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1.
Monoterpenoids and their derivatives from plant essential oils showed good insecticidal activities in previous studies, but the mechanisms of their action as natural insecticides are not known yet. In the present work, we evaluated the pharmacological action of five monoterpenoids (α-terpineol, carvacrol, linalool, pulegone, and thymol) on native insect GABA receptors from house flies and American cockroaches using radiotracer methods. In the [3H]-TBOB binding assay, carvacrol, pulegone, and thymol all enhanced the [3H]-TBOB binding to membrane preparation of house fly heads with EC50 values of 48 μM, 432 μM, and 6 mM, respectively. Moreover, these three monoterpenoids at concentrations of 500 μM and 1 mM also significantly increased the 36Cl− uptake induced by GABA in membrane microsacs prepared from American cockroach ventral nerve cords. These results revealed that carvacrol, pulegone, and thymol are all positive allosteric modulators at insect GABA receptors. The other two monoterpenoids that were tested, α-terpineol and linalool, showed little or no effect in both the [3H]-TBOB binding and 36Cl− uptake assays.  相似文献   

2.
A permethrin-induced antifeedant effect was demonstrated in Drosophila melanogaster topically treated with a dose of 1.25 ng per fly (LD50 and LD10 were 18.5 and 7.4 ng of permethrin per fly, respectively). The reduction in food consumption in treated flies was due to a decrease in the frequency of feeding and not to the duration of individual meals. These results suggested that the sublethal effect occurred before the process of ingestion. Furthermore, a time-sampling study of individual flies, 30 min after treatment, revealed that the relative frequency of the components of general behaviour were altered. Specifically, locomotory behaviour and inactivity were significantly decreased in contrast to preening, which increased. Continuous observation for 30 min revealed that whilst the length of preening bouts was unaltered, their frequency of occurrence was significantly increased in permethrin-treated flies. The length of bouts of locomotory activity was significantly reduced in treated individuals, but the frequency was increased. The length of rest periods was reduced in treated flies, but no influence of the insecticide could be detected on their bout frequency. Sequential analysis of the transition frequencies of the behavioural components suggested that an underlying disorganisation of general behaviour resulted from the insecticide treatment. Further analysis, of the behaviour of those flies that had fed, indicated that the probability of tasting leading to feeding was decreased by permethrin. The increase in preening behaviour was thought to cause the reduction in locomotor activity, that ultimately resulted in the reduction in feeding. This is discussed in relation to the physiological basis of pyrethroid action and a subsequent irritation response to low doses.  相似文献   

3.
The action of avermectin was studied in the leg muscle and the central nervous system of the American cockroach, Periplanata americana L. Avermectin at a low concentration (10?7M) causes a failure of the leg muscles to respond to external stimuli within 30 min without affecting the magnitude of contraction. Avermectin was found to stimulate Cl? uptake by the leg muscles within 4 min at 10?7M. The threshold concentration to cause such stimulation was on the order of 10?8M. This stimulatory action could be antagonized by picrotoxinin (10?4M) and to a lesser extent by bicuculline methiodide (10?4M). The phenomenon is observable under both Na+-free and K+-free conditions. It was concluded that the action of avermectin is to open the chloride channel on the plasma membrane. This action of avermectin does not seem to be mediated through GABA, GABA receptors, diazepine receptors, or picrotoxinin receptor in this insect species, and therefore suggests that avermectin directly attacks the chloride channel proper both in the central nervous and the neuromuscular systems.  相似文献   

4.
Neurophysiological studies were used to characterize the resistance mechanism in a new cyclodiene-resistant strain of Drosophila melanogaster. Suction electrode recordings were taken from the peripheral nerves of transected larval central nervous system. Treatment of nerve preparations with 1 mM GABA reduced the spontaneous firing of peripheral nerves. This inhibition was effectively reversed within 10 min by exposing preparations from susceptible insects (Oregon-R wild type) to 10 μM dieldrin. In contrast, 30 min incubations with 10 μM dieldrin had no effect on preparations from resistant individuals. At 10 μM, picrotoxinin was also effective in antagonizing the action of GABA in susceptible nerve preparations. In recordings from resistant insects (n = 3), picrotoxinin displayed either no antagonism of GABA-dependent inhibition, weak antagonism of GABA, or hyperexcitation indistinguishable from those of susceptible preparations. These results demonstrate that cyclodiene resistance in the Maryland strain of D. melanogaster is present at the level of the nerve, and that the resistance extends to picrotoxinin, albeit at a reduced level. The possible role of an altered GABA receptor in this resistance is discussed.  相似文献   

5.
BACKGROUND: Monoterpenoids are a large group of plant secondary metabolites. Many of these naturally occurring compounds have shown good insecticidal potency on pest insects. Previous studies in this laboratory have indicated that some monoterpenoids have positive modulatory effects on insect GABA receptors. In this study, the key properties of monoterpenoids involved in monoterpenoid binding activity at the housefly GABA receptor were determined by developing quantitative structure‐activity relationship (QSAR) models, and the relationship between the toxicities of these monoterpenoids and their GABA receptor binding activities was evaluated. RESULTS: Two QSAR models were determined for nine monoterpenoids showing significant effects on [3H]‐TBOB binding and for nine p‐menthane analogs with at least one oxygen atom attached to the ring. The Mulliken charges on certain carbon atoms, the log P value and the total energy showed significant relationships with binding activities to the housefly GABA receptor in these two QSAR models. CONCLUSIONS: From the QSAR models, some chemical and structural parameters, including the electronic properties, hydrophobicity and stability of monoterpenoid molecules, were suggested to be strongly involved in binding activities to the housefly GABA receptor. These findings will help to understand the mode of action of these natural insecticides, and provide guidance to predict more monoterpenoid insecticides. Copyright © 2012 Society of Chemical Industry  相似文献   

6.
This study evaluated the direct antifungal activity of tiadinil [N-(3-chloro-4-methylphenyl)-4-methyl-1,2,3-thiadiazole-5-carboxamide], a systemic acquired resistance (SAR) inducer and two formulations of thymol (thymol I and thymol II) against Stagonosporopsis citrulli, the causal agent of gummy stem blight (GSB) disease of watermelon. Tiadinil, thymol I and thymol II completely inhibited the mycelial growth of S. citrulli in vitro at ≥?100 ppm. Conidial germination and germ tube elongation were completely inhibited by tiadinil at ≥?2000 ppm and by thymol-based formulations at ≥?100 ppm. A single foliar application of tiadinil at ≥?10 ppm or a single application of thymol I and II at ≥?1 ppm, 48 h before or after pathogen inoculation, significantly reduced disease severity of watermelon seedlings inoculated with 105/ml conidial suspension of S. citrulli, compared to respective nontreated controls. Plants treated with foliar application of tiadinil at ≥?1000 ppm before pathogen inoculation had significantly lower disease severity than plants that received an equivalent drench application. The efficacy of foliar application of tiadinil was affected by concentration and frequency of application. The study suggests direct antifungal activity of tiadinil, indicating a new mode of action of tiadinil against GSB disease of watermelon. The study also demonstrated direct antifungal action of thymol, a formulated active compound of essential oils, against S. citrulli and GSB disease of watermelon.  相似文献   

7.
The initiation of flight from loss of tarsal contact (flight reflex responses) and the tergotrochanteral muscle (TTM) responses evoked by brain stimulation were analyzed during carbofuran, permethrin, deltamethrin, and DDT poisoning in the house fly. Blockage of the flight reflex by LD50 doses of permethrin or deltamethrin was rapid, but the effects of DDT on the flight reflex took hours to develop. In addition, carbofuran treatment induced spontaneous flight in blocked preparations by an action in the central nervous system. This result suggests that pyrethroid blockage of the flight reflex was due to an action on sensory nerves, since the central flight program and its associated efferent systems were functionally intact. The relevance of this finding in terms of pyrethroid knockdown is discussed. The TTM response was unaffected by permethrin or deltamethrin both early and late in the poisoning process, possibly because the evoked TTM response does not involve peripheral sensory nerves, which seem to be important sites of pyrethroid action early in poisoning. Carbofuran induced repetitive firing and blockage of the TTM response within 1 hr, but normal responses were observed late in poisoning, which is consistent with the reversibility of carbamate inhibition of acetylcholinesterase. DDT caused no change in the evoked TTM response until bursts were recorded about 15 hr after treatment; this was another example of a slowly developing DDT effect. The protracted development of various DDT actions was concordant with a hypothesis of reduced efficacy at a proposed target site, viz., the sodium channels of nerve membranes.  相似文献   

8.

Background

Thermal history may induce phenotypic plasticity in traits that affect performance and fitness. One type of plastic response triggered by thermal history is acclimation. Because flight is linked to movement in the landscape, trapping and detection rates, and underpins the success of pest management tactics, it is particularly important to understand how thermal history may affect pest insect flight performance. We investigated the tethered-flight performance of Ceratitis capitata, Bactrocera dorsalis and Bactrocera zonata (Diptera: Tephritidae), acclimated for 48 h at 20, 25 or 30 °C and tested at 25 °C. We recorded the total distance, average speed, number of flight events and time spent flying during 2-h tests. We also characterized morphometric traits (body mass, wing shape and wing loading) that can affect flight performance.

Results

The main factor affecting most flight traits was body mass. The heaviest species, B. dorsalis, flew further, was faster and stopped less often in comparison with the two other species. Bactrocera species exhibited faster and longer flight when compared with C. capitata, which may be associated with the shape of their wings. Moreover, thermal acclimation had sex- and species-specific effects on flight performance. Flies acclimated at 20 °C stopped more often, spent less time flying and, ultimately, covered shorter distances.

Conclusion

Flight performance of B. dorsalis is greater than that of B. zonata and C. capitata. The effects of thermal acclimation are species-specific. Warmer acclimation temperatures may allow pest fruit flies to disperse further and faster. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.  相似文献   

9.
In 2003, a random survey was conducted across the Western Australian wheatbelt to establish the extent and frequency of herbicide resistance in Raphanus raphanistrum populations infesting crop fields. Five hundred cropping fields were visited, with 90 R. raphanistrum populations collected, representative of populations present in crop fields throughout the Western Australian wheatbelt. Collected populations were screened with four herbicides of various modes of action that are commonly used for the control of this weed. The majority of Western Australian R. raphanistrum populations were found to contain plants resistant to the acetolactate synthase (ALS)‐inhibiting herbicide chlorsulfuron (54%) and auxin analogue herbicide, 2,4‐D amine (60%). This survey also determined that over half (58%) of these populations were multiple resistant across at least two of the four herbicide modes of action used in the screening. Only 17% of R. raphanistrum populations have retained their initial status of susceptibility to all four herbicides. The distribution patterns of the herbicide‐resistant populations identified that there were higher frequencies of resistant and developing resistance populations occurring in the intensively cropped northern regions of the wheatbelt. These results clearly indicate that the reliance on herbicidal weed control in cropping systems based on reduced tillage and stubble retention will lead to higher frequencies of herbicide‐resistant weed populations. Therefore, within intensive crop production systems, there is a need to diversify weed management strategies and not rely entirely on too few herbicide control options.  相似文献   

10.
BACKGROUND: Bicyclophosphorothionates (2,6,7‐trioxa‐1‐phosphabicyclo[2.2.2]octane‐1‐sulfides) are blockers (or non‐competitive antagonists) of γ‐aminobutyric acid (GABA) receptor channels. Twenty‐two bicyclophosphorothionates with different 3‐ and 4‐substituents were synthesised, and [3H]4′‐ethynyl‐4‐n‐propylbicycloorthobenzoate (EBOB) binding assays were performed to evaluate their affinities for housefly and rat GABA receptors. RESULTS: Introduction of an isopropyl group at the 3‐position enhanced the affinity of bicyclophosphorothionates for housefly GABA receptors and reduced the affinity towards rat GABA receptors. The 4‐isopentyl‐3‐isopropylbicyclophosphorothionate showed the highest affinity for housefly GABA receptors (IC50 = 103 nM ) among the analogues tested, while the 4‐cyclohexylbicyclophosphorothionate showed the highest affinity for rat GABA receptors (IC50 = 125 nM ). Among the bicyclophosphorothionates synthesised to date, the former analogue exhibited the highest selectivity for housefly GABA receptors, with an IC50rat/IC50fly ratio of approximately 97. Three‐dimensional GABA receptor models successfully explained the structure–activity relationships of the bicyclophosphorothionates. CONCLUSION: The results indicate that minor structural modifications of blockers can change their selectivity for insect versus mammalian GABA receptors. The substituent at the 3‐position of the bicyclophosphorothionates dictates selectivity for housefly versus rat GABA receptors. This information should prove useful for the design of safer insecticides and parasiticides. Copyright © 2010 Society of Chemical Industry  相似文献   

11.
Low doses of deltamethrin cause prolonged knockdown of the tsetse fly Glossina morsitans morsitans. Fifty per cent of female flies, treated with the LD15-(48 h) of deltamethrin, failed to regain their capacity for normal flight for 30 h, compared with 6 h for bioresmethrin and 4 h for permethtin at the equivalent dose. Recovery after exposure to tetramethrin occurred within 1 h. The knockdown effect of deltamethrin on males was even more pronounced although, with both sexes, the onset of the effect was delayed for about 3 h. It is suggested that this prolonged knockdown effect of deltamethrin, at extremely low application rates, may make a significant contribution to the effectiveness of the compound against the tsetse fly.  相似文献   

12.
Solutions of tetramethrin, RU 11679, or cismethrin caused uncoupled convulsions in 30–40 min in exposed thoracic ganglia from SNAIDM house flies at concentrations down to 10?10M: whereas these same compounds at 10?6M concentrations failed to produce poisoning symptoms when perfused onto the exposed ganglia of the kdr strain of house fly. The pyrethroid analogs examined had a negative temperature coefficient of action on the exposed thoracic ganglia from SNAIDM flies. DDT and GH-74 possessed positive temperature coefficients of action on the exposed thoracic ganglion of susceptible house flies. It is concluded that the central nervous system of the kdr strain of house fly is resistant to pyrethroid action; furthermore, the resistance appears to be widespread throughout the house fly nervous system, involving sensory, motor, and central neural elements.  相似文献   

13.
Fipronil is a relatively new insecticide with great potential for insect control, however widespread use of cyclodiene insecticides has selected for an A302S mutation in the Rdl (GABA gated chloride channel) allele. This mutation gives resistance to cyclodienes and limited cross-resistance to fipronil. Given the concern over the possible reduction in efficacy and/or lifetime that fipronil might be used for pest control (given the extensive use of cyclodienes in the past), it is important to know the frequency of the A302S Rdl mutation in field populations. To ascertain the relative frequency of the A302S Rdl mutation in house fly populations we used three experimental approaches. First, we attempted to select for fipronil resistance by initially treating 33,100 field collected flies and selecting 14 additional generations. We were unable to produce a highly resistant strain. Second, we directly sequenced field collected flies. Third, we tested field collected house flies with a diagnostic dose of dieldrin and then genotyped the survivors. Out of the 4750 flies tested, there were no Rdl resistance alleles detected. We conclude that the resistant Rdl allele is rare in house flies in the US due to decades without cyclodiene use and a fitness disadvantage (in the absence of cyclodienes) of the 302S Rdl allele. The limited cross-resistance provided by the cyclodiene resistant Rdl allele, combined with the very low frequency of this allele in field populations, suggests that fipronil could be a promising insecticide for house fly control.  相似文献   

14.
‘De Groene Vlieg’ (the Green Fly) is an independent company offering various services concerning integrated pest management in open field agriculture in the Netherlands. One such service is the supervised control of carrot fly (Psila rosae). From 1993 to 2008 the company has monitored the carrot fly population on a total of nearly 65 000 hectares resulting in an extensive dataset. The data was not collected according to proper experimental methods, hence it is titled dirty, but the size of the dataset does allow valuable insights to be gained. De Groene Vlieg monitors the carrot fly population on each field separately. Sticky traps are collected weekly and flies are counted in the laboratory. Growers receive messages containing advice regarding when to apply insecticides and they are responsible for doing so. Overall, over a third of the fields require no spraying at all and for 75% of the fields growers are advised to spray three times or less. One insight from the dataset is that small carrots require more insecticide treatments than large carrots (‘winter carrots’). Reasons for this difference are probably both regional and cultural. Additionally, focusing on a small and uniform area reveals that carrot fly population dynamics are highly variable between years. Another insight is that sowing date has a large effect on the number of insecticide sprayings that are required. Fields sown before the first flight have more flies in the second flight than fields sown later. Comparison of biological and conventional carrot fields shows that carrot fly populations are similar for the first flight. However, during the second flight the number of flies is much higher on organic fields than on conventional ones. Finally, insecticide seed treatment with chlorfenvinphos to control the reproduction of the first flight appears slightly more efficient than supervised control. However, supervised control seems as efficient as seed treatment with clothianidin and beta cyfluthrin.  相似文献   

15.
The insecticidal properties of 1-(7-ethoxygeranyl)-2-methylbenzimidazole (EGMB) were investigated on larval and adult house flies. Unsynergised EGMB gave topical LD50 values of 0.53 μg per female fly on NAIDM strain house flies. When flies were pretreated with 5.2 μg piperonyl butoxide, susceptibility was increased (LD50 0.12 μg per female fly). House fly larvae were less susceptible to EGMB (LD50 2.2 μg). Poisoning with EGMB resulted in a rapid reduction in locomotor activity of both larval and adult house flies. This reduction in locomotion was progressive and led to complete paralysis. Various parameters of larval nervous system function were investigated in larvae during these early phases of poisoning. As early as 15 min after dosing larvae with LD95 doses of EGMB, sensory nerves were less responsive. Over a somewhat longer time (2–4 h), neurally evoked contractures were adversely affected by EGMB. In some cases, this effect appeared to be due to reduced postsynaptic potential amplitude; in other instances, it appeared to be due to an effect independent of neuromuscular transmission. The close temporal correlation between behavioural and electrophysiological observations suggests that the nervous and muscular systems are important sites of action of EGMB.  相似文献   

16.
Inoculation     
Terpenes and biogenically related phenols commonly found in plant essential oils are known to be toxic to insect pests. Accordingly thymol was tested for acute toxicity via topical application to diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae) and its parasitoid, Cotesia plutellae (Kurdjunov) (Hymenoptera: Braconidae under laboratory conditions. Topical application to adult female parasitoids versus second instars of P. xylostella showed that thymol was about 62 times less toxic to the parasitoid than to the host larvae with 24 h LD50 of 0.052 and 0.0008M, respectively. Although thymol was less toxic to the parasitoid, some biological parameters of the progeny at sublethal doses of surviving parasitoids were impaired such as rate of emergence and development time of larvae and pupae. The impact on detoxification enzymes was also studied and there was no significant induction in cytochrome P450 and carboxylesterase activities in both treated male and female wasps. Results obtained suggest that parasitoid is able to withstand the impact of thymol significantly.  相似文献   

17.
We investigated the effect of several acaricides on Varroa destructor by monitoring the rhythmic expansion of the sternum, followed by a strong flexion of the legs, initiated when the mite was placed in a dorsal side-down position, as an indication of a mite’s vitality. The pulses generated by the force of the rhythmic expansions had an average duration of 3.11 s, force (amplitude) of 73 μN, and frequency of 0.228 Hz. These parameters remained constant for the first 10 h of recording, whilst significant changes occurred after 15 h. The rhythmic sternal expansion is an indication of a Varroa mite’s gravitational reflex, or attempt to return to an upright position; this reflex is observed in all invertebrates and vertebrates. The sternal expansion can be recorded for over 20 h, or for as long as the Varroa mite remains alive, and the expansion stops as soon as the mite is placed in a normal, upright position. Proper function of the chain of proprioceptors, interneurons, motorneurons, neuromuscular junctions, and muscles of Varroa is required for the initiation and maintenance of such a behavioural motor pattern. Any deleterious effect of synthetic chemicals or natural compounds (acaricides) may have a direct effect on one or more of these links, thereby disturbing or even inhibiting the reflex. Topical application of 1.81 × 10−3 mg/mite of amitraz completely inhibited the gravitational reflex within 60–70 min for all mites tested. The volatile acaricides formic acid (13.83 mg), thymol crystals (250 mg), and Apiguard® (1000 mg) eliminated the reflex within 10–35 min. This bioassay, based on the gravitational reflex, could be a useful tool for accurate assessment of the acaricidal action of numerous compounds under laboratory conditions, saving money and time necessary to conduct field trials.  相似文献   

18.
炭疽菌Colletotrichum和链格孢Alternaria是引起植物病害的重要真菌,给农业生产造成巨大的损失。本研究选取13种萜类化合物,采用菌丝生长速率法对胶孢炭疽菌、链格孢进行抑菌活性分析。研究结果表明:香芹酚、丁香酚、异丁香酚、枯茗醛、百里香酚对两种病原菌有较好的抑菌活性,其中香芹酚对胶孢炭疽菌和链格孢的抑菌活性最强,IC50分别为40.89μg/mL和18.19μg/mL。本试验为植物精油和天然杀菌剂的开发利用提供理论依据。  相似文献   

19.
Patel  N. A.  Facknath  S.  Sookar  P. 《Phytoparasitica》2023,51(2):285-303

In Mauritius, the sterile insect technique (SIT) is being developed to manage the Peach fruit fly, Bactrocera zonata (Saunders) (Diptera: Tephritidae). Novel and economical larval diets are needed to produce millions of artificially reared sterile flies needed to ensure the success of this programme. We assessed the efficacy of conventional (solid) and gel diets with formulations containing modified waste brewery yeast (WBY), an alternative low cost protein source. The WBY is obtained freely from the manufacturing plant located at the Entomology Division of the Ministry of Agro Industry & Food Security, Réduit, Mauritius. Its chemical composition is highly comparable to those of the imported commercial yeast. Formulations of both diet types varied in the ratio of WBY (%) to commercial yeast (CY) (%) (Control: 0:100, A: 25:75, B: 30:70; C: 40:60; D: 50:50). The quality parameters of flies reared on the modified gel larval diets i.e. volume of pupae, pupal weight, pupal recovery, percentage adult emergence and percentage fliers were comparatively better on the gel diet formulations B, C and D, while no significant difference in percentage egg hatch was observed between the conventional diet and the gel diet. The optimum egg seeding rate (larval density) for selected gel diets B, C and D was determined. Formulation C using 0.15 ml of eggs/100 g of diet resulted in the highest pupal recovery, pupal weight, emergence and flight ability. A five-year cost benefit analysis revealed a net cost saving of 38% (US$ 53 418.20) by using the gel diet with WBY instead of the solid diet. The cost for the production for one million flies is US$ 310.67. Our results demonstrate that the selected gel diet formulation in which commercial yeast is partially replaced by waste brewery yeast is a viable alternative to the conventional solid diet for rearing of B. zonata. There are also the added benefits in terms of reduced cost with respect to storage and disposal, due to the elimination of bulking agents.

  相似文献   

20.
BACKGROUND: This paper deals with supervised management of Scaphoideus titanus (Homoptera Cicadellidae) and describes a phenology model designed for improving the understanding of the within‐vineyard dynamics and the timing of insect growth regulator (IGR) applications. RESULTS: The model consists of five components dealing with (a) the beginning of the post‐dormancy development of overwintering eggs, (b) the egg hatching patterns, (c) the duration of first‐instar nymphs, (d) the development and survival of subsequent instars and (e) the stochastic development of cohorts and their passage into the adult stage. Laboratory data permitted the parameterisation of temperature‐dependent development and survival functions. Field data consisting mainly of beating tray catches allowed model parameterisation and validation. The model satisfactorily predicts the dynamics of age structures, the beginning as well as the pattern of egg hatching, the occurrence of the third instar and the emergence of adults. CONCLUSION: The phenology model is useful for timing IGR applications and for setting up monitoring activities in supervised S. titanus control. The model is an entry point into an adaptive management system, in that real‐time weather and monitoring data are continuously integrated into the model for improving its explanatory and predictive capabilities. Copyright © 2011 Society of Chemical Industry  相似文献   

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