Research Key to Understanding and Eliminating Fusarium Head Blight

Swine producers who source cereal grains from Manitoba this year, especially late harvested wheat, are being encouraged to have samples tested to avoid potential problems associated with the mycotoxins produced by fusarium head blight.

Fusarium head blight is a fungal disease that infects cereal grains, including wheat, barley, oats, trictcale and corn. The disease, which attacks the head infecting the plant’s kernels, thrives under warm moist conditions. Wheat is particularly susceptible and is at risk of infection in areas where inoculum is present in the field and when weather conditions turn warm and wet during flowering.

Mycotoxins Cause Concern for Swine Producers

“Fusarium produces a mycotoxin, [Deoxynivalenon, or DON] a compound that affects pigs and specifically reduces feed intake,” explains Dr. Martin Nyachoti a swine nutritionist and associate professor with the University of Manitoba’s Department of Animal Science. “If they reduce feed intake then the animals will also reduce growth rates, or production parameters.”

As well, Dr. Nyachoti points out, feed is one of the main cost inputs in hog production so when you have high levels of fusarium contamination you take away ingredients that otherwise could be used for swine production. It takes away the feed and increases the cost of production because now you have to access those feeds from elsewhere.

Interlake and Southeastern Manitoba Hardest Hit by Fusarium

“In Manitoba, generally speaking, the disease has been particularly bad in the southern area close to the U.S. border,” says Dr. Jeannie Gilbert, a research scientist and plant pathologist working with fusarium head blight and leaf spot diseases at Agriculture and Agri-FoodCanada’s Cereal Research Centre in Winnipeg. “But this year we saw relatively high levels in the Interlake.”

Levels of infection this year have ranged from over just over five percent in southeastern Manitoba and the Interlake to two to three percent moving west.

Dr. Gilbert notes, when the fusarium surveys were conducted in July and early August infection levels were not overly severe.

“What we do know now, though, is that late harvests and rainy conditions under harvest have affected the crop. The fungus has continued to develop in the crops and we’re actually hearing reports of concern over fusarium in the harvest.”

She says most of the wheat, the early harvested crop, will not have any problems. However there could be problems in grain harvested from fields that were planted late where farmers had to wait for the crops to mature and where the harvest was delayed by rain.

Infection Levels Low Compared to Previous Years

Dr. Gilbert notes, based on the survey results, this year’s levels of infection are fairly light. “When we think of the first very very severe epidemic in Manitoba in 1993, crops were coming in at 70 percent fusarium infected. It was very very dire. In more recent years, it’s unusual to see anything much above a ten percent and that’s considered to be very serious.”

“Corn and wheat are the main hosts of the fungus and the residues from these crops are probably the most important in terms of producing inoculum from year to year,” says Dr. Gilbert.

Mycotoxins Become More Virulent

“On the toxin side, the DON also has few derivatives,” says Dr. Dilantha Fernando, a professor with the U of M’s Department of Plant Science. “Chemically we call them 15 Acetyl or 15-A DON and 3-A DON.”

He points out 3-A DON is considered more toxic than 15-A DON and it will produce more toxin. Samples of fusarium infected winter wheat collected from farmers’ fields last year and provided by the Canadian Wheat Board for testing showed a higher percentage of 3-A DON. Those finds were consistent with what Dr. Fernando found in spring wheat.

“We went and collected these samples randomly from farmers throughout Manitoba for four years and we saw an increase in the 3-A DON chemo-types. Sometimes even in the same location we would see a change from one year to the other.”

Dr. Fernando says the key questions scientists are now striving to answer through research are, are these 3-A DON producing isolates more aggressive on the plant; do they cause more infection; is their pathogenicity or virulence higher than the 15 A DON; and more important to the industry is it going to have more DON produced?

Research Needed to Clarify Effects on Swine Productivity

Dr. Nyachoti believes more research is also needed to gain a clearer understanding of how pigs respond to contaminated grain.

“When you speak to producers you hear contradicting information. Some are able to see an effect, some don’t see an effect although they are feeding contaminated grains. I think we need to quantify more clearly the impact of these mycotoxins in terms of animal’s response.”

He recommends looking at the pigs very carefully to assess their response to the diets.

“If you suspect that your grains might be contaminated I think it’s a good thing to have them tested so that at least you know what you’re dealing with and you can make adjustments in the diets. If you have heavily contaminated grain you probably want to avoid that grain or at the very least dilute it with a clean source of grain so that you can reduce the overall concentration of the mycotoxin in the final diets.”

Plant Breeding Key to Solving Fusarium

Dr. Gilbert is convinced the long term solution lies in the development of resistant varieties of grain.

“With a resistant variety there will be less disease, less mycotoxins, there will be less infestation of stubble and less inoculum so the whole disease cycle can be reduced. Generally we are trying to register lines which have at least a minimum level of fusarium resistance and hopefully the most susceptible ones will pass out of the system and we will end up with a safer system because we have resistance in the varieties planted.”

Dr. Gilbert notes scientists are working very hard to try to get resistant varieties out there and progress is being made.

“In the hard red springs especially we’re seeing new varieties such as 5602HR, Waskada, Kane. These have a better level of resistance to fusarium head blight.”

She notes there’s never been much of a problem with two row barley because there seems to be some innate level of resistance in the two row barley. However, with six row barley there’s been a problem finding germ plasm which is resistant that can be used to help breed more resistant varieties.

Dr. Gilbert observes, the biggest struggle is with the durum, a class that is susceptible to fusarium head blight.
However, she is convinced, “Through selection and continued screening we will eventually see improved levels of resistance there as well.”