Ascochyta blight management in chickpea
In years of moderate disease pressure with cultivars rated as intermediate resistance to ascochyta, two foliar fungicide applications were as effective as four applications for disease management, yield protection, and prevention of seed infection.
Chickpea can be a profitable crop in southern Saskatchewan, and is an alternative crop to pea or lentil since it has a reduced risk of Aphanomyces root rot. However, a major production challenge is its high risk from ascochyta blight disease caused by Ascochyta rabiei, which has been primarily managed with foliar fungicides and genetic resistance in chickpea varieties.
A research project was conducted in Saskatchewan over three years in 2019, 2021, and 2022. The goal of the research was to see how kabuli and desi chickpeas, with or without IMI-herbicide tolerance, respond to the timing and number of applications of foliar fungicides and IMI herbicide application.
Small plot trials were conducted at the Swift Current Research and Development Centre of Agriculture and Agri-Food Canada at Swift Current, SK. Four chickpea varieties were compared that included kabuli and desi market types, and IMI-tolerant and susceptible types. The varieties were CDC Orion (kabuli; IMI-susceptible), CDC Orkney (kabuli; IMI-tolerant), CDC Vanguard (desi; IMI-susceptible), and CDC Cory (desi: IMI-tolerant). The varieties were intermediate in ascochyta resistance ranging from a low of 4.3 for CDC Cory to a high of 5.1 for CDC Orion on a rating scale of 0-9. On this scale, scores of less than 4 are considered resistant, 4–6 as intermediate, and >6 are considered susceptible.
The IMI herbicide treatment was an application of Odyssey Ultra (imazamox + imazethapyr; Group 2) compared to an untreated control.
The four fungicide treatments were:
- no fungicide,
- two fungicide applications starting before visual symptoms at around seven to eight nodes (Priaxor 2019/Dyax 2021/22) followed by Proline around flowering;
- two fungicide applications starting with Priaxor (Dyax in 2021 and 2022)after symptoms during vegetive phase followed by Proline at flowering;
- four fungicide applications starting with Priaxor )Dyax in 2021 and 2022) before visible symptoms around seven to eight nodes, followed by Proline at vegetative stage, Delaro at flowering and Bravo ZN at podding.
Priaxor and Dyax contain fluxapyroxad (Group 7) + pyraclostrobin (Group 11) active ingredients. Proline contains Group 3 prothioconazole. Delaro contains prothioconazole + trifloxystrobine (Group 11) and Bravo ZN contains the Group M5 active chlorothalonil.
Chickpea were seeded in mid-May at 6 seeds/ft2 (60 seeds/m2) with a hoe drill with side-band openers. Seed was treated with Apron Maxx fungicide. TagTeam granular inoculant was seed-placed. Seed-placed phosphorus (P) at a rate of 15 lbs/ac (17 kg/ha) actual P was applied as 11-52-0. A pre-seed burndown of glyphosate followed by Aim and Authority was applied, and no other in-crop herbicides were applied except for the IMI-herbicide treatments.
Irrigation was applied to the small plots to increase the risk of ascochyta blight. The pathogen was present in the plots throughout the research.
The severity of ascochyta blight (0–9 scale) was very low in 2019 at 1.3 and 2021 at 0.5. The variety, herbicide and fungicide treatments did not generally differ in disease severity.
In 2022, disease severity was higher with the overall mean severity reaching 4.3 during podding in mid-August. The desi cultivars had less disease at the end of the growing season at 3.1 compared to 4.3 for kabuli cultivars.
Two fungicide applications as good as four
In 2022, under higher but still moderate disease severity, two applications of fungicide had lower ascochyta at 3.5 compared to the control at 4.6. There wasn’t any difference whether the first application started before or after symptoms appeared, although these symptoms were very mild and noticeable as small black dots on leaves or stems. Four applications did not provide additional reductions in disease severity.
The IMI-susceptible cultivars, CDC Vanguard and CDC Orion were injured by the IMI-herbicide application. However, the level of injury was relatively low at 2%–10% in 2019, 2%–5% in 2021, and 1%–9% in 2022 when measured at various timings in June. However, plants can generally recover from injury levels below 15%.
In 2019, an application of IMI-herbicide to CDC Orion (susceptible) significantly reduced yield, but the yields of the other varieties were not affected. In 2021, a hot, dry year with low disease pressure, yield only varied by cultivar with CDC Cory and CDC Vanguard having the highest yields at around 1500 lbs/ac (1700 kg/ha), CDC Orkney was intermediate at 855 lbs/ac (961 kg/ha), and CDC Orion the lowest at 255 lbs/ac (287 kg/ha). Fungicide application did not affect yield in these two years.
In 2022, with higher disease pressure, fungicide application increased yield. Averaged across treatments, fungicides increased yield by 14% to 24% compared to the no fungicide control. The three fungicide treatments were statistically similar, two fungicide applications starting early yielded 1428 lbs/ac (1604 kg/ha), two fungicides starting with disease symptoms yielded 1314 lbs/ac (1476 kg/ha), and the four treatments yielded 1414 lbs/ac (1589 kg/ha) compared to the control at 1152 lbs/ac (1294 kg/ha).
Impact of chickpea cultivar and application of IMI herbicide or fungicide on seed yield in 2019, 2021, and 2022
Source: Hubbard et al. 2024
The fungicide treatments also resulted in lower seed infection, with the no fungicide treatment having seed infection at 1.16 % compared to the fungicide applications that were statistically similar ranging from 0.31% to 0.41%
In summary, under hot and dry conditions when the disease rating is less than 3, there was no benefit to fungicide application to manage ascochyta blight. Under moderate disease conditions ranging from 4 to 6, and with intermediate-rated resistant varieties, two fungicide applications were as effective as four applications. For the first fungicide application, waiting for mild, early ascochyta symptoms to develop prior to fungicide application was just as effective as applying fungicide before symptom development.
Funding was provided by the Saskatchewan Agricultural Development Fund, Ministry of Agriculture, and from Agriculture and Agri-Food Canada for facilities, equipment, and land access, and from BASF, Bayer, and Syngenta for donating fungicide
Michelle Hubbard, Limin Luan, Bunyamin Tar’an, and Bruce D. Gossen. 2025. Impact of fungicide, IMI-herbicide, and cultivar on ascochyta blight severity and yield of chickpea in Saskatchewan, Canada. Canadian Journal of Plant Science. 105: 1-13.
OPEN ACCESS: https://doi.org/10.1139/cjps-2024-0115
