Explore the vast range of titles available.

BackgroundSpodoptera litura (Lepidoptera: Noctuidae), the tobacco cutworm, is an prominent agricultural pest. To reduce the use of chemical pesticides that cause health problems and that leave residue in the environment, some botanical pesticides have been developed. Our research aimed to evaluate the insecticidal efficacy of Acorus calamus L. extract for the control of S. litura under laboratory conditions.ResultsAfter 24 h of topical application, the A. calamus methanolic crude extract showed toxicity against secondary instar S. litura larvae (LD50 ~ 7.438 µg/larva). Chrysin (5,7-dihydroxy flavone), one of the isolated phenolic compounds, showed optimal control efficiency (LD50 ~ 2.752 µg/larva) and showed a reduction in carboxylesterase activities, which have detoxification reduction roles in larvae.ConclusionChrysin in the crude extract of A. calamus may be an active compound to control this pest, and it may be applied as an alternative to minimize the usage of chemical insecticides.

BackgroundSpodoptera litura larvae are polyphagous insects that have become a significant pest in recent years. The spread of this pest has led to the continuous usage of insecticides on crops. Some plant extracts have been used as a mixture to control insect pests and improve productivity.MethodsA plant-based mixture was mixed at a ratio of 1:1 v/v to demonstrate the effect on contact toxicity, feeding (no-choice test), and enzyme activities on S. litura. The active compounds of P. retrofractum and A. calamus were isolated by preparative thin-layer chromatography (PTLC).ResultsOur results showed that binary mixtures from P. retrofractum and A. calamus exhibit the highest contact toxicity and antifeedant activity at a 1:1 ratio of LD30:LD10 dose (3.213 µg/larva P. retrofractum + 3.294 µg/larva A. calamus). The main active ingredient from each crude extract was (2E,4E,14Z)-N-isobutylicosa-2,4,14-trienamide from P. retrofractum, and beta-asarone and alpha-asarone from A. calamus. Additionally, A. calamus seems to be the synergistic compound. Some compound mixtures increased the glutathione-S-transferase activities in vivo; whereas, almost no significant differences in esterase activities were noted.ConclusionThe results indicated that the ethanolic crude extracts of P. retrofractum and A. calamus mixtures could be used as the pesticidal compound and to develop a binary mixture formulation for controlling lepidopteran pests. However, the toxicity of this mixture to mammals needed to be explored before commercial development.

BackgroundPlant secondary metabolites or mixtures in extracts or essential oils are well known to enhance the activity in binary mixtures. The present study is the first to report that thymol synergistically or additively enhances the activity of P. ribesioides extracts and isolated compounds against S. exigua larvae at sublethal doses.ResultsThymol was synergistic when are mixed with hexane extract; however, if the hexane extract level was higher (LD30) than the thymol level (LD10), the reaction was antagonistic. CH2Cl2 extract and thymol were more toxic than the extract or thymol alone, and EtOAc extract was synergized by thymol if the components were combined at similar levels (1:1 thymol:EtOAc extract at the LD10 or LD30). MeOH extract individually had moderate insecticidal activity, but all combinations with thymol were synergistic as binary mixtures. Isolated compounds, piperine, phenethyl cinnamamide and cinnamic acid represented synergistic, additive, and antagonistic action after combining with thymol (1:1 at the LD10 or LD30). Detoxification enzymes after exposure of insects to treatments showed isolated compounds + thymol could inhibit CE, GST and AChE reaction of S. exigua exceptional being piperine + thymol, which induced detoxification enzyme activity.ConclusionThe synergistic activity was extract- and dose-specific. The impact on detoxification enzymes was variable and dependent on the composition of the extract and the doses of extract and thymol used in a binary mixture. In this metabolic model, the major insect compound in an extract may become detoxified, whereas a minor compound will act unimpeded, showing a lower LD50 than acting alone. This model suggests that thymol synergizes with extract components differently, which could depend on the specific metabolites in the extract and the dose applied. Such studies will help design effective insecticides based on natural plant mixtures and a synergistic compound.

BackgroundMosquitoes are vectors for diseases damaging human health and thus, there is an urgent need for insecticidal compounds to control their population. The objective of this study was to determined the efficiency from trans-cinnamic acid isolated from Alpinia galanga (Zingiberales: Zingiberaceae) for control of Aedes aegypti (Dipetera: Culicidae), Anopheles dirus B (Dipetera: Culicidae) and Culex quinquefasciatus (Dipetera: Culicidae).MethodsAlpinia galanga (Zingiberales:Zingiberaceae) was extracted by soaking in a sequence of solvents (hexane, dichloromethane, ethyl acetate and methanol), and the isolated trans-cinnamic was separated by preparative thin layer chromatography. All crude extracts and isolated trans-cinnamic were evaluated for their control and affect on detoxification enzyme activities of the third-instar larvae of each mosquito species in laboratory conditions.ResultsOur results showed that the hexane crude extract had the best control efficiency in all species, particularly in Cx. quinquefasciatus. The trans-cinnamic acid, isolated compound from hexane crude extract showed as active ingredient against third-instar larvae of each mosquito species. Mortality in this case may result from the inhibition of carboxylesterase.ConclusionThese results indicated that A. galanga which had trans-cinnamic acid as active ingredient compound could represent a promising naturally occurring control agent for all three mosquito species. However, this research consider as an initial prospective study, the other side effect on nontarget species need to concerned before used as commercial product.

BackgroundSpodoptera exigua Hübner (Lepidoptera: Noctuidae) is a widely occurring insect pest of several crops conventionally controlled by pyrethroids and organophosphates hazardous for the environment and human health. Thus, the alternatives are biocide-based phytochemicals. Accordingly, the Piper ribesioides Wall. (Piperales: Piperaceae) plant, well distributed in the northern regions of Thailand (Nan Province), was used due to its known bioactivity against insects. The objective was to determine the feeding deterrent activity of P. ribesioides extracts and isolated allelochemicals under laboratory conditions and correlate the efficacy under greenhouse conditions after the extracts were applied to S. exigua larvae infesting potted Brassica oleracea var. alboglabra (Bailey) Musil plants. Another objective was to look at the impact of spray applications on detoxification enzymes to check the possibility of resistance development against such natural extracts.ResultsEthyl acetate extract deterred feeding of larvae better than other extracts with the concentrations causing 50% feeding inhibition (FI50) of 26.25 µg/cm2 and feeding deterrence index (FDI) of 91.8%, which was slightly lower than the positive control (cypermethrin, FDI = 100%; FI50 0.027 µg/cm2). The most effective feeding deterrent compounds against S. exigua were pinostrobin and pinocembrin with FDI range of 77 to 90% and FI50 values of 14.39 and 19.38 µg/cm2. In the greenhouse, the larvae treated on potted B. oleracea at FI50 concentrations (determined in laboratory experiments), ethyl acetate extract gave the highest mortality of 63.33% within 24 h of first spray and total of 73.33% after 24 h of the second spray. Impact on detoxification enzymes (24 h post-treatment) was determined from survived 3rd instars of S. exigua using spray applications. Inhibition of carboxylesterase (CE) was 1.94-fold after hexane extract treatment. However, ethyl acetate extract inhibited glutathione-s-transferase (GST) 1.30-fold.ConclusionsEthyl acetate extract of P. ribesioides twigs and isolated pinostrobin and pinocembrin compounds were potential antifeedants against S. exigua larvae. The data obtained also showed that such antifeedant levels of treatment could be used in greenhouse or field trials directly as an extract after establishing the efficacy of extracts and the active compounds therein under laboratory conditions.

Woodwasps (Hymenoptera: Siricidae) are saproxylic insects and a common forest pest. Siricid woodwasps are classified into two subfamilies: Siricinae and Tremecinae. All known symbiotic fungi of Siricinae are in the genus Amylostereum Boidin while some species of Tremecinae have been observed to have a relationship with the fungus Cerrena unicolor (Bull.) Murrill. Previous studies about the host searching behavior of woodwasps and their parasitoids have focused primarily on the subfamily Siricinae. We analyzed the role of C. unicolor volatiles on the host searching behavior of Tremex apicalis Matsumura (Hymenoptera: Siricidae: Tremecinae) and its parasitoid Ibalia (Tremibalia) japonica Matsumura (Hymenoptera: Ibaliidae). The results of an olfactory response experiment indicated that the females of T. apicalis and its parasitoid find their respective hosts using volatiles from C. unicolor. Using DNA barcode, we identified basidiocarps on the trees infested with T. apicalis. The basidiocarps were all white-rot fungi that cause sapwood decay, including C. unicolor. Two additional species that we identified belonged to genera closely related to C. unicolor. Woodwasp species are known to carry symbiotic fungi in a pair of specialized sacs called mycangia. Notably we found that mycangia-like structures were absent in the abdomens of T. apicalis females. To the best of our knowledge, Xeris spectrum (Linnaeus) (Hymenoptera: Siricidae) is the only reported example of woodwasp species that do not contain symbiotic fungi in their bodies. Our results suggested that: (1) T. apicalis females search for host wood that is already infected with sapwood decaying fungus using volatile compounds; (2) T. apicalis' female parasitoid also uses volatile compounds from fungus to locate wood that is infested with its potential host.

Precopulatory mate-guarding behavior is a common strategy that maximizes male reproductive success when female receptivity to copulation is low. This behavior has been demonstrated in vertebrates, aquatic crustaceans, terrestrial isopods, and some species of insects, but there is very little available information about hymenopteran insects. A few studies have clarified the factor that determines the outcome of a contest between a guarding male and an invader male. We investigated the male–male contest and mating behavior of a saproxylic parasitoid wasp, Ibalia japonica (Hymenoptera: Cynipoidea: Ibaliidae) using field observations in Japan. These observations indicated that I. japonica males show precopulatory mate-guarding behavior and that four types of male–male contests occur on the Magnolia liliiflora (Magnoliales: Magnoliaceae) tree that virgin females emerge from. We show that the arrival order of I. japonica males that found the future emergence point of a female was key factor that allowed males to secure virgin females.

The antifeedant and contact toxicity of Sphagneticola trilobata L. (Asterales: Asteraceae) extracts and isolated alkane compounds were investigated. Leaves of S. trilobata were sequentially extracted with hexane, dichloromethane, ethyl acetate, and methanol. Each extract and the compounds isolated were evaluated against the third instars of Spodoptera litura (F.) (Lepidoptera: Noctuidae), Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae), and Plutella xylostella L. (Lepidoptera: Yponomeutidae). Ethyl acetate extract and isolated alkanes were feeding deterrents as well as contact toxins against all the three species evaluated (FI50 ∼ 0.27–2.34 mg/ml; LD50 ∼ 0.88–4.2 μg/larvae for ethyl acetate extract, and FI50 ∼ 0.06–4.35 mg/ml; LD50 ∼ 0.72–3.54 Ethyl acetate extract for isolated alkane). Impact on detoxifying enzymes was variable. The ethyl acetate crude extract reduced carboxylesterase activity in S. litura and P. xylostella while in S. exigua the enzyme was induced. In contrast, glutathione-S-transferase activity was induced in S. exigua but no significant difference in P. xylostella and S.litura was observed. Our results suggest that the S. trilobata extracts have multiple biological activities that contribute to the toxicity in lepidopterans. Variable enzyme responses to the products evaluated in different lepidopteran species also confirm that some speciesspecific inductions do occur, suggesting the possibility of resistance development in the future, which cannot be summarily ignored. However, for this detailed biochemical studies are required. Multiple bioefficacies of S. trilobata makes it a potential botanical for further exploitation on larger scale so that field potential can be established in any integrated pest management (IPM) system.

Culex quinquefasciatus is a common domestic mosquito that is widespread in many areas of Thailand and serves as a southeastern vector of Japanese encephalitis. The present study investigated the acute toxicity of crude extracts and alkaloid compounds of Piper retrofractum (Piperales: Piperaceae) in Cx. quinquefasciatus third instar larvae. P. retrofractum was sequentially extracted using hexane, dichloromethane, ethyl acetate, and methanol, and the crude extracts were tested on mosquito larvae. Detoxification and neuroenzymes were analyzed to establish the mode of action. Acute toxicity was assessed on Poecilia reticulata (Cyprinodontiformes: Poeciliidae) to determine the possibility of toxicity in a nontarget species. Our results showed crude hexane extract had the highest toxicity in Cx. quinquefasciatus (0.9 ppm). Piperine and piperanine, which are alkaloid compounds from the crude hexane extract, showed LC50 values of 0.27 and 2.97 ppm, respectively, after 24 h of exposure. All the crude extracts showed low toxicity in P. reticulata compared with that in the mosquito larvae. The carboxylesterase, glutathione-S-transferase, and acetylcholinesterase activities in Cx. quinquefasciatus were reduced after treatment with all the extracts and the two alkaloid compounds.Thus, P. retrofractum shows larvicidal effects against Cx. quinquefasciatus and low toxicity for nontarget species. Thus, P. retrofractum could be a choice for controlling Cx. quinquefasciatus.

Woodwasps (Hymenoptera: Siricidae) are saproxylic insects and a common forest pest. Siricid woodwasps are classified into two subfamilies: Siricinae and Tremecinae. All known symbiotic fungi of Siricinae are in the genus Amylostereum Boidin while some species of Tremecinae have been observed to have a relationship with the fungus Cerrenaunicolor (Bull.) Murrill. Previous studies about the host searching behavior of woodwasps and their parasitoids have focused primarily on the subfamily Siricinae.