Mosquito larvicidal properties of Orthosiphon thymiflorus(Roth)Sleesen.(Family:Labiatae)against mosquito vectors,Anopheles stephensi,Culex quinquefasciatus and Aedes aegypti(Diptera:Culicidae)

Objective:To determine the mosquito larvicidal activities of hexane,chloroform,ethyl acetate, acetone and methanol leaf extract of Orthosiphon thymiflorus（O.thymiflorus） against Anopheles stephensi（An.stephensi）,Culex quinquefasciatus（Cx.quinquefasciatus） and Aedes aegypti （Ae.aegypti）.Methods:The larvicidal activity was assayed against three mosquito species at various concentrations ranging from（50-450 ppm） under the laboratory conditions.The LC50 and LC90value of the O.thymiflorus leaf extract was determined by Probit analysis.Results:The LC50 values of hexane,chloroform,ethyl acetate,acetone and methanol extract of O.thymiflorus third instar larvae of An.stephensi were LC50= 201.39,178.76,158.06,139.22 and 118.74 ppm; Cx.quinquefasciatus were LC50=228.13,209.72.183.35,163.55 and 149.96 ppm and Ae.aegypti were LC50=215.65,197.91,175.05,154.80 and 137.26 ppm,respectively.Maximum larvicidal activity was observed in the methanolic extract followed by acetone,ethyl acetate chloroform and hexane extract.The larval mortality was observed after 24 h exposure.No mortality was observed in control.Conclusions:The present results suggest that the effective plant crude extracts have potential to be used as an ideal eco-friendly approach for the control of mosquito vectors.This study provides the first report on the larvicidal activity of this plant crude solvent extract of against An.stephensi,Cx.quinquefasciatus and Ae.aegypti mosquitoes.

Antifeedant and insecticidal activities of selected plant extracts against Epilachna beetle, Henosepilachna vigintioctopunctata (Coleoptera: Coccinellidae)

Six different indigenous plants were screened for antifeedant and insecticidal activity against fourth instar larvae of Epilachna beetle, Henosepilachna vigintioctopunctata, which is a severe pest on brinjal. Among the plants screened, Achyranthes aspera showed higher activity against the selected pest. Ethyl acetate extracts of A. aspera showed higher antifeedant index and insecticidal activity against fourth instar larvae of H. vigintioctopunctata. Preliminary phytochemical analysis revealed that the presence of alkaloid and quinines in the ethyl acetate extracts indicate higher percentage of activities. Hence, it may suggest its use for controlling the vegetables insect pest, H. vigintioctopunctata.

Larvicidal and knockdown effects of some essential oils against <i>Culex quinquefasciatus</i>Say, <i>Aedes aegypti</i>(L.) and <i>Anopheles stephensi</i>(Liston)

Efficacy of 25 essential oils was screened against filarial vector, Culex quinquefasciatus, for their larvicidal and knockdown effects in a preliminary study. Of these, 8 oils viz. calamus oil, cinnamon oil, citronella oil, clove oil, eucalyptus oil, lemon oil, mentha oil and orange oil exhibited 100% larvicidal activity at 1000 ppm and 100% knockdown effect at 10% concentration. These 8 oils were screened further against Cx. Quinquefasciatus, Aedes aegypti and Anopheles stephensi for their larvicial and knockdown effects at different concentrations. Mentha oil was the most promising against An. Stephensi and Ae. Aegypti recording LC50 and LC90 values of 39.74 and 115.67 ppm and 46.23 and 165.36 ppm, respectively for larvicidal activity. Calamus oil was the most effective against Cx. Quinquefasciatus with LC50 and LC90 values of 40.40, and 140.07 ppm, respectively for larvicidal activity. Orange oil showed the most potent knockdown effect with the KT50 and KT95 values of 27.44, 26.22 and 29.91 and 70.81, 65.33 and 68.57 min, against An. stephensi, Cx. Quinquefasciatus and Ae. Aegypti, respectively. The results clearly indicated that mentha oil and calamus oil were the most promising larvicides and orange oil had potent knockdown effect against the tested mosquito species. These oils could be used to develop a new formulation to control mosquitoes.

Ovicidal activity of Atalantia monophylla(L)Correa against Spodoptera litura Fab.(Lepidoptera:Noctuidae)

Objective:To evaluate the efficacy of Atalantia monophylla(A.monophylla)leaf in different solvent crude extracts and fractions against eggs of Spodoptera litura(S.litura).Methods:Hexane,ethyl acetate and chloroform solvent extracts of A.monophylla leaf and 12 fractions from hexane extract were screened at 5.0%t,2.5%,1.0%and 0.5%for crude extracts and 1000,500,250 and 125 mg/kg for fractions against the eggs of S.litura for the ovicidal activity.LC_(50)and LC_(90)were calculated using probit analysis.Results:Hexane crude extract showed maximum ovicidal activity of 61.94%at 5.0%concentration with a correlation value of r^2=0.81,and least LC_(50)value of3.06%.Hexane extract was fractionated using silica gel column chromatography and 12 fractions were obtained.Fraction 9 was active which showed maximum ovicidal activity of 75.61%at 1000mg/kg with the LC_(50)value of 318.65 mg/kg and LC_(90)value of 1473.31 mg/kg.In linear regression analysis,significant and high correlation(r^2=0.81%)was seen between concentration and ovicidal activity of hexane crude extracts and its active frsctien.Conclusions:As per our knowledge,this is the first report for ovicidal activity of A.monophylla against S.litura,A.monophylla could be used for the management of S.litura and other insect pests.

Mosquitocidal activity of indigenenous plants of Western Ghats,Achras sapota Linn.(Sapotaceae)and Cassia auriculata L.(Fabaceae)against a common malarial vector,Anopheles stephensi Liston(Culicidae:Diptera)

Objective:To evaluate the mosquito larvicidal,ovicidal,pupicidal and repellent activities of hexane,diethyl ether,dichloromethane,acetone and methanol extracts of Indian medicinal plants,Achras sapota(A.sapota)and Cassia auriculata(C.auriculata)at different concentrations against Anopheles stephensi(An.stephensi),a malarial vector.Methods:Twenty five early third instar larvae of An.stephensi were exposed to various concentrations(30-210 mg/L)of plants extracts and were assayed in the laboratory by using the protocol of WHO 2005;then after 24 h LC_(50) values of the A.sapota and C.auriculata leaf extract was determined by probit analysis.The ovicidal activity was tested with the extracts ranging from 50-350 mg/L.The pupicidal activity was recorded after 24 h of exposure to the extract.The repellent efficacy was determined against mosquito species at two different concentrations 1.5 and 3.0 mg/cm^(2) under laboratory conditions.Results:Among the five different extracts tested against the An.stephensi,methanol extract of A.sapota proved to be an more effective solvent extract in almost all the parameters studied than C.auriculata.Conclusions:It is inferred that the leaf extract of A.sapota and C.auriculata could be used in vector control programme.

Role of plants and plant based products towards the control of insect pests and vectors:A novel review

Insect pests bear harmful effects causing great loss to the agricultural crops,stored agricultural products and vector mosquitoes can cause diseases to human.Plants possess an array of vast repository of phytochemicals and have been used to cure many diseases and to control the infestation of insect pests from time immemorial.Plants are easily biodegradable and ecologically safe for treating on the stored or on the field crops against pests to prevent from further damage or loss of stored products or preventing human from mosquito bites,thus preventing the spreading of dreadful diseases such as chikungunya and malaria.Hence,this review can give a clear insecticidal,pesticidal and mosquitocidal property of several plants against the insect pests and vectors.

Protective effect of probiotic diets on haematobiochemical and histopathology changes of Mystus montanus(Jerdon 1849)against Aeromonas hydrophila

Objectives:To evaluate the protective effct of probiotic diets on haemotobiochemical and histopathology changes of Mystus montanus against Aeromonas hydrophila(A.hydrophila).Methods:Three experimental groups of fish were fed with a diet supplemented with Lactobacillus acidophilus(L.acidophilus)(Sporolac),comprising about 0.1 g,0.2 g and 0.3 g.Control group of fish were fed without L.acidophilus.After 60 d of feeding the fishes in experimental group were injected with 1 mL of A.hydrophila and were supplemented with probiotic diets.The control group fishes were injected with 1 mL of physiological saline solution alone.Results:Blood samples were collected for haematobiochemical analysis,while samples of the liver,and gills were examined for path histology after 7 d of infection.The result showed that the growth parameters,weight gain,specific growth rate were better in infected group maintained on the probiotic diet compared to those in control group.The haematology parameters,erythrocyte sedimentation rate,red blood cell,white blood cell,total serum protein,Mg^(2+),Ca^(2+),Cl,glucose,cholesterol and total immunoglobulin concentration and the pathohistology of the liver,gills were better in the infected fish maintained on the probiotic diet than those in the group fed the control diet.Conclusions:The result of the present study showed that L.acidophilus is useful as a probiotic agent in Mystus montanus against A.hydrophila.

Comparison of the Artemia salina and Artemia fransiscana bioassays for toxicity of Indian medicinal plants

Objective:To evaluate leaves extract of Azima tetracantha and Gmelina asiatica for lethality to brine shrimp larvae(Artemia salina and Artemia fransiscana).Methods:The plant materials were extracted based on polarity gradients of petroleum ether,benzene,chloroform,acetone,ethanol and methanol.The extracts were investigated for their cytotoxic potential.Results:In the brine shrimp lethality assay of all extracts,exception of acetone,ethanol and petroleum ether extracts Gmelina asiatica displayed 100%mortality at 1000μg/mL by Artemia salina and Artemia fransiscana.Chloroform extract was the most potent and presented the highest percentage of mortality with the lowest LC_(50)values by both assay too.Conclusions:The results of the present study suggest the presence of photochemical possessing cytotoxic agents.

Bioefficacy of Caesalpinia bonducella extracts against tobacco cutworm,Helicoverpa armigera(Hub.)(Lepidoptera:Noctuidae)

Objective:To evaluate the antifeedant,oviposition deterrent,ovicidal and larvicidal activities of benzene,dichloromethane,diethylether,ethyl acetate and methanol extracts of Indian medicinal plant,Caesalpinia bonducella(C.bonducella)at different concentrations against Lepidopteran agricultural field pest Helicoverpa armigera(Lepidoptera:Noctuidae).Methods:Antifeedant activities of the selected plant extract were studied using leaf disc no-choice method and oviposition deterrent,ovicidal and larvicidal activities were also assessed by adapting the standard protocols.Results:The antifeedant activity of C.bonducella showed significant antifeedant activity in methanol extract.Oviposition deterrency is higher in methanol extract than the other solvent extracts.Similarly,maximum egg mortality was observed in methanol leaf extract of C.bonducella Lethal concentration,LC_(50)value of benzene,diethylether,dichloromethane,ethyl acetate and methanol extract of C.bonducella were 470.02,469.00,465.47,460.52 and 443.87 mg/L respectively.The Chi-square values are significant at P<0.05 level.Among five solventextracts,the methanol extract was responsible for strong lethal activity observed against selected pest species.Conclusions:Results of this study show that the selected Indian medicinal plant C.bonducella could be a potent source of natural antifeedant,oviposition deterrent,ovicidal and larvicidal agent against the field pest Helicoverpa armigera.

Mosquitocidal properties of Oxystelma esculentum(Asclepiadaceae)-Indian medicinal plant tested against Ades aegypti(Linn.)(Diptera:Culicidae)

Objective:To evaluate the mosquitocidal activities of various solvent extract of Oxystelma esculentum(O.esculentum)against the medically important dengue vector mosquito,Aedes aegypti(Ae.aegypti)L.Methods:A total of 25 early third instar larvae of Ae.aegypti were exposed to various concentrations(60-300 mg/L)and were assayed in the laboratory by using the protocol of World Health Organization,2005;the 24 h LC_(50) values of the O.esculentum leaf extract was determined by probit analysis.The ovicidal activity was determined against the freshly laid eggs of Ae.aegypti to various concentrations ranging from 50-300 mg/L under laboratory conditions.The pupicidal activity was determined against pupae of Ae.aegypti to various concentrations ranging from 70-280 mg/L after 24 h of exposure to the concern extract.The repellent efficacy was determined against adult female mosquito species at 1.0,2.0 and 3.0 mg/cm^(2) under laboratory conditions.Results:The LC_(50) value of methanol extract of O.esculentum against 3rd instar larvae of Ae.aegypti was 125.82 mg/L.The same extract showed 100%egg mortality at 250 mg/L and also pupicidal activity observed against the pupae of Ae.aegypti at 280 mg/L.Conclusions:The present results suggest that the O.esculentum leaf extracts provided an excellent,potential phytopesticide for controlling Ae.aegypti mosquito.

Geographic variation in cypermethrin insecticide resistance and morphometry in Spodoptera litura(Fabricius)(Lepidoptera:Noctuidae)

Objective:To find out the most resistant strain of Spodoptera litura(S.litura)from Tamil Nadu,Kerala and Karnataka by synthetic insecticide treatment.Methods:Using leaf disc no-choice method,the insects were tested with different doses for pesticides.The LC_(50)and LC_(90)values were calculated by probit analysis.Results:In the insect bioassay,the cypermethrin insecticide showed significantly higher LC_(50)values of 14.699 g/L and 15.738 g/L against the Tamil Nadu and Kerala S.litura insect cultures respectively.The body length of 2nd,3rd and 4th instar larvae were significantly higher(P≤0.05)in TTP insect population[(19.2±2.3)mm,(28.05±3.20)mm,(36.1±2.0)mm],when compared with KTK[(18.5±2.7)mm,(23.38±2.00)mm,(31.75±2.70)mm]and control,KBB[(15.65±2.30)mm,(23.65±2.70)mm,(33.2±2.2)mm]populations.The body breadth of 3rd instar larvae was significantly higher(P≤0.05)in TTP insect population(4.9±1.1)mm,when compared with KTK(3.93±0.80)mm and control,KBB(3.65±0.70)mm populations.Conclusions:The present study clearly showed that field collected strains were highly resistant when compared to control.Based on our study,we conclude that reduced use of synthetic pesticides is necessary and IPM is a better way to reduce the development of pesticide resistance among strains of S.litura.

Screening of antibacterial drugs from marine gastropod Chicoreus ramosus(Linnaeus,1758)

Objective:To screen the antibacterial drugs from different solvent extracts of tissue and egg of marine gastropods Chicoreus ramosus against clinically isolated human pathogenic bacteria.Methods:Vibrio parehaemolyticus(J13300),Aeromonus hydrophilla(IDH1585),Salmonella typhi(C6953),Salmonella paratyphi A(C6915),Vibrio cholerae(IDH5439)and Escherichia coli(H10407)using standard well diffusion method and its minimum inhibitory concentration.Results:Different solvent extracts of Chicoreus ramosus was screened for their activity against egg inhibited the growth of the tested pathogenic bacterial strains.The minimum inhibitory concentration of both the extract ranged from 4 to 12 mg/mL.The study revealed that the acetone and chloroform extract of both the tissues and Conclusions:These results suggest that marine gastropods tissue and egg extract contains comparatively good antibacterial activity.

Medicinal plants as immunostimulants for health management in Indian cat fish

Objective:To study the effect of three medicinal plants on growth,survival and immunoprotection in Mystus montanus fingerlings.Methods:The three experimental groups of fish were fed with a diet supplemented of Ocimum tenuiflorum,Zingiber officinale and Allium cepa(0.5 g each),and control group was fed without supplementation of herbal diet.After 45 d of feeding the experimental group fishes were injected with 0.5 mL of Aeromonas hydrophila and were supplemented with herbal diet.In the control group fishes were injected with 0.5 mL of physiological saline solution alone.Results:The blood samples were collected for haemotological analysis after 7 d of post infection.The results showed that the haematological parameters of haemoglobin,serum glutamic-oxaloacetic transaminase,serum glutamic pyruvic transaminase,serum glucose,red blood cell and white blood cell were found to be more in challenged fish.The survival rate of pathogen challenged fish maintained on the herbal diet is better than those in the control group which is supplemented with non-herbal diet.Conclusions:These results indicated that herbal diet is useful as a growth promoter and for disease resistance of Mystus montanus against Aeromonas hydrophila infection.