Wheat and more wheat, multiple varieties grown in one field

Researchers have found that several wheat varieties mixed in the same crop offer disease and insect protection

LEFT: In a wheat field in one year of researchers’ experiments, different varieties are noticeable because of physical differences – namely colour or hue and whether the head has awns. RIGHT: The difference is apparent in a fungicide application within one variety. The left side of the photo shows the control that had no chemical fungicide applied. The slightly darker colouring of the wheat is largely due to disease. RIGHT: The fungicide-sprayed plot. The lighter colouring is healthier wheat, which often has a few additional days to mature, thereby increasing yield.

Glacier FarmMedia – Growing multiple varieties of wheat together can reduce disease pressure just as much as a fungicide application does, according to research out of Pennsylvania State University.

Julie Baniszewski led a research project that compared a wheat crop composed of four different varieties, to a single wheat variety that received a fungicide application. The study also had a check that did not get any fungicide.

Why it matters: By growing multiple varieties of wheat together, insect and pathogen pressure can be reduced, which can decrease herbicide use. 

The three-year field experiment was designed to see if the mixtures could suppress diseases, increase predation of insect pests and increase yield and economic value.

Insect predation was quantified by using aphid populations, and disease, yield and economic return over variable costs for each plot were assessed.

“The mixed variety plots had inhibited the spread of foliar disease in the field comparable to the fungicide application,” Baniszewski said.

The plot with four wheat varieties inhibited foliar disease by 20 to 25 per cent. However, she cautioned the intra-specific treatment was not the highest yielding, nor did it provide the greatest return over variable costs.

Various head diseases are shown among the different varieties of wheat in the study. photo: Julie Baniszewski

There was low aphid presence throughout the study and no difference was observed between the treatments.

Intra-specific crops contain multiple varieties of the same crop, while inter-specific crops have different species in the same crop.

Some growers use inter-specific crops, or multi-crops, to reduce disease pressure, including a paired row lentils and flax system.

In this practice, the two rows of flax stop disease such as ascochyta from spreading through the lentils.

Baniszewski said instead of a physical barrier, the inter-specific wheat crop has a dilution effect in terms of susceptibility to pathogens.

“If you apply different varieties and only one was susceptible to spread the disease and the other varieties that are resistant to that disease, it’s not as likely to spread,” Baniszewski said.

By deploying a wide variety of resistance in the germplasm of the multiple varieties, it’s more likely that some varieties will be resistant to any particular disease.

“Each variety would have a different set of traits. One may be high yielding, another resistant to insect pests and yet another resistant to specific diseases,” Baniszewski said.

“By combining these different sets of traits, the crop is more consistent year to year. The field is more diverse genetically and better able to reduce or withstand pest abundances and diseases.”

Selecting the right wheat varieties is key to making this system work. Growers want to choose varieties with diverse disease resistance packages that will mature at the same time and have similar height.

Baniszewski said it’s likely that, in most years, an intra-specific crop will not yield as well as a mono crop with a higher yield potential than the average among varieties in the mixed crop.

However, she said the practice can serve as a risk management move or an insurance policy. If there is a pest or disease infestation, drought or excessive rain, seeding a diverse set of wheat varieties at the same time could be beneficial.

“I’m actually in the entomology department, and one of the main ideas behind this was to see if, by having these different varieties, we could attract more beneficial insects. The problem was that we didn’t have any pests at all while we were doing the study,” Baniszewski said.

This article was originally published at The Western Producer.

About the author

Glacier FarmMedia staff

Robin Booker is a reporter with Glacier FarmMedia.

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