Submitted to: Plant Disease Management Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/10/2022
Publication Date: 8/9/2022
Citation: Chen, W., McGee, R.J., Vandemark, G.J. 2022. Evaluation of fungicides in seed treatment for control of chickpea damping-off caused by metalaxyl-resistant Pythium spp. 2021. Plant Disease Management Reports. 16. Article ST011. https://doi.org/10.1094/PDMR16.
Interpretive Summary: Chickpeas, especially large seeded chickpeas, are very vulnerable to seed rot and damping-off caused by Pythium spp. This disease has been traditionally managed successfully using seed treatment with metalaxyl fungicide. However, metalaxyl control failure occurred in 2014 due to development of metalaxyl resistance in Pythium in the inland Pacific Northwest. We previously found that seed treatment with ethabaxom alone or in combination with metalaxyl was effective at protecting chickpea from seed rot and damping-off caused by metalaxyl-resistant Pythium. In 2021, we evaluated additional fungicides as seed treatments. The field trials in 2021 showed that picarbutrozon and GXP-60445, as well as ethaboxam, were effective against metalaxyl-resistant Pythium. These new seed treatment options could be used as alternatives in managing metalaxyl-resistant Pythium.
Technical Abstract: Pythium seed rot and damping-off of chickpea has been successfully managed by using seed treatment with fungicide metalaxyl. However, metalaxyl-resistant Pythium spp. have emerged and rendered metalaxyl ineffective. Recent studies showed that ethaboxam was effective in protecting chickpea seeds from seed rot and damping-off caused by metalaxyl-resistant Pythium. Additional effective fungicides are needed for rotation with ethaboxam. Two field trials were carried out in 2021 to identify additional seed treatment fungicides effective against metalaxyl-resistant Pythium. High levels of disease pressure were induced by irrigation immediately after planting and severe seed rot and pre-emergence damping-off occurred during the trials. Essentially no seeds emerged in the check treatment plots. Due to the presence of metalaxyl-resistant Pythium, virtually no seeds emerged in plots treated with metalaxyl alone. Two fungicides picarbutrazon and GXP-60445 significantly improved chickpea germination and were as effective as ethaboxam. In summary, picarbutrozon and GXP-60445 as well as ethaboxam, were effective against metalaxyl-resistant Pythium, providing effective fungicides for rotational applications.