Acute toxicity of the bird repellent,methyl anthranilate,to fry of Salmo salar,Oncorhynus mykiss,Ictalurus punctatus and Lepomis macrochirus

Several laboratory and field studies have shown methyl anthranilate to be an effective, non-toxic and non-lethal bird repellent, with application potential for protecting crops, seeds, turf and fish stocks from bird damage. Furthermore, methyl anthranilate can be added to liquids for the purposes of protecting migratory birds, e.g. addition to waste water associated with mining and to standing water pools at airports. Mammalian toxicity data are favorable. Methyl anthranilate is used as a fragrance and food flavoring and is GRAS listed by the US Food and Drug Administration. Despite the favorable outlook for methyl anthranilate's use as a safe repellent, no data exist on its environmental fate and effects. We have tested the acute toxicity of methyl anthranilate in a static system against the fry of four species of fish. The LC₅₀ at 24 h for Atlantic salmon (Salmo salar L.) was 32.3 mg liter^?1, with the no observable effect limit at 6 mg liter^?1. The LC₅₀ at 24 h for rainbow trout (Oncorhynus mykiss Richardson) was 23.5 mg liter^?1, with the no observable effect limit at 5 mg liter^?1. The LC₅₀ at 24 h for channel catfish (Ictalurus punctatus Raf.) was estimated to be 20.1 mg liter^?1, with the no observable effect limit at 7 mg liter^?1. The LC₅₀ at 24 h for bluegill sunfish (Lepomis macrochirus Raf.) was estimated to be 19.8 mg liter^?1, with the no observable effect limit at 7 mg liter^?1..     

Pesticidal properties of parthenin (from Parthenium hysterophorus) and related compounds

Eleven sesquiterpene lactone derivatives of parthenin ( 1 ), obtained from wild feverfew, Parthenium hysterophorus, were prepared by chemical and photochemical transformations. The compounds tested were a pyrazoline adduct ( 2 ) of parthenin, its cyclopropyl ( 3 ) and propenyl ( 4 ) derivatives, anhydroparthenin ( 5 ), a dihydro‐deoxygenated product ( 6 ), a formate ( 7 ) and its corresponding alcohol ( 8 ) and acetate ( 9 ), a rearranged product ( 10 ), lactone ( 11 ) and hemiacetal ( 12 ). All these derivatives, along with parthenin, were tried for their antifeedant action against sixth‐instar larvae of Spodoptera litura, for insecticidal activity against the adults of store grain pest Callosobruchus maculatus, for phytotoxic activity against Cassia tora, and for nematicidal activity against the juvenile stage‐II (J₂) of the root knot nematode Meloidogyne incognita. Antifeedent bioassay revealed that parthenin is moderately antifeedant. Among the derivatives, the saturated lactone ( 11 ) was found to be about 2.25 times more active than parthenin. The pyrazoline adduct ( 2 ) was found to be the most effective as an insecticide, with LC₅₀ values after 24, 48 and 72 h of 96, 43 and 32 mg litre⁻¹, respectively, which are comparable with neem extract. Compound 4 was found to be the most effective inhibitor of germination and seedling growth of C tora, with ID₅₀ values for germination, plumule length and radicle length of 136, 326 and 172 compared with 364, 738 and 427 mg litre⁻¹, respectively, for parthenin. Compound 10 was found to be the most effective in terms of nematicidal activity. The LC₅₀ values for this compound were 273 and 104 mg litre⁻¹, respectively, after 48 and 72 h compared with 862 and 512 mg litre⁻¹ observed for parthenin after 48 and 72 h. © 2001 Society of Chemical Industry     

Susceptibility pattern and development of resistance in the diamondback moth,Plutella xylostella L,to Bacillus thuringiensis Berl var kurstaki in India

Base‐line susceptibility for six‐day‐old larvae of the diamondback moth, Plutella xylostella, against Bacillus thuringiensis var kurstaki (Biobit^®) was studied by a cabbage leaf disc dip bioassay technique. Diamondback moth from 13 locations in seven different states spread over a distance of about 3000 km longitudinally was used for these studies. Forty‐eight‐hour LC₅₀ values varied from 1.0 to 10.97 mg AI litre⁻¹. Further investigations on the development of resistance under laboratory conditions showed an increase in LC₅₀ from 2.76 (for unselected F₁ generation) to 5.28 mg AI litre⁻¹ (for selected F₉ generation), using a selection concentration of 6.4 mg AI litre⁻¹. This suggested a possibility of the development of resistance under field conditions if there were to be extensive and indiscriminate use of B thuringiensis. These findings are discussed in relation to integrated pest management and the mechanisms of resistance in resistance management tactics. © 2000 Society of Chemical Industry     

Being exposed to low concentrations of pirimiphos-methyl and chlorfenapyr has detrimental effects on the mobility of Trogoderma granarium

BACKGROUND

Sublethal effects of insecticides may negatively affect several biological and behavioral traits of insects. The lethal effects of pirimiphos-methyl and chlorfenapyr have been previously showed on Trogoderma granarium, but little knowledge is available about their sublethal effects at low concentrations on both sexes. Herein, the sublethal effects of pirimiphos-methyl and chlorfenapyr on the mobility of T. granarium males and females were investigated.

RESULTS

Lethal concentration (LC) values of pirimiphos-methyl and chlorfenapyr were lower for T. granarium females than males. LC values on males were LC₁₀ = 0.000788 and 0.00139 mg active ingredient (a.i.) cm⁻², LC₃₀ = 0.00350 and 0.00535 mg a.i. cm⁻², and LC₅₀ = 0.00986 and 0.0136 mg a.i. cm⁻² for pirimiphos-methyl and chlorfenapyr respectively. LC on females were LC₁₀ = 0.000704 and 0.00110 mg a.i. cm⁻², LC₃₀ = 0.00323 and 0.00428 mg a.i. cm⁻², and LC₅₀ = 0.00925 and 0.0110 mg a.i. cm⁻² for pirimiphos-methyl and chlorfenapyr respectively. The walking duration of beetles exposed to LC₃₀ of pirimiphos-methyl was significantly lower than the individuals exposed to LC₁₀ and LC₃₀ of both insecticides and control ones. Pirimiphos-methyl LC₃₀-exposed males remained more time on their back (101.7 s) than females (46.9 s), while the latter stayed immobile longer than males (381.7 s versus 371.9 s). The highest speed was recorded for control beetles (14.17 mm s⁻¹ females vs. 12.44 mm s⁻¹ males), while the lowest speed was observed in pirimiphos-methyl LC₃₀-treated males (8.36 mm s⁻¹) and females (9.66 mm s⁻¹).

CONCLUSIONS

Overall, males and females exposed to low concentrations of pirimiphos-methyl and chlorfenapyr showed reduced motility. This knowledge can be exploited further to unlock behavioral effects of insecticides for effective pest management programs in warehouses. © 2023 Society of Chemical Industry.     

Ovicidal,larvicidal and juvenilizing activity of a picolinephenoxyanilide against Cydia pomonella

N‐(4‐phenoxyphenyl)‐2‐pyridinecarboxamide (1) was synthesized from commercially available materials and its ovicidal and larvicidal activity against Cydia pomonella (L) was tested. The compound showed a LC₅₀ of 0.98 mg ml⁻¹ when eggs less than 24 h were sprayed using a Potter Tower, but it had no effect when eggs older than this were sprayed. The compound did not have larvicidal activity when larvae were treated with 1200 µg g⁻¹. However, the larval head capsules were smaller than those in the controls when treated at this concentration. To assess its possible juvenile‐hormone‐like activity, the compound was topically applied to young pupae of Tribolium confusum duVal, where it produced clear juvenilization effects, which were dependent on the applied dose. © 2000 Society of Chemical Industry     

A new aqueous suspension concentrate formulation of cis‐permethrin and its insecticidal activity

Isomers of pyrethroids usually have different insecticidal activities. Permethrin, a non‐cyano pyrethroid, is not an exception and cis‐permethrin is much more active than the trans‐isomer against Triatoma infestans, vector of Chagas' Disease in Argentina. The large‐scale separation of cis‐ and trans‐permethrin was performed by successive recrystallizations from ethanol‐water mixtures. An aqueous suspension concentrate (flowable) formulation of pure crystalline cis‐permethrin was prepared and assayed for its insecticidal activity on wood and ceramic surfaces against nymph V of T infestans. This formulation was at least three times more effective than deltamethrin, with LC₅₀ values on ceramic of 0.11 µg cm⁻² and 0.33 µg cm⁻² respectively. On wood surfaces, the LC₅₀ value was 0.57 µg cm⁻² compared with 3.20 µg cm⁻² for deltamethrin. Against other insect species such as Periplaneta americana, Aedes aegypti and Culex quinquefasciatus, the suspension concentrate formulation of cis‐permethrin was, however, less effective than similar formulations of deltamethrin or β‐cypermethrin. © 2000 Society of Chemical Industry     

Laboratory and field evaluation of spinosad against the gypsy moth,Lymantria dispar

The toxicity of the naturally derived insecticide spinosad was tested against the gypsy moth, Lymantria dispar. Bioassays using red oak leaf disks, treated with spinosad in a Potter spray tower, yielded an LC₅₀ value of 0.0015 µg AI cm⁻² (3‐day exposure; 13‐day evaluation; 2nd instar larvae). Applied to foliage to run‐off in the laboratory (potted red oak seedlings) and the field (4 m‐tall birch trees), spinosad effectively controlled 2nd instar larvae at concentrations ranging from 3 to 50 mg litre⁻¹. Toxicity in the laboratory, and efficacy and persistence in the field, were comparable to those achieved with the insecticide permethrin. Laboratory studies supported field observations that control was achieved in part by knockdown due to paralysis. In addition, laboratory results demonstrated that crawling contact activity may play an important role in field efficacy; 50% of treated larvae were paralyzed 16 h after a 2‐min crawling exposure to glass coated with a 4 mg litre⁻¹ spinosad solution. © 2000 Society of Chemical Industry     

Organosilane insecticides. Part I: Biological and physical effects of isosteric replacement of silicon for carbon in etofenprox and MTI-800

Substitution of silicon for carbon was explored in etofenprox and MTI-800, primarily to establish the suitability of silicon for pesticide construction and to probe steric effects. It was shown that silicon is an effective building block for insecticides with subtle qualitative and quantitative differences relative to the carbon analogs. The silanes were slightly less toxic to insects than the carbon analogs (relative potency of 0.2-0.6) but the silane analog of MTI-800 was considerably less toxic to fish (0% mortality at ≥50 mg liter^?1) than MTI-800 itself (LC₅₀ = 3 mg liter^?1). The mode of action of both carbon and silicon compounds was similar in the intact, electrode-implanted cockroach and involved repetitive firing of a sensory nerve; potency measurements were also made using an in-vitro nerve assay. The possible metabolic and physicochemical contributions to the observed insecticide potencies were explored using synergism studies, physical chemistry measurements and quantum mechanical calculations.     

Lethal and sublethal effects of the neem insecticide formulation, ‘Margosan-O’, on the pea aphid

The effects of ‘Margosan-O’ (MO) on the pea aphid, Acyrthosiphon pisum (Harris), were determined. MO significantly reduced population increase of A. pisum in a concentration-dependent manner. At a concentration equivalent to 100 mg litre^?1 of azadirachtin, population increase was c. 3.5 times lower than the control. In more detailed studies, MO significantly reduced the number of molts, longevity, and fecundity of A. pisum that had been reared on treated broad bean. Viciafaba L., plants. MO also reduced the longevity and fecundity of young adult A. pisum exposed to MO-treated broad bean. MO was slow-acting against A. pisum. Mortality caused by MO stabilised seven days after newborn A. pisum were exposed to treated broad bean and 10 days for adults. The seven day LC₅₀ for individuals exposed from birth was 27.50 mg azadirachtin liter^?1 while the 10 day LC₅₀ for adults was 53.32 mg liter^?1. Contrary to previous studies suggesting that neem insecticides are not contact toxicants, we found that MO applied topically to adult A. pisum caused effects similar to those found in individuals that fed upon treated plants. However, MO was slower-acting when applied topically. Mortality in adult A. pisum caused by topically applied MO stabilised 17 days after treatment with a resultant LD₅₀of 2.91 μg azadirachtin g^?1.     

Laboratory Evaluation of the Novel Naturally Derived Compound Spinosad against Ceratitiscapitata

Laboratory studies were conducted to determine the effect of the naturally derived compound spinosad on Ceratitis capitata Wied. (Diptera, Tephritidae). The organophosphate fenthion was used as a standard. Direct dose-dependent mortality and reduced fecundity were observed in oral treatment of adults with spinosad. The LC₉₀ values 14 h and seven days after treatment were 19·50 and 0·49 mg litre⁻¹ respectively. Fenthion was less active (the LC₅₀ eight days after treatment was 1·17 mg litre⁻¹) and did not affect the fecundity of the fly. Adults were also very susceptible to spinosad and fenthion via residual contact. For spinosad, 100% mortality was recorded 48 h after treatment for a dose of 10 mg litre⁻¹. Spinosad was more effective than fenthion in suppressing larval development when neonate larvae were reared on treated diet supplemented with a range of concentrations from 0·02 to 0·83 mg kg⁻¹ diet. Last-instar larvae were much less susceptible to spinosad or fenthion when exposed via dipping or when they pupated in treated medium and both products had similar performance. A lack of ovicidal activity was observed in direct egg-treatments with spinosad but significant reductions from 1 mg litre⁻¹ onwards were recorded for fenthion.     

Mode of action of the fungicide flusilazole in ustilago maydis

Flusilazole is a potent inhibitor of Ustilago maydis sporidial growth (I₅₀= 20 μg liter⁻¹). Incorporation of [¹⁴C]acetate into ergosterol of growing sporidia is inhibited 50% by 0.5 μg liter⁻¹of the fungicide. Inhibition of ergosterol biosynthesis is concomitant with the accumulation of the precursors eburicol, obtusifoliol and 14α-methylfecosterol. A novel cell-free assay has been developed to measure the 14α-demethylation of [³H]dihydrolanosterol. Flusilazole inhibits the cell-free demethylation with an I₅₀of 15 μg liter⁻¹. These data provide strong evidence that the mode of action of flusilazole is by inhibiting ergosterol biosynthesis through direct inhibition of the 14α-demethylation of ergosterol precursors.     

Bioactivity of short-chain aliphatic ketones against adults of the granary weevil, Sitophilus granarius (L.)

BACKGROUND: The granary weevil, Sitophilus granarius (L.), is one of the most damaging pests of stored grains, causing severe quantitative and qualitative losses. Sustainable control means, alternative to the commonly used fumigants and broad‐spectrum contact insecticides, are urgently needed owing to legislative limits, the development of resistant insect strains and increasing consumer demand for safe food. Short‐chain aliphatic ketones, known to be emitted by cereal grains and previously identified as repellents to adult granary weevils, were evaluated for their ability to disrupt insect orientation towards wheat grains and as possible natural fumigants. RESULTS: In behavioural bioassays, 2‐pentanone, 2‐hexanone, 2‐heptanone and 2,3‐butanedione significantly reduced insect orientation towards odours of wheat grains, with 2‐hexanone and 2‐heptanone being the most active. In fumigation tests, all compounds were effective in killing weevil adults, but they performed differently according to chemical structure, speed of action and presence of wheat grains. In the presence of grains, the highest fumigant toxicity was shown by 2‐pentanone (LC₅₀ = 8.4 ± 1.0 mg L^?1) after 24 h exposure, and by 2‐pentanone (LC₅₀ = 4.5 ± 0.3 mg L^?1), 2‐heptanone (LC₅₀ = 7.1 ± 0.3 mg L^?1) and 2‐hexanone (LC₅₀ = 8.1 ± 0.6 mg L^?1) 1 week after the treatment end. CONCLUSION: Short‐chain aliphatic ketones have potential for applications in IPM programmes for the granary weevil because of their behaviour‐altering activity and fumigant toxicity. Copyright © 2011 Society of Chemical Industry     

Evaluation of semiochemical toxicity to Aedes aegypti,Ae. albopictus and Anopheles quadrimaculatus (Diptera: Culicidae)

BACKGROUND: Mosquitoes are the most important vectors of human pathogens. Wide‐scale use of pesticides has led to the development of resistance to most common insecticide groups. The need to develop novel products that have a low impact on human health and the environment is well established. The toxicity of selected semiochemicals with molecular structures indicative of insecticidal activity was determined against adult Aedes aegypti (L.) and Anopheles quadrimaculatus (Say). The two most active insecticides against Ae. aegypti were also evaluated against Ae. albopictus (Skuse). RESULTS: Fifteen semiochemicals classified as terpenoid alcohols, ketones or carboxylic esters showed toxicity to both mosquito species. Geranyl acetone (LC₅₀ = 38.51 µg cm^?2) followed by citronellol (LC₅₀ = 48.55 µg cm^?2) were the most toxic compounds to Ae. aegypti, while geraniol and lavonax, with LC₅₀ values of 31.88 and 43.40 µg cm^?2, showed the highest toxicity to An. quadrimaculatus. Both geranyl acetone and citronellol were highly toxic to Ae. albopioctus. No semiochemical showed fumigation activity against either species. All semiochemicals persisted for less than 24 h when tested on filter paper. CONCLUSION: Quantification of LC₅₀ values of several semiochemicals against Ae. Aegypti, An. quadrimaculatus and Ae. albopioctus showed that semiochemicals not only modify insect behaviors but also hold potential as potent insecticides for mosquito control programs. Copyright © 2010 Society of Chemical Industry     

The response of pyriproxyfen-resistant and susceptible Bemisia tabaci Genn (Homoptera: Aleyrodidae) to pyriproxyfen and fenoxycarb alone and in combination with piperonyl butoxide

Pyriproxyfen was effective against susceptible Bemisia tabaci eggs at a LC₅₀ of 0.003 mg litre⁻¹ and against nymphs at 0.02 mg litre⁻¹. In comparison, eggs of a laboratory selected, pyriproxyfen-resistant B tabaci strain, originating in an Israeli greenhouse, exhibited 6500-fold resistance and nymphs exhibited 1100-fold resistance. Eggs and nymphs of a strain from an Israeli sunflower field exhibited 450 and 210-fold resistance in comparison to the susceptible standard. Fenoxycarb was generally less effective than pyriproxyfen against B tabaci eggs and nymphs but was unaffected by pyriproxyfen resistance. Piperonyl butoxide (PB) was antagonistic to pyriproxyfen, and this increased with increasing pyriproxyfen resistance. PB had no effect on the toxicity of fenoxycarb. Collectively, these data imply that the modes of action of pyriproxyfen and fenoxycarb are distinct, despite the structural similarities of these molecules. Possible reasons for the antagonism of PB against pyriproxyfen are discussed. © 1999 Society of Chemical Industry     

Effects of anti-ecdysteroid azole analogues of metyrapone on the larval development of the fleshfly,Neobellieria bullata

Based on our previous finding that PIM (phenyl-imidazolyl-metyra-pon; 2-(1-imidazolyl)-2-methyl-1-phenylpropan-1-one, 1) is a strong inhibitor of ecdysone 20-monooxygenase (IC₅₀ = 7.89 × 10^?7 M) from the fleshfly, Neobellieria bullata (Parker) and has also a good toxic action in vivo against this insect, 17 imidazole and 1,2,4-triazole analogues of metyrapone were synthesized and evaluated for their action against N. bullata larvae in terms of toxicity, length of larval development, weight of the puparium as well as special symptoms, i.e. malformations of the anterior and posterior spiracles, and of the mandibles. The introduction of p-methoxy (LC₅₀ = 49 mg kg^?1 in diet) or p-chloro (LC₅₀ = 97 mg kg^?1) substituents on the benzene ring of PIM resulted in a significant increase in toxicity compared to that of metyrapone (LC₅₀ = 561 mg kg^?1) and PIM (LC₅₀ = 148 mg kg^?1). The hybridization state of the carbon atom adjacent to the benzene ring was not an important factor for toxicity because the acetoxy derivative ( 13 ) was almost as toxic as PIM. At least one methyl group was required on the carbon atom adjacent to the azole ring to maintain activity, while an ethyl group ( 4 ) enhanced the toxic effect. At the applied doses some compounds including metyrapone itself, extended the duration of the larval development. Only metyrapone and PIM decreased the puparium weight. Several derivatives induced lethal malformations of mandibles as well as the anterior and posterior spiracles.     

Fumigant Toxicity of Citruspeel Oils against Adult and Immature Stages of Storage Insect Pests

The biological action of citruspeel oils was shown to depend on a strong fumigant action. Bioassays conducted in air-tight glass chambers showed that all the six citrus oils tested had vapour toxicity towards adults of Callosobruchus maculatus F., Sitophilus zeamais Motsch. and Dermestes maculatus Deg. The 24-h LC₅₀ value of limepeel oil (a typical citrus oil) vapour against C. Maculatus was 7·99 μl litre⁻¹ which made it 1·5 and 1·6 times less toxic against the smaller S. zeamais and the larger D. maculatus adult insects. When immature stages were fumigated, limepeel oil vapour had 24-h LC₅₀ values of 7·8 and 21·5 μl litre⁻¹ against eggs of C. maculatus and D. maculatus respectively, and 9·1, 17·8 and 23·1, 23·9 μl litre⁻¹ against early larvae, pupae of C. maculatus and late larvae, pupae of D. maculatus respectively. X-ray studies showed that fumigated C. maculatus larvae within cowpea grains died immediately without further development. The bioactivities of five other citruspeel oils were similar to that of limepeel oil. Bioassays showed that sorption of citruspeel oil fumes occurred in the presence of grains or strips of dried fish, and that this tended to reduce the amount available for fumigant action outside the materials. The problems presented by sorption may hinder the development of citrus oils into practical fumigants for large-scale treatments of stored commodities.     

Correction: Pestic. Sci. 53, 201–208 (1998)

In the paper ‘Proinsecticides effective against insecticide-resistant peach-potato aphid (Myzus persicae (Sulzer)),’ by D. Hedley et al., in Table 3 the units of both columns headed LC₅₀ should be (mg litre⁻¹)     

Monitoring of resistance to spirodiclofen and five other acaricides in Panonychus citri collected from Chinese citrus orchards

BACKGROUND: Citrus red mite, Panonychus citri (McGregor), is one of the most important pesticide‐resistant pests in China. In order better to understand its resistance status, six populations of the mite were collected from Chinese citrus orchards for monitoring of resistance to spirodiclofen and another five acaricides. RESULTS: All the samples collected in the field in 2006 were susceptible to spirodiclofen. However, the LC₅₀ values in populations sampled in 2009 ranged from 3.29 to 418.24 mg L^?1 spirodiclofen, a 127‐fold difference between the least and most sensitive populations. Compared with a susceptible strain, 50‐fold and 90.8‐fold resistance to spirodiclofen was detected in populations sampled from Pinghe and Fuzhou in 2009, as well as cross‐resistance to spirotetramat. The LC₅₀ values for abamectin, fenpropathrin, hexythiazox and pyridaben in the collected samples ranged from 0.041 to 3.52 mg L^?1, from 23.91 to 696.16 mg L^?1, from 13.94 to 334.19 mg L^?1 and from 48.90 to 609.91 mg L^?1 respectively. CONCLUSION: Great variations in resistance to the tested acaricides were observed among the sampled populations. The Pinghe population developed resistance to all the acaricides tested. The Jianning population was susceptible to most acaricides tested, except pyridaben. Resistance management strategies were conducted on the basis of these observations. Copyright © 2010 Society of Chemical Industry     

Composition of essential oil of Chinese Chenopodium ambrosioides and insecticidal activity against maize weevil, Sitophilus zeamais

BACKGROUND: In a screening programme for new agrochemicals from Chinese medicinal herbs, Chenopodium ambrosioides L. was found to possess strong fumigant activity against the maize weevil Sitophilus zeamais (Motsch.). Essential oil of C. ambrosioides was obtained by hydrodistillation, and the constituents were determined by GC‐MS analysis. The active compounds were isolated and identified by bioassay‐directed fractionation. RESULTS: Five active compounds [(Z)‐ascaridole, 2‐carene, ρ‐cymene, isoascaridole and α‐terpinene] were isolated and identified from the essential oil from Chinese C. ambrosioides. The LC₅₀ values (fumigation) of the crude essential oils and the active compound (Z)‐ascaridole against S. zeamais adults were 3.08 and 0.84 mg L^?1 air respectively. The LD₅₀ values (contact toxicity) of the crude essential oil and (Z)‐ascaridole against S. zeamais adults were 2.12 and 0.86 µg g^?1 body weight respectively. CONCLUSION: The findings suggested that the essential oil of Chenopodium ambrosioides and its main active constituent, (Z)‐ascaridole, may be explored as a natural potential fumigant. Copyright © 2011 Society of Chemical Industry     

Insecticidal activity against Aedes aegypti of m-pentadecadienyl-phenol isolated from Myracrodruon urundeuva seeds

BACKGROUND: Myracrodruon urundeuva Fr. Allemao is a common tree in the Caatinga that has been widely used for various medical purposes. Previous studies showed that the ethanol seed extract of M. urundeuva has potent activity against the larval stage of the dengue vector Aedes aegypti. Given this potential insecticidal activity, bioguided separation steps were performed in order to isolate the active compound(s). RESULTS: The isolation process resulted in only one active chemical compound, identified by infrared spectroscopy and mass spectrometry as m-pentadecadienyl-phenol. This compound presented potent larvicidal and pupicidal activity (LC₅₀ 10.16 and 99.06 µg mL⁻¹ respectively) and great egg hatching inhibitory activity (IC₅₀ 49.79 µg mL⁻¹). The mode of action was investigated through observations of behavioural and morphological changes performed in third-instar larvae treated with m-pentadecadienyl-phenol solution after 1, 6, 12, 16 and 20 h of exposure. Some changes were observed as flooding of the tracheal system, alterations in siphonal valves and anal gills and lethargy, probably caused by the strong anticholinesterasic activity reported previously. CONCLUSION: The compound isolated from M. urundeuva seeds, m-pentadecadienyl-phenol, showed potent activity against immature stages of dengue vector, Ae. aegypti, being considered the main larvicidal principle. Copyright © 2012 Society of Chemical Industry