Potential of Bioagents in Castor Wilt Management

Isolates of Trichoderma from wilt-sick castor (Ricinus communis L.) growing fields of Nalgonda district of Andhra Pradesh state, and also from rhizosphere of other crops along with a few plant extracts @ 2 per cent (w/v), carbendazim @ 0.1 per cent and carbofuran @ 13.6 mg ml⁻¹ were tested in vitro against Fusarium oxysporum f. sp. ricini (For) and Rotylenchulus reniformis (Rr). Ten effective bioagents along with neem (Azadirachta indicd) leaf extract, carbendazim as seed treatment and carbofuran @ 3 kg a.i. ha⁻¹ as pre-sowing soil application were tested for their effect on castor wilt incidence in two sets of field experiments in two separate wilt-sick plots (E1 and G1). Highest reduction of wilt over control was recorded in G1 by Trichoderma viride Pers isolated from healthy safflower plant root (T6), which was the best among the bio-agents in E1 and second to carbendazim among all treatments of the plot. Some of the bioagents including T6 could overcome the effect of stunting caused by the disease while they showed reduction in population of For and Rr in soil. Significantly higher yields were recorded in all the treatments compared to control.