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Disease Scouting at Harvest: Is It Worth It?

The combine is rolling, your crop is looking good, but that yield monitor isn’t hitting the bushels you expected. Did you assess your crop for disease?

Why Scout for Disease? #

Disease scouting during harvest should be seen as a proactive measure. Sure, harvest is busy enough as it is, but pulling and assessing plants for disease can help make it less stressful. When you assess your crop for disease, you help determine your yield loss to specific diseases, if there are any. BrettYoung Agronomic & Regulatory Services Manager, Justine Cornelsen, recommends pulling up a few plants from different parts of the field so it’s entirely represented. Then, looking at each plant from the roots up, you’ll be able to tell a lot about your crop’s health.

“Disease scouting is a task that can tell you a lot about your variety selection and management practices from the season,” said Cornelsen. “But it also provides valuable information to help you alter practices for future years.”

Many plant diseases cause similar symptoms like premature ripening and plant lodging. This is where it becomes beneficial to be able to identify pathogen signs in the field to pinpoint which plant disease is causing the damage. Reviewing the environmental conditions can also help you to determine which plant disease did well in a specific year. 

“With the past few years being relatively hot and dry in the summer, a crop disease like sclerotinia hasn’t caused much damage,” said Cornelsen, adding, “whereas verticillium stripe in canola has thrived in those conditions.”

Canola Plant Diseases #

The best time to scout your canola crop for disease is at around 60% seed colour change (SCC), or at swathing time to differentiate between plant diseases. If you’re straight cutting your field, though, Cornelsen recommends scouting closer to the time of harvest so you can get a better yield loss estimate from diseases like sclerotinia and blackleg.

One way to quickly differentiate between canola diseases is by taking a look at the roots of the plant. Cutting into the tissue at the base of the plant will then help you determine if blackleg, verticillium stripe, or root rot has been ravaging your crop.

A trained eye can tell the difference between plant diseases, but you can get further confirmation of pathogen presence by submitting samples to a diagnostic lab. Swelling of the roots (galls) can lead quickly to a clubroot diagnosis, which should drastically change future crop rotation plans, hybrid selection, and sanitation protocols on your farm. 

“When looking to identify between blackleg and verticillium stripe, look for black spots or wedges in the root cross section cuts for blackleg,” said Cornelsen. “Verticillium stripe will leave the root tissue a greyish hue and eventually tiny microsclerotinia will start forming in the plant stalk tissue.”

Both sclerotinia and verticillium stripe cause the stem to bleach, she said, which then allows it to become fragile and shred easily. Plants with sclerotia will develop a sclerotinia body within the stem and verticillium stripe-infected plants will form microsclerotia in the plant stem below the stem epidermis.

Powdery mildew has been popping up in canola this season, leaving clouds of white dust covering machinery. Although alarming, the disease doesn’t typically take much yield away from canola, so Cornelsen said it shouldn’t worry growers too much. Another late season disease that could affect your crop is Alternaria pod spot, which leaves the pods speckled and weakened, eventually leading to some harvest challenges. 

Soybean Plant Diseases #

With soybeans needing to dry right down for harvest, it’s best to assess your crop for foliar and stem diseases at the R5 to R6 stage — that’s when they can be assessed for bacterial blight, Septoria brown spot, downy mildew, frogeye leaf spot, northern stem canker, white mould, pod/stem blight, and anthracnose.

Septoria brown spot and frogeye leaf spot are common in Western Canadian soybean production regions. The small dark brown spots on the plant coalesce and cause infected leaves to turn yellow. Frogeye leaf spot forms irregular shaped leaf lesions that are commonly grey with a reddish-purple border. 

Pulling up your soybean plants and looking at the roots can reveal a lot, especially soybean cyst nematode (SCN). For this disease, Cornelsen says to look for tiny, lemon-shaped cysts on the plant roots that are smaller than nodules. Phytophthora root rot (PRR) is another disease to watch out for that can develop at any stage in your soybean plant’s life. With PRR, your plants will form brown lesions on the stem, restricting the flow of water and nutrients to the plant. Luckily, these diseases can be managed through variety selection.

Disease Management   #

Though there isn’t much that can be done to minimize yield losses from plant diseases at harvest, you can use the information gathered from disease scouting in future years’ crop planning and product selections. This information can also help you to understand why fields and products yielded differently on your farm this season.

When it comes to canola products and disease management, look for the DefendR® designation on your BrettYoung hybrid. Each product with the DefendR logo on it has superior harvest management and disease resistance genetics. Many BrettYoung canola hybrids have DefendR-rated resistance to clubroot and/or blackleg, along with pod shatter tolerance.

Our soybean varieties also come equipped with their own defensive packages, helping them stand up to diseases like PRR, white mould, and SCN.

To learn more about BrettYoung products and their disease management traits, go to

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