Field evaluation of fungicides and essential oils for managing Ascochyta blight on chickpea, 2020

Authors: Chen, Yung Chun; Vandemark, George; McGee, Rebecca; PARIKH, LIPI - Montana State University; BURROWS, MARY - Montana State University; WU, SARAH - University Of Idaho

Submitted to: Plant Disease Management Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/13/2021
Publication Date: 8/16/2021
Citation: Chen, Y., Vandemark, G.J., Mcgee, R.J., Parikh, L., Burrows, M., Wu, S. 2021. Field evaluation of fungicides and essential oils for managing Ascochyta blight on chickpea, 2020. Plant Disease Management Reports. 15:CF218.

Interpretive Summary: Ascochyta blight is one of the most important foliar diseases of chickpea. It is caused by the fungal pathogen Ascochyta rabiei. There is no complete resistance to this disease in chickpea varieties. Consequently, fungicide application is a common practice for managing Ascochyta blight. Fungicides are available for controlling Ascochyta blight but the pathogen is prone to develop resistance to certain groups of fungicides. For example, resistance to QoI fungicides has been reported in Ascochyta rabiei. Alternative fungicides should be evaluated and made available to prevent development of fungicide resistance in the pathogen population. Additionally, there are no treatments available for organic chickpea production. To evaluate foliar fungicides and essential oils against Ascochyta blight of chickpea, a field trial was established near Pullman, WA in 2020. A number of fungicides were found to be effective, and the essential oil (oregano oil) showed promise as a management option for organic production. The information on fungicide efficacy is useful for registering new fungicides for controlling chickpea Ascochyta blight and identifying alternative fungicides to prevent development of fungicide resistance. Additionally, the results showed that oregano oil should be evaluated further as a potential treatment for managing Ascochyta blight that is compatible with organic chickpea production practices.

Technical Abstract: Application of fungicides is a common practice in managing Ascochyta blight of chickpea. Frequent applications of fungicides of the same class often result in development of fungicide resistance. Resistance to QoI fungicides has been reported in Ascochyta rabiei. Additionally, there are no treatments available that are compatible with organic chickpea production. Consequently, new and different classes of fungicides are needed for rotational applications and for organic chickpea production. A field trial was established near Pullman, WA in 2020 to evaluate foliar fungicides against Ascochyta blight of chickpea, and essential oils as treatments compatible with organic production. The fungicide trial employed a randomized complete block design with four replications. Plots were inoculated with a mixture of conidia of two pathotypes of Ascochyta rabiei. Disease severity of each whole plot was evaluated based on a 1-to-9 scale. Disease severity increased over time in the control plots, showing the conducive conditions for Ascochyta blight due to the daily irrigation. Significant differences were observed in disease severity among the treatments for data collected on 8 July and thereafter. Six fungicides were very effective at managing Ascochyta blight, and all significantly reduced severity of the disease and increased yield. Among the two essential oils, oregano oil showed promise and reduced disease score numerically, but not statistically, at P=0.05. Increasing application rate or the frequency of applications will improve efficacy of oregano oil in managing Ascochyta blight. In summary, all the chemical fungicides tested were effective against Ascochyta blight. These fungicides are available for rotational applications to prevent development of fungicide resistance. Oregano oil showed potential for use in organic productions.