The Kansas wheat crop is in the heading stage, which is when wheat becomes most susceptible to Fusarium head blight (FHB), or head scab, says Erick De Wolf, Kansas State University (K-State) plant pathologist. FHB was a significant problem on wheat in some areas of Kansas in 2008.
Several factors are important in the development of FHB, says De Wolf, who is a wheat specialist with K-State Research and Extension. These include:
- Previous crop: The fungus that causes head scab survives in the residues of many grass crops. The fungus is also a pathogen of corn and the most severe disease often occurs when wheat is planted in fields with large amounts of corn residue left on the soil surface.
- Variety susceptibility: Most wheat varieties grown in Kansas are susceptible to the head scab, but some varieties are especially vulnerable to the disease. (The varieties Overley, Jagalene and 2137 are all highly susceptible to scab.)
- Weather conditions: FHB infection of wheat takes place at flowering or during the early stages of the grain filling period. This time period clearly influences the amount of disease present. However, the weeks preceding flowering are also important.
The reproduction of the fungus that causes head scab is favored by frequent rainfall and extended periods of high relative humidity. Some of the worst epidemics of scab occur when conditions are favorable for reproduction of the fungus prior to flowering followed by a few days that are conducive for infection during the flowering or early stages of grain fill.
A disease prediction system is currently available to help farmers evaluate the risk of scab in their areas. The risk of disease can change rapidly, depending on weather conditions. "I suggest that growers access the FHB prediction Web site frequently during the next few weeks to monitor the risk of disease as the wheat approaches flowering," says De Wolf. The prediction tool can be found at at Penn State.
If the factors indicate a moderate to high risk of head scab, a fungicide may be needed to help suppress the disease. Selection of an appropriate fungicide is important for head scab. "The fungicides in the strobilurin class offer little protection and are not recommended for control of head scab,” says De Wolf. “The triazole fungicides – Folicur, Prosaro, Proline and Caramba – are available for use in Kansas and can help suppress disease development by 40-60%.
The fungicides must be applied to the heads to have any activity against scab, and they should be applied as close to flowering as possible. The growth stage cut-off for these fungicides is 50% flowering, and they have a 30-day preharvest interval," says De Wolf.
FHB is also a problem in Kentucky. "The disease is not quite at 1991 levels (in Kentucky), but it's definitely the worst it's been since 1991," says Don Hershman, University of Kentucky plant pathologist. Fortunately, many of the state's wheat producers were able to apply a fungicide to protect their crops from FHB when conditions were favorable for infection a few weeks ago, he says, adding that the additional spray applications appear to have made a significant difference in most fields when compared to untreated fields. However, the fungicides only have about a 50% suppression rate with head scab, so some treated fields still have a lot of disease.
USDA Fusarium Head Blight Insurance Info
While Fusarium head blight may not be as big a problem for some this year, many wheat farmers, however, are not likely to forget last year’s instances of head scab, which caused great difficulty for farmers trying to deliver wheat to the grain elevator during harvest.
Rebecca Davis, director of USDA’s Topeka, KS, regional Risk Management Agency (RMA) office, says producers who carry multi-peril crop insurance policies subsidized and reinsured by the Federal Crop Insurance Corporation may be eligible for quality loss adjustments if the reason for the loss in value is due to a covered event, such as this spring’s excess precipitation.
“To protect your rights, it is imperative that you always report any damage in the required timeframes and seek advice from your insurance company before proceeding with harvest or destruction of the damaged crop,” says Davis. “Crop insurance policies require that farmers notify their company within 72 hours of noticing a loss. It is important that farmers be proactive in checking their fields to determine if there is any damage to the crop before harvest.”
Quality adjustments are available for loss in value for conditions such as low test weight, damaged kernels and shrunken or broken kernels. Discounts made for crop-loss purposes may not be the same as those seen at the elevator. For example, quality discounts begin when the test weight is below 50 lbs./bu., defects are above 15% or grade is U.S. No. 5 or worse.
RMA discount factors for wheat are constructed by compiling and using loan discount data from the Farm Service Agency and national average loan rates for the past 10 years. These discount factors remain uniform between the actual production history, crop revenue coverage and revenue assurance plans of insurance throughout all counties in Kansas, says Davis.
Any production of extremely poor-quality wheat that has a value not located on the discount factor charts in the Special Provisions of Insurance (“off the discount tables”) is adjusted by taking the actual sale price based upon the reduction in value divided by the local market price to equal the discount factor for the production.
“In the event that the production has zero market value, RMA loss procedures require insurance providers to make every effort to find a market for the production before declaring a zero value. Therefore, insurance providers will not be making declarations of zero market value until they can firmly establish that there is no market for poor-quality grain,” adds Davis.
Quality adjustments are based on samples obtained by the adjuster or other disinterested parties previously authorized by the insurance provider, such as an elevator employee. Harvested and delivered production samples taken from each conveyance and then blended may be accepted under certain conditions.
More details on changes to the grain-quality adjustment provisions and examples of the application of quality adjustment factors, is available online.