Be on the lookout for these soybean seedling diseases

With the weather we have been experiencing and the saturated soil conditions we currently have, I have fielded several questions about the current state of the crop that is currently in the ground. Below is a good summary of some common soybean seedling diseases we will need to be on the lookout for when we evaluate stands. I have also attached a PDF with the full publication including pictures with detailed descriptions. If you have any questions or would like to go look at any of your fields, don’t hesitate to call.

Table 1. Symptoms and distribution of common soybean seedling blights and disorders.

Cause

Seedling Symptoms

Field Pattern

Fusarium root rot

• Lack of secondary roots

• Light to dark lesions on roots extending to hypocotyls

• Patchy

Rhizoctonia seedling blight

• Red-brown sunken lesions on hypocotyl

• Patchy or entire row sections

• Can be severe in sandy soils

Phytophthora root rot

• Internal discoloration in lower stem cortex

• Soft, water-soaked lesions

• Patchy

• Most common in low-lying or compacted areas prone to flooding

Pythium seedling blight

• Rotting brown root tissue

• Wilting

• Soft, water-soaked lesions

• Plants are easy to pull from the soil

• Patchy

• Most common in low-lying or compacted areas prone to flooding

Fluopyram fungicide effects

• Yellow to brown necrosis near the tips and edges of cotyledons

• Uniform in field where fluopyram-treated seeds were planted

• May be more severe where soils are cool and wet

Pre-emergence herbicide damage

• Speckled brown necrotic spots on cotyledons, hypocotyls, or trifoliate leaves

• Usually follow herbicide application patterns, but may be scattered if caused by splashing rain

• Higher incidence in coarse soils

Environmental/Planting issues• Water-soaked discoloration of hypocotyls and cotyledons

• Uniform or in low spots of field

• Follows period of frost and/or unseasonably cold temperatures

 

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