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Poster: Biology & Disease Mgmt: Chemical Control


Timing of fungicide applications is critical for blackleg control in canola
L. DEL RIO MENDOZA (1), S. Ruud (1), S. Mansouripour (1) (1) North Dakota State University, U.S.A.

Blackleg, caused by Leptosphaeria maculans, is an important disease affecting rapeseed/canola (Brassica napus) production worldwide. The genetic resistance currently available in most commercial cultivars is ineffective against strains of blackleg that have become prevalent in recent years and because of this, growers are relying more frequently on fungicide use to manage this disease. To optimize fungicide use, greenhouse studies evaluated the efficacy of different timings of application of azoxystrobin, pyraclostrobin, and fluxapyroxad on blackleg severity. These active ingredients, present in four of the six fungicides registered to manage blackleg in North Dakota, were applied two days before and 0, 2, 4, 8, or 16 days after seedlings of cv. Westar were inoculated with an L. maculans spore suspension. Disease severity was evaluated 12 days after inoculation and before harvest. For each fungicide, trials were conducted separately using a randomized complete block design. Each study was replicated and conducted three times. All three fungicides were most effective when applied within eight days from inoculation and lost their efficacy when applied at a later time. This information highlights the need for early protection of seedlings as well as for the development of disease warning systems that could identify help growers optimize spraying schedules.