Definitive Study Guide on Seed Treatments in Spring Wheat Production

Introduction to Seed Treatment in Spring Wheat

  • A common inquiry during spring is whether to treat seeds.
  • Seed treatment cannot enhance seed quality but can help in preserving it.
  • Preservation of seed quality contributes to improved plant establishment.

The Role of Seed Treatments

  • Seed treatments are not a silver bullet for disease management.
    • They are, however, beneficial when used along with other Best Management Practices (BMPs).
    • Key disease BMPs include:
    • Diverse crop rotations
    • Seed testing
    • Residue management
    • Foliar fungicide applications
    • Variety selection
  • Implementing these BMPs can alleviate disease pressure, thereby making seed treatments potentially beneficial or even unnecessary.

Challenges of Spring Seeding Conditions in Saskatchewan

  • Seeding conditions vary significantly across the province.
  • Issues such as moisture levels (too wet or too dry) and suboptimal soil temperatures contribute to:
    • Slower crop starts
    • Increased susceptibility to diseases.

Common Wheat Seedling Diseases and Management Options

Table 1: Overview of Common Wheat Seedling Diseases

  • Alternaria alternata

    • Symptoms: Leaf spotting disease.
    • Note: Seed treatment does not protect against in-crop disease development.
    • Management: Utilize clean seed, seed treatment for overall plant health.

  • Aspergillus spp., Penicillium spp.

    • Description: Storage molds that typically do not impact germination.
    • Note: Consider seed treatment if levels are high.

  • Bunts (Tilletia tritici, T. laevis)

    • Ideal Conditions: Cool soil at germination supports infection.
    • Symptoms: Appear at plant maturity.
    • Management: Use clean seed, resistant varieties, systemic and contact seed treatments, warm soil for seeding, and crop rotation.

  • Seed Rot/Damping Off (Cochliobolus sativus)

    • Symptoms: Poor emergence and damping off of seedlings.
    • Management: Implement crop rotation and seed treatment.

  • Common Root Rot (Cochliobolus sativus)

    • Conditions: Favorable with drought, warm weather, and nutrient deficiency.
    • Symptoms: Patchy emergence, stunting, and reduced root growth.
    • Management: Crop rotation, ensure adequate nitrogen (N) and phosphorus (P) for root growth, warm soil at seeding, seed treatment.

  • Fusarium spp. (seed-borne)

    • Ideal Conditions: Thrives under warm and wet conditions.
    • Symptoms: Can lead to seed rot, damping off, root rot, or seedling blight.
    • Management: Identification of Fusarium species through seed testing aids management decisions, along with crop rotation, variety selection, clean seed practices, foliar fungicide, and seed treatment.

  • Pythium spp.

    • Conditions: Prefers wet and cool soil conditions.
    • Symptoms: Infects roots of germinating seeds and seedlings, leading to poor emergence and stunting.
    • Management: Crop rotation and seed treatment.

  • Rhizoctonia spp.

    • Conditions: More common in sandy, light soils.
    • Symptoms: Causes bare patches and uneven emergence, with pathogens pruning roots.
    • Management: Crop rotation and control of host weeds, along with seed treatment.

Research on Dual Seed Treatments

  • Research indicates using dual seed treatments (fungicide + insecticide) can improve seedling survivability.
    • Improvement observed under abiotic stress conditions (Larsen & Falk, 2013).
  • Insecticide-treated seeds are recommended in fields with historical yield loss due to insect pests like wireworms.

Overview of Insecticidal Seed Treatment Options

Table 2: Insecticidal Seed Treatment Options for Spring Wheat

  • Diseases and conditions that warrant management:
    • Septoria spp. (seed-borne): Leaf spotting disease managed by clean seed and overall plant health treatments.
    • Smut (Ustilago tritici): Managed by resistant varieties and clean seed.
    • Take-All (Gaeumannomyces graminis): Control through crop rotation and volunteer management.
  • Insect products listed include:
    • Alias 240 SC, Cruiser 5FS, Cruiser Vibrance Quattro, Lumivia CPL, among others, with some providing suppression only.

Wheat Seed Treatment Products

Table 3: Wheat Seed Treatments from the Guide to Crop Protection 2023

  • Various diseases and corresponding products including:
    • Alternaria alternata, Aspergillus species, Bunts, Seed rot, Damping off, Common Root Rot, Fusarium spp., Pythium spp., Rhizoctonia spp., Septoria spp., Smut, Take-all.
  • Examples of products:
    • Allegiance FL, Belmont 2.7 FS, Cruiser Vibrance Quattro, Dividend Extreme, Raxil PRO, among others with specific controls and suppressions outlined.

Importance of Seed Testing

  • Seed testing helps gauge the value of seed treatment.
    • It reveals disease presence on seeds but does not reflect soil or residue-borne pathogens.
  • Fields with short rotations may harbor more soil-borne pathogens.
  • Different seed treatments target various diseases and insects; select treatments specific to the threats on the farm.

Fusarium Species: A Significant Pathogen

  • Fusarium spp. represents a critical threat in spring wheat and durum production.
  • Fungicidal seed treatment aids in mitigating seedling blights and infections during germination.
  • Seed test results provide:
    • Total Fusarium spp.
    • Fusarium graminearum (Fg): Notable for high aggressiveness in Fusarium head blight (FHB) infections and production of the mycotoxin deoxynivalenol (DON).

Guidelines for Fusarium graminearum Infected Seed

  • Seed exhibiting >5% Fg infection is discouraged in non-infested areas.
  • Validate local Fg establishment by checking records and communicating with neighbors regarding FHB history.
  • Recognition of total Fusarium spp. is critical for treatment decision-making regarding:
    • Emergence issues,
    • Seedling blights,
    • Reduced tillering and yield loss.
  • Recommendation for treatment exists when
    • Seed shows >2% but <5% Fg,
    • Total Fusarium spp. exceeds 10%.

Factors Affecting Disease Management in Seed

  • Total Fusarium spp. includes the Fg value.
  • The Provincial Seed Survey maps provide insights into region-specific infection levels fluctuating yearly based on environmental factors.
  • Research affirms Fusarium graminearum can endure in soil for at least two years, necessitating a review of prior infection levels over three to four years.

Application of Seed Treatments

  • Fungicide seed treatments defend against pathogens on seed surfaces, in the embryo, and in the soil.
  • Essential points for effective application include:
    • Ensuring complete seed coverage.
    • Avoiding sub-freezing temperatures during application to prevent poor adherence.
    • Required agitation of seed treatment before application to maintain uniform coating.
  • Following label instructions and calibrating equipment contribute to accurate rate application for the target pest.