Efficacy of Ridomil MZ and protectant fungicides to control white rust (Albugo candida) and their effect on seed yield, oil content and fatty acid composition in mustard

Abstract

Ridomil MZ alone or Ridomil MZ followed by protectant fungicides was tested to manage white rust (Albugo candida) (Pers. ex Lev.) Kuntze on Brassica juncea L. var. RL-1359, sown at the normal time in 1989–90 and 1990–91 and under delayed sown conditions in 1990–91 at 2 different geographical locations of the Punjab state. Two spray applications of aqueous suspension of Ridomil MZ at 450 g a.i./ha or 1 foliar application of Ridomil MZ at 450 g a.i./ha, followed by another spray of Dithane M-45 at 600 g a.i./ha or Blitox-50 at 375 g a.i./ha at 15- or 20-day interval to a 70-day-old crop significantly reduced both foliage and floral infections. These treatments significantly increased the seed yield over control and other treatment combinations, without having an adverse affect on the oil content and fatty acid composition of the oil. The same fungicide regime was effective to control white rust when applied to a 50- or 60-day-old crop under delayed sown conditions. The seeds harvested from the plots treated twice with Ridomil MZ exhibited no detectable residue of metalaxyl and mancozeb. The timing of application of these fungicides may be critical in the control of white rust, particularly in the late sown crop.