Impact of different fungicides and bioagents, and fungicidal spray timing on wheat stripe rust development and grain yield

Abstract

Stripe rust of wheat caused by Puccinia striiformis f. sp. tritici is a major constraint for wheat production worldwide. Present investigation was carried out for two consecutive rabi seasons during 2014-15 and 2015-16 to evaluate some fungicides and bioagents for their effectiveness against yellow rust development on wheat and also to find out the appropriate time of fungicidal spray so as to avoid the yield losses caused by the disease. Two years data revealed that minimum mean disease severity of 1.22 per cent was recorded with a strobilurin fungicide azoxystrobin 25SC (Amistar @ 0.1%). This treatment gave a mean disease control of 98.67 per cent, thus increasing the grain yield and thousand grain weight by 77.33 and 44.14 per cent, respectively. It was followed 92.89 per cent disease control achieved in difenoconazole 25EC (Score @ 0.1%) which gave an increase of 66.15 and 37.09 per cent in grain yield and thousand grain weight, respectively. Bioagents Pseudomonas fluorescence (Pf3 @ 5 gm/L water with 2 x 10⁹ cfu/ml) and Bacillus subtilis (Bs1 @ 5 gm/L water 2 x 10⁹ cfu/ml) were moderately effective in controlling stripe rust by 41.83 and 39.92 per cent, respectively. Penconazole 100EC (Topas @ 0.1%) and mancozeb 75WP (Dithane M45 @ 0.2%) were found least effective in controlling the stripe rust. Further to achieve maximum protection against stripe rust and increase the grain yield, fungicide need to be sprayed either at flag leaf emergence or at 20 per cent leaves having stripe rust infection.