Downy Mildew Disease Severity on Different Dates of Sowing Under Variable Weather Conditions in Different Varieties of Isabgol

Abstract

The downy mildew incited by Peronospora plantaginis Underwood is one of the economically important diseases of Isabgol. It is important to study and understand the role of different dates of sowing on the development of diseases and their eco-friendly management. The downy mildew symptoms appeared in four different varieties viz. GI-2, Niharika, H1-5, and HI-2009 sown on 28th October (1st DOS) on 74-76 DAS whereas it was 52-54 days when sown on 12th November (2nd DOS) and 51-52 days on the crop sown on 28th November (3rd DOS). The maximum disease intensity of 62.77% was observed during the second date of sowing and the least disease intensity was recorded on the third date of sowing (27.77%). The maximum average disease progression (7.50 cm) was observed on the first date of sowing and a minimum of 6.49 cm on the third date of sowing. As the disease intensity increased AUDPC values also increased and these values were almost similar for all four varieties with the date of sowing. The apparent infection rate increased to a greater extent from the first date of sowing to the second date of sowing thereafter, decreased during the third date of sowing.