Impact of seed dressing and systemic fungicidal sprays in controlling the magnitude and spread of the late blight (Phytophthora infestans) disease in addition to augmenting the yield of superior grade potato tubers
Creators: name: S H Peerzada
name: Viswanath H S
name: K A Bhat
Publisher: name: figshare
Year: 2020
Subjects: subject: 60704 Plant Pathology
subject: FOS: Biological sciences
subject: FOS: Biological sciences

description: Potato late blight is one of the devastating plant diseases. The pathogen is primarily seed borne and polycyclic in nature dispersing many secondary sporangiospores from foliar infected plants to healthy ones spreading rapidly within short span causing heavy yield losses. So, in the present study, two different experiments were conducted separately, where in the first one, seed dressing with different fungicides was carried out under pot conditions followed by second experiment in finding the effect of systemic foliar fungicidal sprays under field conditions against the incidence and intensity of late blight disease. Four different fungicides (one protectant and three systemic) viz., mancozeb 75 WP, dimethomorph 50WP, cymoxanil 8 + mancozeb 64 WP and metalaxyl 8 + mancozeb 64 WP, were evaluated as seed dressers against late blight (Phytophthora infestans) of potato cv. Kufri Jyoti in pot experiments during 2016 and 2017cropping seasons. The results obtained during both cropping seasons revealed that all the fungicidal seed dressers delayed the appearance of first symptoms of the disease. The disease incidence and intensity recorded indicated that all the fungicides significantly reduced the late blight at all the periods compared to control (water). The ‘A’(AUDPC) values were significantly reduced when tubers were treated with different fungicides. Tuber treatment with dimethomorph or metalaxyl + mancozeb showed minimum ‘A’ value of 125.91 compared to the maximum “A” value of 185.20 for undressed control during 2016 and similar trend of results was observed during 2017 cropping season. In the second experiment of systemic foliar fungicidal sprays, three systemic fungicides viz. dimethomorph 50 WP at 0.05% (C1), 0.10% (C2) and 0. 15%(C3) concentrations, metalaxyl 8+mancozeb 64 WP and Cymoxanil 8 + mancozeb 72 WP at 0.15% (C1), 0.20% (C2) &amp; 0.25% (C3) concentrations sprayed at ten days interval after symptom development till dehaulming stage were evaluated against the disease incidence and intensity during 2016 &amp; 2017 cropping seasons. The results obtained during 2016 cropping season revealed that, among the systemic/translaminar fungicidal foliar sprays, all the fungicides were equally superior to water-sprayed control in reducing the blight incidence from 74.04 to17.03 per cent. On an average, foliar spray with dimethomorph yielded the minimum blight intensity of 11.64 per cent followed by cymoxanil 8 + mancozeb 72 WP 13.02 per cent spray compared to 56.27 per cent obtained in water- sprayed check. Dimethomorph foliar sprays at C2 and C3 concentrations were found most effective recording the lowest blight intensities of 8.38 and 8.44% respectively and least “A” value followed by foliar spray with cymoxanil 8+mancozeb 72 WP (10.35-10.41%) compared to water sprayed check (56.27%) during 2016 and similar trend was observed during 2017 cropping season. It was also found that the foliar sprays with dimethomorph resulted in the highest tuber yield (206.14 q tubers per hectare) and large sized tubers followed by foliar sprays with metalaxyl 8+mancozeb 64 WP as compared to water-sprayed control plots (152.72 q/ ha)with small sized tubers.