Project Details:

Title:
Development of Genetic, Chemical and Population-Based Tactics to Manage Soybean Stem Borer in Kansas

Parent Project: This is the first year of this project.
Checkoff Organization:Kansas Soybean Commission
Categories:Soybean diseases
Organization Project Code:1526
Project Year:2016
Lead Principal Investigator:C Michael Smith (Kansas State University)
Co-Principal Investigators:
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 Edwards, Barton, Kiowa, Ford and Pawnee counties in 1985 (Buschman and Sloderbeck 2010). Borer larvae cause severe lodging problems in north-central and southwestern Kansas, where infestations of 50 to 80 % of plants with tunneling are common (Sloderbeck et al. 2003). In Republic Co., some sites have approached 100% infestation. Severity ratings for soybean stem borer have increased in approximatley 30% of counties across Kansas based on a survey conducted in 2015 (Fig.1). 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 soybean stem borer has increased, strategies remain limited. For example, early harvesting has helped reduce some yield losses if infestations

Change in severity of soybean stem borer damage in Kansas, 2008-2015. are detected early in the growing season (Buschman and Sloderbeck 2010). Commercial insecticides do reduce adult stem borer numbers, but several applications are necessary for better

results, making this option cost-prohibitive. Fipronil seed treatments serve to effectively control larvae in the plant stem, but this insecticide remains commercially unregistered for use on soybean stem borer and unavailable (Sloderbeck and Buschman 2011).

To date, soybean varieties adapted to the High Plains or Midwestern U.S. contain no genetic traits for resistance to soybean stem borer larval damage. However, previous results from KSC-funded research have identified reliable methods for identifying resistance (Niide et al. 2102) and a multigenic source of resistance from PI165673 (Aguirre-Rojas 2013) to demonstrate that borer resistant soybean cultivars will benefit Kansas producers. Similary, results from coPD McCornack’s group have demonstrated that adult stem borer colonization patterns vary between fields and through time.

Project Objectives

Project Deliverables

The proposed studies will to lead to improved crop protection and management practices that suppress losses caused by soybean stem borer. Commercial insecticides reduce adult stem borer numbers, but several applications are required for effective results, making this option cost-prohibitive. Thus, our efforts for the past several years have focused on identifying plants with heritable resistance to borer stem damage; on monitoring borer movement and distributions in soybean fields to refine an optimum time for insecticide application; and on determining the impact of alternate borer hosts and environmental factors to better predict the appearance of early season adult borer populations.

Progress of Work

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Objective 1: Map the genes contributing to soybean stem borer resistance in PI165673 and determine factors mediating resistance. Lina Aguirre, PhD student, has successfully developed a soybean stem borer colony to supply eggs and larvae for future experiments. Larvae collected in the field from stems of soybean plants in Ashland Bottoms, KS in August, 2015 fed on artificial diet originally developed for larvae of the pink bollworm, Pectinophora gossypiella, and became adults in early 2016. These beetles mated, produced viable eggs that hatched and these larvae now developing on artificial diet. Experiments have developed degenerate PCR primers that successfully amplify the soybean stem borer laccase2 (Lac2) gene required for skin development. Larvae from the colony will be injected with or fed particles of silenced Lac2 to determine the best silencing technique. Future experiments will involve silencing larval gut membrane proteins with RNAi particles to suppress larval development or kill larvae.

Objective 2. Improve insecticide efficacy by using host plant developmental stages and other environmental cues or conditions to adjust timing of application. Alice Harris, the current PhD on this project is working to complete her dissertation by May 2016. Alice finished analyzing her small plot study aimed at quantifying differences infestation rates on soybean plants by measuring changes in near infrared (NIR) imaging using vegetation indices this past month. This included collection of soybean biometric data (e.g., number of pods, seeds per pod, stem diameter, etc.), which she used to compare infested and non-infested plants to better understand yield loss. She found that that larval feeding and subsequent tunneling of the main stem did not alter soybean leaf reflectance. However, soybean significantly responded to D. texanus infestations by producing more nodes and stems with a larger diameter. The results of this study indicate that regardless of infestation level, D. texanus did not alter the leaf reflectance and consequently the GNDVI and VPMs. This study suggests that there is a plant response to D. texanus infestation, with infested plants generally being larger than (stem diameter and number of nodes) than non-infested plants. With further investigation, this information may be able to serve as indicators to at risk areas in the field and possible variety selection in regions known to have heavy D. texanus infestation. We also collected NIR images of a test field using unmanned aerial systems (UASs); orthomosaic images of the field were constructed and are currently being compared to yield monitor data provided by the soybean producer. Alice is diligently writing up her dissertation work with the intention of publishing her results in peer-reviewed journals after her defense in May. For example, Alice’s field study describes for the first time the within-field spatial distribution on adult and larvae D. texanus in Kansas soybean fields. Results from aggregation analyses provide insights into the spatial and temporal distributions of adults and larvae in large, production soybean fields. In addition, spatial distribution patterns show changes in adult activity during the growing season as well as spatial associations between adults and larvae. The results of this study indicate that adults are aggregated along field edges during the growing season. The aggregation occurs during July when adult activity is at its highest, mid-late July. This study suggests that site-specific insecticide applications may be potential methods to control adult and larvae D. texanus populations in soybean.

Objective 3. Expand web pages and other educational materials associated with soybean insect pests. Recent updates by co-PD Whitworth include the 2015 Insecticide Efficacy Trials http://entomology.k-state.edu/extension/efficacy-trials/soybeans.html; the KSU Soybean Insect Management Guide http://www.ksre.ksu.edu/bookstore/pubs/Mf743.pdf; and the 2016 Soybean Production Handbook http://www.ksre.ksu.edu/bookstore/pubs/MF3154.pdf.

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Final Project Results

Benefit to Soybean Farmers

Performance Metrics

Project Years