2020
Evaluating the presence of Dectes stem borer in soybean fields, weeds and assessing the tolerance of cultivars in Kentucky Year 1
Contributor/Checkoff:
Category:
Sustainable Production
Keywords:
Biotic stressCrop protectionField management Pest
Parent Project:
This is the first year of this project.
Lead Principal Investigator:
Raul Villanueva, University of Kentucky
Co-Principal Investigators:
Project Code:
Contributing Organization (Checkoff):
Institution Funded:
Brief Project Summary:

In 2017 and 2018, the soybean stem borer (Dectes texanus) was observed infesting commercial soybean fields and experimental plots in Kentucky. Although there are publications reporting no effect of this pest on soybean yields, farmers in KY noticed yield reductions in 2017 and 2018. In one case, a farmer in McLean Co. said that the younger pods had unfilled beans, leading to reductions of yields. Another farmer in Hickman Co. noticed the difference of yields in two soybean cultivars. In the first case, soybean plants were >50% infested by Dectes. In the second case, yields were reduced >15 bu/A. This proposal will study infestations in commercial fields, detect additional host plants (weeds...

Unique Keywords:
#insects and pests
Information And Results
Project Deliverables

Final Project Results

Updated November 11, 2020:

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SUMMARY: This study had three major parts, that took place in 2019 and extended to 2020. In 2020 we studied the aggregation of Dectes in the field, an evaluation of Dectes effects on yields using cages, and assessing the tolerance of commercial soybean cultivars to Dectes (data still not completely collected).

Dectes aggregation on border vs. inner rows in commercial farms of Kentucky: Tallies of Dectes texanus were conducted in four commercial soybean fields located in Hardin, McLean, Hickman and Daviess counties in 2019. Sweep nets were used to conduct this sampling in three different dates in each site. Samples were conducted in edge rows and rows 100 m from the edge. Results showed that number of D. texanus per sweep in edge rows versus center rows repeatedly demonstrated that location of sampling was irrelevant on samples conducted every two weeks. The 4 commercial soybean fields sampled during three different dates on each field resulted only in one single date in one field where D. texanus was more abundant in the edge. Therefore, based in these results we conclude that sampling can be conducted randomly in a border or inner part of a field throughout the high peak flight or oviposition period of D. texanus. Although previous studies showed edge tallies had larger numbers of Dectes in border rows compared with inner rows; a 2-year study conducted in Nebraska showed that aggregation of D. texanus adults in the field were not consistent in seven scouted fields. The latter finding agrees with our finding. It is hypothesized that the aggregation of high number of D. texanus in border soybean might be due to field facing a weedy area or on fields that had soybeans the precedent year.

Cages studies with and without Dectes in the field: Full-season soybeans of the cultivar 470 RR/STSn (Caverndale Farms) was planted on 22 May 2019; and double-crop soybeans AG27X7 (Asgrow Seed Co LLC, Bayer Co.) was planted on 8 July 2019. Sixteen outdoor netting cages (1.8 m x 1.8 m x 1.8 m) were constructed using Proteknet Exclusion Insect Netting (Dubois Agrinovation, Quebec, Canada), and two crossed 6-m long steel rebar. These cages were set in experimental plots of soybeans in the University of Kentucky’s Research and Education Center at Princeton. Each full-season and double-crop soybeans had 8 exclusion cages. In 2019, 40 D. texanus adults (1:1 sex ratio) were released into each study cage in full season and double crop at the R2 and V3 stages, respectively. Soybean plants from 2 ft of the middle row were hand-harvested from each cage plus 4 sites outside the cages. Percentages of plants with tunnels caused by D. texanus larvae in plants were tallied. Results in this study showed that mean percentages of plants with tunnels and with D. texanus larva were not significantly different (p>0.05) between the caged plants with D. texanus releases (83.5% tunnels) and plants in the open fields (96.3% tunnels) (p>0.05). Dectes texanus larvae or tunnels were not found in all caged plants where D. texanus was not released. The short-season plants in 2019 escaped the oviposition of D. texanus. Planting of short season soybeans was too late; the pith in the stem had not developed, and D. texanus only oviposits on plants with a well-developed pith for feeding of the larva. Yield in cages with or without D. texanus and open field did not show significant difference.

Assessing the tolerance of cultivars in Kentucky: In 2020, 40 commercial soybean cultivars were planted in the Research and Education Center. Data of this study are being processed and plants have not been harvested yet. By the end of November all this information will be available and analyzed.

The United Soybean Research Retention policy will display final reports with the project once completed but working files will be purged after three years. And financial information after seven years. All pertinent information is in the final report or if you want more information, please contact the project lead at your state soybean organization or principal investigator listed on the project.