[BIO-INSECTICIDAL ACTIVITY OF ALPINIA GALANGA (L.) ON LARVAL DEVELOPMENT OF SPODOPTERA LITURA (LEPIDOPTERA: NOCTUIDAE).

The aim of the study was to assess the bio-efficacy of four Alpinia galanga rhizome crude extracts against the second and third instars of Spodoptera litura, an important field pest. The growth of younger larvae was significantly affected while that of the older larval stage was less influenced. In both stages, the methanol crude extract showed the greatest efficiency which caused the highest number of abnormal adults to occur and produced a large LD50 value (12.816 µg/ larvae) pupicidal percentage after treatment, whereas, hexane extract caused the highest mortality during the larval-pupal stage after treatment with an LD50 value of 6.354 µg/ larvae. However, the larval development was not significantly different among all treated larvae compared to the control. This study suggests that secondary larval instars of S. litura are more susceptible to the larval growth inhibitory action of Alpinia galanga extracts and these extracts could also be applied for use in the management of pests.

TOXICITY OF THE SEEDS OF PHASEOLUS LATHYROIDES (LEGUMINOSAE) AGAINST SPODOPTERA LITURA (LEPIDOPTERA: NOCTUIDAE).

The seeds of Phaseolus lathyroides were extracted with hexane, dichloromethane, ethyl acetate and methanol, respectively by Soxhlet apparatus. Each crude extract was examined for toxicity against the second instars of Spodoptera litura using a topical application method under laboratory conditions. The ethyl acetate extract showed the most effective mortality (LD50 = 11,964 and 9,169 ppm after treated at 24 and 48 hours, respectively). Furthermore, in vivo enzyme based experiments revealed that acetylcholinesterase activity of survived S. litura (24 hours post-treatment) was increased by 12% compared to control experiments. Our result showed the possibility to develop alternative strategies by using extract from the seeds of Phaseolus lathyroides for the control of S. litura.