Chemical control of leaf scald of rice

Leaf scald of rice caused by Rhynchosporium oryzae is emerging as an important fungal disease found virtually all over the rice growing regions of world. Nine fungicides consisting of four systemic viz. Bavistin 50 WP, Beam 75 WP, Contaf 5 EC and Tilt 25 EC, three non systemic viz. Blitox 50 WP, Dithane M-45 75 WP and Dithane Z- 78 75 WP and two coordinated fungicides viz. SAAF 75 WP and Vitavax 200 75 WP were evaluated against Rhynchosporium oryzae for their efficacy under both in vitro and in vivo conditions. In vitro studies revealed that among systemic fungicides, Tilt 25 EC and Contaf 5 EC at 5 and 10 ppm provided cent per cent mycelial inhibition of Rhynchosporium oryzae whereas SAAF 75 WP among coordinated and Dithane M-45 among non-systemic fungicides exhibited same results at 5 and 200 ppm respectively. In field the foliar applications of all the fungicides except Blitox (2.5%) significantly controlled the disease as well as increased the grain yield over check. Tilt 25 EC (0.1%) provided maximum disease control (54.02%) and yield gain (38.49%) followed by Beam (0.1 and 0.05%), SAAF (0.25%), Contaf (0.1%), Tilt (0.05%) and Contaf (0.05%) with three sprays at 15 days interval starting from the first appearance of leaf scald symptoms in the field. Among non-systemic fungicides Dithane Z-78 and Dithane M-45 at 0.25 per cent concentration provided disease control of 21.49 and 18.68 per cent and yield gain of 15.15 and 19.70 per cent respectively.