DB Diseases, FP Diseases, Soybean Diseases

Scouting for Early Season Diseases

Seedling Disease/Root Rot

The terms “seedling disease” and “root rot” generally refer to the root rot complex that can infect pulse and soybean crops. Diseases that make up the root rot complex differ slightly among these crops. Fusarium spp., Pythium spp. and Rhizoctonia solani can infect all pulses and soybeans, Phytopthora sojae can infect only soybeans and Aphanomyces euteiches mainly infects peas and lentils. Dry beans, faba beans and chickpeas are also host crops to Aphanomyces, but to a lesser extent.

Symptoms may be present on the cotyledons, young true leaves or root system. In general, symptoms may include patchy emergence, wilted, chlorotic or necrotic portions of the plant and lesions on the root or stem tissue.

Fusarium spp.

Rhizoctonia solani

Pythium spp.

Phytopthora sojae

Aphanomyces euteiches

Scouting and Diagnosis of Root Rot/Seedling Disease

  1. Assess five areas of the field in a W- or zigzag-pattern. Visually inspect the crop for patchy emergence, chlorosis, necrosis, wilting or other symptoms.
  2. If root rot/seedling disease is suspected, submit a sample to the Manitoba Agriculture Crop Diagnostic Centre. For suspected Aphanomyces in peas, submit samples to 20/20 Seed Labs. Dig around the plant to obtain the full plant and root system.
  3. Place plant samples in a plastic bag with paper towel or with the roots wrapped in foil.
  4. Ship or drop off samples the day they are collected. Store samples in the fridge if same-day drop-off or shipping is not possible. Shipped samples should be in a container or cardboard box to avoid crushing. Avoid sending samples immediately before the weekend.
  5. Do not collect or ship dead plants and do not wash seedlings prior to submitting.

Adapted from the Crop Protection Network.

Additional Resources

Soybean root rot/seedling disease publications – Crop Protection Network
Soybean Disease Diagnostic Series – NDSU
Pea Disease Diagnostic Series – NDSU
Aphanomyces Root Rot in Peas – 20/20 Seed Labs Inc.
Root Rot in Peas and Lentils in Western Canada – MPSG/SPG/APG
Dry Edible Bean Disease Diagnostic Series – NDSU