Sensitivity of field populations of Ascochyta rabiei to chlorothalonil, mancozeb and pyraclostrobin fungicides and effect of strobilurin fungicides on the progress of ascochyta blight of chickpea

Abstract

2007. Sensitivity of field populations of Ascochyta rabiei to chlorothalonil, mancozeb, and pyraclostrobin fungicides, and effects of strobilurin fungicides on the progress of ascochyta blight of chickpea. Can. J. Plant Sci. 87: 937-944. Chickpea production faces a major challenge from ascochyta blight (Ascochyta rabiei), a devastating disease that can cause total crop loss. To assess the effect of repeated fungicide application on disease progress, strobilurin fungicides, primarily alternating pyraclostrobin and azoxystrobin treatments, were applied up to five times per year in each of 2 yr. A single application or two early applications reduced blight severity. A third application resulted in additional benefits in 1 of 2 yr, but additional applications did not reduce severity further. To monitor for fungicide tolerance in populations of A. rabiei, 66 single-spore isolates were collected and grown on growth media amended with chlorothalonil, mancozeb, or pyraclostrobin. Insensitivity to one or more of the fungicides was detected in 49 (74%) of the isolates. Based on the effect on conidial germination, insensitivity to pyraclostrobin or chlorothalonil was observed in 26 of 37 isolates (70%). Repeated fungicide application may be selecting for insensitive isolates of the pathogen; fungicide application should be combined with cultural measures to control ascochyta blight. des populations naturelles de Ascochyta rabiei au chlorothalonil, au mancozèbe et à la pyraclostrobine, et incidence des fongi-cides à la strobilurine sur la progression de la brûlure ascochytique chez le pois chiche. Can. J. Plant Sci. 87: 937-944. La brûlure ascochytique (Ascochyta rabiei), maladie dévastatrice pouvant détruire complètement une culture, pose un sérieux prob-lème aux producteurs de pois chiches. Afin d'évaluer l'incidence d'un usage répétitif de fongicide sur la progression de la mal-adie, les auteurs ont appliqué des fongicides à la strobilurine, principalement de la pyraclostrobine et de l'azoxystrobine en alternance, jusqu'à cinq fois par année pendant deux ans. Une seule application ou deux applications précoces de fongicide atténu-ent la gravité de la maladie. Une troisième application a eu des effets bénéfiques additionnels une année mais pas l'autre. Les applications supplémentaires n'ont pas réduit la gravité de la maladie davantage. Pour déterminer la tolérance de A. rabiei aux fongicides, les auteurs ont recueilli 66 isolats d'une spore qu'ils ont cultivés sur un milieu de croissance contenant du chlorothalonil, du mancozèbe ou de la pyraclostrobine. Quarante-neuf (74 %) des isolats étaient insensibles à un ou à plusieurs fongicides. D'après la germination des conidies, on a décelé l'insensibilité à la pyraclostrobine ou au chlorothalonil chez 26 des 37 isolats (70 %). L'application répétitive de fongicide pourrait favoriser la sélection d'isolats insensibles du pathogène; il con-viendrait de combiner le traitement antiparasitaire à des méthodes de lutte culturales pour combattre la brûlure ascochytique.

Perspectives and Challenges for Sustainable Management of Fungal Diseases of Mungbean [Vigna radiata (L.) R. Wilczek var. radiata]: A Review

“…However, disease management failures in legume crops associated with fungicide resistance have been reported from several countries (Chang et al, 2007;Lonergan et al, 2015;Price et al, 2015). For example, Price et al (2015) reported that isolates of C. kikuchii (Cercospora leaf spot) from soybean fields in Louisiana State, USA were insensitive to thiophanate methyl.…”

Development of screening techniques and identification of new sources of resistance to Ascochyta blight disease of chickpea

“…Fungicidal management of AB is not economical and is hazardous to the environment as several applications of fungicides are required (Chang et al 2007). Further, the use of fungicides having a site-specific mode of action such as QoI fungicides (azoxystrobin and 4 pyraclostrobin) increases the risk of fungicide resistance emerging in A. rabiei (Gossen et al 2004;Wise and Gudmestad 2009 (Nene et al 1981;Singh et al 1984;Sharma et al 1995, Chen et al 2005.…”

Control of ascochyta blight (Ascochyta complex) in pea under Lithuanian conditions

“…Research done in india evidenced that the best ascochyta blight control was given by seed treatment with thiram, and during the growing season by a three-time sprayapplication of chlorothalonil (Panicker, Ramraj, 2010). However, such intensive use of fungicides may result in the development of fungicide resistance in ascochyta blight causal agents (Chang et al, 2007).…”

“…The third application still gave some extra effect but the subsequent ones did not give any reduction in the disease severity. Having investigated the susceptibility of A. rabiei spores to the fungicides used, it was found that 70% of isolates were resistant to piraclostrobin or chlorothalonil (Chang et al, 2007).…”