Intercropping may hold keys to disease management

By Tim Kalinowski

The key to future disease management in barley might be intercropping, Lacombe Agriculture and Agri-Food Canada research scientist Kelly Turkington told the Farming Smarter Lethbridge conference back in December.

In a three-year field study carried out between 2013-2016, Turkington and his colleagues at several research stations tested the principles of intercropping within vulnerable varieties against the “Four Horsemen of Barley Apocalypse,” as he called them: Net blotch, spot net blotch, spot blotch and scald.

“The problem with crop rotation in terms of disease management is there are many other factors that influence a farmer’s cropping system choice, from commodity price, local market opportunities, and there may be issues for farm feed systems so you have to grow feed crops in a fairly tight rotation,” explained Turkington regarding the thought behind the field tests. “I can advocate for crop rotation, but if the reality is the producer has to tighten up their rotations for valid reasons, what can I recommend then in terms of managing issues? So if a producer needs to produce silage for on farm feed requirements, how do we mitigate some of that disease risk?”

“There was lots of interest in intercropping,” he stated. “So we started the trial in 2008, and we had three phases— a three-year cycle of rotation over that period and we looked at the impact of these different strategies.”

As Turkington explained, one element of the trials compared single barley varieties year over year to crop rotations where the genetic mixtures were static over the same three-year time period. These two trials were also compared to rotations where the seed mixtures and genetics were changed over that same time period. Researchers also compared rotations which used static variety intercropping, combining oats, triticale and barley, to intercropping rotations where the genetics of the oats, barley and triticale were also changed over that same three-year trial period.

They also tried out spring triticale in the intercropping mixes versus winter triticale.

“The idea was,” stated Turkington, “the winter triticale would form a vegetative barrier of leaf material to prevent spore dispersal from the infested barley residue to help reduce disease development.”

Turkington says the results of the trials were quite clear.

“Our lowest tonnage (of yield) was with our continuous barley production, same variety,” he explained. “Once we went to a barley mixture with different components each year, we saw a significant increase in tonnage. But it was our intercrops that provided the highest level of productivity in terms of that particular experiment.”

And within the intercrop mixtures being tested, Turkington said changing of the genetics every rotation resulted in the best outcomes for disease reduction.

“You can see as we added diversity, especially in terms of changing the components and using intercrops, we can drive that disease level down significantly,” he said. “The addition of diversity either in terms of crop types or genetics helped to reduce disease and improve silage productivity.”

Turkington was quick to add while intercropping is effective in reducing crop disease in barley on its own, it becomes next level effective when producers also choose the most disease resistant varieties possible to intercrop and combine them with a single application of flag leaf or head emergence fungicide where the disease is already present.

“Flag leaf and head emergence of Fungicide increased yield and resistance in vulnerable plants, but there is no point in spraying if you do not have a disease problem,” he cautioned. “It’s a waste of money, and has little effect on yield when those diseases aren’t present.”