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PubMed2003

Use of repellents as prophylactic agents.

Many biting insects are able to transmit diseases or are a regarded as pests. The use of repellents is one personal protection measure to avoid to been bitten. The first components which were used for this purpose were of plant origin. Some are still used, e.g., citronella oil. Systematic evaluation of synthetic repellents began during the Second World War. The most important compound resulting from these efforts is Deet, followed by less important ones such as dimethylphthalate or ethyl hexane diol. Compounds of more recent research are MERCK 3535 (aminopropionic acid ethylester), p-menthane-3,8 diol, CIC 4 (a lacton) and the piperidine derivatives AI3-37220 and Bayrepel (Icaridin). An overview of the toxicity and efficacy is given. A chance to improve the cosmetic properties and long duration efficacy is the development of new formulations. Applications other than the dermal one are the use of repellents as slow release formulations to achieve a long range effect and the development of systemic compounds, which are taken orally. To date, neither strategy has led to successful solutions.

Animals↗

PubMed1999

Possibilities of long-term protection against blood-sucking insects and ticks.

Insecticidal and repellent properties and residual action of permethrin and deltamethrin and two commercial preparations Peripel 55 and Permanone were investigated under laboratory and field conditions. The tests were conducted on ticks, mosquitoes and houseflies. Permethrin in concentrations of 0.036-2.276 mg.m-2 caused 90-100% mortality and deltamethrin in concentrations of 0.012-0.75 mg.m-2 induced 78-100% mortality in ticks after 24 hrs exposure (Table 1). Good repellent properties of the preparation Peripel 55 were confirmed in experiments on mosquitoes Aedes aegypti (Table 2 and Fig. 1). Experiments confirmed good residual effects (Fig. 3 and 4) of the preparations tested. Peripel 55 retained 100% effectiveness up to 4 months and following two washings. The preparation Permanone exhibited 100% effectiveness for 1 month and a decrease in effectiveness to 52% after the first washing. In the period from June to September, the repellent properties of Permanone were observed in a group of 17 forestry women workers in a field trial. The index of repellency ranged from 57 to 80 (average 71) in June and July and from 40 to 100 (average 74) in August and September. The difference in the number of ticks that clung to the workers in the experimental group who had their clothes treated with the preparation tested was significant in comparison with the control group at p < 0.1, 0.05 and 0.01.

Aedes↗

PubMed2003

[Advances of studies on the effects of plant volatiles on insect behavior].

Plant volatiles show different effects on insect behaviors, which included luring, repelling and killing. After damaged by phytophagous insects, some host plants could send volatiles luring natural enemies as an indirect defense. A summarize on the new advances of plant volatiles was given. The role of plant volatiles in integrated pest management in future was also discussed.

Animals↗

PubMed2006

Repellent and deterrent effects of SS220, Picaridin, and Deet suppress human blood feeding by Aedes aegypti, Anopheles stephensi, and Phlebotomus papatasi.

A series of behavioral tests with Aedes aegypti (L.), Anopheles stephensi Liston, mosquitoes, and the sand fly Phlebotomus papatasi Scopoli in the presence of Deet, SS220, and Picaridin topically applied to the skin of human volunteers showed that the insects were deterred from feeding on and repelled from surfaces emanating the compounds. When offered a 12- or 24-cm2 area of skin, one-half treated with compound and one-half untreated, the insects fed almost exclusively on untreated skin. The sand flies and mosquitoes did not at any time physically contact chemically treated surfaces. When treated and untreated skin areas were covered with cloth, insects contacted, landed, and bit only through cloth covering untreated skin. These observations provided evidence that the compounds deterred feeding and repelled insects from treated surfaces primarily as a result of olfactory sensing. When cloth, one-half untreated and one-half treated with chemical, was placed over untreated skin, insects only touched and specifically bit through the untreated cloth. This showed that the activity of the chemicals does not involve a chemical x skin interaction. In the presence of any of the three chemicals, no matter how they were presented to the insects, overall population biting activity was reduced by about one-half relative to controls. This reduction showed a true repellent effect for the compounds. Results clearly showed that Deet, SS220, and Picaridin exert repellent and deterrent effects upon the behavior of mosquitoes and sand flies. Heretofore, the combined behavioral effects of these compounds upon mosquito and sand fly behavior were unknown. Moreover, protection afforded by Deet, SS220, and Picaridin against the feeding of these three disease vectors on humans is mechanistically a consequence of the two chemical effects.

Aedes↗

PubMed2005

New insight into the biosynthesis and regulation of indole compounds in Arabidopsis thaliana.

In spite of their silent and sessile life, plants are dynamic organisms that have developed advanced defence strategies in their adaptation to the pressure of herbivores and pathogens. Natural plant products play an important role as chemical weapons in this warfare. Characteristic of cruciferous plants is the synthesis of nitrogen- and sulphur-rich compounds, such as glucosinolates (Mikkelsen et al. 2002) and indole alkaloids (Pedras et al. 2000). Glucosinolates are believed to be largely non-toxic, but upon tissue disruption, they are hydrolyzed by endogenous beta-thioglucosidases (myrosinases) (Rask et al. 2000) to primarily isothiocyanates and nitriles, which have many biological activities. These include not only important roles as repellents against herbivorous insects and microorganisms, but also as volatile attraction of specialized insects (Wittstock and Halkier 2002). For humans, these compounds serve as cancer-preventive agents, biopesticides, and flavor compounds (Talalay and Fahey 2001). Indole alkaloids are phytoalexins and production of specific alkaloids is usually limited to only a few species. Cruciferous plants include the model plant Arabidopsis, which produces the indole alkaloid camalexin. This review will focus on the central role of indole-3-acetaldoxime (IAOx) in the biosynthesis of indole glucosinolates, camalexin, and the phytohormone IAA.

Arabidopsis↗

PubMed2006

Response of Drosophila to wasabi is mediated by painless, the fly homolog of mammalian TRPA1/ANKTM1.

A number of repellent compounds produced by plants elicit a spicy or pungent sensation in mammals . In several cases, this has been found to occur through activation of ion channels in the transient receptor potential (TRP) family . We report that isothiocyanate (ITC), the pungent ingredient of wasabi, is a repellent to the insect Drosophila melanogaster, and that the painless gene, previously known to be required for larval nociception, is required for this avoidance behavior. A painless reporter gene is expressed in gustatory receptor neurons of the labial palpus, tarsus, and wing anterior margin, but not in olfactory receptor neurons, suggesting a gustatory role. Indeed, painless expression overlaps with a variety of gustatory-receptor gene reporters. Some, such as Gr66a, are known to be expressed in neurons that mediate gustatory repulsion . painless mutants are not taste blind; they show normal aversive gustatory behavior with salt and quinine and attractive responses to sugars and capsaicin. The painless gene is an evolutionary homolog of the mammalian "wasabi receptor" TRPA1/ANKTM1 , also thought to be involved in nociception. Our results suggest that the stinging sensation of isothiocyanate is caused by activation of an evolutionarily conserved molecular pathway that is also used for nociception.

Animals↗

PubMed2002

Food experience on the predatory behavior of the ant Myrmica rubra towards a specialist moth, Acrolepiopsis assectella.

Entomophagous insects are often repelled by the secondary compounds of the plants eaten by their prey. These compounds, therefore, take on a defensive role for the phytophagous species that sequester them. Given that numerous entomophagous species are capable of learning, the effects on the foraging behavior of a repeated experience were investigated in the predatory ant Myrmica rubra. The sulfur amino acids methyl-cysteine sulfoxide (MCSO) and propyl-cysteine sulfoxide (PCSO) produced by Allium plants were identified in caterpillars of the leek moth Acrolepiopsis assectella. Three behavioral studies were carried out, with or without prior familiarization with caterpillars reared either on leek or on an artificial diet containing no Allium compounds. In choice tests with the two types of caterpillars, unfamiliarized ants displayed a preference for caterpillars reared on the artificial diet, but this preference disappeared or was reversed in both young and old ants after familiarization.

Allium↗

PubMed2004

Evidence that insect herbivores are deterred by ant pheromones.

It is well documented that ants can protect plants against insect herbivores, but the underlying mechanisms remain almost undocumented. We propose and test the pheromone avoidance hypothesis--an indirect mechanism where insect herbivores are repelled not only by ants but also by ant pheromones. Herbivores subjected to ant predation will experience a selective advantage if they evolve mechanisms enabling them to avoid feeding within ant territories. Such a mechanism could be based on the ability to detect and evade ant pheromones. Field observations and data from the literature showed that the ant Oecophylla smaragdina distributes persistent pheromones throughout its territory. In addition, a laboratory test showed that the beetle Rhyparida wallacei, which this ant preys on, was reluctant to feed on leaves sampled within ant territories compared with leaves sampled outside territories. Thus, this study provides an example of an ant-herbivore system conforming to the pheromone avoidance hypothesis.

Animals↗

PubMed2003

[Twenty-eight day repeated dose oral toxicity test of synergist of a pyrethroid insecticide, 2,3,3,3,2',3',3',3'-Octachlorodipropyl ether (S-421) in rats].

2,3,3,3,2',3',3',3'-Octachlorodipropyl ether (Abbreviation; S-421) is originally developed as synergist of a pyrethroid insecticide. In recent years, S-421 is used widely at home, for a mosquito-repellent incense, electric mosquito-repellent, an insect-killing spray, a vacuum cleaner paper pack, etc. as well. On the other hand, S-421 has been detected in vacuum cleaner dust samples as well as human milk samples in Japan indicating that our living environment is already contaminated by this compound. Long term toxicity studies including a carcinogenesis study have been performed and NOEL of chronic toxicity has been settled. However, it is clear that S-421 is used in close proximity so that acute or subacute exposure at relatively higher dose levels than chronic NOEL values are easily assumed, such as use of a spray in an ill-ventilated room, etc. This study, 28 day repeated oral dose toxicity study of S-421 was performed to monitor the outcome of acute and subacute exposure assuming possible exposure accidents mentioned above. The protocol is as follows; Groups of 10 rats of each sex(5 week-old), were treated with intragastric administration of S-421 with a dose of 0 (olive oil, control), 10, 40, 160 or 640 mg/kg body weight. For recovery test, 14 day after the last treatment, the control and 640 mg/kg groups were examined, respectively. All animals of all groups in both sexes survived. In the 640 mg/kg groups of the both sexes, all animals were set to drowsiness from about 5 hours after administration, however, they recovered by the next morning. In the hematology examination, Hb, MCH, MCHC, WBC values were significantly decreased and MCV value was significant increased in the 640 mg/kg group of both sexes. In the serum biochemistry, items increased in the 640 mg/kg groups of both sexes returned to normal level after 14 days recovery period. Absolute and relative liver weight increase seen in the 160 mg/kg and above also returned to control level after recovery. Histopathologically, slight hepatocellular swelling was observed in the 160 mg/kg groups and severe hepatocellular swelling with vacuolization and slight necrosis was seen in the 640 mg/kg group. In conclusion, the no-observed-effect levels (NOEL) of S-421 under these conditions was judged to be 40 mg/kg/day.

Administration, Oral↗

PubMed2004

NTP toxicology and carcinogenesis studies of trans-cinnamaldehyde (CAS No. 14371-10-9) in F344/N rats and B6C3F1 mice (feed studies).

UNLABELLED: Cinnamaldehyde is used in foods, beverages, medical products, perfumes, cosmetics, soaps, detergents, creams, and lotions. Cinnamaldehyde has been used as a filtering agent and a rubber reinforcing agent and is used as a brightener in electroplating processes, as an animal repellent, as an insect attractant, and as an antifungal agent. trans-cinnamaldehyde was nominated for study by the Food and Drug Administration based on its widespread use as a flavor and fragrance ingredient and its structural similarity to cinnamyl anthranilate and 3,4,5-trimethoxy cinnamaldehyde, two known rodent carcinogens. Male and female F344/N rats and B6C3F1 mice were exposed to trans-cinnamaldehyde (at least 95% pure) in feed for 3 months or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, cultured Chinese hamster ovary cells, Drosophila melanogaster, and mouse peripheral blood erythrocytes. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female F344/N rats were fed diets containing 4,100, 8,200, 16,500, or 33,000 ppm microencapsulated trans-cinnamaldehyde (equivalent to average daily doses of approximately 275, 625, 1,300, or 4,000 mg trans-cinnamaldehyde/kg body weight to males and 300, 570, 1,090, or 3,100 mg/kg to females) for 3 months. Additional groups of 10 male and 10 female rats received untreated feed (untreated controls) or feed containing placebo microcapsules (vehicle controls). All rats survived to the end of the study. Mean body weights of all exposed groups of males and 16,500 and 33,000 ppm females were significantly less than those of the vehicle controls, and 33,000 ppm males lost weight during the study. Feed consumption by exposed groups of males and females was less than that by the vehicle controls throughout the study. Clinical chemistry results of these studies indicated that trans-cinnamaldehyde administration, at the doses selected, induced an increase in serum bile acid concentration that suggests a hepatic effect in both male and female rats. Gross lesions observed at necropsy included multifocal to diffuse white nodules of the forestomach mucosa in 8,200 ppm or greater males and females. Increased incidences of nonneoplastic lesions of the forestomach included squamous epithelial hyperplasia in 8,200 ppm or greater males and females and chronic active inflammation in 33,000 ppm males and 16,500 and 33,000 ppm females. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female B6C3F1 mice were fed diets containing 4,100, 8,200, 16,500, or 33,000 ppm microencapsulated trans-cinnamaldehyde (equivalent to average daily doses of approximately 650, 1,320, 2,550, and 5,475 mg/kg to males and 625, 1,380, 2,680, and 5,200 mg/kg to females) for 3 months. Additional groups of 10 male and 10 female mice received untreated feed (untreated controls) or feed containing placebo microcapsules (vehicle controls). One vehicle control male, one 4,100 ppm male, and one 33,000 ppm male died during the first week of the study due to inanition that resulted from difficulty with the feeder. Five 16,500 ppm and eight 33,000 ppm male mice died during weeks 2 and 3 due to unpalatability of the dosed feed. Mean body weights of all exposed groups of males and of females exposed to 8,200 ppm or greater were significantly less than those of the vehicle controls. Feed consumption by 16,500 and 33,000 ppm mice was less than that by the vehicle controls during weeks 1 and 2. The incidence of squamous epithelial hyperplasia of the forestomach mucosa in 33,000 ppm females was significantly increased, and olfactory epithelial degeneration of the nasal cavity occurred in 16,500 and 33,000 ppm males and females. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female F344/N rats were fed diets containing 1,000, 2,100, or 4,100 ppm microencapsulated trans-cinnamaldehyde for 2 years. Additional groups of 50 male and 50 female rats received untreated feed (untreated controls) or feed containing placebo microcapsules (vehicle controls). Dietary concentrations of 1,000, 2,100, or 4,100 ppm delivered average daily doses of approximately 50, 100, or 200 mg/kg to males and females. Survival of 4,100 ppm males was greater than that of the vehicle controls. Mean body weights of 4,100 ppm males and females were generally less than those of the vehicle controls throughout the study. Feed consumption by 2,100 and 4,100 ppm males and 4,100 ppm females was less than that by the vehicle controls at the beginning and end of the study. There were no neoplasms or nonneoplastic lesions that were attributed to exposure to trans-cinnamaldehyde. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female B6C3F1 mice were fed diets containing 1,000, 2,100, or 4,100 ppm microencapsulated trans-cinnamaldehyde for 2 years. Additional groups of 50 male and 50 female mice received untreated feed (untreated controls) or feed containing placebo microcapsules (vehicle controls). Dietary concentrations of 1,000, 2,100, or 4,100 ppm delivered average daily doses of approximately 125, 270, or 550 mg/kg to males and females. Survival of males in the 2,100 ppm group was less than that of the vehicle control group. Mean body weights of 2,100 and 4,100 ppm males and females were generally less than those of the vehicle controls throughout the study, and mean body weights of 1,000 ppm males were less after week 74. Feed consumption by exposed mice was similar to that by the vehicle controls. The incidences of olfactory epithelial pigmentation in 4,100 ppm males and in 2,100 and 4,100 females were significantly greater than those in vehicle controls. There were no neoplasms that were attributed to exposure to trans-cinnamaldehyde. GENETIC TOXICOLOGY: trans-cinnamaldehyde was mutagenic in S. typhimurium strain TA100 in the presence of induced mouse liver S9 activation enzymes only. All other strain and activation combinations, including the standard rat and hamster derived liver S9 fractions yielded negative results. trans-cinnamaldehyde induced sister chromatid exchanges in Chinese hamster ovary cells with and without induced rat liver S9 activation. No significant increase in the frequency of chromosomal aberrations occurred in Chinese hamster ovary cells cultured with trans-cinnamaldehyde, with or without induced rat liver S9. In tests for induction of germ cell genetic damage in male Drosophila melanogaster, trans-cinnamaldehyde induced a significant increase in the frequency of sex-linked recessive lethal mutations when administered by abdominal injection; however, no induction of reciprocal translocations occurred in germ cells of treated males. No increase in the frequency of micronucleated erythrocytes was observed in peripheral blood of male or female mice administered trans-cinnamaldehyde in dosed feed for 3 months. CONCLUSIONS: Under the conditions of this 2-year feed study, there was no evidence of carcinogenic activity of transcinnamaldehyde in male or female F344/N rats exposed to 1,000, 2,100, or 4,100 ppm. There was no evidence of carcinogenic activity of trans-cinnamaldehyde in male or female B6C3F1 mice exposed to 1,000, 2,100, or 4,100 ppm. Exposure to trans-cinnamaldehyde resulted in olfactory epithelial pigmentation in male and female mice.

Acrolein↗

PubMed1998

Safety and efficacy of DEET and permethrin in the prevention of arthropod attack.

Many preventable diseases affecting troop strength are directly attributed to disease-carrying insects. The first line of defense against arthropod vectors is the use of personal protective measures. The concurrent application of DEET (N,N-diethyl-m-toluamide) repellent on the skin and permethrin [(3-phenoxy-phenyl)methyl(+/-)cis,trans-3-(2,2-dichloroethenyl)-2, 2- dimethylcyclopropane-carboxylate] insecticide on the battle dress uniform, while the uniform is worn properly, is a personal protective strategy officially known as the DOD Insect Repellent System. It is important for troop commanders and field leaders to enforce the use of personal protective measures to prevent insect-borne infectious diseases and to ensure troop and soldier readiness. DEET is a safe and effective repellent. Permethrin is a synthetic pyrethroid insecticide and repellent. Used in conjunction with proper clothing and other personal protective equipment, these repellents provide the best known protection available and are critical in minimizing the occupational health threat of arthropod-borne diseases to troops in the field.

DEET↗

PubMed2006

Lethal and behavioural effects of three synthetic repellents (DEET, IR3535 and KBR 3023) on Aedes aegypti mosquitoes in laboratory assays.

The knock-down, mortality and 'irritancy' effects of three synthetic repellents (DEET, IR3535 and KBR 3023) on Aedes aegypti (L) (Diptera: Culicidae) were evaluated in the laboratory in the absence of animal bait. Filter paper tests were carried out to assess the knock-down effect (KDt(50) and KDt(95)) and mortality (LC(50) and LC(95)) induced by each repellent. 'Irritancy' tests were carried out to compare the flight response (time to first take-off, or FT) to increasing concentrations of repellents (2-7%) and at five distances from the treated surface (0-40 mm). DEET had an insecticidal effect (KDt(50) = 9.7 min at 7%; CL(50)= 1165 mg/m(2)), whereas IR3535 and KBR 3023 did not. Relative to an untreated control, IR3535 was an irritant (relative irritancy or RI > 1) at doses of 5% and 7% (RI = 17.7 and 9.9, respectively), whereas DEET was an irritant at lower concentrations (RI = 12.3 at 2% DEET). KBR 3023 was the weakest irritant over the same range of concentrations (RI(max) = 3.6 at 6%). DEET was more of an irritant (RI(20) = 9.4) than IR3535 (RI(20) = 2.9) over a range of distances (0-20 mm), and KBR 3023 was not an irritant unless mosquitoes made contact with the treated surface. All three repellents had a significant effect on mosquitoes, but DEET exhibited a more complex mode of action than the others due to its insecticidal properties. The repellents do not behave as a single class of compounds with a common mode of action, but most probably affect different physiological systems in insects. The physiological and molecular mechanisms of repellents, especially DEET, should be investigated to ensure a better use of these molecules for skin applications and/or for treating materials against mosquitoes.

Aedes↗

PubMed2001

[The prescription of repellents].

Repellents are chemical products designed to ward off insects. They are effective against a wide range of arthropods including mosquitoes and flies but not against bees and wasps. Choosing the proper repellent can be difficult because no single product repels all pests. This article compares the performance and toxicity of various repellents based on reports describing systemic, topical, or physical repellents made from natural or synthetic ingredients. Essential oils are the most common natural ingredient. Synthetic ingredients range from dimethyphtalate, ethylexanediol, and diethyltoluamide (DEET) to new molecules such as 35/35, piperidine, bayerepel, and KBR 3023. Our findings indicate that DEET, used as the gold standard in most studies, is still the most effective repellent. There is no synergy between any of these products but combinations (e.g. ethylhexanediol and DEET) can optimize protection. In conclusion we propose guidelines for prescribing repellents to achieve the required level of protection in function of the duration of exposure and benefit-to-risk ratio. Several recommendations are made on the safe use repellents for adults and children.

Animals↗

PubMed2001

[Protection against biting mosquitoes].

The protection against arthropods especially disease transmitting mosquitoes is becoming more and more important. The problems with drugs used for treatment and prophylactic of malaria are rapidly growing due to emergence of resistant parasites and unwanted side effects. Furthermore the population living in endemic area often can't afford the new expensive drugs. A safe and effective way of preventing insect bites is needed. One can prevent arthropod born diseases by avoiding insect bites through physical and chemical means or a combination of both. Repellents are substances applied to the skin, which effectively prevent insects from biting. The gold standard is still Diethylbenzamine (DEET), which is highly effective, well documented and in use for more than 50 years. The new repellent Bayrepel (hydroxyethyl isobutyl piperidin carboxylate) available to the consumer since 1998, seems to have an efficacy comparable with DEET. Insecticides have a direct toxic effect on the nervous system of arthropods. Mainly synthetic pyrethroids, which produce less ecological problems than the older products, are used. They are supplied in form of sprays, vaporising mats or coils. An important progress is the combination of insecticides with physical means. Insecticide treated bed nets or clothes give an excellent protection. Topical or systemic Vitamin B1, acoustic devices and electrocuters are still sold and widely used although their complete ineffectivity is documented in many studies.

Animals↗

PubMed1998

Survey of U.S. Army soldiers' knowledge, attitudes, and practices regarding personal protection measures to prevent arthropod-related diseases and nuisance bites.

This study examined U.S. Army soldiers' knowledge, attitudes, and practices regarding personal protection measures (PPMs) to prevent arthropod-related diseases and nuisance bites. Soldiers attending 1 of 13 U.S. Army training courses either completed a written questionnaire (N = 1,007) or participated in a group interview (N = 65). Respondents primarily used repellents to prevent nuisance insect bites (55%) rather than to prevent disease (38.7%). Less than one-third correctly identified the military-issue repellents to be used on skin (31.7%) or clothing (26.1%). More than half (57.6%) thought that commercial products were better than military-issue repellents, but most (74.2%) reported that they did not have enough or any information about the U.S. military's system of PPMs. Soldiers have poor knowledge of U.S. military doctrine regarding PPMs and still prefer to use commercial products. A focused strategy to ensure the appropriate use of PPMs by service members should be developed, implemented, and evaluated.

Adult↗

PubMed1988

The relationship of insects to the deterioration of stored grain by fungi.

The data presented tests the hypothesis that knowledge of basic biological relationships between insects and fungi in the stored grain ecosystem can open new paths for management of the system. Evidence indicates: (1) some storage insect species are disseminators of storage fungi and some are exterminators; (2) some storage fungi attract storage insects and promote their population increases and other repel and secrete toxins harmful to insects; (3) certain morphophysiologic, biochemical similarities of fungi and the early developmental stages of insects suggest that new protective chemicals, 'insecticidal fungicides', could be designed or specifically sought. A specific example of a naturally occurring compound with dual action, sorbic acid (2,4-hexadienoic acid), is given and its effect on both insects and fungi is discussed. Sorbic acid is the only compound in the U.S. presently labelled by the FDA (Food and Drug Administration) as GRAS (Generally Regarded as Safe) and registered by the EPA (Environmental Protection Agency) for use on grain (maize) in storage.

Animals↗

PubMed2002

Feeding deterrence and contact toxicity of Stemona alkaloids-a source of potent natural insecticides.

On the basis of chronic feeding bioassays with neonate larvae of Spodoptera littoralis reared on an artificial diet, the methanolic leaf and root extracts from Stemona collinsae displayed very high insect toxicity compared to those of two Aglaia species, a commercial Pyrethrum extract, and azadirachtin, whereas S. tuberosa extracts demonstrated low activity in roots and no activity in leaves. Beyond that, in leaf disk choice tests against fifth instar larvae, S. collinsae showed strong antifeedant activity, whereas S. tuberosa was characterized by remarkable repellency. The anti-insect properties of both species were based on pyrrolo[1,2-a]azepine alkaloids, from which didehydrostemofoline (asparagamine A) was the major compound of the roots of S. collinsae, exhibiting the highest toxicity in feeding assays. Saturation and hydroxylation of the side chain in the co-occurring stemofoline and 2'-hydroxystemofoline, respectively, led to an increasing loss of activity. Contact toxicity tests with stemofoline and didehydrostemofoline exhibited even higher activities than those of Pyrethrum extract. Tuberostemonine was the dominating alkaloid in the roots of S. tuberosa, showing outstanding repellency but no toxic effects.

Aglaia↗

PubMed1998

Effects of azadirachtin on Ctenocephalides felis in the dog and the cat.

Azadirachtin-containing neem seed extract is a powerful insect growth regulator, a feeding deterrent and repellent with low toxicity. Unfortunately, azadirachtin degrades rapidly in light, excessive heat or alkalinity. Evaluations of azadirachtin on ectoparasites on animals have been scarce. The purpose of this work was to describe the effects of normal and potentiated azadirachtin on Ctenocephalides felis in the dog or cat. Groups of kennelled greyhounds and domestic cats infested with C. felis were sprayed once with azadirachtin containing neem seed extract with or without diethyltoluamide (Deet) and/or citronella. Methanolic extracts with 200, 1000 or 2400 ppm azadirachtin reduced fleas in a dose-dependent manner. Compared with fleas counted on treated dogs just before treatment and untreated infested dogs, 1000-2400 ppm azadirachtin reduced fleas 93-53% for 19 days. However, combined with 500 ppm Deet and 33% w/v citronella, only 500 ppm azadirachtin reduced fleas 95-62% for 20 days. On cats inoculated with 50 fleas 2 days before treatment, the combination reduced fleas and eggs 100% to day 6 and 83-51% from day 7 to 9. On petri dishes, the combination achieved 100% egg mortality up to day 7 and 80% to day 14 and 48-52% to days 21-28. Deet, with or without neem seed extract or citronella, and citronella, with or without neem, did not reduce fleas significantly. The results show that azadirachtin reduced fleas in a dose-dependent manner in flea-contaminated environments. In cats, the combination killed most fleas within 24 h, providing effective flea control for 7 days. The results suggest that Deet with citronella potentiated the effect of azadirachtin on C. felis.

Animals↗