NPIPM:Fusarium head blight
Authors:
Causal Organism
Fusarium Head Blight (FHB), also known as scab, can be caused by a number of different species of Fusarium. The most common species is Fusarium graminearum.
Symptoms and Signs
Symptoms begin to show shortly after flowering and begin in the spikelets. The heads will become bleached prematurely. In a warm and moist environment, light pink spores often appear on the rachis and glumes of an infected head. Eventually, black perithicia will appear on spikelets. The kernels will become shrunken and wrinkled, and are often discolored, ranging in color from pink to gray to light brown.
Disease Impacts
FHB impact on yield is dependent on the severity of the infection. Infected wheat spikes produce light and sometimes non-viable seed. The Fusarium head blight pathogens produce mycotoxins mainly deoxynivalenol (DON) which are harmful to livestock and humans. Grains with more than 2 ppm of DON may be rejected or docked for price at the grain elevator
Life Cycle and Epidemiology
Fusarium spp. overwinter as fruiting fungal structures known as perithicia on crop residue from the previous growing season. Once the temperature and moisture levels begin to rise in spring, perithicia release spores called ascospores into the air. These are carried by wind and when they land on wheat flowers, infection is initiated. If the anthers become infected, the fungus will kill florets and no kernels will develop. Kernels that become infected at a later stage may not show symptoms, but may still contain DON. If left untreated, infected seed will have poor germination and may develop Fusarium seedling rot.
Management Approaches
- Some cultivars have shown some resistance to scab, but none are completely resistant.
- Crop sequence with broad-leaf crops and tillage will help to decrease the level of inoculum available for infection.
- Triazole fungicides timed at flowering have variable efficacy in controlling scab as well as in reducing DON.
- Some bacteria and fungi have been shown to be partially effective in suppressing scab when applied to wheat heads as biological control agents. Examples are bacteria in the genus Bacillus and the fungus Clonostachys rosea.
Integrated management with the use of moderately resistant cultivars, rotation, and timely trazole fungicides has been proven to be most effective in minimizing scab impact on grain yield and mycotoxin accumulation.
Scouting and Threshold
Fusarium head blight develops after wheat flowering. Infection takes place through the flower. The main risk factor for this disease is rainy and warm weather starting from heading through completion of flowering. Since by the time the symptoms of this disease are seen it is too late to apply a fungicide, monitoring of conducive weather prior to flowering is very important. Visit the Fusarium head blight prediction center website to assess the risk for Fusarium head blight in your area http://www.wheatscab.psu.edu/fusarium
Other Online Resources
Fusarium head blight prediction center http://www.wheatscab.psu.edu/fusarium
FAQ on Fusarium head blight http://fyi.uwex.edu/fieldcroppathology/fusarium-head-blight-scab-of-wheat/
University of Nebraska Fusarium head blight Fact Sheet extensionpublications.unl.edu/assets/pdf/ec1896.pdf
Related NPIPM/HPIPM Resources
General principles of plant disease management http://wiki.bugwood.org/Disease_Management
