Progress report for SW21-922
Wireworms, the larval stage of click beetles (Coleoptera: Elateridae), are a major pest of many crops in the Pacific Northwest and Intermountain regions of the USA. In cereals, the foundational crops of the region, prophylactic neonicotinoid seed treatments are presently the only available insecticides to control this pest. Neonicotinoids, however, do not reduce wireworm populations and often fail to protect the crop. Our producers are in dire need for effective alternative management options that fit their regional agricultural practices and that contribute to soil health and sustainability of our agricultural production systems. Moreover, the lack of data on economic losses to wireworms limits agricultural extension expert ability to develop recommendations regarding economic injury levels and action thresholds for this pest in cereals. To address these shortfalls, through a series of on-farm trials and follow-on evaluations, we propose to: i evaluate the effectiveness of brown mustard rotation, and a newly developed concentrated brown mustard seed meal extract, in reducing wireworm damage, ii examine impacts of adoption of these treatments on several soil health parameters, iii develop an early detection method for predicting and estimating economic loss to wireworms, and iv develop extension educational materials for wireworm damage detection, management, and farm profitability implications associated with adoption of these wireworm management strategies. Objectives 1 and 2, as well as the yield aspects of profitability calculations, will be achieved through setting up on-farm research plots in each of the 4 to 5 fields in northern Idaho, southeastern Idaho, and eastern Washington. Farm-scale aerial imaging combined with high resolution wireworm count and yield data will be used to determine the relationship between yield and wireworm pressure at a field scale. This project will result in development of decision-making guidelines and ecologically based pest management tactics that can be cost-effective, and are environmentally benign, sustainable, and most importantly, applicable to cropping systems across the PNW and elsewhere. Findings from this study are of great interest to cereal producers in the PNW and Intermountain West regions. In addition to Idaho and Washington, our findings will be communicated to producers in Oregon and Utah and Montana, with support from Extension specialists in each of those states (see letters of support).
Objective 1. Examine brown mustard, its seed meal and a newly developed concentrated extract in reducing wireworm damage to spring wheat. (Research)
Objective 2. Evaluate the impact of brown mustard manure and its products on soil health parameters, (Research)
Sub-objective 1: Quantify the impact of the green manure, seed meal, and concentrated seed meal extract on soil microbial community abundance and structure.
Sub-objective 2: Determine the potential impact of the green manure and seed meal applications on local entomopathogenic nematodes.
Objective 3. Determine yield effects due to wireworms at the field scale and estimate farm profitability implications of wireworm damage and adoption of the wireworm management strategies in Obj. 1. (Research)
Objective 4. Disseminate findings to stakeholders and promote adoption of successful IPM tactics in affected fields across the region. (Education/Extension)
Table 1 presents timelines for various research and extension activities and the major milestone of this project. Objective 1 includes late-summer/fall planting and incorporation with evaluations harvest extended into spring and summer of the subsequent season. Therefore, two field season replicates are expected to be completed by the end of project in March 2024. Similarly, the field experiments outlined in Objectives 2 and 3 are expected to be completed in two field seasons (2021-2022 and 2022-2023) However, laboratory evaluations for objective 2 may continue into winter 2024. Threshold developments and estimates and the development of an online calculator of economic losses will be finalized by March 2024. Extension activities will continue throughout the life of the project. All co-PIs have extensive experience with the type of research proposed here, and two graduate students hired for the project will work under their supervision in Idaho. By staggering the experiments over time, we expect to complete these objectives within the three-year time-frame. Research and extension manuscript preparations are expected to be initiated at the end of the second year and completed within the proposed time-frame.
Wireworms are key pests of the Pacific Northwest cropping systems resulting in significant losses annually. We hypothesized that brown mustard (Brassica juncea) green manure, its seed meal, and concentrated extract can reduce wireworm populations and subsequent crop damage due to the biocidal effects of their glucosinolate compounds. This hypothesis was developed based on our initial data, which demonstrated the efficacy of brown mustard concentrated extracts can be as high as 70% in the greenhouse. As a part of this project, we will also evaluate any potential effects of mustard and its products on the soil microbial community and the beneficial indigenous entomopathogenic nematodes. Yield effects due to wireworms will be determined, and economic analyses of the evaluated management practices will be conducted by the end of the project.
Objective 1- examine the efficacy of brown mustard, its seed meal, and a newly developed concentrated seed meal extract against wireworms: Trials are being conducted in 5 experimental plot areas in dryland fields located in southern Idaho (3), northern Idaho (1), and eastern Washington (1). All five plot areas have been monitored for the presence of wireworms. Limonius californicus (southern Idaho) and L. infuscatus (northern Idaho and eastern Washington) were the most abundant wireworm species. One of the initial field sites in Ririe had to be removed since enough wireworms were not present. That site was replaced with an additional plot area in Arbon Valley in southeastern Idaho.
Prior to field applications, we demonstrated the effect of brown mustard products on wireworm survival in the absence of environmental stress. For that, we performed a series of greenhouse experiments between 2020 and 2022. Experiments were conducted in square plastic pots (10.16 ´ 10.16 ´ 12.7-cm (W´ L´ H)) filled with 70% sand and 25% peatmoss. The sugar beet wireworm (Limonius californicus) was the target pest in these experiments. The nine treatments pertinent to the field trials included: 1) brown mustard soil-incorporated plant tissue; 2) canola soil-incorporated plant tissue as control; 3) brown mustard seed meal applied at the rate of 8.9 t/ha (8 g/pot); 4) brown mustard concentrated seed meal extract applied at the rate of 2.2 t/ha (2 g/pot); 5) brown mustard concentrated seed meal extract applied at the rate of 3.3 t/ha (3 g/pot); 6) brown mustard concentrated seed meal extract applied at the rate of 4.5 t/ha (4 g/pot); 7) neonicotinoid seed treatment (CruiserMaxx); 8) non-treated control and 9) non-treated no-wireworm control. Treatment 9, non- wireworm control, was added in the experiment to evaluate the germination rate of planted wheat seeds by excluding wireworm disturbance and excluded from statistical analysis due to 100 percent germination. This study was conducted in three time-blocks, with eight replicates per treatment in each time-block (a total of 24 replicates/treatment). Brown mustard (Brassica juncea) and canola (Brassica napus) were planted in pots eight weeks before starting the experiment. At flowering, plants were chopped and mixed into the soil. At the same time, seed meal and concentrated extract of brown mustard were added and incorporated into the soil for respected treatments. All pots were sealed with parafilm for 24 hours. The applied rates were selected based on seed meal efficacy studies in other pest systems (Dandurand et al. 2017). However, since the brown mustard concentrated seed meal extract is a newly developed product, we tried three applications rates. Pots were arranged in a completely randomized design. Wireworm mortality was recorded after four weeks.
Field Study and Treatments: There were eight treatments planned in each location (or plot area; there are now three plot areas in Arbon Valley). Treatments included: 1) winter fallow followed by CruiserMaxx-treated spring wheat; 2) winter fallow followed by non-treated spring wheat; 3) fall brown mustard (Brassica juncea) followed by non-treated spring wheat; 4) winter canola (Brassica napus) followed by non-treated spring wheat; 5) brown mustard seed meal at the rate of 37.8 lb/plot followed by non-treated spring wheat; 6) brown mustard concentrated seed meal extract at the rate of 2.5 gal/plot followed by non-treated spring wheat; 7) winter fallow followed by brown mustard concentrated seed meal extract at the rate of 2.5 gal/plot followed by non- treated spring wheat; and 8) winter fallow followed by Teraxxa-treated spring wheat. Individual plots are 10 ft by 20 ft in size, arranged in a randomized complete block design, with four replicates per treatment. Due to the volume of the needed concentrated extracts, the compound was prepared and shipped from Mustgrow Biologics Corp. Wireworm numbers were estimated in each plot before planting by using solar bait traps (Rashed et al. 2015). Except for one plot area in the Arbon Valley location, winter canola and brown mustard were planted in the first week of September 2021 at the rate of 12 seed/ft in 1-1.5-inch depth (due to the lack of moisture). Brown mustard concentrated extract and seed meal were applied on selected plots in early November 2021. Planted mustard, canola, and applied treatments were incorporated into the soil within two hours after application using a 25-ft disk cultivator. A 2-week interval between extract application and seeding was required to prevent phytotoxicity, so plots were planted with spring wheat during the latter part of May 2022. CruiserMaxx- treated seed and Teraxxa-treated seed will allow us to compare the effects of seed treatments with mustard products on wireworm mortality. Broflanilide (Teraxxa) is a newly registered insecticide in cereal crops (2021) against wireworms, with the suggested mortality effects of more than 90%. The wireworm population were re-evaluated in early June after completing planting operations. Wireworm count, stand count (number of plants), and yield were used to compare treatments.
For 2023, locations were modified following the change of project leaders. The Arbon Valley locations were not continued and in place, sites were added in Moscow, ID and Latah, WA in addition to existing trial locations in Kimberly, ID and Asotin, WA. Oilseed crops were seeded in May of 2022 and terminated in August using discing to a depth of 4 to 6 inches. Seed meals and extract were applied 2 weeks prior to seeding in the spring of 2023. Rather than different timing for the extracts, the extract treatments were modified to incorporate three rates of the material, including 5, 10 and 15 gal/A. Immediately after application of the seed meal and extracts, the products were incorporated by discing to a depth of 4 inches. Spring wheat will be seeded into these plots and measurements of wireworm, microbial activity and yield recorded as described for 2022.
Objective 2- The impact of brown mustard manure and its products on soil health parameters: We proposed two sub-objectives to examine the effects of mustard green manure and extracted products on soil microbial community (Sub-objective 1) and local entomopathogenic nematodes (Sub-objective 2).
In Sub-objective 1, soil samples from experimental plots in all four locations were collected within two weeks of treatment applications in the fall of 2021 to evaluate the immediate effects of mustard products on the resident microbial population. Additional samples were collected from each treatment in the spring of 2022 at the same locations following spring wheat to determine the residual effects of mustard products on microbial communities within the subsequent crop. The second-year sampling was conducted in the spring of 2023 two weeks after treatment application and just prior to seeding spring wheat. Samples were again collected from within the subsequent spring wheat. In each plot, ten core soil samples were collected and homogenized and were lyophilized and stored at -80 ºC. Subsamples were weighed and prepared for phospholipid fatty acid (PLFA) and neutral lipid fatty acid (NLFA) analysis. All of 2021/22 samples have been analyzed and a summary of that data will be reported here. Spring 2023 samples have had pH and percentage of moisture data collected. PLFA and NLFA analysis on spring 2023 samples is in progress.
Sub-objective 2, the impact of mustard product applications on beneficial entomopathogenic nematodes was assessed. Two soil samples were collected from each plot from each plot using a 6-inch augur two weeks after incorporating mustard products into the soil in the spring of 2022 before planting the spring wheat. Soil samples were mixed, a subsample of 250 g of soil was placed in a plastic container, and five waxworms were placed in each container to trap nematodes. After 3 days, dead waxworm larvae were transferred to White traps (White 1927), consisting of one 25 mm petri dish containing wet filter paper inside a large (10 cm) petri dish filled with water to recover nematodes from waxworm cadavers. The number of infective juveniles recovered from a single waxworm in 1 ml suspension was counted, and the average of nematodes recovered was used to estimate the nematode population in each experimental plot in relation to the non-treated control plots.
Objective 3- Determine yield effects due to wireworms: In year 1, a fixed-wind unmanned aerial vehicle (UAV) equipped with a high-resolution RGB camera was flown at 80 m height over a 15-acre section of fields which we have established our experimental plots. The captured RGB images by UAV flights were mosaicked and georeferenced for visualization at field scales (Figure 1). In addition to RGB images, reflectance images were also generated based on multispectral sensor information to compute the normalized difference vegetation index (NDVI). Moreover, satellite images at 10-meter resolution were downloaded and compared with UAV-based images to explore optimal spatial solutions for the project. Our large field-scale evaluations had to be revisited due to unexpected challenges. The first challenge was the extreme heat and drought stress that Idaho dryland production suffered from in 2021, which prevented us from obtaining yield records (yield monitors were unable to accurately record yields below 10 bushels/acre) or characterizing wireworm damage (from drought stress). Most importantly, since the arrival of Teraxxa in the market, nearly all planted small grain acreage is now treated, forcing us to revisit our approach, focusing on obtaining data from plot experiments. We used a 5 x 20 (4 untreated and four treated with fipronil, an insecticide with high efficacy against wireworms) to estimate the economic loss in fields infested with wireworms.
In our mustard plots, RGB images were captured by UAVs at 80-meter height. NDVI was computed, and the calibration effort for reflectance images was made to better characterize wireworm damage. In spring and summer of 2022, two more UAV flights were made, three and eight weeks after plant emergence. According to our ecological survey, three weeks after emergence is the peak of wireworm activity. In the 2022 growing season, again in partnership with growers, additional flights were made around 10 weeks after emergence. At the end of this project, a supply chain assessment will be conducted to identify any barriers to the adoption of the treatments, such as commercial availability or access to mustard seed or the extract.
Objective 4- Disseminate our research findings among producers and stakeholders: We proposed a combination of traditional extension activities along with online services. A summary of our 2021-2022 activities is presented below.
Objective 1. The results of our greenhouse experiments showed that the mortality of wireworms was significantly affected by treatments (F= 5.759, df = 7, 182, p < 0.001). The high application rate of the concentrated brown mustard seed meal extract of 4.5 t/ha (4 g/pot) resulted in the highest wireworm mortality (68%) compared to the non-treated control. Although both brown mustard seed meal and green manure caused significantly higher wireworm mortality (33%) compared to non-treated control (8.7%), their efficacy was considerably lower than concentrated than the concentrated extract treatment. The lower application rates of the concentrated extract (2 or 3 g/pot) resulted in 46% mortality. Canola green manure was also included as a negative control. A mortality rate of 16.7% mortality was found for this treatment, which was not statistically different from the non-treated control.
These results confirmed that brown mustard products could cause wireworm mortality ranging from 33 – 68%. It has been shown that some of the plant species from the Brassicaceae family, such as mustard species release glucosinolate compounds which in the presence of water have biocidal effects on a wide range of pests, including insects, pathogens, and weeds (Dandurand et al. 2017; Mojtahedi et al. 1993; Popova et al. 2017; Williams et al. 1993). However, there are some studies have suggested the efficacy of brown mustard against wireworms (Furlan et al. 2004) and potato cyst nematodes (Dandurand et al. 2017). In our study, brown mustard plant tissue was not as effective as its seed meal or concentrated extract product. Our greenhouse findings suggested that higher concentrations of concentrated seed meal extract (at least 4.5-5 t/ha) would be needed to significantly reduce wireworm numbers.
From wireworm counts conducted within the field sites using traps, relatively low numbers of wireworms were found in 2022. Figure 1 shows the average number of wireworms collected per trap at Arbon B and C. While the values are low, treatments with brown mustard seed meal or extract significantly reduced the number of wireworms per trap compared to the non-treated control. The reduction in wireworm population for the spring applied brown mustard extract was similar to the insecticide seed treatment Terraxa. Incorporation of plant residue from canola, yellow mustard and brown mustard plants did not impact wireworm populations. However, the timing of incorporation of these materials did not coincide with wireworm activity in the soil. Likewise, yellow mustard seed meal did not significantly reduce wireworm populations relative to the non-treated control. While similar trends were observed at the other locations and wireworm populations were greater, there were no significant differences. Additional data collected in 2023 will be needed to strengthen the data set to confirm these reductions in wireworm populations.
Objective 2. In both fall 2021 and spring 2022 samples few differences were observed in fungal, bacterial and total PLFA biomass among the control and brown mustard, yellow mustard and canola incorporated plant material (Table 1). This is most likely due to low germination and establishment of these treatments leading to small amounts of plant biomass being incorporated. However, many significant differences were observed among the seed meal and concentrated seed meal extract treatments compared to the control and incorporated brassica plant treatments. An increase in fungal, bacterial, and total PLFA biomass was observed in the seed meal and concentrated extract treatments compared to the control and brassica plant incorporated treatments at most locations. Fungal biomass in the fall following incorporation was significantly higher in the seed meal treatments at Arbon A, Arbon C, Asotin and Lenville locations (Table 1). Samples in the spring generally showed an increase bacterial and total PLFA biomass associated with the concentrated extracts. The increased fugal biomass observed in the fall was still observed at the spring sampling but to a lesser extent.
The increase in fungal biomass mentioned was also observed in the field within the seed meal treatments at the Lenville location. Visible dense mats of fungal hyphae could be seen associated with incorporated seed meal (Figure 2). In addition to completing PLFA and NLFA analysis on the spring 2023 samples we plan to further investigate the increase in fungal biomass associate with the seed meal treatments. Subsamples have been stored in a -80 ºC and we plan to send them off for sequencing to identify if this is a beneficial or pathogenic fungal species.
Brown mustard concentrated extract significantly affected the efficacy of beneficial entomopathogenic nematodes in our experimental plots (Figure 3). In plots treated with the brown mustard concentrated extract, significantly fewer nematodes were recovered from the infected waxworms compared to the non-treated control. Canola, yellow mustard green manure, and the insecticide Teraxxa did not have a negative impact on the efficacy of the entomopathogenic nematodes in our experimental plots.
Objective 3. Several flights were conducted over experimental fields (Figure 4), and wireworm populations were monitored by placing 1-2 traps per acre. Extreme drought and the widespread use of the newly marketed broflanilide (Teraxxa) by grain producers require us to modify our approach and focus our evaluation on our non-Teraxxa plots only. For the time being, however, we were able to estimate wireworm losses based on data from previous plot experiments in 2019. The experiment included four untreated spring wheat plots and four plots treated fipronil in one of our field sites in eastern Idaho (Ririe, ID). The field data showed wireworm damage in the untreated plots reached up to 10%, while no damage was reported in fipronil-treated plots. The average yield for the untreated plots was 28.2 bu/acre, whereas it was recorded at 41.1 bu/acre for the fipronil-treated plots. This implies a difference in average yields of 12.9 bu/acre between the treated and untreated plots or a yield reduction of 31.3% due to wireworm damage. The USDA World Agricultural Supply and Demand Estimates reports released during the experiment period showed a marketing year average wheat price of $4.73/bu. Using this price and multiplying it by the implied yield losses in fields had 5% incidence of wireworm damage results in a loss of $61/acre. University of Idaho enterprise budgets for Eastern Idaho dryland spring wheat for 2019, for which the used yields and prices were like those used above, show estimated revenues of $237.50/acre. Based on this expected revenue, the estimated losses due to wireworm infestation would have caused revenue losses of over 25%, indicating that interventions to reduce wireworm infestations can substantially benefit wheat farmers. In the following stages of the analysis for objective 3, we will use field-scale data for the brown mustard intervention to make inferences like those above. Combining these field data with cost data for implementing the different types of brown mustard interventions will provide more detailed profitability implications.
Grain was collected from all test sites in 2022 to estimate yield. A summary of the six locations is shown in Table 2. There were very little differences in yield with none of the treatments being significantly different from the non-treated control. However, the brown mustard extract applied in the fall only or both fall and spring resulted in some of the highest yields, as did the canola green manure. Due to wet spring conditions in 2022, application of brown mustard extracts and subsequent tillage was delayed, resulting in later than normal seeding of spring wheat toward the end of May. The late seeding of spring wheat combined with wireworm pressure resulted in very low yields. Addition yield data will be required to from the 2023 trials to make conclusions about the impact of oilseed green manure, seed meal and brown mustard extracts on spring wheat yield in fields infested with wireworm.
Table 2. Average spring wheat yield across all study locations from plots amended with oilseed plant, yellow or brown mustard meal, or brown mustard extract in 2022.
|Non-treated control||20.5 ab|
|Brown mustard plant||21.8 a|
|Yellow mustard plant||21.0 a|
|Canola plant||23.5 a|
|Brown mustard meal||21.3 a|
|Yellow mustard meal||21.8 a|
|Brown mustard extract (fall)||23.0 a|
|Brown mustard extract (spring)||17.5 b|
|Brown mustard extract (fall/spring)||22.0 a|
|Teraxxa control||20.8 a|
Objective 4. Our study activities and outputs are being communicated to the regional stakeholder via several venues, especially the northern and southern Idaho cereal schools and field days. Funding support through Western SARE is acknowledged in all presentations (one exception of omission error). We also communicated findings through published reports and abstracts. We have one peer-reviewed factsheet in preparation.
Education and Outreach
Rashed, A., A. Nikoukar, S. Henricks, & K. Andrews. The challenges and future of integrated pest management of wireworms (Coleoptera: Elateridae). Symposium presentation. Entomological Society of America Annual Meeting, Vancouver, Canada, November 2022.
Nikoukar, A., I. Popova, K. Schroeder, J. Hansen & A. Rashed. Efficacy Evaluation of Yellow and Brown Mustard Concentrated Extract Against Sugar beet wireworm, Limonius californicus (Coleoptera: Elateridae), in Wheat: 81st Annual Pacific Northwest Insect Management Conference, January 2022. Online Oral Presentation.
Nikoukar, A. Integrated pest management of sugar beet wireworm (Limonius californicus). Entomology, Plant Pathology and Nematology Seminar. Moscow, ID, October 2021.
Rashed, A., Aphids and wireworms of the PNW: where they are and how to manage them. Northern Idaho Cereal School, January 2022.
Rashed, A., Pests of Small Grains. Wireworms of the PNW- Where they are and how to manage them. Southern Idaho Cereal School, February 2022.
Randall, J. R., Nikoukar, A., Sadeghi, R., Odubiyi, S., Rashed, A., & Popova, I. The Use of Wireworms As Bioindicators for Monitoring Biopesticides’ Fate in Soil [Abstract]. ASA, CSSA, SSSA International Annual Meeting, Salt Lake City, UT, 2021.
Nikoukar, A., Popova, I., Rashed, A. 2021. Sugar Beet Wireworm (Limonius californicus) Mortality in Response to Yellow and Brown Mustard Green Manure. p. 19-20. In: Dryland Field Day Abstracts: Highlights of Research Progress (eds. S. Crow, B. Schillinger, K. Schroeder, D. Finkelnburg, A. Rashed, S. Philips, and D. Satur). Idaho Agricultural Experiment Station Technical Report UI-2021-1.
Nikoukar, A. Popova, I. Schroeder, K. Hansen, J. Rashed, A. 2022. Efficacy Evaluation of yellow and brown Mustard concentrated extract against sugar beet wireworm, Limonius californicus, in wheat. 81st Annual Pacific Northwest Insect Management Conference Research Reports. Pp. 55-57.
Project website: Wireworm Management System (uidaho.edu)
A. Rashed Laboratory website: Soil Health & Pest Management Practices – Welcome to the Southern Piedmont Entomology Laboratory (vt.edu)
Education and Outreach Outcomes
- Cultural practices