Page 1 Page 2 Page 3 Page 4 Page 5 Page 6 Page 7 Page 8 Page 9 Page 10 Page 11 Page 12 Page 13 Page 14 Page 15 Page 16 Page 17 Page 18 Page 19 Page 20 Page 21 Page 22 Page 23 Page 24 Page 25 Page 26 Page 27 Page 28 Page 29 Page 30 Page 31 Page 32 Page 33 Page 34 Page 35 Page 36 Page 37 Page 38 Page 39 Page 40 Page 41 Page 42 Page 43 Page 44 Page 45 Page 46 Page 47 Page 48 Page 49 Page 50 Page 51 Page 52 Page 53 Page 54 Page 55 Page 56 Page 57 Page 58 Page 59 Page 60 Page 61 Page 62 Page 63 Page 64 Page 65 Page 66 Page 67 Page 68GETTING KEY MESSAGES INTO THE HANDS THAT NEED THEM. For a handout on this topic, visit Germination.ca.. Send us your company name and logo and we'll develop a customized PDF for you to distribute. The blackleg fungus may also occur at low levels in the seed. Research shows that seed infection is seldom more than one to two per cent; however, this amount can introduce the fungus into new areas. The fungus is spread by rain-splashed spores, wind borne spores and by infected seed. Leaf spots can occur from the seedling stage to maturity, according to information from the government of Manitoba. Whitish, round to irregu- lar spots dotted with numerous black fruiting bodies appear on the leaves and stem in the summer. Later in the season, superficial lesions may occur at the stem base. The lesions are col- oured white to grey (mild strain) or brown to greyish black (aggressive strain). The brown to greyish black stem lesions become sunken, girdling the stem near the soil line and cause premature death. Scouting for Blackleg According to the CCC, scouting for canola blackleg is an important man- agement tool. There are three main scouting periods for blackleg disease during the growing season. These include: prior to planting, during the vegetative stage and at swathing. Prior to planting, growers and agronomists should be examining canola residue to see if pseudothecia are present. During the vegetative stage, a W-pattern should be used to scout the field, starting at the edge of a field. Focus on edges where new canola resi- due might be present in an adjacent field. The CCC recommends examining at least 50 plants for the presence of lesions. If lesions are found on more than 10 per cent of plants, then there is risk of significant disease development. At swathing is the best time to scout for the disease as the basal cankers, which cause significant yield loss are easy to see. In this stage, growers and scouts will want to pull up at least 50 plants in a W-pattern as described above. Clip with clippers at the base of the stem or top of the root and look for blackened tissue inside the crown of the stem. The amount of infection present will help identify the level of risk and the best management practices for that field in the following years. Management Advice To help control and mitigate blackleg, retailers and agronomists are urged to stress the importance of using disease-free seed when working with farmers. Seed from diseased areas should be treated with a fungicide seed treatment. Additionally resistant varieties are available. The use of moderately sus- ceptible or moderately resistant vari- eties may still result in low levels of blackleg. Most new Argentine canola varieties are moderately resistant or resistant. However, all Polish varie- ties are susceptible, according to the Manitoba government. Another tip to control blackleg is to incorporate infected stubble after harvest. Blackleg survives in slowly decomposing canola stubble. A four- year rotation between canola crops is recommended once blackleg has been detected in a field. Furthermore, con- trolling volunteer canola and wild mus- tard in other crops will help to mitigate the presence of blackleg. Hwang says when it comes to meas- uring the agronomic efficacy and eco- nomic benefits of control methods, one must understand the disease-yield rela- tionships. As such, he conducted field experiments in 2013, 2014 and 2015 to determine the relationship between blackleg disease severity and yield in a susceptible cultivar and in moderately resistant to resistant canola hybrids. Based on his research, Hwang says that disease severity was lower, and seed yield was 120 per cent to 128 per cent greater in moderately resistant to resistant hybrids compared with the susceptible cultivar. “Regression analysis shows that pod number and seed yield declined lin- early as blackleg severity increased,” he explains. “Seed yield per plant decreased by 1.8 gram for each unit increase in disease severity, corre- sponding to a decline in yield of 12.7 per cent for each unit increase in dis- ease severity.” JANUARY 2017 19 “Regression analysis shows that pod number and seed yield declined linearly as blackleg severity increased.” — Sheau-Fang Hwang