Ascochyta blight, caused by Ascochyta rabiei, is a serious constraint to chickpea production, managed primarily via foliar fungicides and genetic resistance. Imidazolinone (IMI) herbicides, used for in-crop weed management, can injure susceptible chickpea cultivars and so increase ascochyta risk. The impact of IMI application on susceptible and tolerant cultivars was assessed in combination with blight management options (starting fungicide application prior to symptom development, two versus four fungicide applications, genetic resistance) in small plot trials in Saskatchewan in 2019, 2021, and 2022. Two kabuli-type chickpea cultivars (CDC Orion, CDC Orkney) and two desi-types (CDC Vanguard, CDC Cory) were grown with or without IMI herbicide. CDC Orion and CDC Vanguard were susceptible to IMI herbicides, CDC Orkney and CDC Cory were tolerant. The severity of ascochyta blight (0–9 scale) was very low in 2019 and 2021 (1.3 in 2019, 0.5 in 2021) and generally did not differ among treatments. In 2022, the desi cultivars had less disease at the end of the season than kabuli cultivars (mean 3.1 vs. 4.3). In 2022, two applications of fungicide (starting before or after symptoms appeared) reduced severity relative to the control (3.5 vs. 4.6). Four applications did not provide additional reduction. IMI herbicides resulted in <15% injury on IMI-susceptible and none on IMI-tolerant cultivars. Waiting for ascochyta symptoms, rated 1, to apply fungicide was just as effective as applying fungicide before symptom development. Fungicides provide yield and disease management benefits when disease is moderate, but not when weather is hot and dry.
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27 January 2025
Impact of fungicide, IMI-herbicide, and cultivar on ascochyta blight severity and yield of chickpea in Saskatchewan, Canada
Michelle Hubbard,
Limin Luan,
Bunyamin Tar'an,
Bruce D. Gossen
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Ascochyta rabiei
disease management
foliar fungicide
genetic resistance
IMI resistance