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How to Manage Pests

UC Pest Management Guidelines

The crown and lower stem of plant with common root rot; a healthy stem is on the right.

Small Grains

Common Root Rot and Scab

Pathogens: Fusarium spp., Bipolaris sorokiniana

(Reviewed 2/07, updated 2/07)

In this Guideline:


Symptoms of this disease include darkened and poorly developed roots and crown. Spikes turn white before healthy plants begin to mature. Heads and kernels do not fill normally. Plants are usually stunted and produce few tillers. Infected heads turn white; pink or orange fungal mycelium develops on the surface of bleached spikelets.


The fungi survive on host residue and in soil as mycelium and/or resting spores, and are favored by warm weather. Water stress following infection accentuates the disease. Root and crown tissues are infected if conditions are wet or warm enough to allow fungal growth. Scab is caused by strains of the same Fusarium spp. that cause root rot. Spores splash onto spikes and infect flower parts if they remain continually wet for several days.


Follow good cultural practices: plant late in the fall to avoid excessively warm soil conditions; provide adequate nitrogen but avoid excessive fertilization; irrigate to avoid moisture stress; and rotate out of grain, or use oat, which is not affected. There are no recommended chemical treatments for this disease.


[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Small Grains
UC ANR Publication 3466
R. M. Davis, Plant Pathology, UC Davis
L. F. Jackson, Agronomy, UC Davis

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