Plant-derived Insecticides Research Articles

Larvicidal effectiveness of acethonilic and methanolic Ipomoea cairica extract using two extraction methods and its effects on the morphology of Culex quinquefasciatus Say mosquito

Plants produce a rich source of chemicals, drugs and secondary metabolites that can act as insect killer. The larvicidal activity of various part of Ipomoea cairica extracts was evaluated against Culex quinquefasciatus. The highest percentage of yield extract was given by Soxhlet with acetone solvent for all of the different plant parts. While, maceration technique only provided 1/3 of the yield compared to Soxhlet technique. Using 24 h larvicidal bioassay technique, third instar larvae of Cx. quinquefasciatus were exposed to concentrations ranging from 10 to 600 ppm of the acetone and methanol extracts of I. cairica from leaves, stem and flower bud. Acethonilic extract of I. cairica leaves was extracted using a Soxhlet apparatus which exhibited the most promising larvicidal activity against Cx. quinquefasciatus larvae with significantly lower LC50 value of 110.65 ppm, meanwhile methanolic leaves extract exhibited LC50 value of 143.47 ppm. Larvae exposed to the I. cairica extracts for 24 h showed morphological malformation that included a detachment of thorax, disruption of the digestive tract and pigmentation of cuticle on their death. Thus, suggested that I. cairica plant extract, especially acethonilic leaves extract can be considered as one of plant-derived insecticides for control of Cx. quinquefasciatus, a vector of filariasis.

The full repertoire of Drosophila gustatory receptors for detecting an aversive compound.

The ability to detect toxic compounds in foods is essential for animal survival. However, the minimal subunit composition of gustatory receptors required for sensing aversive chemicals in Drosophila is unknown. Here we report that three gustatory receptors, GR8a, GR66a and GR98b function together in the detection of L-canavanine, a plant-derived insecticide. Ectopic co-expression of Gr8a and Gr98b in Gr66a-expressing, bitter-sensing gustatory receptor neurons (GRNs) confers responsiveness to L-canavanine. Furthermore, misexpression of all three Grs enables salt- or sweet-sensing GRNs to respond to L-canavanine. Introduction of these Grs in sweet-sensing GRNs switches L-canavanine from an aversive to an attractive compound. Co-expression of GR8a, GR66a and GR98b in Drosophila S2 cells induces an L-canavanine-activated nonselective cation conductance. We conclude that three GRs collaborate to produce a functional L-canavanine receptor. Thus, our results clarify the full set of GRs underlying the detection of a toxic tastant that drives avoidance behaviour in an insect.

Effects of 10-hydroxycamptothecin on intrinsic mitochondrial pathway in silkworm BmN-SWU1 cells

10-Hydroxycamptothecin (HCPT), a plant alkaloid isolated from Camptotheca acuminate, is known as a planted-derived insecticide, however, the specific mechanism in insect cells is still unclear. In this study, we treated the ovarian cell line of the silkworm, BmN-SWU1, with different HCPT doses for durations ranging from 0 to 72h. The apoptosis morphology was evident after 72h of incubation and included cell protuberance, concentrated cytoplasm and apoptotic bodies. We observed DNA fragmentation and cell apoptosis after HCPT treatment. The disruption of mitochondrial distribution, activation of the intracellular mitochondrial permeability transition pore, and release of cytochrome c during HCPT-induced apoptosis in dose and time-dependent manner indicate the involvement of mitochondria in BmN-SWU1 cells. Caspase-9 and -3 activities increased gradually with the duration of incubation time. In conclusion, HCPT has a significant effect to initiate the intrinsic mitochondrial pathway in silkworm cells, providing a theoretical basis for better application of plant-derived insecticide in pest control.

Evaluation of Insecticidal Potential of Capsicum chinense Jacq. and Aframomum melegueta K. Schum. Against Trogoderma granarium Everts (Coleoptera: Dermestidae) in Groundnut

The insecticidal potential of seed powders of Capsicum chinense Jacq. (Solanaceae) and Aframomum melegueta K. Schum. (Zingiberaceae) was tested against Trogoderma granarium (Coleoptera: Dermestidae) in the laboratory at (28±2)°C and 70%±5% relative humidity. The seed powders were tested at the rates of 0.0%, 0.5%, 1.0% and 1.5% (w/w) of groundnut seeds replicated three times. At the highest rate of treatment, C. chinense caused 56.7% and 76.8% larval mortality at 3 and 7 days post treatment (DPT) respectively while A. melegueta exerted 53.4% and 73.8% larval mortality at 3 and 7 DPT, respectively. Results showed that insecticidal potential of the seed powders against adult mortality of T. granarium and seed damage followed similar trend. The various rates of C. chinense seed powder performed better than A. melegueta seed powder in causing larval and adult mortality and in reducing seed damage. The activity of the seed powders on mortality of the insect, seed weight loss and seed damage were exposure time and rate dependent. A significant reduction (p<0.05) in seed weight loss and seed damage was recorded among the treatments and maximum reduction was observed in the seeds treated with the highest rate of C. chinense seed powder. Percentage seed damage significantly (p<0.05) decreased with increase in the rate of treatment while the highest seed weight loss and seed damage were obtained in the control. The study showed that C. chinense seed powder had higher activity against the test insect pest than A. melegueta seed powder. The two seed powders had high bio-activity against the insect and therefore could be used in formulating environment friendly plant-derived insecticide.

Insecticidal activity of Torricellia tiliifolia extracts against Musca domestica and Aedes albopictus.

Insecticidal toxicity of extracts from leaves, stems, and bark of Torricellia tiliifolia de Candolle against adult Musca domestica L. and larval Aedes albopictus (Skuse) was evaluated in this study. Bark extract proved to be the most toxic to these two species with the chloroform fraction the most active with LC50 values of 306.15 microg/g and 23.05 microg/ml for the house fly and mosquito, respectively. At the same time, water fractions against M. domestica and petroleum ether against Ae. albopictus were comparatively less toxic. Two compounds from T. tiliifolia extracts, torrilliolide and torricelline, were highly toxic to both species. The LC50 values of torrilliolide and torricelline in adult M. domestica 48 h after topical application were 0.40 and 0.33 microg per adult, respectively, and equal to the commercially available, plant-derived insecticide, rotenone. These results showed that T. tiliifolia possess compounds with considerable bioactivity and worthy of further research.

Grain Protection Potential of Decaleside II, a New Plant-Derived Natural Insecticide

Decaleside II is the novel trisaccharide isolated from the edible roots of Decalepis hamiltonii that belong to a new class of natural insecticides. In the present study we have investigated grain protection potential and persistence activity of Decaleside II against stored-product pests such as Rhyzopertha dominica, Sitophilus oryzae, Tribolium castaneum and Callosobruchus chinensis. Decaleside II usually increased parental mortality and reduced F1 progeny in residual toxicity bioassays. At 7 days of the storage period of treated grains and pulses, the mortality was 100% of all four stored product insects. Both wheat and green gram treated with Decaleside II were totally free from infestation for the longer period of storage up to 210 d. Decaleside II being a natural trisaccharide, does not pose any toxic hazard from the treated grain and the lack of toxicity is attributed to the 1, 4 α linkage of the sugars which are easily hydrolyzed by the digestive enzymes such as glucosidases. Therefore, the insect selectivity and mammalian safety of Decaleside II make them highly suitable for use as novel grain protectants of natural origin.

Larvicidal efficacy of different plant parts of railway creeper, Ipomoea cairica Extract Against Dengue Vector Mosquitoes, Aedes albopictus (Diptera: Culicidae) and Aedes aegypti (Diptera: Culicidae).

Natural insecticides from plant origin against mosquito vectors have been the main concern for research due to their high level of eco-safety. Control of mosquitoes in their larval stages are an ideal method since Aedes larvae are aquatic, thus it is easier to deal with them in this habitat. The present study was specifically conducted to explore the larvicidal efficacy of different plant parts of Ipomoea cairica (L.) or railway creeper crude extract obtained using two different solvents; methanol and acetone against late third-stage larvae of Aedes albopictus (Skuse) and Aedes aegypti (L.) (Diptera: Culicidae). Plant materials of I. cairica leaf, flower, and stem were segregated, airdried, powdered, and extracted using Soxhlet apparatus. Larvicidal bioassays were performed by using World Health Organization standard larval susceptibility test method for each species which were conducted separately for different concentration ranging from 10 to 450 ppm. Both acetone and methanol extracts showed 100% mortality at highest concentration tested (450 ppm) after 24 h of exposure. Results from factorial ANOVA indicated that there were significant differences in larvicidal effects between mosquito species, solvent used and plant parts ( F = 5.71, df = 2, P < 0.05). The acetone extract of I. cairica leaf showed the most effective larvicidal action in Ae. aegypti with LC 50 of 101.94 ppm followed by Ae. albopictus with LC 50 of 105.59 ppm compared with other fractions of I. cairica extract obtained from flower, stem, and when methanol are used as solvent. The larvae of Ae. aegypti appeared to be more susceptible to I. cairica extract with lower LC 50 value compared with Ae. albopictus ( F = 8.83, df = 1, P < 0.05). Therefore, this study suggests that the acetone extract of I. cairica leaf can be considered as plant-derived insecticide for the control of Aedes mosquitoes. This study quantified the larvicidal property of I. cairica extract, providing information on lethal concentration that may have potential for a more eco-friendly Aedes mosquito control program.

Bait spray for control of European cherry fruit fly: an appraisal based on semi‐field and field studies

The European cherry fruit fly, Rhagoletis cerasi, is the major insect pest of sweet and tart cherries. Its management is becoming increasingly difficult in many countries as formerly effective but broad-spectrum insecticides are removed from the market. With the objective of identifying suitable and environmentally safe alternatives, we investigated bait sprays containing two families of plant-derived insecticides: azadirachtins (NeemAzal-T(®) and NeemAzal-T/S(®) ) and pyrethrins (Spruzit Neu(®) ). In 12 semi-field trials conducted within cages, weekly applications of 0.0001 or 0.0005% neem in a bait formulation effectively reduced fruit infestation. However, addition of 0.000125-0.001% pyrethrins did not improve the efficacy of the neem formulations, and when used alone pyrethrins were less effective than neem alone. Two years of field trials were also conducted within orchards wherein an insecticidal barrier of treated trees excluded immigration of fertile R. cerasi from elsewhere. In blocks treated with 0.0005% neem in a bait formulation, we observed 94% (2011) or 86% (2012) reduction of fruit infestation over control blocks. Bait sprays containing neem are a promising alternative for the management of R. cerasi, especially where the risk of immigration of fertilized females is low, as in isolated orchards or as part of area-wide treatments.

Deleterious effects of Myracrodruon urundeuva leaf extract and lectin on the maize weevil, Sitophilus zeamais (Coleoptera, Curculionidae)

Deterioration and degradation of grains by storage insect pests lead to economic losses of several billion dollars and affect food security. Sitophilus zeamais is responsible for pre- and post-harvest damages to maize. The high toxicity of synthetic insecticides and the development of resistance by insects to the chemicals currently used stimulate the investigation of plant-derived insecticides as new alternatives for pest control. In this study, we report the effects of diets containing Myracrodruon urundeuva leaf extract (10–150 mg/g) and lectin (MuLL; 3–150 mg/g) on the survival, feeding, and nutrition of the storage pest S. zeamais. The digestive enzyme activity in gut extracts from the insects reared on the leaf extract (25 mg/g) or MuLL (15 mg/g) diets was also evaluated. The leaf extract induced mortality (LC50: 72.4 mg/g), while MuLL (30–150 mg/g) exerted strong feeding deterrence. The leaf extract and MuLL promoted the loss of biomass, as reflected in the negative values for relative biomass gain rates and efficiencies in converting ingested food. Protease, trypsin-like, acid phosphatase, and amylase activities in the insects reared on leaf extract or MuLL diets were significantly (P < 0.05) lower than those in the control insects. MuLL ingestion also significantly reduced (P < 0.05) endoglucanase and alkaline phosphatase activities. In conclusion, the leaf extract and MuLL have the potential for S. zeamais control by killing adults and preventing the use of a food source, respectively. The deleterious effects of the extract and lectin on S. zeamais may be linked to enzyme inhibition and consequent suppression of digestive processes.

Increasing use of pyrethroids in Canadian households: should we be concerned?

Pyrethroids are a class of plant-derived insecticides and their man-made analogues that are increasingly applied in Canada as first choice for pest control in many agricultural and residential settings. Their popularity is partly due to their alleged safety compared to the older organochlorine and organophosphate insecticides. Application of pyrethroids is expanding because of recent increases in the level of pest infestations--such as bed bugs--and the decreased susceptibility of target species to many pest control products. Pyrethroid residues have been documented in homes, child care centres and food. While pyrethroids are considered of low health risk for humans, their increased use is of concern. Our current understanding of the adverse effects of pyrethroids derives mainly from studies of short-term effects in laboratory animals, case reports of self- and accidental poisonings, and high-dose occupational exposures, for which the levels and formulations of pyrethroid products differ from those relevant for long-term exposure in the general population. The available data suggest that the reproductive and nervous systems, endocrine signalling pathways, and early childhood development may be targets for adverse effects in the case of repeated exposure to pyrethroid formulations. Given uncertainty about the existence of long-term health effects of exposure to pyrethroids, particularly under realistic scenarios, we should be cautious when promoting pyrethroid products as safe methods for pest control.

Increasing Use of Pyrethroids in Canadian Households: Should We Be Concerned?

Pyrethroids are a class of plant-derived insecticides and their man-made analogues that are increasingly applied in Canada as first choice for pest control in many agricultural and residential settings. Their popularity is partly due to their alleged safety compared to the older organochlorine and organophosphate insecticides. Application of pyrethroids is expanding because of recent increases in the level of pest infestations--such as bed bugs--and the decreased susceptibility of target species to many pest control products. Pyrethroid residues have been documented in homes, child care centres and food. While pyrethroids are considered of low health risk for humans, their increased use is of concern. Our current understanding of the adverse effects of pyrethroids derives mainly from studies of short-term effects in laboratory animals, case reports of self- and accidental poisonings, and high-dose occupational exposures, for which the levels and formulations of pyrethroid products differ from those relevant for long-term exposure in the general population. The available data suggest that the reproductive and nervous systems, endocrine signalling pathways, and early childhood development may be targets for adverse effects in the case of repeated exposure to pyrethroid formulations. Given uncertainty about the existence of long-term health effects of exposure to pyrethroids, particularly under realistic scenarios, we should be cautious when promoting pyrethroid products as safe methods for pest control.

Gustatory Receptors Required for Avoiding the Insecticide l-Canavanine

Insect survival depends on contact chemosensation to sense and avoid consuming plant-derived insecticides, such as L-canavanine. Members of a family of ∼60 gustatory receptors (GRs) comprise the main peripheral receptors responsible for taste sensation in Drosophila. However, the roles of most Drosophila GRs are unknown. In addition to GRs, a G protein-coupled receptor, DmXR, has been reported to be required for detecting L-canavanine. Here, we showed that GRs are essential for responding to L-canavanine and that flies missing DmXR displayed normal L-canavanine avoidance and L-canavanine-evoked action potentials. Mutations disrupting either Gr8a or Gr66a resulted in an inability to detect L-canavanine. We found that L-canavanine stimulated action potentials in S-type sensilla, which were where Gr8a and Gr66a were both expressed, but not in Gr66a-expressing sensilla that did not express Gr8a. L-canavanine-induced action potentials were also abolished in the Gr8a and Gr66a mutant animals. Gr8a was narrowly required for responding to L-canavanine, in contrast to Gr66a, which was broadly required for responding to other noxious tastants. Our data suggest that GR8a and GR66a are subunits of an L-canavanine receptor and that GR8a contributes to the specificity for L-canavanine.

Effect of dihydrodillapiole on pyrethroid resistance associated esterase inhibition in an Indian population of Spodoptera litura (Fabricius)

Resistance in Spodoptera litura (Fabricius) has been attributed to enhanced detoxification of insecticides by increased levels of esterases, oxidases and/or glutathione S-transferases. Enzyme inhibiting insecticide synergists can be employed to counter increased levels of such enzymes in S. litura. Dihydrodillapiole induced synergism of pyrethroid toxicity was examined in the laboratory-reared third instar larval population of S. litura collected in Delhi (susceptible), and Guntur (resistant) region of Andhra Pradesh, India. The Guntur population was found to be 7.04 and 10.19 times resistant to cypermethrin and lambdacyhalothrin, respectively. The activity of cypermethrin, lambdacyhalothrin and profenophos against susceptible and resistance populations of S. litura, was gradually increased when used along with a plant-derived insecticide synergist dihydrodillapiole. The α-naphthyl acetate hydrolysable esterase activity in Delhi population was less as compared to the Guntur population. Resistance associated esterases in Delhi population were inhibited by pre-treatment with dihydrodillapiole. The esterase level in insect was instantly reduced initially, sustained for about 3 h and equilibrated at 4 h post treatment. The esterase activity of Guntur population was increased to 1.28 μmoles/mg/min at 2 h post treatment and subsequently reduced to lower than 0.70 μmoles at 4–12 h post treatment. The variation in esterase activity is suggestive of its homeostatic regulation in test populations. Dihydrodillapiole thus caused significant reduction of resistance in S. litura to cypermethrin, lambda cyhalothrin and profenophos.

Bioactivity of Argentinean Essential Oils Against Permethrin-Resistant Head Lice,Pediculus humanus capitis

Infestation with the head louse, Pediculus humanus capitis De Geer (Phthiraptera: Pediculidae), is one of the most common parasitic infestation of humans worldwide. Traditionally, the main treatment for control of head lice is chemical control that is based in a wide variety of neurotoxic synthetic insecticides. The repeated overuse of these products has resulted in the selection of resistant populations of head lice. Thus, plant-derived insecticides, such as the essential oils seem to be good viable alternatives as some have low toxicity to mammals and are biodegradable. We determined the insecticidal activity of 25 essential oils belonging to several botanical families present in Argentina against permethrin-resistant head lice. Significant differences in fumigant activity against head lice were found among the essential oils from the native and exotic plant species. The most effective essential oils were Cinnamomum porphyrium, followed by Aloysia citriodora (chemotype 2) and Myrcianthes pseudomato, with KT50 values of 1.12, 3.02 and 4.09; respectively. The results indicate that these essential oils are effective and could be incorporated into pediculicide formulations to control head lice infestations once proper formulation and toxicological tests are performed.

Tobit Analysis of Acceptability of Natural Plant Products for Control of Crop Pests in Northern Nigeria

This study was conducted to test the hypothesis that perceptions of attributes of phytochemicals significantly influence their adoption for crop pest control by farmers in northern Nigeria. Primary data were collected from 560 farmers across seven States in 2007 and subjected to analysis using Tobit model. The results showed that among farmers’ specific factors, farming experience (b=0.91) and pest problem (b=0.48) significantly (P=0.05) influenced acceptance of plant-derived insecticide. Among plant product attributes, effectiveness (b=0.46), safety (b=0.43), and cheapness (b=0.42) influenced acceptance. It implies that further research to improve these attributes will enhance acceptance and use intensity of plant products for pest control.

Ovicidal and adulticidal effects of monoterpenoids against permethrin‐resistant human head lice, Pediculus humanus capitis

The improper use of pediculicides containing permethrin has led to the development of resistance. Thus, new alternatives for control are needed. Plant-derived insecticides are attractive alternatives to common chemical insecticides because most of them are environmentally friendly and non-toxic to mammals. The toxic activity of 23 monoterpenoids belonging to several chemical classes was tested against the eggs of permethrin-resistant head lice, Pediculus humanus capitis De Geer (Phthiraptera: Pediculidae). Significant differences in ovicidal action were observed among the tested substances. The most effective chemicals were hydrocarbons and ethers, followed by ketones, alcohols, phenols and esters. A linear relationship between egg mortality and knockdown time (KT(50)) on adults by the tested components revealed that most of the components were effective on both egg and adult stages. The monoterpenoids described herein are good candidates as effective pediculicides.

Calcium-Activated Potassium Channels in Insect Pacemaker Neurons as Unexpected Target Site for the Novel Fumigant Dimethyl Disulfide

Dimethyl disulfide (DMDS), a plant-derived insecticide, is a promising fumigant as a substitute for methyl bromide. To further understand the mode of action of DMDS, we examined its effect on cockroach octopaminergic neurosecretory cells, called dorsal unpaired median (DUM) neurons, using whole-cell patch-clamp technique, calcium imaging and antisense oligonucleotide strategy. At low concentration (1 microM), DMDS modified spontaneous regular spike discharge into clear bursting activity associated with a decrease of the amplitude of the afterhyperpolarization. This effect led us to suspect alterations of calcium-activated potassium currents (IKCa) and [Ca(2+)](i) changes. We showed that DMDS reduced amplitudes of both peak transient and sustained components of the total potassium current. IKCa was confirmed as a target of DMDS by using iberiotoxin, cadmium chloride, and pSlo antisense oligonucleotide. In addition, we showed that DMDS induced [Ca(2+)](i) rise in Fura-2-loaded DUM neurons. Using calcium-free solution, and (R,S)-(3,4-dihydro-6,7-dimethoxy-isoquinoline-1-yl)-2-phenyl-N,N-di-[2-(2,3,4-trimethoxy-phenyl)ethyl]-acetamide (LOE 908) [an inhibitor of transient receptor potential (TRP)gamma], we demonstrated that TRPgamma initiated calcium influx. By contrast, omega-conotoxin GVIA (an inhibitor of N-type high-voltage-activated calcium channels), did not affect the DMDS-induced [Ca(2+)](i) rise. Finally, the participation of the calcium-induced calcium release mechanism was investigated using thapsigargin, caffeine, and ryanodine. Our study revealed that DMDS-induced elevation in [Ca(2+)](i) modulated IKCa in an unexpected bell-shaped manner via intracellular calcium. In conclusion, DMDS affects multiple targets, which could be an effective way to improve pest control efficacy of fumigation.

Assessment of Some Plant-Derived Insecticides on the Organoleptic Properties of Smoked Catfish, Clarias gariepinus Burchell

Assessment of Some Plant-Derived Insecticides on the Organoleptic Properties of Smoked Catfish, Clarias gariepinus Burchell

Effect of neem seed kernel extracts on stem borer damage and yield of upland rice in southeastern Nigeria

Stem borers are considered important insect pests of rice in most parts of the world. They have been implicated as the major constraint to rice production in West Africa (Ukwungwu 1990). Reliable data on yield loss caused by stem borers are not available in southeastern Nigeria. However, a screenhouse experiment at Badeggi, in the middle belt of Nigeria, showed that yield loss caused by Diopsis thoracica (West) ranged from 5% to 19% (Akinsola 1980). Dakuo et al (1991) reported a yield loss of 33% in irrigated rice caused by lepidopterous stem borers (Chilo zacconius, C. diffusilineus, Maliarpha separatella, and Sesamia calamistis) in Burkina Faso. Various control strategies have been adopted against stem borers, one common method being the use of synthetic insecticides, which can be environmentally disruptive and can result in the accumulation of residues in the harvested produce (Chinniah et al 1998). The use of synthetic insecticides is rare in southeastern Nigeria, where farmers produce the bulk of the rice. Although some risks accompany the use of synthetic insecticides, some insecticides of plant origin are safer to handle and use. Neem products are examples of such plant-derived insecticides, which have been used in some Asian countries. Their use on field crops is not yet popular in Nigeria. Our study reports the effect of the frequency of application of 5% neem seed kernel extract (NSKE) on rice stem borer damage and grain yield.

Effects of plant-derived compounds on larvae of a blow fly species that causes secondary myiases: laboratory studies.

No-choice and binary-choice bioassays were used to test the effect of a range of plant-derived insecticides on the behaviour of larvae of the black blow fly Phormia regina (Meigen). Azadirachtin (100 and 10 ppm), pyrethrum extract (10 ppm) and the naphthoquinone BTG 505 (1000 ppm) acted as deterrents for P. regina larvae. The mortality of larvae was reduced in instances where they moved away from a treated diet. Larvae given a choice were heavier, when compared with larvae reared exclusively on diets containing either azadirachtin (100 or 10 ppm) or the naphthoquinones, BTG 504 (1000 ppm) or BTG 505 (1000 ppm). The deterrent effect of azadirachtin, pyrethrum and the naphthoquinone BTG 505 together with their larvicidal activity, could be utilized in prophylaxis against myiasis infections due to larvae of Phormia regina.