About Fusarium Head Blight
Fusarium head blight is caused by a number of different Fusarium species, the most common one being F. graminearum. This fungus will overwinter in plant debris or host seeds as resting spores. Spores spread easily through water, making rain a main cause for a broadened reach of infection. Infection is likely to be worse in July when flowering occurs. This is due to the easy point of entry through the floret. However, spores can also infect the plant through a point of injury caused by a pest (insects, birds, etc.) or hail. If warm and moist conditions are present, the infection can continue to spread to other kernels after seed set. F. graminearum is also capable of reproducing sexually when the spores overwinter. These spores can be airborne and thus easily spread via wind and are more likely to travel far distances than those spores that travel through water. Once a spore reaches a viable infection area, symptoms can occur within 72 hours if the conditions are favorable for the fungi. When the fungus enters a plant, it produces mycotoxins, which are toxic metabolites and are not killed during processing and production of the grain. This means that there is no allowance for any grains that have been infected with deoxynivalenol (the most common mycotoxin) in malting barley and there is only a small tolerance for its presence in grain used for livestock feed.
Fusarium Head Blight Identification and Habitat
This disease may infect either a few spikelets on the plant or the entire head, depending on disease severity. When entire heads are infected, significant losses in yield may occur from the damaged kernels. Symptoms are commonly seen early in August and will start out as glumes that appear to have dark, moist spots at their base. When kernels are damaged, they are sometimes referred to as “tombstone kernels” to reflect their shriveled appearance and vacant interior that can occur as the infection worsens. The kernels will develop into an either pink or white color and will be light weight. In barley, infected spikelets may turn tan to dark in color. If weather conditions favor this fungus, orange or white spores sometimes develop at the base of glumes or at the point of infection. Kernel damage severity is also based on when the infection occurs. If infection occurs during flowering, total kernel abortion is likely to take place. After this point, the kernel damage mentioned above is most common. If infection takes place even later in the season, kernels may not exhibit symptoms; however, they can still carry the fungus. When infected seeds are used in planting, poor emergence and seedling blight may take place.
- • F. avenaceum
- • F. poae
- • F. graminearum
In order for spores to germinate, high humidity or precipitation must be present for at least 12 hours. Infection is most common when temperatures are between 60 and 86 degrees Fahrenheit, especially between 77 and 82 degrees for F. graminearum. Along with these warm weather conditions, infection is likely to occur when rigorous farming practices are used, or when there is limited crop rotation and variety selection. Sometimes changes take place in the pathogen, which can also alter the severity of the fungal infection.
Fusarium Head Blight Management and Control Methods
Always practice crop rotation. This allows any plant debris that the fungus survives on to break down and lessens the chance of infection the following year. Rotate cereal crops with a plant type that is not suitable to Fusarium head blight for at least a year. Minimize grassy weeds in susceptible fields as these can also harbor the fungus. Since cereal residue is a prime overwintering site, limit its presence as much as possible. This can be done with tillage; however, it is still unlikely to destroy all of the resting spores. Less susceptible varieties are available. For example, infection with winter wheat is less likely since this variety tends to flower before the spores have a chance to spread. With that being said, having satisfactory control is often dependent on using an integrated management system that includes the use of both cultural and chemical methods.
To help manage seedling blight from infected seed, use a seed treatment. However, this does not prevent damage to kernels when the plant has matured. There are foliar fungicides available to help suppress this disease. In order for fungicides to be effective, they must be applied during the early flowering stage to ensure as few plants as possible are susceptible to infection. Typically, application is most effective when at least 50% of the heads are in flower on the main stem. When applying the fungicide ensure coarse sprays are used, low boom heights are maintained, and angle the nozzle forward (the greater the angle, the better). Some fungicides that have had successful results with managing Fusarium head blight are Bravo 500, Echo 720, Folicur 432F, Fuse, Palliser, Proline 480SC, and Prosaro 250EC. Both Proline and Prosaro have also been effective with barley. The fungicide Caramba can be used for wheat, barley, oats, and rye. Always be sure to carefully read all fungicide labels for cautions and proper application before use
Alternative Fusarium Head Blight Names