Objective 1. The Koehler lab received funding to build rhizoboxes to aid in extension demonstrations. These boxes have a clear Plexiglas front that allows for visualization of root systems. Two soybeans will be planted into each box. Using RKN populations maintained at the Carvel Research and Education Center Greenhouses, we will extract RKN eggs from roots. We will allow eggs to hatch and use infective stage J2 nematodes to inoculate. Inoculations will be at various thresholds to visualize symptoms and signs observed at low, moderate, and high populations. Once soybeans are planted into our SCN trial field for 2022, we will extract SCN females from 20-30 day old soybean plants for inoculation of SCN boxes and for mixed population boxes. SCN females will be extracted following a root blast protocol where females are washed from the roots and collected in a sieve for enumeration. Photos and time-lapse videos will be captured to preserve visualization of symptoms.

Objective 2. This portion of the trial will be conducted in field trials set up by Dr. David Owens as part of a previously funded DSB proposal “Cover Crop Selection and Termination Implications for Slugs”. Briefly, large field plots will be planted on two cooperator farms in the same location of the field in 2021 and 2022. At each location, 4 cover crops (rye, barley, crimson clover, tillage radish and winter rape), were planted in October in 50’ x 100’ plots. In the spring, plots will be subdivided with half being terminated early and half terminated late along with vertical tillage. Four plots will be left bare ground as a no-cover control. When plots are sampled in the spring and fall for slugs, select nematode soil samples will also be collected to represent a range of cover crop and tillage combinations at the field site with highest base levels of nematodes. The cash crop will be assessed in season for nematode damage.

Objective 3. Findings from this project will be shared through the University of Delaware’s Weekly Crop Update, which reaches over 700 growers, consultants, and stakeholders and provides a platform to discuss disease concerns and other production issues. Data will also be shared through training events and extension presentations such as Mid Atlantic Crop School, and the 2022 Delaware Ag week.

Updated January 2, 2023:

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Soybean cyst nematode (SCN) (Heterodera glycines) and Root knot nematode (Meloidogyne spp.) consistently rank as top destructive pathogens of soybeans (Glycine max (L.) Merrill) across the United States. In surveys conducted across DE and MD from 2019-2021 SCN and RKN were widely prevalent across the state, particularly in Sussex County. Nematodes often go undiagnosed, but can be very damaging to soybean production reducing both yield and quality. Visualizing stunting and other silent symptoms can assist recognition of unnoticed yield impacts. The PI88788 resistance gene once effectively managed soybean cyst, but populations are now able to reproduce at high levels, reducing the effectiveness of this resistance source. Growers are in need of additional tools to manage nematode populations and often ask questions about the impact of cover crop decisions on nematode populations. Project objectives included: 1) Utilize rhizoboxes to visualize economic damage thresholds for Soybean Cyst Nematode (SCN), Root Knot Nematode (RKN), and the interaction of SCN and RKN. 2) Track in-season nematode populations following the use of winter cover crops. 3) Share research findings through extension events and use findings to inform future management trials. In rhizobox trials, effect of SCN and RKN on reduced growth and pod set were visualized and optimizations to the rhizobox system will be made to continue to develop photo and video resources at varying nematode population levels. Nematode soil samples were collected from different cover crops to provide insight on the nematode species present and their relative abundance among plots after winter cover crops. No notable nematode populations were recovered in any of the plots in the spring, fall results are pending analysis and final conclusions will be updated upon their arrival.