Farmers should be aware of potential problems associated with head scab and take precautions when selling grain or using it for seed purposes.
Due to prolonged and heavy spring rains head scab has been a threat to this year’s wheat crop in Kansas. Farmers should have scouted fields prior to harvest for disease to avoid price reductions at grain elevators and are encouraged to take necessary procedures to attain acceptable seed quality.
Head scab also known as known as Fusarium Head Blight, is caused by wet and humid weather from flowering time to seed maturity. Continuous wet weather develops a Fusarium mold specie called Gibberella zeae. This fungus yields a mycotoxin called Vomitoxin or Deoxynivalenol (DON). These chemicals at high enough levels are considered harmful or toxic to human and livestock health.
Head scab is mainly confined in the wheat head. The first noticeable sign of infection is when developing spikelets become bleached while the healthy spikelets remain green. The base of the diseased spikelets may also develop small pink or orange masses of spores which are produced by the fungus.
Seeds seriously infected by head scab will shrivel and turn a white chalky color. The embryo inside these seeds are generally killed by the disease and will not sprout when planted. Eric Fabrizius, Seed Laboratory Manager for the Kansas Crop Improvement Association (KCIA), says the disease is not just limited to seeds killed off by the fungus.
“Severe infections of head scab are also going to infect seeds that would appear normal,” said Fabrizius. “Some of the more normal looking seeds also have a lighter infection in the seed coat. When these seedlings begin to grow the disease finally overtakes them and kills the seedling.”
The only way to determine the full impact of head scab on a wheat crop is by testing the germination ability and seed quality. Wheat producers can submit samples to the KCIA seed laboratory, for germination testing for $17.
Infected Wheat for Seed Use
Wheat infected with head scab, however, does have the potential to be used for seed purposes, but will require extra care and preparation before being planted. Fabrizius says the four key components to achieving acceptable seed quality after it has been affected by head scab is to clean the seed, give it time, apply fungicide treatment and to test the germination ability.
Seriously affected wheat kernels will generally be shriveled and have a lighter density than healthy wheat. Due to the lighter density, many of the dead kernels can be removed by air screen cleaners and gravity tables to improve both test weight and germination ability.
“Time is another factor. This fungus doesn’t have a long life span and some will actually die when it goes through the heat of the summer,” said Fabrizius.
A fungicide seed treatment will also help increase the germination ability. Seed treatments do not prevent head scab from occurring the following year, but will help control seed rots and seedling blights caused by the fungus. Fabrizius says the treatment keeps the fungus at bay and allows the seedling to grow normally.
“Certified seed has gone through all of these four components,” said Fabrizius. “Farmers know when they buy the seed that it has been cleaned well and that it has been tested for quality. Additionally, a fungicide seed treatment has been applied, if necessary, for that seed to meet quality standards for germination.”
Planting back seed affected by head scab will likely result in thin stands. The more severely a crop is affected, the more reason a farmer should buy certified seed for the next year’s crop.
Selling Infected Wheat
Elevators will dock truckloads of wheat containing high levels of vomitoxin from head scab resulting in a discounted price or the requirement to destroy the grain.
Therefore it is important farmers are proactive in checking their fields to determine if there is any damage or quality loss to their crop before harvest. It is key that farmers report any serious damage within the required time of 72 hours of noticing loss to notify their insurance company and seek advice before proceeding with harvest or destruction of the damaged wheat.
Farmers with damaged wheat from head scab may be covered for quality loss adjustments if they carry multi-peril crop insurance policies subsidized and reinsured by the Federal Crop Insurance Corporation. If farmers carry these insurance policies they may be eligible for quality loss adjustments if the reason for the loss in value is due to an event such as the excessive rain received this spring.
For wheat containing vomitoxin, the Risk Management Agency (RMA) had established procedures calculating a reduction value. These procedures are outlined in Section C of the Special Provision of Insurance for each county. This can be found in RMA’s Actuarial Information Browser. Section C includes discount factors for vomitoxins in the range of .1 to 10.0 parts per million. It also has procedures for levels greater than 10.0 ppm.
By Audrey Schmitz, Kansas Wheat Communications Intern