EFFECTS OF AZADIRACHTIN ON CUTICULAR PROTEINS OF SPODOPTERA LITURA (LEPIDOPTERA: NOCTUIDAE) VIS-A-VIS THE MODES OF APPLICATION.

Azadirachtin is a known botanical insecticide with multiple modes of action. Whether these effects have any relation with the modes of application, specifically during ecdysis process, has been the objective of the present study and accordingly the impairment, if any, among cuticular proteins of Spodoptera litura (Fab.) was determined. Azadirachtin was applied topically, via injection or oral administration. Azadirachtin administered via injection and topical applications severely impaired the ecdysis by 86.67 and 80.0%, respectively. However, this impairment via oral administration was significantly lower (73.33%). Using SDS-PAGE, the cuticular proteins were determined for treated insects under all the three modes of application. In all cases 6 protein bands (MW 9-34 kDa) were identified using markers as standard. In all treatments 3 induced proteins (MW. ~16, 20 and 23 kDa) and 1 reduced protein (~19 kDa) were observed. In case of the topical treatment a different induced protein of ~18 kDa was identified. The change in cuticular proteins, their possible role in ecdysis impairment vis-a-vis the mode of application of azadirachtin is being correlated. This will help in understanding the mode-of-action at cuticular level and also will allow developing a suitable application strategy under field conditions in insect pest management.

[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.

INSECTICIDAL ACTIVITIES OF THYMOL ON EGG PRODUCTION AND DEVELOPMENT IN THE DIAMONDBACK MOTH, PLUTELLA XYLOSTELLA (LEPIDOPTERA).

The insecticidal activity of thymol was evaluated in the laboratory against third instar Plutella xylostella by topical application. Our previous results described mortality in P. xylostella by thymol and the present study continues investigation for its possible efficacy on egg production and development in surviving treated P. xylostella. Our results showed that thymol at a sublethal dose (0.43 µg/larvae, LD30) caused pupation inhibition, adult-emergence inhibition and abnormal adults at rates of 30, 33.33 and 23.33%, respectively. Moreover, the number of eggs was also reduced by 54.33%. These results showed that thymol was active against P. xylostella larvae and can effectively control this pest.

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.

TOXICITY OF ALPINIA GALANGA (ZINGIBERACEAE) RHIZOME EXTRACTS AGAINST SPODOPTERA LITURA (LEPIDOPTERA: NOCTUIDAE).

The objective of this study was to develop an alternative strategy for the control of Spodoptera litura larvae by using botanical insecticides. Rhizomes of Alpinia galanga were extracted with hexane, dichloromethane, ethyl acetate and methanol, respectively. Each crude extract was examined for toxicity against the second instars of S. litura according to a topical application method. The dichloromethane extract was found to show the highest toxicity of all the extracts, with LD50 = 3177 and 2099 ppm at 24 and 48 h post-treatment, respectively.

BIOEFFICACY OF PIPER RIBESIOIDES (PIPERACEAE) EXTRACTS AGAINST NILAPARVATA LUGENS STAL. (HOMOPTERA: DELPHACIDAE).

The extracts of stem and seeds of Piper ribesioides (Piperaceae) were prepared in hexane, dichloromethane, ethyl acetate and ethanol and evaluated for their efficacy against 3-day-old adult brown plant hoppers, Nilaparvata lugens Stal under laboratory conditions. The treatment was given topically and results suggest the dose dependent response related to exposure time. The ethyl acetate extract was the best with an LC50 = 738 ppm-, 24 h post-treatment. There was substantial increase in activity (LC50 = 27.298 ppm) with the increase in duration of exposure. This trend was observed in all treatments that suggests the potential of Piper ribesioides as an insecticide for N. lugens as an alternative control.

ANTIFEEDANT ACTIVITY OF CRUDE EXTRACTS FROM STEMS AND LEAVES OF TADEHAGI TRIQUETRUM (L.) OHASHI AND SEEDS OF PHASEOLUS LATHYROIDES AGAINST HELICOVERPA ARMIGERA HÜBNER (LEPIDOPTERA: NOCTUIDAE).

Efficacy of hexane, dichloromethane, ethyl acetate, and methanol crude extracts of stems and leaves of Tudehagi triquetrum (Legumin: Papilionaceae) and seeds of Phaseolus lathyroides (Leguminiale: Papilionaceae) was examined for the antifeedant activity against third instars larvae of Helicoverpa armigera using leaf disc no-choice method in the range of 0 to 2% concentrations for 6 and 12 hours. The ethyl acetate extract from T. triquetrum was the most effective at 6 hours with FI50 of 0.5346%, while the hexane extract from P. lathyroides only exhibited 0.7228% FI50 value at 6 hours. The antifeedant effect appeared to be time and concentration dependent, i.e. feeding deterrence depleted with increased exposure. Moreover, it is obvious from our study that both extracts could be used under short-term applications in an integrated pest management strategy of pest control.

Bio efficacy of some piperaceae plant extracts against Plutella xylostella L. (Lepidoptera: Plutellidae).

The extracts of Piper sarmentosum Roxb., Piper retrofractum Vahl, Piper interruptum Opiz and Piper nigrum plants belonging to the family Piperaceae were evaluated for their efficacy against diamondback moth, Plutello xylostella L. third instars under laboratory conditions. Comparative toxicity of various extracts prepared in hexane, dichloromethane, ethyl acetate and ethanol following sequential extraction procedure were applied topically to the larvae. The hexane extract of Piper retrofractum was most active (LD = 237 ppm). The toxicity was dose dependant and correlated to duration of exposure. The hexane extract of P. nigrum was least active with an LD50 of 18,435 ppm. The mode of action of these extracts and effect on other developmental parameters is in progress.

Toxicological study of Wedelia trilobata (Asteraceae) extracts as alternative control strategies for Plutella xylostella (Lepidoptera: Plutellidae).

The Diamondback moth (Plutella xylostella (L)) is an economically important pest in Thailand and the indiscriminant use of chemical pesticides against this pest has been responsible for environmental hazards. Present research, therefore, is trying to develop alternative strategies by using plant based-products for the control of this pest. Wedelia trilobata (L) Hitchc extracts prepared in hexane, dichloroethane, ethyl acetate and ethanol were used initially against the second instars of P. xylostella by topical application to determine the dose dependent toxicity. The highest yield of the extracts was obtained with EtOH extract followed by hexane, EtOAc and dichloroethane. However, the EtOAc extract exhibited the highest toxicity (24h-LC50 = 442.8 ppm) that became more prominent after 48 h (LC50 = 376.71 ppm). This suggests there was an increase in toxicity with the duration of exposure to the treatment. With the exception of the hexane extract, all other treatments were significantly correlated, which suggests that W. trolobata contains a varied profile of anti-insect allelochemicals that can be exploited in any integrated pest management strategy. The identification of the active ingredients is in progress.

Bioefficacy of Alpinia galanga (Zingiberaceae) rhizome extracts, (E)-p-acetoxycinnamyl alcohol, and (E)-p-coumaryl alcohol ethyl ether against Bactrocera dorsalis (Diptera: Tephritidae) and the impact on detoxification enzyme activities.

The application of insecticides to control oriental fruit fly, Bactrocera dorsalis Hendel (Diptera: Tephritidae), is a principal component of the current management of these fruit flies. However, we evaluated four extracts of Alpinia galanga Wild Linn (Zingiberaceae) rhizomes against adult flies and found hexane and ethanol extracts to be most effective (LC50 = 4,866 and 6,337 ppm, respectively, after 24 h). This suggested that both nonpolar and polar compounds could be active in the candidate plant. Accordingly, the hexane extract was further processed to isolate nonpolar active compounds from this plant source. Two compounds, (E)-p-acetoxycinnamyl alcohol and (E)-p-coumaryl alcohol ethyl ether, were identified as active ingredients and found to be more active than total hexane extract (LC50 = 3,654 and 4,044 ppm, respectively, after 24 h). The data suggested that the compounds were not synergistic but may have some additive effect in a mixture. The activity of the hexane extract against detoxification enzymes, carboxylesterase (CE) and glutathione transferase (GST) also was determined in vitro. CE was inhibited by 70%, whereas GST was not significantly inhibited. Insect CEs mediate insecticide resistance via their induction; therefore, inhibition of these enzymes by plant allelochemicals could be a useful alternative approach for the management of the pest in the field.

Impact of Alpinia galanga rhizome extract on Bactrocera dorsalis population.

The Bactrocera dorsalis (Hendel) is one of the most economically damaging pests and generally is controlled by insecticides. This research was done by evaluate the impact of rhizomes of Alpinia galanga extract on population of B. dorsalis. The rhizome of A. galanga was extracted by Soxhlet's apparatus using hexane, dichloromethane, ethyl acetate and 95% ethanol as separated solvent system. Various concentrations of all crude extracts were trailed by Topical spray application with adult B. dorsalis, completely randomized designs, 5 replicates. The results showed hexane crude extract gave the highest control efficiency to adult B. dorsalis which the 24 hours-LC50 values was 4,866.06 +/- 184.52 ppm (hexane), 24,156.66 +/- 880.33 ppm (dichloromethane), 16,744.73 +/- 641.27 ppm (ethyl acetate) and 6,337.54 +/- 145.42 ppm (95% ethanol). Thus, this extract may an alternative way for control this insect pest in the future.

Toxicity of ethyl acetate extract from Jatropha gossypifolia senescent leaves against Spodoptera exigua Hübner (Lepidoptera: Noctuidae) and Meteorus pulchricornis (Hymenoptera: Braconidae).

This study explored the insecticidal effects of Thai botanical, senescent leaf Jatropha gossypifolia extracts on second instar Spodoptera exigua larvae by the dipping method and topical sprayer method. The leaf crude extract was extracted using Soxhlet apparatus with ethyl acetate as solvent. The leaf crude extracts showed insecticidal activity with a LC50 of 6182 ppm at 24 hours after treatment. In addition, this research was observed its toxicity to worm parasitoid, Meteorus pulchricornis by contact method. The result shows 60 percent mortality of this parasitoid species at dose up to 40,000 ppm. Thus, Jatropha gossypifolia leaf crude extracts can be as alternative IPM control tool for Spodoptera exigua which friendly to benefit insect such as Meteorus pulchricornis.