Exploiting Biofumigant Mustard for Cereal Cyst Nematode Control by Optimizing Termination Timing

Commodities

• Agronomic: mustard

Practices

• Pest Management: biofumigation

Cereal cyst nematodes (CCN; Heterodera avenae) are an increasing threat to wheat and barley production in Idaho and across the Pacific Northwest, annually reducing wheat profitability by >$3.4 million (Hafez et al., 1992; Smiley, 2016). These microscopic pests damage roots, reducing water and nutrient uptake and limiting yield. Because symptoms look like nutrient or water deficiency, CCN infection may remain undiagnosed for many years. Although chemical fumigants and nematicides can reduce CCN, these tools are costly, hazardous to apply, and rarely economical in cereal rotations. Growers, commodity groups, and Extension educators are seeking practical, affordable, and environmentally sound alternatives.

Biofumigant mustard (Sinapis alba and Brassica juncea) offers a promising option. When mustard biomass is chopped and incorporated into the soil, natural compounds (glucosinolates and isothiocyanates) are released that suppress soilborne pests, including nematodes (Brown & Morra, 1997; Kruger et al., 2013). Past research shows results vary widely depending on mustard biomass, soil conditions, and termination and incorporation timing (Björkman et al., 2015; Ngala et al., 2015; Oregon State University Extension Service, 2025). Growers note uncertainty about termination timing and the effectiveness of biofumigation as barriers to adoption.

This project will evaluate how mustard termination timing influences CCN suppression, mustard biomass and glucosinolate levels, and grower profitability. Single-year on-farm trials will be conducted at multiple CCN-infested locations over three growing seasons. Mustard will be terminated at key growth stages (bolting, flowering, and post-harvest regrowth), including single and sequential (multiple-termination) strategies. Each site will also include non-planted control and conventional nematicide treatment comparisons.

Soil samples will be collected before planting, before termination, two weeks after termination, and again in the fall. We will measure CCN juvenile populations, cyst viability, mustard biomass, glucosinolate concentration, and nematode infestations of mustard roots. These data will determine whether certain timings consistently improve biofumigation effectiveness. A partial-budget economic analysis will compare mustard-based practices to chemical nematicides using University of Idaho enterprise budgets, accounting for input costs, operational feasibility, and potential mustard value.

This project includes a strong education and outreach component developed with growers, Extension educators, and commodity organizations. On-farm field days, crop schools, video demonstrations, and Extension publications will share results and demonstrate practices directly with producers. Producer collaborators and commodity groups will help guide research decisions, ensure treatments reflect real-world constraints, and provide feedback on feasibility. We will also facilitate peer-to-peer learning where growers share challenges, successes, and economic considerations to help build confidence and encourage adoption.

Expected outcomes include clear, research-based guidelines for mustard termination timing that maximize CCN suppression while maintaining or improving profitability. Previous Brassica research suggests biofumigation can reduce plant-parasitic nematode populations by 20-75%, and reduced reliance on chemical fumigants could save growers $400 to $1000 per acre (NCFAP, 2000; Clark, 2007; Price et al., 2007; Li et al., 2025; Oregon State University Extension, 2025). Overall, this project directly supports Western SARE's goals of environmental stewardship, economic viability, and diversification by evaluating a practical, biologically based tool for CCN management in small grain systems.

Research Objectives:

1. Quantify mustard biomass production and glucosinolate concentration at multiple termination timings under irrigated and dryland conditions.
2. Determine the effect of mustard termination timing on cereal cyst nematode population density and cyst viability in on-farm field conditions.
3. Evaluate the efficacy of single versus sequential planting and termination strategies for nematode suppression.
4. Assess the economic performance of mustard biofumigation strategies relative to conventional chemical nematicide approaches.

Education Objectives:

• At least 70% of producers attending field days or crop schools will report increased knowledge of cereal cyst nematode management options.
• At least 40% of surveyed producers will indicate intent to adopt or trial mustard biofumigation within two years.
• At least 25% of engaged producers will implement at least one recommended mustard termination strategy within three years.
• Extension educators will incorporate project findings into at least three regional education programs.