Strategic IPM interventions for management of Sclerotinia rot in oilseed Brassicas

Abstract

The explosive Pathogenicity of Sclerotinia sclerotiorum (Lib.) de Bary causing rot in oilseed Brassicashas made it very difficult to guard the crop from its infection in India, where it causes seed yield losses up to 74%. Identification of improved source of resistance is an important prerequisite for disease management but only resistance breeding is not able to keep pace with the development of this virulent pathogen. Trichoderma has been found effective against S.Sclerotiorum of Indian mustard. Therefore, field studies were conducted for evaluation of efficacy of Trichoderma harzianum. Field studies consisting of six different treatments in RBD, four on the basis of different combination of T.harzianum (PCI strain), standard fungicide control, carbendazim along with untreated control was conducted using variety Rohini with T. harzianum (2x106 c.f.u./g) during rabi season of 2011-12 and 2012-13. Field experiments were also conducted in IARI, New Delhi for virulence assessment of 70 genotypes under artificial Sclerotinia rot development conditions. Similarly, large scale multilocational validation of strategic IPM interventions was conducted against Sclerotinia rot at 188 locations in Haryana and Rajasthan on 117 ha, which were identified for assured incidence of Sclerotinia rot on farmers’ fields in Alwar, Rajasthan and Mewat and Mohindergarh district in Haryana from rabi 2011-12 to 2013-14.Out of four different combination of T. harzianum (PCI strain), least (4.2%) Sclerotinia rot incidence was found in combination of seed treatment @10g/kg, soil application @ 2.5 kg/ha and two foliar sprays of T. harzianum @ 0.2% at 50 and 70 days after sowing and gave maximum seed yield (2080 kg/ha.). In virulence assessment studies, eight genotypes viz., Pusa Aditya, NPC 16, DMH 1, HYT 8, Pusa Swarnim, RGN 73, Bio-YSR and EJ 15 having < 5% incidence and low severity (0-1 grade) were rated as tolerant. The strategic IPM interventions (cultural practices as well as T. harzianum, 2x106 cfu/g, PCI strain) conducted on large scale in three districts comprising state of Haryana and Rajasthan, includes improved cultural practices viz., deep summer ploughing, preparation of levelled and well drained field, balanced use of nitrogenous fertilizers, sowing from 16 - 31 Oct, use of clean and certified seed along with soil application of Potash (K2O) @ 40.0 kg, Sulphur @ 40.0 kg and T. harzianum (2x106c.f.u./g) @ 2.5kg/ha pre-incubated in 50 kg well rotten FYM followed by seed treatment with T. harzianum @ 10g/kg, maintenance of optimum plant population with wide spacing,judicious use of irrigation water at different crop stages. The strategic IPM interventions were found better over Farmers’s practices (FP) in reducing the disease incidence atvillages Sali Khurd in Alwar, Rajasthan, Dingerheri in Mewat; Kakarala and Khampura in Mohindergarh, Haryana and finally increasing the mean seed yield over farmers’s practices. In strategic IPM interventions tolerant host plant along with improved cultural practices as well as all possible combinations of T. harzianum, 2x106 cfu/g, reduced the disease incidence and increased the seed yield. In large-scale multilocational validation of these strategic IPM interventions was ppreciated by farmers. This strategy is expected to reduce the indiscriminate use of chemical pesticide and safeguard the other beneficial microbes.