grooming than convergent ladybird beetles, possibly due to their round shape making righting themselves after getting turned upside down more difficult. Figure 5: Ladybird beetle in a Petri dish Figure 6: Convergent ladybird beetles can with treated (T) and untreated (U) western be an important species that feeds on bean cutworm egg masses. western bean cutworm egg masses in corn fields. 8 Project #3: Investigating the Role of Spiders in Integrated Pest Management for Biological Control of Nebraska Crop Pests Authors: Samantha R. Daniel (M.S. Project), Robert Wright, Eileen Hebets, Julie A. Peterson, Objectives: 1. Describe the diversity and abundance of spider communities in western Nebraska corn agroecosystems. 2. Determine the strength of the trophic