Page 308 - PC2019 Program & Proceedings

PLANT CANADA 2019

P189. A novel approach to blackleg management in canola: Combining a new fungicide seed
treatment with improved flea beetle control
1
1
Huang, S. ; D. Fernando ; D. McLaren ; G. Peng
2
2
1 University of Manitoba
2 Agriculture and Agri-Food Canada (AAFC)
Blackleg or stem canker, caused by the fungal pathogen Leptosphaeria maculans Ces. & de Not, is a
serous disease on canola (Brassica napus L.). The disease is managed primarily with resistant cultivars
carrying major and/or minor resistance genes. However, the genetic resistance, especially that relying
only on specific R genes, can often be eroded due to race shits in the fungal populations. Prior work has
shown that cotyledon is the key pathway to stem infection, but wounds are possibly required for
successful infection of cotyledons by L. maculans in western Canada due to generally dry conditions after
seeding. Flea beetles often wound cotyledons, especially under warm and dry conditions, potentially
favoring blackleg infection. Here, we initiated a study to explore a novel approach combining new
fungicide seed treatment based on a succinate dehydrogenase inhibitor (SDHI) with improved flea beetle
control to minimize the early infection that can lead to blackleg of canola. To test this hypothesis, the
susceptible canola cultivar Westar was treated with (1) one of the current industry-standard seed
treatments Prosper EverGol (PEG), (2) PEG plus SDHI and (3) PEG plus foliar insecticide applications
targeting flea beetles up to the 4-leaf stage of canola. 74-44 BL, a Canadian canola cultivar with blackleg
resistance, will be treated similarly to assess the benefit of the treatments on a representative resistant
cultivar in western Canada.

Shuanglong Huang (Shuanglong.Huang@umanitoba.ca)

P190. Sensitivity of Pseudoperonospora humuli to the systemic fungicides, metalaxyl and fosetyl-Al.
2
1
Munawar, A. ; M. Filatos ; C. Bakker ; M. McDonald ; K. Jordan
1
1
1
1 University of Guelph
2
Ontario Ministry of Agriculture, Food and Rural Affair

Pseudoperonospora humuli causes systemic downy mildew in hops (Humulus lupulus). Currently, the
only systemic fungicide registered for hops in Canada is metalaxyl (Ridomil). Another systemic fungicide
with potential for registration is Aliette (fosetyl-Al). However, sensitivity of P. humuli to both metalaxyl
and fosetyl-Al is unknown in Ontario. This study was designed to determine the sensitivity of Ontario
isolates to these systemic fungicides. From 2017-2019, the entire population on each of 61 basal spikes,
collected from 1 research and 8 commercial hop yards were tested using a leaf disk assay for metalaxyl.
The population from spikes having less than 50% growth on the control plate or showing irregular
response by growing only onto higher concentrations of metalaxyl was excluded from the data. Based on
these two criteria, the population from 25 spikes were included in the data analysis. The population from
ten spikes was found resistant to metalaxyl at 50 and 100 ug/ml. Twenty spikes from a total of 46,
collected from 8 hop yards from 2018-2019, showed 50% or more sporulation in leaf disk assay for
fosetyl-Al. The population from six spikes showed resistance to fosetyl-Al at either 100 ppm, or 100-200
ppm or 100-400 ppm. The results of the current study indicate the presence of resistant isolates of P.
humuli in Ontario to both fungicides and requires further investigation to improve management practices.

Asifa Munawar (munawara@uoguelph.ca)

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