Rotation, rotation, rotation are a farmer’s best friend in the field

Not rotating crops and chemistries might just be the opportunity crop pests were waiting for

Figuring out all the angles on rotation can be a complex challenge for farmers.

[UPDATED: April 1, 2021] Rotation isn’t a new word, but applying it to all aspects of annual crop production might be a newer concept for western Canadian farmers looking to keep a step ahead of various crop pests, say specialists with Corteva Agriscience.

A proper crop rotation, a proper variety rotation, a proper herbicide rotation, a proper rotation of seed treatments and fungicides — you name it. If you’re applying some strategy to control or protect your crop from diseases, weeds and insects, then get those plant genetics and chemistries in rotation to keep treatments effective and reduce the risk of the targeted pest developing resistance to the control measure.

Why it matters: Rotate it all: crops, varieties, herbicides, seed treatments and fungicides to keep treatments effective and to reduce the risk of the targeted pest — diseases, weeds or insects — from developing resistance to the control measure.

Figuring out all the angles on rotation can be a complex challenge for farmers say Steve King, canola breeding leader with Corteva based in Guelph, Ont., and Kerry Freeman, Corteva canola category leader based in Calgary, Alta. However, for reducing the risk of clubroot resistance in canola or Group 2 herbicide resistance in weeds, for example, it is worth figuring out.

Kerry Freeman. photo: Supplied

“And farmers shouldn’t hesitate to ask for help,” says Freeman. Producers have access to consultants, agronomists and retail specialists with thorough product knowledge who can advise on rotations.

“Our staff agronomists and product specialists are familiar with the Corteva portfolio of products and the range of tools that are available. It really comes down to developing a plan for each individual farm and figuring out what strategy is best for your operation. And with a wide range of products and tools available, it can be a complex discussion.”

Rotation suppresses pest numbers

King advocates a holistic approach when it comes to rotations — apply the best rotation possible in all aspects of crop production. He recommends at least a three-year break between canola crops, along with cereals, pulse crops or forages to create an ideal rotation that helps break the disease cycle — it reduces disease buildup and also interrupts the reproduction cycle of other crop pests.

“The wider rotation helps to keep pests at bay,” says King, although he appreciates that for a number of reasons, including economics, it may not always be possible. He says that’s why Corteva also invests in the Pioneer Hybrid and Brevant brand seedlines of hybrid canola, corn, soybeans, wheat, forages and other specialty crops to provide farmers with profitable, rotation-extending, cropping options.

Steve King. photo: Supplied

As the global lead of canola breeding programs in Canada and Europe as well as mustard varieties in India, King says one important challenge in breeding work, for example, is to improve genetic resistance to key canola crop diseases, such as clubroot, blackleg and sclerotinia. The objective is to keep pace and hopefully be at least one step ahead of diseases that are always mutating and reinventing themselves.

Using clubroot as an example, Corteva has developed hybrid canola varieties that have resistance to the certain races of clubroot in the first generation of the disease pathogen. “But our breeding program is always working ahead to develop varieties that will have resistance against new races of the disease in the second, third, fourth and fifth generations as the clubroot pathogen mutates,” says King.

Finding genetic material with disease resistance involves expanding the search into some exotic sources of germplasm, he says, and then transferring that genetic resistance into canola. As plant breeders work to develop varieties with improved genetic resistance to leading diseases, they also have to be careful to maintain or potentially improve other desirable traits, such as high yield, high oil quality and agronomic features that make that variety appealing to grow.

Freeman says it is not only important for producers in areas where there is increased risk of clubroot disease to grow resistant varieties, but it can also be a proactive measure against the disease in areas where there is lower risk. Corteva’s goal is to include clubroot resistance in all new lines of canola.

Again, in the spirit of rotation, farmers are advised to rotate canola varieties with different clubroot disease resistance in order to keep that resistance effective against different races of the disease.

Herbicide options

It is a similar approach on the weed control and herbicide resistance front. Corteva is working to develop canola, corn and soybean varieties with herbicide-tolerant traits to different herbicide chemistries, such as glyphosate, LibertyLink and Clearfield. This gives farmers the option to grow top-performing varieties and be able to use herbicides with different active ingredients to control weeds. They can grow a canola variety with tolerance to glyphosate one year, for example, and then switch that up in subsequent years and grow a variety with tolerance to LibertyLink or Clearfield herbicides, which lowers the risk of herbicide-resistant weed development.

On one hand, farmers can rotate the herbicide-tolerant platforms, but they can also use herbicide products with different modes of action to improve weed control efficacy. Prospect is one product from Corteva that’s a combination of the Group 4 and 14 active ingredients halauxifen and carfentrazone. When used ahead of canola as a pre-seed herbicide and tank mixed with glyphosate, it provides effective control against a wide range of weeds including some of the toughest broadleaf weeds — cleavers and hemp-nettle.

*Also coming along from Corteva is a new herbicide-tolerant trait called Optimum Gly, expected to be launched in 2022. With its “advanced glyphosate-tolerant trait technology,” it is described as providing excellent in-crop weed control in canola over a much wider window of application ranging from the cotyledon stage right up to first flower.

Get the crop growing

King says along with all the product and variety rotation, the real foundation to producing a high-quality and high-yielding crop, is a nice even germination that gets vigorously growing seedlings through the soil. And proper seed treatment with an insecticide, such as Lumiderm, that controls flea beetles and wireworm and helps get the crop off to a robust start.

“Along with all the other tools available, that vigorously growing crop will have a much better chance to withstand disease pressure and also compete against weeds,” says King.

Freeman says a unique feature of the Corteva strategy is to provide farmers with a wide range of options not only in herbicide choices, but in variety and disease resistance.

“Looking at the canola portfolio in particular, it is being developed with varieties that work in all herbicide segments — glyphosate-tolerant, LibertyLink and Clearfield systems,” he says. “But plant breeders are also working to develop varieties with improved resistance to clubroot, blackleg and sclerotinia. Our plan is to deploy all those key agronomic traits across all three of the herbicide systems.

“Farmers will really be able to utilize all of the technology while they are rotating between herbicide traits as well as rotating between disease-resistance genes. If a farmer is selecting one herbicide system this year, they will also have access to varieties that work with that system that also have effective clubroot, blackleg and sclerotinia resistance as well.”

*Update: The article was updated to indicate Optimum Gly as a herbicide-tolerant trait.

About the author

Field Editor

Lee Hart

Lee Hart is editor of Cattleman’s Corner based in Calgary.

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