Red crown rot (RCR) is spreading in Illinois soybean fields, resulting in losses approaching 30 bushels per acre as recently as 2020. RCR infects and colonizes soybean roots, inhibits plant growth, and affects yield.

The fungus can infect soybean roots at any stage during the season, although roots are more susceptible during the first week after seedling emergence. However, the significance of different infection timings, such as whether early infections generate higher impacts than later ones, remains unstudied. In this study, the effects of host age at the time of infections on the final disease intensity will be explored.

Soybean cyst nematode (SCN) has been associated with an increase in the severity of RCR. Consequently, it has been established that managing SCN may help reduce potential interactions between SCN and RCR. However, this management strategy has not yet been validated in IL. In this study, we aim to explore the potential cross-interaction between both diseases, which are significant in Illinois soybean production.

Objective 1: Determine the effects of host age at infection time on disease intensity

Plants will be grown under controlled conditions in pathogen-free soil. Glass tubes will be inserted to facilitate soil inoculation. Subsequently, the tubes will be removed, and microsclerotia suspensions will be added at various growth stages. The progression of the disease will be monitored by observing symptoms such as chlorosis, defoliation, and root rot.

Objective 2: Study the interaction between SCN and RCR

Plants will be grown as previously described. Soils will be inoculated with pathogen-infested grains and SCN eggs at different initial population densities (e.g., 5000, 10000 eggs/100 cm3). Pots will be kept under controlled conditions for 30 days. Roots will be processed to extract SCN females, and then plated on media to evaluate fungal colonization. The progression of RCR will be monitored as previously described.

Objective 3: Evaluate the effects of commercial products applied in furrow on RCR and SCN

Greenhouse experiments will assess the efficacy of fungicides and fertilizers applied in furrow in reducing disease effects. Soil will be inoculated with SCN and fungus for high disease pressure. Seeds will receive a base treatment ineffective against RCR. Fungicides and fertilizers selected for testing will be applied at planting to simulate in-furrow treatments. Stand counts and root evaluations will be conducted after 6 weeks. One plant per plot will be kept and monitored for RCR symptoms.

Objective 4: Assess the efficacy of commercial seed treatments against RCR under field conditions

Experimental trials will be conducted in a Pike Co. plot infected with the pathogen to ensure high disease levels. Seeds will be treated with commercial products according to the manufacturer's instructions. Treatments will also include a non-treated control and a commercial base treatment.

The proposed research aims to address critical aspects of plant disease management, focusing on the timing of infections, interactions with SCN, and the efficacy of commercial products.

This project aims to furnish farmers with unbiased information, enabling them to make informed decisions regarding the use of commercial products available in the market for disease control. Additionally, this project will provide information on the effect of these products on SCN.