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 ...... 4

Project #2: Insecticide application on western bean cutworm eggs and response of predators to treated eggs ...... 6

Project #3: Investigating the Role of 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 in industrial hemp fields of Nebraska . . . . .14

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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, 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 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

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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) (: ) 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

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• 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

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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).

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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

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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.

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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 communities in western Nebraska corn agroecosystems. 2. Determine the strength of the trophic relationship between spiders and western corn rootworm and western bean cutworm.

Methods: For the first objective of this project, the spider community as well as the abundance of two key pests of corn were evaluated. In 2017, spiders were collected from eight corn fields from May 30 through August 22 while in 2018, spiders were collected from four corn fields from May 31 through August 22. Western bean cutworm (Striacosta albicosta) populations were surveyed in each field through scouting for egg masses. Western corn rootworm (Diabrotica virgifera virgifera) adult abundance was determined with the use of sticky traps. All collected spiders were identified to species level where possible. For the second objective of this project, molecular gut-content analysis was conducted on targeted spider families to determine whether significant predation of insect pests of corn is occurring in the field. In 2019, feeding trials were conducted with the targeted spider families to determine the amount of time prey DNA is detectable in the spiders’ guts. In 2020, the DNA of collected spider specimens was extracted and the resultant samples were evaluated using PCR and gel electrophoresis, which revealed the presence or absence of pest DNA in each sample. Results:

Other 2017 Thomisidae

Gnaphosidae

Spider Family Spider 2018 Linyphiidae

Lycosidae

0% 10% 20% 30% 40% 50% 60% 70% 80% % of All Spiders Collected

Figure 1. Most Abundant Spider Families Collected

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• In 2017, a total of 662 spiders were collected represented by 36 species in 17 genera while 324 total spiders were collected in 2018, comprised of 23 species in 12 genera • For both years, the family Lycosidae, commonly known as wolf spiders, were the majority of all spiders collected (53% in 2017 and 71% in 2018) • Due to their abundance and ground-level cursorial hunting strategy, Lycosidae was considered a potential predator of D. v. virgifera and was subsequently chosen for molecular gut-content analysis

Schizocosa

Immature ocreata Pardosa Schizocosa avida Trochosa Schizocosa retrorsa Tigrosa Schizocosa crassipalpata

Schizocosa aulonia

Schizocosa mimula

Figure 2. Composition of Lycosidae community Figure 3. Composition of Schizocosa (n=555) (n=294)

• For both years combined, a total of 555 lycosids were collected with 21 species in 9 genera represented • Over 50% of collected lycosids belonged to the genus Schizocosa (Figure 2) • Within the genus Schizocosa, two species were dominant: Schizocosa ocreata (77%) and Schizocosa avida (17%) (Figure 3)

Figure 4. The two most common species found in Nebraska corn fields: Schizocosa avida and S. ocreata

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Adults Larvae Pupae 100 80 60 # Lycosidae 40

# Collected # 20 # WCR

0

5-Jul

7-Jun

2-Aug 9-Aug

12-Jul 19-Jul 26-Jul

14-Jun 21-Jun 28-Jun

16-Aug 23-Aug 30-Aug 31-May Collection Date

Figure 5. Lycosid and D. v. virgifera abundance (2018)

• Lycosid and D. v. virgifera abundance through the 2018 season is depicted in Figure 5 to illustrate predator and pest population dynamic relationships. • The final step of this project will be to finalize and statistically analyze community composition and molecular results.

Figure 6. The spiders collected from one pitfall trap in a Nebraska corn field

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Project #4: Modeling the potential global geographic distribution of Striacosta albicosta using MaxEnt

Authors: Poliana S. Pereira, Julie A. Peterson, Rodrigo S. Ramos, Katharine A. Swoboda Bhattarai, Renato A. Sarmento and Marcelo C. Picanço Study Outline: Striacosta albicosta (Smith) (Lepidoptera: Noctuidae), the western bean cutworm, can severely damage corn and dry beans. It occurs in parts of the United States, Canada, and Mexico, having undergone a major range expansion in the past 20 years. Therefore, further introduction and establishment of this pest is of concern. The objective of this research was to determine the regions in the world that are currently suitable for S. albicosta. Information on the occurrence of S. albicosta, corn and dry beans (latitude and longitude) were collected from scientific articles and online databases (like Field Crop News, USDA, GBIF). We considered 19 environmental variables related to temperature and precipitation obtained from the WorldClim dataset (http://www.worldclim.org/bioclim) and one soil sand content from the International Soil Reference and Information Centre (https://www.isric.org/geonetwork). We used the software MaxEnt (version 3.3.3k) to classify areas as suitable or unsuitable for the species based on maximum test sensitivity. We used ArcGIS (version 10.3.1) to extract maps of geographic areas suitable for S. albicosta. Results: The climatic variables that contributed to the distribution of S. albicosta were temperature annual range, annual mean temperature, precipitation of the driest month, mean diurnal range in temperature, precipitation seasonality, sand content and mean annual precipitation (Table 1). Although S. albicosta is currently restricted to North America, our results show suitable or highly suitable areas in regions of South America, Europe, Asia, Oceania and two countries in Africa (Morocco and South Africa). Additional regions of the world presented areas suitable for corn and dry beans production, but most of these areas are not suitable for the establishment of the pest (Figure 1). Our study can be used to help government agencies implement strategies such as inspection and quarantine barriers to prevent entry and establishment in areas still free of S. albicosta. Better understanding of the climatic factors that contribute to current distribution also increase our knowledge of the pest’s biology. Table 1. Environmental variables considered in the niche model for Striacosta albicosta and their average percentage contribution to the model; the values were calculated using 10 repeated runs.

Variable value average Percent Description (variable) (minimum - maximum) contribution

Temperature annual range (°C) 37.71 (22.8 - 47.6) 34.5

Annual mean temperature (°C) 7.68 (2.0 - 17.4) 31.8

Precipitation of the driest month (mm) 53.4 (3 - 94.0) 23

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Mean diurnal range in temperature (°C) 10.31 (8.1 - 18.6) 4.9

Precipitation seasonality 20.3 (7.9 - 98.7) 3.3

Sand content (gravimetric) (%) 43.3 (5.8 - 71.2) 1.5

Mean annual precipitation (mm) 941.9 (248.0 - 1320.0) 1.1

Figure 1. Suitable areas under current climate conditions using MaxEnt model for (A) Striacosta albicosta (western bean cutworm), (B) Zea mays (corn), and (C) Phaseolus vulgaris (dry beans).

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Project #5: Diversity and abundance of arthropods in industrial hemp fields of Nebraska

Authors: Ruby Anderson, Milos Zaric, Andrea Rilakovic, Greg Kruger, and Julie Peterson

Research Outline: Industrial hemp, Cannabis sativa, is in its second year as a commercially available crop in Nebraska. Since this time, there has been a lot of interest in pest and beneficial arthropod populations that may be found in hemp fields, since this information is currently unknown for Nebraska. Finding potential pests is a high priority as industrial hemp is a high value crop with strict pesticide and growing requirements. A general arthropod survey was conducted from July until September of 2020 with samples being collected every other week for a total of five sampling periods. The field was 0.2 ac in size and had 6 sampling sites. For this survey three different types of sampling methods were used. Wet pitfall traps with propylene glycol were set out for 3 days, yellow sticky cards were placed on bamboo poles at the height of the foliage for 3 days, and sweep-net collection was done by using 10 figure-8 sweeps while walking through the plot. Arthropods were then identified to the appropriate level, and some of interest were identified to species. Results: The most common beneficial arthropod taxa were small parasitoid wasps, Carabidae (ground beetles) and Orius insidiosus (minute pirate bugs). The most common potential pest taxa were Thysanoptera (thrips), Aphididae (aphids), and Cicadellidae (plant hoppers). One identified pest of importance was the Eurasian hemp borer, delineana (Walker), which was found throughout the season boring into stems and seeds. This preliminary survey has shown that industrial hemp has a diverse community of arthropods and that there is a high abundance of beneficial arthropods, particularly predators.

Figure 1. a) Yellow sticky trap for collecting in hemp; and b) view of hemp plots early in the season.

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