Effectiveness of four commercial products of Bacillus thuringiensis viz., Biobit WP®, Dipel DF®, Delfin WG® and Halt WP® were evaluated at 0.1, 0.2, 0.5, 1.0 and 1.5 g/l against first to fifth instars larvae of H. puera. The test insect was highly susceptible to B. thuringiensis irrespective of products. Larval death started after 24h and maximum larval mortality occurred after 48h of continuous feeding of B. thuringiensis sprayed leaves. Among the tested products, all the products were found to be best in killing larvae at higher concentrations, i.e, 1.0 and 1.5 g/l. Higher larval mortality up to 100 per cent was observed irrespective of concentrations and products in younger larvae up to third instars than later ones.
Fifty-seven clones of Teak representing nine provenances of Karnataka were field evaluated for their natural resistance against Hyblaea puera in a twenty-three-year-old clonal seed orchard of Teak of South India. Results, based on average leaf-damage intensity over two years of observations, revealed that six Teak clones viz., MyMK-3 from Southern provenance, MyKN-1, MyKN-46 from Central provenance, STG-3, STG-06 of state graft series as well as Teli Teak of Dandeli were found to be resistant and other 23 clones were moderately resistant to Teak defoliator. The clone MyHuT-3 of Southern provenance was most susceptible and the remaining 27 clones were susceptible to H. puera. These findings suggest the existence of quantitative resistance among Teak clones against H. puera, and suggest the possibility of using resistant clones in the integrated pest management. This is perhaps the first report wherein a large number of Teak clones of Karnataka have been field evaluated for the resistance against H. puera.
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