Project Details:

Title:
Development of Genetic, Chemical and Population-Based Tactics to Manage Key Kansas Soybean Insect Pests

Parent Project: This is the first year of this project.
Checkoff Organization:Kansas Soybean Commission
Categories:Insects and pests
Organization Project Code:1726
Project Year:2017
Lead Principal Investigator:C Michael Smith (Kansas State University)
Co-Principal Investigators:
Brian McCornack (Kansas State University)
William Schapaugh (Kansas State University)
Jeff Whitworth (Kansas State University)
Keywords:

Contributing Organizations

Funding Institutions

Information and Results

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Project Summary

Infestations of the soybean stem borer, Dectes texanus, were first reported in Kansas in 1985 (Buschman and Sloderbeck 2010). Borer larval infestations of 50 to 80 % cause severe lodging problems in north-central and southwestern Kansas, (Sloderbeck et al. 2003). Damage severity ratings for soybean stem borer increased in one-third of Kansas counties from 1985 to 2015. Expansion may be due to reduced availability of alternate host plants such as wild sunflower, increased borer larvae winter survival, increased soybean acreage, or increased adoption of non-tillage practices (Campbell 1980, Buschman and Sloderbeck 2010). Though interest in management and control of stem borer has increased, strategies remain limited.

For example, early harvesting has helped reduce some yield losses if infestations are detected early in the growing season (Buschman and Sloderbeck 2010). Commercial registered insecticides do reduce adult stem borer numbers, but several applications are necessary for better results, making this option cost-prohibitive. Fipronil seed treatments effectively kill larvae in the plant stem, but this insecticide remains commercially unregistered for use on soybean stem borer (Sloderbeck and Buschman 2011). To date, no U. S. soybean cultivars contain genetic traits for resistance to soybean stem borer larval damage. However, previous KSC-funded research has identified borer resistance in plant introduction PI 165673 (Niide et al. 2102), and has shown that if a cultivar containing PI 165673 resistance can be developed it will greatly benefit Kansas producers (Aguirre-Rojas 2013). In addition, the insect RNAi gene silencing technique has recently been shown to work in a close relative of soybean stem borer and has been used to kill western corn rootworm beetles in corn and Colorado potato beetles in potato (Baum and Roberts 2014, Zhang et al. 2015). RNAi gene silencing in soybean stem borer larvae is a new viable way to create borer-resistant plants, and promising results of experiments in late 2015 and 2016 suggest this may be possible. Results from co-PD McCornack's group demonstrate that adult colonization patterns vary between fields and through time and need to be better predicted.

Project Objectives

Objective 1. Create soybean plants resistant to soybean stem borer by inserting borer RNA into soybean plants to interfere (RNAi) with genes necessary for borer survival.
Objective 2. Improve insecticide efficacy by using host plant and other environmental cues or conditions to adjust timing and placement of application.
Objective 3: Expand web pages and other educational materials associated with soybean insects.

Project Deliverables

Procedures for Objective 1. Sub-objective 1 is to verify gene silencing by RNAi in soybean stem borer larvae by silencing Lac2, a gene required for borer skin. Sub-objective 2 is to determine if silenced Lac2 or other beetle membrane proteins can be moved to soybean plants and expressed at levels sufficient to kill stem borer larvae and/or adult beetles. Progress on Sub-objective 1 by Lina Aguirre, the PhD student conducting this research, has included developing a laboratory stem borer colony for experiments to test the effects of silencing Lac2; isolating stem borer Lac2; injecting larvae with silenced Lac2; and assessing changes in larvae and adults emerging from larvae. In a Sub-objective 1 replicated study just completed, 95% of stem borer larvae injected with RNAi silenced Lac2 died as larvae or beetles. A few treated larvae have become adults, and those have atrophied wings, un-tanned cuticle, curled antennae, do not feed and have died. Additional replicated experiments will be conducted with RNAi injected larvae to verify results of the first study. Sub-objective 2 experiments will be conducted in FYI9.
Procedures for Objective 2. Sub-objectives are: 1) incorporate key factors influencing adult pest distribution patterns into treatment placement decisions for stem borer and other important soybean pests, 2) devise and update spray recommendations to optimize efficacy of newer chemistries that target soybean stem borer, stink bugs, and soybean podworm and 3) determine the economic value of reducing insecticide coverage at mitigating losses by key pests in Kansas soybean. Due to year-to-year and field-to-field variability in pest abundance and community composition, we propose repeating experiments in several locations over the next 2 years of this project. This is especially important when management recommendations will be direct outcomes from this work. We will continue to use several geostatistical techniques to model the spatial distributions of key pests through time and compare infestation patterns with targeted insecticide treatments, either as border treatments or large-scale insecticide trails. We will continue to test the appropriateness of site-specific strategies (i.e., spraying on the field edges) not only for soybean stem borer but for other economically important soybean pests as well. We will continue to examine the use of site-specific management practices by conducting large-scale field studies that aim to quantify adult pest movement into and around soybean fields at risk of infestation. Field-collected samples of soybean pests will be obtained using sweep nets samples from each waypoint (n > 40 per field, 10 to 15 commercial fields). Samplers will navigate to predetermined waypoints and a 20-sweep sample will be taken in each of the cardinal directions. Adults from each 20-sweep set will be bagged and identified in the lab. To relate timing of infestation by key pests and product efficacy (i.e., reduced plant damage, lodging etc.), we will use field-level vegetation maps collected from small unmanned aerial systems (sUAS); funds for aerial imaging are being leveraged from an existing, international grant (McCornack, lead PI).
Evaluating the efficacy of candidate insecticides for pest insect control will continue, based on production needs, loss in severity by key soybean pests and industry interest (see Accomplishments below). In addition, we will expand this sub-objective to explore effective product carrier volumes, appropriate nozzel types, and other potential factors affecting insecticide penetration or distribution into the soybean canopy, especially during late-season infestations. This research is imperative to reliable use of newer insecticide chemistries. We have accepted a graduate student for this project to begin in January 2017 whose primary focus will be to model the value of site-specific management strategies in general and ways to optimize insecticide applications for controlling key pests in soybean.
Procedures for Objective 3. Efforts will continue to develop text-based discussions, maps, tables, and graphs posted to the KSRE Soybean Insect Management Guide
(http://www.ksre.ksu.edu/bookstore/pubs/Mf743.pdf). Work is in progress to update the insect pest management information section for the Kansas Soybean Management 2017 publication. https://www.bookstore.ksre.ksu.edu/pubs/MF3154.pdf. Co-PI Whitworth and Dr. Holly Schwarting wrote the insect pest chapter for the just completed publication: Ciampitti et al. 2016. Soybean Production Handbook. (KSRE #C449)
(http://www.bookstore.ksre.ksu.edu/pubs/c449.pdf). All new information will also be inserted in our soybean pest management web-based decision support systems like myFields.info
(http://myfields.info/pests/dectes-stem-borer) and discussed during field days, radio programs, newsletters, and via other educational opportunities as appropriate. For a list of all soybean pests and associated management guides on myFields.info, visit http://myfields.info/pests. The support of the Kansas Soybean Commission will continue to be highlighted in all of these endeavors.

Progress of Work

Update:
Accomplishments since last report
Objective 1: Create soybean plants resistant to soybean stem borer by inserting borer RNA into soybean plants to interfere (RNAi) with genes necessary for borer survival. Lina Aguirre, the PhD student conducting this sub-objective, has established replicated greenhouse – and field cage experiments (3 x 3m plots) of sunflower, ragweed and soybean plants infested with soybean stem borer adults. RNA of larvae emerging from each host is being collected to determine differences between stem borer gene expression using RNASeq analysis. This information will be used to identify candidate genes that can be efficiently silenced to kill borer larvae.

Objective 2. Improve insecticide efficacy by using host plant developmental stages and other environmental cues or conditions to adjust timing and placement of application. Twelve commercial production fields and cooperators identified in Clay and Washington Counties are being used to evaluate efficacy of newer insecticide chemistries for defolioators (e.g., loopers), pod- (e.g., Helicoverpa zea or soybean podworm) and stem feeders (Dectes texanus). Fields range in size (55-200 acres), variety, and production practices (irrigated vs. dryland, row spacing, plant population, etc.). Fields are being sampled weekly using sweep nets (30 locations per field) in the perimeter and interior portions of each field. Once pest levels reach detectable levels across all plots, insecticides will be applied at different rates and carrier volumes using appropriate nozzel types/tips. Other potential factors affecting insecticide penetration or distribution into the soybean canopy, especially during late-season infestations, will be considered in the treatment list. This research is imperative for reliable use of newer insecticide chemistries. A graduate student for this project begins in January 2018, to model the value of site-specific management strategies and ways to optimize insecticide applications for controlling key pests in soybean.

Objective 3. Expand web pages and other educational materials associated with soybean insect pests. Co-PI Whitworth and Dr. Holly Schwarting have been established trials for soybean seed treatments coated with new chemistry insecticide in north central Kansas. Seed treatments are being evaluated to determine efficacy against early season soybean pests, such as bean leaf beetles, thrips, wireworms, and white grubs. New and different rates of foliar-applied insecticides are also being tested on plots established adjacent to seed treatment plots. Efficacy against pod-feeding bean leaf beetles and corn earworms will be determined. Results of these trials then will be available to all stakeholders via the KSU entomology website to help Extension personnel and others make the most judicious recommendations relative to pest control and integrated pest management.

View uploaded report Word file

Update:
Accomplishments since last report
Objective 1: Create soybean plants resistant to soybean stem borer by inserting borer RNA into soybean plants to interfere (RNAi) with genes necessary for borer survival. Giant ragweed and other weed species are native hosts of Dectes stem borers in North America, but borers have adapted to use soybean and cultivated sunflower as hosts. Changes in the number of expressed genes and/or gene expression level may be associated with borer adaptation to feed and survive on soybean. Lina Aguirre, the PhD student conducting this sub-objective, completed a replicated 2017 field cage experiment of sunflower, ragweed and soybean plants infested with soybean stem borer adults. Larvae collected from plants were stored at -80°C, and for each instar, RNA was extracted from three biological replicates per diet source. Each biological replicate contained whole bodies of 6 third-instar or 3 sixth-instar larvae, respectively. PolyA cDNA libraries were sequenced using Illumina paired-end technology RNASeq analysis. This information will be used to identify candidate genes that may be able to be efficiently silenced to kill borer larvae. Transcriptome assembly and differential expression analyses are in progress to describe genes expressed in response to feeding on each of the larval hosts.

Objective 2. Improve insecticide efficacy by using host plant developmental stages and other environmental cues or conditions to adjust timing of application. Cooperators were identified early in the growing season and twelve commercial production fields were used in our pest survey study, which started shortly after plants emerged (V3-4) and finished in the late reproductive stages (R6-7); fields were located across a north to south gradient and covered several counties in Kansas. A subset of these fields (8 total), which were located primarily in Clay and Washington Counties, was more extensively surveyed for stinkbugs and other key pests until soybean reached the R6 growth stage. All stink bug specimens were sent to the University of Minnesota as part of a North Central Soybean Research Program project, which aims to develop sampling plans for stinkbugs in soybean using data from across the North Central US. In addition, these data are being used to study how landscape or land use around these fields impacts stink bug populations and/or abundance. For the Kansas study, we swept the interior and perimeter of all 8 fields using sweep nets; a total of 12 sets of 25 sweeps per field was collected and all major pests were identified to species. These data will be used this winter to model the utility of site-specific management strategies (i.e., interior versus perimeter insecticide treatments). In addition, these data add to our sample database and will be used to develop sampling plans for several of the species we observed. In three of these fields we initiated a small-scale (approx. 2 acres) study focused on evaluating the effectiveness of newer insecticide chemistries at different carrier volumes. Fields ranged in size (55-200 acres), variety, and production practices (irrigated vs. dryland, row spacing, plant population, etc.), and a corner of each field was divided into plots (6 rows by 50 feet with a 6-row buffer between plots). The goal of this first year was to develop an experimental design that can be scalable to larger plots and increased replication; these experiments are planned for the 2018 field season. Prior to insecticide treatments, we sampled plots using sweep nets (10 sweeps per plot per location) and individual specimens from the most abundant pests, which in this case green clover worm and thistle caterpillar, were individually weighed. Plots were swept 6 days post application and individuals from the same two species were weighed. Carrier volumes tested were 10 and 20 gallons per acre (GPA) and Prevathon and Steward were the two insecticides applied. We also harvested a 1.5 m section of row from each plot and are currently evaluating individual pods by node for damage. This data will be used to evaluate the level and location of protection these products provide against seed-feeding insects. In addition, these data will be used to correlate changes in plant biomass with changes in herbivore biomass and any impacts on soybean yield. The primary objective of this first year was to ensure a suitable experimental design (e.g., plot spacing, minimized drift, etc.). A graduate student for this project begins in fall of 2018, and his focus will be to model the value of site-specific management strategies and identify ways to optimize insecticide applications for controlling key pests in soybean.

Objective 3. Expand web pages and other educational materials associated with soybean insect pests. Co-PI Whitworth and Dr. Holly Schwarting established foliar insecticide trials to test new products and differing rates of application for registered products against green cloverworm, thistle caterpillar and bean leaf beetles. The efficacy of 12 new-chemistry seed treatments for bean leaf beetle control were also tested. Efficacy results and resultant yields are still being determined for these trials. Results of all trials will be posted to the KSU Extension Entomology website and made available to all stakeholders via the KSU entomology website to help Extension personnel and others make the most judicious recommendations relative to pest control and integrated pest management. Insecticide products and links to labels were added to the Chemical Selection tool (https://www.myfields.info/chemical/selector/search) on myFields.info web-based platform. Users can select a crop, time of year, and easily find product labels for registered products. Other features that may be of interest can be found at: https://www.myfields.info/features.

View uploaded report Word file

Update:
Accomplishments since last report
Objective 1: Create soybean plants resistant to soybean stem borer by inserting borer RNA into soybean plants to interfere (RNAi) with genes necessary for borer survival. Giant ragweed and other weed species are native hosts of Dectes stem borers in North America, but borers have adapted to use soybean and cultivated sunflower as hosts. Changes in the number of expressed genes and/or gene expression level may be associated with borer adaptation to feed and survive on soybean. Lina Aguirre, the PhD student conducting this sub-objective, completed a replicated 2017 field cage experiment of sunflower, ragweed and soybean plants infested with soybean stem borer adults. Larvae collected from plants were stored at -80°C, and for each instar, RNA was extracted from three biological replicates per diet source. Each biological replicate contained whole bodies of 6 third-instar or 3 sixth-instar larvae, respectively. PolyA cDNA libraries were sequenced using Illumina paired-end technology RNASeq analysis. This information will be used to identify candidate genes that may be able to be efficiently silenced to kill borer larvae. Transcriptome assembly and differential expression analyses are in progress to describe genes expressed in response to feeding on each of the larval hosts.

Objective 2. Improve insecticide efficacy by using host plant developmental stages and other environmental cues or conditions to adjust timing of application. Cooperators were identified early in the growing season and twelve commercial production fields were used in our pest survey study, which started shortly after plants emerged (V3-4) and finished in the late reproductive stages (R6-7); fields were located across a north to south gradient and covered several counties in Kansas. A subset of these fields (8 total), which were located primarily in Clay and Washington Counties, was more extensively surveyed for stinkbugs and other key pests until soybean reached the R6 growth stage. All stink bug specimens were sent to the University of Minnesota as part of a North Central Soybean Research Program project, which aims to develop sampling plans for stinkbugs in soybean using data from across the North Central US. In addition, these data are being used to study how landscape or land use around these fields impacts stink bug populations and/or abundance. For the Kansas study, we swept the interior and perimeter of all 8 fields using sweep nets; a total of 12 sets of 25 sweeps per field was collected and all major pests were identified to species. These data will be used this winter to model the utility of site-specific management strategies (i.e., interior versus perimeter insecticide treatments). In addition, these data add to our sample database and will be used to develop sampling plans for several of the species we observed. In three of these fields we initiated a small-scale (approx. 2 acres) study focused on evaluating the effectiveness of newer insecticide chemistries at different carrier volumes. Fields ranged in size (55-200 acres), variety, and production practices (irrigated vs. dryland, row spacing, plant population, etc.), and a corner of each field was divided into plots (6 rows by 50 feet with a 6-row buffer between plots). The goal of this first year was to develop an experimental design that can be scalable to larger plots and increased replication; these experiments are planned for the 2018 field season. Prior to insecticide treatments, we sampled plots using sweep nets (10 sweeps per plot per location) and individual specimens from the most abundant pests, which in this case green clover worm and thistle caterpillar, were individually weighed. Plots were swept 6 days post application and individuals from the same two species were weighed. Carrier volumes tested were 10 and 20 gallons per acre (GPA) and Prevathon and Steward were the two insecticides applied. We also harvested a 1.5 m section of row from each plot and are currently evaluating individual pods by node for damage. This data will be used to evaluate the level and location of protection these products provide against seed-feeding insects. In addition, these data will be used to correlate changes in plant biomass with changes in herbivore biomass and any impacts on soybean yield. The primary objective of this first year was to ensure a suitable experimental design (e.g., plot spacing, minimized drift, etc.). A graduate student for this project begins in fall of 2018, and his focus will be to model the value of site-specific management strategies and identify ways to optimize insecticide applications for controlling key pests in soybean.

Objective 3. Expand web pages and other educational materials associated with soybean insect pests. Co-PI Whitworth and Dr. Holly Schwarting established foliar insecticide trials to test new products and differing rates of application for registered products against green cloverworm, thistle caterpillar and bean leaf beetles. The efficacy of 12 new-chemistry seed treatments for bean leaf beetle control were also tested. Efficacy results and resultant yields are still being determined for these trials. Results of all trials will be posted to the KSU Extension Entomology website and made available to all stakeholders via the KSU entomology website to help Extension personnel and others make the most judicious recommendations relative to pest control and integrated pest management. Insecticide products and links to labels were added to the Chemical Selection tool (https://www.myfields.info/chemical/selector/search) on myFields.info web-based platform. Users can select a crop, time of year, and easily find product labels for registered products. Other features that may be of interest can be found at: https://www.myfields.info/features.

View uploaded report Word file

Updated April 9, 2018:
Accomplishments since last report
Objective 1. Create soybean plants resistant to soybean stem borer by inserting borer RNA into soybean plants to interfere (RNAi) with genes necessary for borer survival. Lina Aguirre, the PhD student conducting this sub-objective, established a replicated 2017 field cage experiment of sunflower, ragweed and soybean plants infested with soybean stem borer adults. Larvae collected from plants displayed major differences in the types of genes they express in response to feeding on the three plants. Results to date indicate that larvae fed soybean turn on more than 80 genes not expressed by larvae feeding on sunflower. Of these genes, many are involved in destroying or neutralizing ingested substances in the larval gut. The ability of larvae fed soybean to upregulate the expression of these genes may enable larvae to use soybean as a host. This information will be used to identify candidate genes that can be efficiently silenced to kill borer larvae.

Objective 2. Improve insecticide efficacy by using host plant developmental stages and other environmental cues or conditions to adjust timing of application. Cooperators were identified early in the growing season twelve commercial production fields and cooperators identified in Clay and Washington Counties were used to survey soybean for defoliators (e.g., loopers), pod (e.g., Helicoverpa zea or soybean podworm) and stem feeders (Dectes texanus). Fields range in size (55-200 acres), variety, and production practices (irrigated vs. dryland, row spacing, plant population, etc.). The survey started shortly after plants emerged (V3-4) and finished in the late reproductive stages (R6-7); fields were located across a north to south gradient and covered several counties in Kansas. Fields were sampled weekly using sweep nets (30 locations per field) in the perimeter and interior portions of each field. All stink bug specimens were sent to the University of Minnesota as part of a North Central Soybean Research Program project, which aims to develop sampling plans for stinkbugs in soybean using data from across the North Central US. In addition, these data are being used to study how landscape or land use around these fields impacts stink bug populations and/or abundance. All other pest species data collected from Kansas soybean are currenlty being used to model the utility of site-specific management strategies (i.e., interior versus perimeter insecticide treatments). In addition, these data add to our sample database and are being used to develop sampling plans for several of the species observed; these models are still under development. In three of these fields we initiated a small-scale (approx. 2 acres) study focused on evaluating the effectiveness of newer insecticide chemistries at different carrier volumes; only one field had treatable levels of defoliators and insect feeders, so it was used to evaluate interations between carrier volumes and insecticide rates. Prior to insecticide treatments, we sampled plots using sweep nets (10 sweeps per plot per location) and individual specimens from the most abundant pests, which in this case green clover worm and thistle caterpillar, were individually weighed. Plots were swept 6 days post application and individuals from the same two species were weighed. Carrier volumes tested were 10 and 20 gallons per acre (GPA) and Prevathon and Steward were the two insecticides applied. We also harvested a 1.5 m section of row from each plot and are currently evaluating individual pods by node for damage. There were no significant differences between treatments when comparing pest weights per 10 sweeps prior to the application of insecticides for either green cloverworm (F = 1.32; df = 8,62; P = 0.249) or thistle caterpillar (F = 0.74; df = 8,62; P = 0.636). This was expected and this location provided a uniform infestation to test for effects of application rate at varied carrier volumes. Post application wegihts of these two pests were significantly different. For example, green cloverworm (F = 6.83; df = 8,57; P < 0.0001) decreased 120 fold in treated plots compared to the untreated control; however, there were no significan differences between treatments. There are several factors that could attribute to this non-result, one of which is drift between plots. We are currently exploring vegetation data maps from these plots, both from satellite sensors and those deployed on small unmanned aircrafts (sUAS). In general, these data will be used to evaluate the level and location of protection these products provide against seed-feeding insects. We plan to further explore these data to correlate changes in plant biomass with changes in herbivore biomass and any impacts on soybean yield. The primary objective of this first year was to ensure a suitable experimental design (e.g., plot spacing, minimized drift, etc.). A similar experiment is planned for the 2018 field season but for multiple locations; county agents have been identified and a list of collaborating growes is currently being drafted.

Objective 3. Expand web pages and other educational materials associated with soybean insect pests. Co-PI Whitworth and Dr. Holly Schwarting established foliar insecticide trials to test new products and differing rates of application for registered products against green cloverworm, thistle caterpillar and bean leaf beetles. The efficacy of 12 new-chemistry seed treatments for bean leaf beetle control were also tested. Efficacy results and resultant yields are still being determined for these trials. Results of all trials will be posted to the KSU Extension Entomology website and made available to all stakeholders via the KSU entomology website to help Extension personnel and others make the most judicious recommendations relative to pest control and integrated pest management. Insecticide products and links to labels were added to the Chemical Selection tool (https://www.myfields.info/chemical/selector/search) on myFields.info web-based platform. Users can select a crop, time of year, and easily find product labels for registered products. Other features that may be of interest can be found at: https://www.myfields.info/features.

View uploaded report Word file

Final Project Results

A major accomplishment occurred toward the goal of creating soybean stem borer-resistant soybean plants. Genes specifically used by borer larvae as they feed in the soybean plant stem were identified. Experiments are in progress using some of these genes, which have silenced (turned off) and inserted into modified soybean plants to determine if larvae die when feeding on these modified plants. Statewide sampling was conducted in 2017 for presence of soybean for defoliators, pod feeders or stem feeders, to study how landscape or land use around crop fields impacts pest populations and/or abundance. Efficacy results and resultant yields from 2017 foliar insecticide trials are posted on the KSU Extension Entomology website (https://www.myfields.info/chemical/selector/search) on myFields.info web-based platform.

Benefit to Soybean Farmers

Performance Metrics

Project Years