Cause: Fusarium graminearum, F. culmorum, F. pseudogarminearum.
Occurrence: September - July, during periods of moisture stress.
Key Symptoms:
· Brown/red discoloration of crowns and lower stem tissues.
· Brown to tan lesions on primary and secondary roots and subcrown internode.
o A chocolate colored subcrown internode is indicative of common root rot, caused by Cochliobolus sativus.
· Yellowing of plants in spring.
· Poor tillering.
· Scattered pockets of dead and dying plants in the spring.
o Can be more common in the headlands, which are double-seeded.
· Spindly plants with small heads.
· Completely white heads.
o Partial white heads are indicative of Fusarium head scab.
o Completely white heads on plants with a shiny black lower stem is indicative of take-all.
o Insect damage to stems (e.g. from stem maggots) may also cause individual heads to bleach. Pulling on these usually results in their breaking off at the point of damage.
· Symptoms usually more acute on wind-prone hills and knobs, probably related to water stress.
Pathogen: Survives in host debris (residue). Incidence has been increasing with reduced tillage practices.
· Plant varieties that consistently yield in your geographic area. Use tolerant varieties, if available.
· Plant into a firm, mellow seedbeds (loose seedbeds promote disease).
· Control weeds in summer fallow land (weeds deplete soil moisture which predisposes plant roots to infection in the fall.)
· Rotate to a broadleaf crop such as peas.
· Always plant good quality (high germination, >92%) seed. Bin-run seed is at higher risk.
· Plant at the recommended date for your geographic area. Early planting or extended, warm fall weather promotes disease.
· Cultural practices recommended for crown and root rot also reduce the risk of winter injury.
· Seed treatment fungicides provide protection of the seed and promote healthy seedling growth.
· When selecting a seed treatment product, pick one that has activity against common bunt and loose smut as well as common root rot.
Vitavax Extra (carboxin + imazalil + thiabendazole)
Dividend XL (difenoconazole + mefenoxam)
Raxil XT or MD (tebuconazole + metalaxyl)
Raxil MD Extra (tebuconazole + metalaxyl + imazalil)
RR, Flo-pro, NuZone (imazalil)
Baytan (tridimenol)
· Uniformly coat the seed when applying the seed treatment product.
· Read and follow all label directions for mixing and application.
Categories: Small grains, Diseases, Fusarium crown rot
Date: 2/6/08
