Lakshmi Kanta Hazarika

Safety of Chromolaena odorata (Asteraceae) leaf extracts against Trichogramma japonicum Ashmead

Solvent extracts of leaves of Chromolaena odorata, a widely distributed neo-tropical shrub having insecticidal properties, was tested for its safety to Trichogramma japonicum, a popular egg parasitoid of lepidopteran pests of rice, which revealed that extract toxicity could be arranged as petroleum ether < water < methanol < acetone < chloroform in terms of safety to adults causing 28.3% < 40.0% < 43.3% < 53.3% < 65.0% adult mortality at 1.0% concentration after 24 hours of treatment. Respectively, the LC50 values of solvent extracts were 7.98%, 5.20%, 3.65%, 1.62% and 0.02%. Petroleum ether, water and methanol extracts of C. odorata at 1% concentration were ranked as harmless, however, remaining extracts were moderately harmful to the egg parasitoid even after 24 hrs of treatment.

In vitro compatibility of entomopathogenic fungi, Beauveria bassiana (Bals.-Criv.) Vuill. with leaf extracts of Chromolaena odorata (Asteraceae)

The compatibility of Beauveria bassiana (Bals.-Criv.) Vuill. with Chromolaena odorata (L.) King & H. Rob. (Asteraceae) was evaluated in vitro. Aqueous and solvent extracts of leaves of C. odorata at concentrations of 0.1, 0.5 and 1% were evaluated on the growth, conidial density and germination of B. bassiana by using the poisoned food technique. The extracts exhibited varying effects on growth of the fungus ranging from toxicity to inhibitory action, which increased with increase in the concentrations. The reduction percentage of radial growth of B. bassiana over control was found to be significantly less with the aqueous extracts of C. odorata. Inhibitory action was found to be highest (96.93%) with the chloroform extracts at 1% concentration. Similarly, as the concentrations increased from 0.1 to 1%, there was a significant reduction in the conidial density and germination in all the test concentrations. Based on the findings, the order of compatibility based on percentage reduction of radial growth is as follows: water > petroleum ether > methanol > acetone > chloroform. Hence, the aqueous extracts of C. odorata at 0.1% concentration can be integrated along with B. bassiana in any biointensive pest management programme.