Disease Severity Increased

By: Bill Strautman, Saskatoon Newsroom

Many plant diseases become worse when glyphosate is used in the field, says an American soil scientist. Many of these diseases are what Don Huber calls root nibblers and haven't yet been recognized as economically important. 
"Under our glyphosate management programs, we're starting to see diseases increase in severity," he told Agri-Trend's recent Farm Forum. 

"We can directly demonstrate that glyphosate increases the severity in some of these diseases." 

He listed nearly 30 cases where glyphosate increased disease problems, including root rot in barley, crown rot and wilt in canola, and glume blotch, root rot, head scab and take-all in wheat. 

"It's nothing we should be surprised about if we realize the relationship of nutrition and disease," Huber said. 

Producers are beginning to see potassium deficiencies in corn, he added, even though they have followed the traditional potassium application rates. 

He said they are not only starting to see potassium deficiency, but also a poor response when additional potassium is applied. 

"We know that glyphosate stimulates fusarium 
in general," Huber said.

"Richard Dick's work in Ohio State shows that the stimulation of fungi in the soil can actually account for as much as 150 pounds of potassium immobilized—sequestered in fungal mycelium."

Promotes fusarium

Huber said glyphosate was once patented as a herbicide for weed control because it increased fusarium in the target weed. 

"If you take glyphosate and put it on a plant in a sterile environment, you will rarely kill the plant. It's only when you have it in a non-sterile environment that you get stimulation of the pathogens. That's how you get good control of most weeds with glyphosate". 

The chemical stimulates fusarium organisms. In Alberta, one fusarium species has been impli­cated in canola wilt disease. 
"With head scab (fusarium), the old cardinal principle used to be that we needed flowering, precipitation and temperatures above 80 F all occurring at the same time. That's no longer necessary. 

"We now see head scab without the temperature component. That's because temperature and glyphosate do the same thing to the nitrogen metabolism of the plant, and that is what's responsible for susceptibility and resistance to head scab."