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Source: Syngenta Seed Care

With crop prices that haven’t been seen in decades, many canola growers are looking to capitalize on this opportunity.  However, some are casting aside tried and true management practices that could haunt them in the long run.  Some regions of North Dakota are tightening their crop rotations, pushing a wheat-canola-wheat-canola rotation that can quickly turn a desert oasis into a mirage.  In fact, the shimmer has started to lose its luster this year as researchers are seeing more fields decimated from blackleg infections.

Previously managed through varietal resistance and long rotations of canola once every three or four years, blackleg is evolving and changing from the non-threatening pathogroup (PG) 1 to the more aggressive, early attacking PG2 and even some PG3 and PG4 strains.

“We are starting to notice more of the aggressive blackleg strains,” reported Terry Gregoire, area extension specialist in cropping systems for North Dakota State University, based in Devils Lake.  “In the past three to four years, I estimate that some fields have experienced yield losses in the 80 percent range, particularly those planted to a less resistant variety in a high pressure situation.  This has been infrequent, but I have seen fields that have gone down and yielded in the hundreds instead of thousands of pounds.”

Bryan Hanson, agronomist at the Langdon Research Extension Center, is observing the same thing.  “We’re tending to see more blackleg.  Even when the varieties are moderately resistant or resistant, we’re still seeing spots of blackleg showing up.”

History, biology of blackleg

Blackleg was once a serious concern among canola growers.  In 1991, blackleg was identified in all 23 North Dakota fields that were examined, infecting about 28 percent of plants in those fields.  In 1993, the number infected jumped to 30 percent in the 40 fields examined and climbed to 33 percent in the 75 fields in 1995.  Since 1991, growers have switched from the highly susceptible Westar variety and now plant varieties that have moderate to low susceptibility.  As a result, disease incidence had been relatively low to non-existent.

But as Gregoire and Hanson can attest, that trend appears to be changing.  Blackleg survives for several years on infected crop residue and is also seed-borne.  “With every-other-year canola, there generally are enough spores in the crop residue from the previous canola year, or even up to two crop years ago, that when combined with cool, rainy weather, may result in early growth infections,” Gregoire explained.  “These early infections cause stand reductions and yield losses, especially where aggressive strains have become established.”

The aggressive strains of blackleg attack the crop early, causing leaf spots from the seedling stage through maturity.  Plants are more susceptible to blackleg when they’re attacked by insects, damaged by hail or injured by a herbicide application.  Early infections cause premature plant death and may result in plant lodging.  Later in the season, infected pods split open, leading to seed loss, and seeds become shriveled and gray.

Management considerations

Gregoire and Hanson point to longer crop rotations and resistant varieties as the cornerstone to keeping blackleg in check.  They recommend a rotation where canola is planted once every three to four years using varieties with MR or R ratings (see Table 1).

Table 1.  Canola Variety Rating Index

The second line of defense would be a fungicide seed treatment.  Even if a seedlot has tested negative for blackleg, there could be a few infected seeds, and just one infected seedling can spread the infection to many surrounding plants.  Applying Helix XTra^® seed treatment insecticide and fungicide can more fully protect the crop from this and other diseases.

“Because Helix XTra does such a great job against flea beetle, many growers don’t realize the high-quality fungicide package that comes already built into the product,” said Cliff Watrin, technical crop manager with Syngenta Seed Care^™.

Helix XTra combines the active ingredients from three top-performing fungicides – Apron^® XL, Dividend^® and Maxim^® 4FS – to protect canola seedlings from disease damage and improve stand establishment, as demonstrated by research conducted at the University of Manitoba (see Chart 1).

Chart 1. Trial #1: Dr. W.G. Dilantha Fernando, University of Manitoba, Winnipeg, Canada

“Helix XTra will act on any blackleg remaining on seeds so that the seeds may be more viable germinators,” Watrin explained.  “As a result, the crop often gets off to a faster start, more even stand and is better equipped to maximize yield potential.”

In addition to seed-borne blackleg, Helix XTra protects against the seedling disease complex caused by Pythium, Rhizoctonia and Fusarium.  This complex wrecks havoc on the seed’s ability to germinate and establish strong seedlings.

“Helix XTra protects vulnerable canola plants from the start.  It not only has excellent performance against flea beetle, but also does a great job against seedling diseases,” Watrin said.  “Helix XTra combines the active ingredients from three top-performing fungicides and one high-powered insecticide to protect canola seedlings from disease and insect damage so they can maximize their yield and quality potential.”

Syngenta is a world-leading agribusiness committed to sustainable agriculture through innovative research and technology.  The company is a leader in crop protection, and ranks third in the high-value commercial seeds market.  Sales in 2006 were approximately $8.1 billion.  Syngenta employs around 21,000 people in over 90 countries.  Syngenta is listed on the Swiss stock exchange (SYNN) and in New York (SYT).  Further information is available at www.syngenta.com.

Important: Always read and follow label directions before buying and using these products.

Apron^®, Dividend^®, Helix XTra^™, Maxim^®, Seed Care^™ and the Syngenta logo are trademarks of a Syngenta Group Company. 
Prosper^™ is a trademark of Bayer CropScience.

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