This project will build collaborations with farmers across Delaware, Maryland, and Virginia to survey nematode genera and further clarify root knot nematode (RKN) species and soybean cyst nematode (SCN) HG types in soybean fields across the region. Survey results will be complimented by regional field trials at three locations to assess seed treatments as a management tool for SCN and RKN. The effect of seed treatments on nematode populations over the course of the season will be monitored by collecting soil samples at planting, 1 month after planting, and at harvest. Results from this project will provide insight on the nematode species and HG types present across the region along with efficacy data for seed treatment products labeled for nematode control. Project results will be shared through extension publications, field days, news articles, and a regional webinar.

Objective 1: Conduct nematode surveys across DelMarVa farms while further characterizing SCN HG type and identifying root knot nematodes to species.

Objective 2: Screen seed treatment products for efficacy to reduce soybean yield loss from soybean cyst nematode or root knot nematode.

Objective 3: Share research findings through extension publications, web outputs, and extension events. Foster regional dialogue concerning nematode sampling observations across DE, MD, PA, and NJ.

Objective 1: Across DE, MD, and VA 10 farms from the 2021 survey and up to 10 newly identified cooperator farms will be targeted for soil sample collection. At each field site, one farm-representative nematode sample will be submitted by collecting soil using the zig zag method. Soil samples will be submitted to the Virginia Tech Suffolk AREC to be processed for presence and population counts of SCN, root knot nematode, lesion, lance, ring, spiral, and stubby root nematodes. In samples with confirmed SCN, partitions of each soil sample will be used to grow HG type indicator soybean lines in the greenhouse to screen for SCN HG Type. In samples with RKN present, molecular screening with species specific PCR primers will be conducted to identify correct species.

Objective 2: Two seed treatment products, ILeVo and Saltro, along with a non-treated control will be set up in a randomized complete block design with five replications at one test location in DE with a field history of SCN, at 1 location in MD with SCN, and at 1 location in VA with RKN present. Trials will be planted in a variety susceptible to both SCN and RKN. Plots will be approximately 25 ft in length and 10 ft wide. Within each of the 15 treatment plots, a plot-representative soil sample will be collected by combining 30-40 soil cores per plot at three time points throughout the growing season. Plots will be assessed for nematode populations at the time of planting, approximately 30 days after planting, and at harvest. Samples will be submitted to a Nematode assay service to be processed. Population counts will be provided for SCN, root knot nematode, lesion, lance, ring, spiral, and stubby root nematodes. After the seed is planted, soybean seedlings will be monitored for phytotoxicity. Scouting for other soybean diseases, including soybean sudden death syndrome (SDS), will be conducted throughout the duration of the trial. Plots will be harvested at the end of the season using a small plot combine.

Objective 3: Findings from this project will be shared digitally through the University of Delaware’s Weekly Crop Update, Maryland Agronomy News, factsheets, and other University web publications. Data will also be shared through extension presentations such as Mid Atlantic Crop School, Delaware Ag Week, training events, and field days. In addition to communicating with the public, this project also seeks to foster regional discussion by hosting a webinar at the end of the project. The webinar will share project results with agricultural professionals in DelMarVa and invite extension agents and
academic collaborators from Pennsylvania (Penn State) and New Jersey (Rutgers University).

Updated July 1, 2022:
Fields and grower collaborators have been identified for sampling as part of objective 1 and soil samples will be collected in Aug-Sept. Collected soil samples will be set up to test HG Type and fields with RKN will have a molecular screen to determine species. Two field sites were identified for objective 2. One site is a replicated small plot in Georgetown, DE and the other is strip trials in a grower field in VA. Both sites have a history of high nematode populations. In Georgetown, plots were planted April 27 and stand counts were conducted to examine any differences in emergence among treatments. Soil samples were collected at the time of planting. On May 31, five plants in row 1 of each plot were destructively sampled to enumerate female cysts. Beginning soil samples and cyst counts were lower than previous seasons, indicating the colder winter may have had some effect on starting populations for the season. Soil samples were collected again on June 1 and the next round of samples will be collected at the end of the season. Updates will be shared throughout the summer in the DE Weekly Crop Update and MD Agronomy news. A nematode field day is planned for August 18 in Georgetown, DE and a virtual region-wide webinar is being planned for November.

Updated October 31, 2022:
Fields and grower collaborators were identified and sampling completed for objective 1. Soil samples collected for HG testing have been collected and will be processed over the next 2 months. Two field sites were identified for objective 2. One site is a replicated small plot in Georgetown, DE and the other is strip trials in a grower field in VA. Both sites have a history of high nematode populations. In Georgetown, plots were planted April 27 and stand counts were conducted to examine any differences in emergence among treatments. Soil samples were collected at the time of planting. On May 31, five plants in row 1 of each plot were destructively sampled to enumerate female cysts. Beginning soil samples and cyst counts were lower than previous seasons, indicating the colder winter may have had some effect on starting populations for the season. Soil samples were collected again on June 1 and September 20. Plots are awaiting harvest. Updates on SCN soil sampling were shared throughout the summer in the DE Weekly Crop Update and MD Agronomy news. A nematode field day was hosted on August 18 in Georgetown, DE and a virtual region-wide webinar is being planned for December 5. This project was extended and a full report will be provided once final harvest and sampling data are completed.

In 2019, the Koehler lab conducted nematode soil sampling across MD and DE to gather a baseline understanding of nematodes currently affecting soybean fields. Soil samples were collected from 60 organic and conventional soybean fields. Within sites sampled, SCN was recovered in 57% of fields, root knot nematode in 17%, lesion nematode in 60%, and dagger nematode in 17%. Based on the widespread finding of nematodes across the region, a project was submitted to and funded by the ASC in 2020 to expand nematode sampling to an additional 135 field sites over DE and MD in 2021. This sampling effort is underway and will serve as a baseline understanding of nematode distribution at the genera level (Heterodera, Meloidigyne, etc.). Within SCN, nematodes can be further classified by HG type, which provides insight on the level of reproduction observed on the PI88788 resistance gene. Additionally, within RKN there are multiple species of Meloidigyne. In the continuation of this survey project, a smaller number of samples will be targeted in 2022 to more intensively characterize the nematodes observed within Delaware, Maryland, and Virginia. Growers in DelMarVa and across the US are in need of management options for SCN and RKN. A SCN seed treatment trial is currently being conducted at the Carvel Research and Education Center in Georgetown, DE in a field with a known history of SCN and at the Wye Research Station in Wye Mills, MD. In these trials, the effects of ILeVo and Saltro are being compared to plain seed with no nematicide applied. So far in the 2021 season, Saltro has had lower initial phytotoxicity than ILeVo, and both products had higher emergence rates than non-treated seed. This proposal aims to repeat this trial in 2022 and to add additional RKN screening in Virginia. Findings from this project will be shared through the University of Delaware’s Weekly Crop Update and Maryland Agronomy News, which collectively reach over 1,400 growers, consultants, and stakeholders while providing a platform to discuss disease concerns and other production issues.