Management of Helminthosporium leaf blight of wheat in Nepal.
Helminthosporium leaf blight (HLB) caused by a combination of Helminthosporium sativum [Cochliobolus sativus] and Pyrenophora tritici-repentis is a major disease of wheat in Nepal, causing 3.1-23.8% losses in grain yield. Field experiments were conducted at NWRP, Bhairahwa, during 1991-96 to develop an integrated approach to disease management through the use of resistant varieties, cultural practices and chemical sprays. Ning 8319, DL 153-2, Ocepar-7, Annapurna-I, BL 1249, NL 590 and NL 625 were observed as tolerant to HLB. LFN/1158, ALD/PVN/YMI#6, PEAU 'S'/VEE#5'S', LAJ 2519/BOW, Agropyron curvifolium derivatives have also shown resistance. The area under disease progress curve (AUDPC) was low in resistant/tolerant genotypes and was used to measure the effects of HLB. Thousand grain weight, plant height, days to heading and grain yield were negatively correlated with AUDPC. HLB development and number of irrigations were negatively correlated either on the flag leaf or the whole plant. Seed rate (120 and 150 kg/ha) had no significant effect on HLB development. The application of Tilt (propiconazole) at 125 ml a.i./ha with three sprays at two week intervals under field conditions gave effective control. These interactions suggest that HLB can be managed through an integrated approach by use of host resistance, cultural practices and adequate fungicide application.