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.

Highlights

• Isabgol (Plantago ovata) is the most important and commercially grown medicinal crop in India for its dietary fiber.
• The seed husk is having great medicinal properties and is used to cure inflammation of the mucus membrane of gastrointestinal and genito-urinary tracts, chronic constipation, dysentery, duodenal ulcers, gonorrhea, and piles.
• It is also being used in the food industry especially in ice creams, biscuits, candies, and calico printing and setting lotions.
• The crop is affected by various biotic and abiotic factors. Downy mildew caused by Peronospora plantaginis is one of the major limiting factors for its production and quality.
• The growth of the fungal mycelium and disease development is highly influenced by the predisposition factors viz. temperature, relative humidity, and precipitation of dew on leaves during night hours.
• The sporangiospores germination take place early in the morning when leaves remain wet by the dew precipitation, positively correlated with the incidence and severity of the disease. Early sowing significantly reduces the disease incidence and losses in the crop.