Effect of sowing dates and of intercropping on disease severity of white rust in mustard caused by Albugo candida

A detailed field experiment was conducted in Northern India to investigate the effects of (1) sowing dates, (2) intercropping, and (3) inter-crop orientation, on the severity of White Rust of mustard (Brassica juncea L.) caused by Albugo candida. Field plots (4 m by 3 m) with three sowing dates at ten-day intervals and with four mustard-wheat intercropping treatments were established at the Experimental Farm of GB Pant University of Agriculture & Technology, Pantnagar, India. The four intercropping treatments were: (i) Sole mustard; (ii) 2 wheat rows with 1 mustard row (2v1); (iii) 5 wheat rows with 1 mustard row (5v1); and (iv) 8 wheat rows with 1 mustard row (8v1). Assessments of White Rust severity made at different layers in the crop canopy indicated in all four treatments a vertical gradient of increasing disease from the top to the lower layers of the crop canopy. Results further indicated that both sowing date and intercropping had significant (P <0.05) effects on disease severity. White Rust severity was highest in the Sole mustard stands, followed in decreasing order by 2v1, 5v1 and 8v1. White Rust severity also decreased in delayed sowing dates, i.e., severity was much higher in the early (1st week of November) than in the late (third week of November) crop establishment dates. White Rust severity was higher in plots with an East-West orientation compared to a North-South orientation, presumably reflecting the more conducive microclimate (e.g., leaf wetness duration, shade) conditions in the East-West orientation. This work is indicative of the value of intercropping mustard to control White Rust in the field.