Studies on stemphylium blight of lentil (Lens culinaris) and its management practices

Abstract

A field survey was conducted to know the prevalence of stemphylium blight caused by Stemphylium botryosum of lentil (Lens culinaris) growing 11 districts viz. Jessore, Kushtia, Faridpur, Pabna, Rajshahi, Maherpur, Madaripur, Barisal, Jhalokathi, Khulna and Satkhira in Bangladesh during cropping season of 2012-13 in the farmers’ field. Out of 11 districts the highest disease incidence was found in Jhalokathi (Sadar) (77.90%) and the lowest disease incidence was found in Pabna (Ishardi) (45.50%). The highest disease severity was found in Faridpur (Sadar) and the lowest disease severity was found Kushtia (Kumarkhali). Farmers used six different varieties in 11 districts. Local variety performed highly susceptible (HS), BARI Masur-3 and BARI Masur-4 showed moderately susceptible (MS) and BARI Masur-5, BARI Masur-6 and BARI Masur-7 showed moderately resistant (MR) disease reaction under field condition. Isolation and identification of the pathogen with proof of pathogenicity were carried out under laboratory condition. First appearances of stemphylium blight disease in lentil in the field were found at pre-flowering or flowering stages from another experiment. Out of 8 weed species, Bathua (Chenopodium album) was identified as an alternate host of Stemphylium botryosum and it was first report in Bangladesh. A total of 214 lentil lines/varieties were screened out against stemphylium blight in the field under artificial inoculated condition in three subsequent years of 2011-2014 in Barisal. In the first year screening program out of 214 lines/varieties 22 lines were selected as resistant to Stemphylium botryosum. In the second year out of 24 lines/varieties 3 lines namely BD-6002, BD-3837 and BD-3926 were selected. In the third year out of selected 5 lines/varieties including 2 check varieties BARI Masur-1 and BARI Masur-7 were screened at Barisal and Rajshahi and finally 2 lines viz. BD-6002 and BD-3837 showed the highest yield (1628 Kg/ha and 1447 Kg/ha). In case of effect of different dates of sowing and varieties on stemphylium blight, the highest yield and the lowest disease severity were recorded in November 08 and November 15 sowing with BARI Masur-7 and the lowest yield and the highest disease severity were recorded in October 25 and November 01 sowing. But late sowing (November 29 and December 06) performed the lowest disease severity as well as lower yield. Among the fungicides (Rovral 50WP, Compenion, Nativo, Amistar Top 325 SC and Secure 600 SC) tested for controlling stemphylium blight in Barisal and Rajshahi, 3 sequences foliar spray with Rovral (Iprodione) @ (0.2%) and Amistar Top (Azoxystrobin 20% + Difenoconazole 12.5%) @ (0.1%) at an interval of 12 days effectively controlled the disease and increased yield of lentil by 55.50% and 53.58 %, respectively. In another experiment, efficacy of different fungicides with foliar spray and seed treatment were evaluated against stemphylium blight of lentil in Rajshahi in 2014-15. Seed treatment with Bavistin or Provax and selected fungicide Rovral was sprayed as foliar spray were effectively controlled the stemphylium blight of lentil in a susceptible variety BARI Masur-1.