Studies on Boll Rot Complex of Cotton
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Date
2018-08
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University of Agricultural Sciences, Dharwad
Abstract
The present investigation on cotton boll rot complex was carried out during kharif 2017-18 at Agricultural Research Station, Dharwad and Department of Plant Pathology, College of Agriculture, Dharwad. This included, survey for the disease, isolation and identification of pathogens involved in the disease complex and management of the disease through integrated approach. Roving survey was conducted in five districts of northern parts of Karnataka viz., Belagavi, Dharwad, Gadag, Haveri and Uttara Kannada. Maximum disease severity was noticed in Uttara Kannada district at both boll initiation and maturity stages. Maximum disease incidence was observed on bolls at lower part of the plant compared to those of mid and upper parts.
Isolation of pathogens and their identification through morphological and molecular characters indicated the presence of fungal pathogens like Alternaria macrospora, Fusarium oxysporum f. sp. vasinfectum, Exserohilum rostratum, Colletotrichum gossypii, Phoma sp., Trichothecium roseum, Aspergillus niger, Nigrospora oryzae and Rhizopus stolonifer and a bacterial pathogen viz., Xanthomonas citri subsp. malvacearum in the infected boll samples collected during survey. Standardization of artificial inoculation methods indicated that injection infiltration method as the best.
Out of 118 genotypes (20 varieties of UAS, Dharwad which are under pipeline, 81 germplasm lines of AICRP and 13 private Bt hybrids and 4 UAS, Dharwad released
non Bt varieties/ hybrids) tested, 3 genotypes viz., FDK 281, ANGH-1607 and GShv 894/13 showed highly resistant reaction and 31 genotypes showed moderately resistant reaction against the disease under natural epiphytotic conditions.
Among 11 treatments evaluated, trifloxystrobin 25 % + tebuconazole 50 % WG at the rate of 1.0 g/ lit was found effective against the disease complex. However,
tebuconazole 25.9 % EC at the rate of 1.0 ml/ lit was found economical with the highest B: C ratio.