[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.

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.

Essential oil compounds as stress reducing agents in rats.

Essential oil compounds were studied to demonstrate their potential as stress reducing agents against rats. Rats were intraperitoneal administered with Linalool, Cineole and Thymol, respectively. Anxiety-related behaviors were determined by open field test and elevated plus maze test. Thymol reduced anxiety-related behavior of the animals. Linalool had no effect in both sexes of rats in the open field test. Thus, the results suggested that Thymol and Linalool are safe to control pets without harming non-target mammals

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.

Effect of thymol on reproductive biology of Helicoverpa armigera Hübner (Lepidoptera: Noctuidae).

The objective of this study was to determine the possibilities for use of thymol, a common compound in essential oils of Thymus and Origanum plants, as an alternative biopesticidal compound to control Helicoverpa armigera. Thymol was applied to Helicoverpa armigera larvae topically and also administered orally at sublethal levels to determine the effects on their reproduction and development. Thymol did affect egg development and oviposition was reduced by 9.42 and 38.86% under two different applications, respectively. Growth inhibition was also observed and 6.7% of insects were dead as larvae, 42.4% as pupae and 6.6% as pupal-adult intermediates. The present studies clearly indicate that thymol used at sublethal levels can alternatively control bollworms by altering reproductive mechanisms.

Antifeedant effect of Jatropha gossypifolia senescent leaf extract on Spodoptera exigua.

Spodoptera exigua is one of the economic polyphagous pests that is widespread and has been able to develop rapid resistance, thus the development of pest control strategies are required urgently. Botanical insecticides have long been touted as attractive alternatives to synthetic chemical insecticides for pest management because the former pose little threat to the environment or to human health. This research studied the antifeeding effect of Jatropha gossypifolia senescent leaf extract on second instar larvae. J. gossypifolia leaves were extracted using a Soxhlet apparatus with ethanol as the solvent. Concentration in the range from 1 to 4 mg/mL was mixed with the artificial diet and then was put on a plate with the control diet as choice and no-choice assays. A dual standard check was run along with the treatment using no solvent (control A) and ethanol (control B). The mortality and behavior of larvae were observed every day whereas the weight of larvae was observed every 3 days. Observation continued until the larvae developed into the pupal stage. In the no-choice assay, at 4 mg/mL concentration, absolute mortality (100%) was recorded 17 days post-treatment. All concentrations showed toxicity at the first day of exposure. No toxicity was recorded in the control A or B groups. In the choice assay, the results showed that 70-85% of larvae seemed to ignore consumption of the treated diets. Larvae mortality occurred after 3 days of exposure, especially for the larvae that fed on the treated diet. The weight and rate of weight increase of the larvae feeding preferentially on the treated diet were less than for the control diet. However, when larvae moved to feed on the control diet, there was an increase in the rate of weight increase. Larvae that preferred to feed on the control diet reached the adult stage faster than larvae that preferred feeding on the treated diet. In addition, the treated diet produced some abnormal larvae at metamorphosis in the pupal stage from both assays.

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 botanical insecticides on golden apple snail (Pomacea canaliculata).

The molluscicidal activity of crude extracts from five highly potential plants, Annona squamosa seed, Nerium indicum Leaves, Stemona tuberose root, Cyperus rotundus corm and Derris elliptica root was assessed to Pomacea canaliculata. D. elliptica root and C. rotundus corm extracts showed the highest toxicity against 3-month old snails which have LC50 as 23.68 +/- 2.96 mg/l and 133.20 +/- 7.94 mg/l, respectively. The C. rotundus corm extracts were chosen for detoxification enzyme in vivo assay which shows esterase and glutathione S-transferase activity in stomach, intestinal tracts and digestive glands of survival treated P. canaliculata were inhibited.

Acute toxicity of Amanranthus viridus extract on guppies, Poecilia reticulata.

Many Thai plant species shows the responsible for controlling insects from the host plants. To avoid potential toxic pollutant contaminating aquatic ecosystems, this present study was investigated for acute toxicity from Amaranthus viridis to Guppy fish (Poecilia reticulata) were selected for the bioassay experiments. The experiments were repeated 5 times and the 1-, 3- and 24-h LC50 was determined for the guppies. The acute toxicity experiments were carried out by static method and behavioral changes in guppies were determined for Amaranthus viridis concentration extract which extracted by Soxhlet's extraction method with ethanol as solvent. Water temperature was regulated at 20 +/- 1 degrees C. Data obtained from the acute toxicity tests were evaluated using the Probit analysis statistical method. The 24-h LC50 value for guppy was estimated as ca. 947 mg L(-1) (r2 = 0.95). However, in this concentration, no mortality was observed at higher concentration for 30 second.

The novel botanical insecticide for the control brown planthopper (Nilaparvata lugens Stal.).

Brown planthopper, Nilaparvata lugens Stal., (BPH) was the most devastating insect pest on rice in many partS of Asia. The Outbreak of BPH? which is resistant to many synthetic insecticides can cause total rice crop loss. This research was done to evaluate the efficiency of mangostin from the pericarp of mangosteen fruit extract (Garcina mangostana L.) as the alternative control of BPH. The pericarp of mangosteen fruit was extracted by Soxhlet apparatus using ethanol as a solvent and purified by chromatography method then qualified structure by 2D-NMR, MS and IR. The crude extracts contained mangostin ca. 2.956% w/w. This extract was trailed by the topical sprayer method with 1st, 2nd, 3rd, 4th and 5th nymph and adult BPH shows toxicity in term of LC50 ca. 1.39, 2.26, 5.44, 4.49, 4.03 and 3.84 % w/v at 24 h exposure, respectively. The in vitro enzyme activity from BPH survived after 24 h exposure and showed to inhibit the carboxylesterase (CarE), acetylchoinesterase (AchE) and glutathione-S-transferase (GST) activities which the correction factors of CarE, AchE and GST indicated ca. 1.21-2.05 fold, 1.24-2.50 fold and 1.01-3.34 fold, respectively. Moreover, the data shows that the carboxylesterase may play an important role to detoxify this extract. The results suggested that pericarp of mangosteen fruit extract which have mangostin as active ingredient compound shows mechanism as the inhibitor of detoxification enzymes. Thus, it is likely to be uses this extract as an insecticide alternative to the control of BPH.