Update:
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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