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1.
Stuart E. Reynolds 《Pest management science》1987,20(2):131-146
The functions, structure and biochemistry of the insect cuticle in relation to the moulting cycle are briefly reviewed as an introduction to the actions of insecticides that act on the cuticle, particularly acylureas. The symptoms of poisoning with diflubenzuron (DFB) and other acylureas are consistent with ultra-structural and biochemical evidence that these insecticides inhibit the formation of chitin microfibrils in newly synthesised cuticle. It is probable that DFB acts at a late stage in chitin biosynthesis, perhaps inhibiting chitin synthase (CS) itself. However, the results of studies using cell-free preparations of CS have not, on the whole, supported this hypothesis. A number of alternative suggestions as to the mode of action of DFB are reviewed. Among the most attractive of these is the possibility that DFB may inhibit the transmembrane transport of chitin synthesis precursors from their site of production within the epidermal cells to the site of the final poly condensation reaction, presumably at the apical membrane of the epidermal microvilli. 相似文献
2.
Effects of the chitin synthesis inhibitor diflubenzuron (DFB) on the integument of 5th instarGalleria mellonella L. larvae were investigated. When larvae were fed with semi-artificial diets containing 250, 500 and 1000 ppm of the compound,
DFB affected the integument. The affected larvae failed to ecdysis, their cuticle was ruptured, lost haemolymph and blackened.
In treated larvae, cuticle deposition was disrupted and the cuticle thickness was decreased by ∼50% compared with the untreated
control, particularly at day 3 1/2. However, statistically there was no significant difference among the three concentrations
(P>0.05). This may indicate that all three concentrations are equally effective in decreasing level. DFB at 500 and 1000 ppm
also affected the epidermal cells and caused the occurrence of vacuoles.
http://www.phytoparasitica.org posting Dec. 16, 2003. 相似文献
3.
Susan A. Lee Barry S. Clarke Donald W. Jenner Francis A. Williamson 《Pest management science》1990,28(4):367-375
Flufenoxuron (“Cascade”) is a novel acylurea with acaricidal and insecticidal properties. It acts in a similar manner to diflubenzuron (DFB) by impairing chitin incorporation into insect cuticle. Chitin can be localised cytochemically using the lectin, wheat germ agglutinin (WGA), which binds specifically to N-acetylglucosamine-containing polymers. WGA adsorbed to monodisperse colloidal gold (WGA-gold) was used as an electron-dense marker for localising chitin in the cuticle of sixth-instar Spodoptera littoralis. In the cuticle of control insects, the deposition zone and endocuticle were heavily labelled. In flufenoxuron- and DFB-treated insects, only the endocuticle (formed before treatment) was labelled, the deposition zone being devoid of label. These results show that flufenoxuron and DFB act in similar manner in reducing chitin incorporation in the cuticle of S. littoralis. 相似文献
4.
The knowledge of the biochemical mode of action of 1-(4-chlorophenyl)-3-(2,6-difluorobenzoyl)urea (diflubenzuron) is presented, explaining the insecticidal effect. Like its structural analog, 1-(2,6-dichlorobenzyl)-3-(3,4-dichlorophenyl)urea (Du 19111), it inhibits chitin synthesis in the cuticle of larvae. Virtually complete inhibition was demonstrable 15 min after the application of diflubenzuron. Neither diflubenzuron nor Du 19111 has any effect upon chitinase activity either in vivo or in vitro. The insecticidal effect upon the cuticle, therefore, must be explained as an inhibition of chitin synthesis and not as an activation of chitin degradation. In contrast to the action of Du 19111, no accumulation of N-acetylglucosamine occurs upon treatment of larvae with diflubenzuron. Similarities and differences in the mode of action of both compounds are discussed, together with other effects reported in the literature. 相似文献
5.
Noureddine Soltani 《Pest management science》1984,15(3):221-225
When fed to adults of Tenebrio molitor, diflubenzuron reduced the longevity, the weight of the adults and the thickness of the post-ecdysial adult cuticle. It also affected the production of the peritrophic membrane. The loss of weight and the decrease of longevity of the treated adults may have been because of alterations to the peritrophic membrane, caused by the inhibition of chitin biosynthesis by diflubenzuron. 相似文献
6.
Arnold C. Grosscurt Martin Ter Haar Berend Jongsma Andries Stoker 《Pest management science》1988,22(1):51-59
PH 70–23 is a new benzoylphenylurea interfering with chitin deposition. In larvae of Spodoptera littoralis, incorporation of N-acetyl-glucosamine into chitin was equally inhibited by PH 70–23 and diflubenzuron, the first commercially available benzoylphenylurea. In contrast to diflubenzuron, which is active only against insects and eriophyid mites, PH 70–23 has the advantage of also being highly active on spider mites. The latter activity might be partly due to leaf penetration of PH 70–23. Laboratory experiments indicate PH 70–23 to have a better ovo-larvicidal activity than the commercial acaricides tested (cyhexatin, dicofol, fenbutatin oxide and tetradifon) against Tetranychus cinnabarinus, T. turkestani, T. urticae and Panonychus ulmi. A method in which eggs were deposited on residues of cyhexatin or fenbutatin oxide resulted in much lower activities than application of the spray liquid after egg deposition. Activities of PH 70–23, dicofol and tetradifon were hardly influenced by this difference in the test method. The direct contact activity of PH 70–23 on eggs of mites is influenced by the relative humidity and the age of the eggs. The total ovolarvicidal activity of PH 70–23 is only slightly positively influenced by the relative humidity, however. Ovicidal activity of PH 70–23 is also achieved by transovarial transmission. The compound does not influence the fertility of the mites. Comparison of a strain of T. urticae, resistant to dicofol, parathion and tetradifon, with a susceptible strain indicated absence of cross-resistance to PH 70–23. Compared to diflubenzuron, PH 70–23 shows an interesting shift in the spectrum of insecticidal activity. 相似文献
7.
This research project examined the potential hazards of a major class of insect growth regulators (IGRs) to survival, reproduction and larval growth in bumblebees Bombus terrestris L. Eight chitin synthesis inhibitors (CSIs) were tested: buprofezin, cyromazine, diflubenzuron, flucycloxuron, flufenoxuron, lufenuron, novaluron and teflubenzuron. These different IGRs, which are important in the control of pest insects in greenhouses, were applied via three different routes of exposure under laboratory conditions: dermal contact, and orally via the drinking of sugar/water and via pollen. The compounds were tested at their respective maximum field recommended concentrations (MFRC) and also in dose-response assays to calculate LC(50) values. In general, none of the CSIs showed acute worker toxicity. However, there was a dramatic reduction in brood production, especially after oral treatment with pollen and sugar/water. Conspicuously, egg fertility was reduced in all treatments with diflubenzuron and teflubenzuron. In addition to egg mortality, the worker bumblebees removed larvae from the treated nest, and in most cases these individuals were dead first-second instars. Under a binocular microscope, such larvae showed an abnormally formed cuticle leading to mechanical weakness and death. In another series of experiments using (14)C-diflubenzuron and (14)C-flufenoxuron, cuticular penetration in workers was studied for a better understanding of the differences in toxicity. With (14)C-diflubenzuron, transovarial transport and accumulation in the deposited eggs supported the strong reproductive effects. Overall, the present results suggest that CSIs should be applied with caution in combination with bumblebees. The compatibility of each compound to be used in combination with B. terrestris is discussed in relation to calculated LC(50) values, routes of uptake and effects. 相似文献
8.
ABSTRACT Ontogeny of the invasion process by Colletotrichum acutatum and C. fragariae was studied on petioles and stolons of the strawberry cultivar Chandler using light and electron microscopy. The invasion of host tissue by each fungal species was similar; however, each invasion event occurred more rapidly with C. fragariae than with C. acutatum. Following cuticular penetration via an appressorium, subsequent steps of invasion involved hyphal growth within the cuticle and within the cell walls of epidermal, subepidermal, and subtending cells. Both species of fungi began invasion with a brief biotrophic phase before entering an extended necrotrophic phase. Acervuli formed once the cortical tissue had been moderately disrupted and began with the development of a stroma just beneath the outer periclinal epidermal walls. Acervuli erupted through the cuticle and released conidia. Invasion of the vascular tissue typically occurred after acervulus maturation and remained minimal. Chitin distribution in walls of C. fragariae was visualized with gold-labeled wheat germ agglutinin. The outer layer of bilayered walls of conidia, germ tubes, and appressoria contained less chitin than unilayered hyphae in planta. 相似文献
9.
John R. DeLoach Shirlee M. Meola Richard T. Mayer J.Mark Thompson 《Pesticide biochemistry and physiology》1981,15(2):172-180
Biochemical assays of stable fly pupae treated with diflubenzuron at the white prepupal stage and then injected with either [3H]thymidine or [14C]thymidine showed no differences in uptake of the thymidine at 0–4, 0–24, 20–21, or 22–24 hr after injection of the radiolabeled thymidine. However, at 32–36 hr the diflubenzuron pupae incorporated only 10–11% of the amount of labeled thymidine incorporated by the untreated pupae. Autoradiographs taken from diflubenzuron-treated pupae at 22–24 and 32–36 hr after injection of the labeled thymidine showed that a reduction in DNA synthesis had occurred in cells originating from the imaginal epidermal histoblasts. The reduction in DNA synthesis at 22–24 hr was not detectable by the biochemical assay since the number of proliferating epidermal cells was too small a proportion of the total number of cells undergoing histogenesis at this time period. Thus, the insect growth regulator, diflubenzuron, appears to be cell specific in this species of fly in that the reduction in DNA synthesis is observed only in cells originating from the imaginal epidermal histoblasts. However, it is not known at this time whether this effect is primary or secondary. 相似文献
10.
The chitin precursor [14C] N-acetylglucosamine injected into the haemolymph of Spodoptera littoralis (Boisduval) larva was incorporated into the chitin exponentially with time. When caterpillars were injected with precursor at the commencement of feeding on acylurea-treated leaf discs, flufenoxuron, teflubenzuron and diflubenzuron were found to be equally effective inhibitors of chitin synthesis, measured after 21 h. The dose response curves by feeding are not parallel, indicating that the relative potency of the compounds will vary across the dose range. When chitin precursor was injected simultaneously with topically applied diflubenzuron, flufenoxuron or teflubenzuron, all three acylureas were found to be equally effective as inhibitors of chitin synthesis when measured after five hours. The I50values (50% inhibition of chitin synthesis) were not significantly different; average 600 ng, compared with LD50values (50% lethal dose) of ～ 13 ng for flufenoxuron and teflubenzuron but 130 ng for diflubenzuron (topical application). Injection of precursor 24 h after topical application of insecticide gave an I50value which had dropped 670- and 150-fold for flufenoxuron and teflubenzuron respectively but only 20-fold for diflubenzuron. It is postulated that the reason for the low increase in diflubenzuron effectiveness with time was due either to less diflubenzuron than flufenoxuron reaching the site of action, or more probably, a faster rate of metabolism and excretion for diflubenzuron. The lower toxicity of diflubenzuron compared with flufenoxuron and teflubenzuron may not be due to any inherent differences in biochemical effectiveness, but rather to different penetration/metabolism properties. 相似文献
11.
Radiolabelling of isolated cuticles from foliar discs used as a test of cuticle biosynthesis 总被引：1，自引：0，他引：1
The radiolabelling of isolaled Hedera helix L, (ivy) leaf cutieles was investigated after incorporation of [14 C]acetate in foliar discs Cuticle radioactivity greatly decreased as leaf age inereased. The percentage of radioactivity incorporated in the upper cuticles decreased from 0.5% to 0.08% of the total radioactivity of foliar dises from young to old leaves. Cuticle radioactivity was recovered in waxes, cutin and polar components. It was considerably greater for waxes when expressed in terms of cuticle mass. The methodology was validated using S-ethyl-dipropylthiocarbamate (EPTC). The radioactivity incorporation in cuticles was significanly reduced when 1 m m EPTC was deposited as a 20-μL droplet on lo foliar dises 6 h before the incorporation of radiolabelled acetate. EPTC inhibited radioiabelling of wax and cutin fractions in the upper and lower cuticles. Some acetylenic fatty acid analogues inactivating lauric and oleic acid ω-hydroxylases, used as acid and sulphonate forms in the same experimental conditions as EPTC, induced no reduction in cuticle radiolabelling. An inhibitory effect was observed only for the acetylenic and the saturated C12 fatty acid analogues, used as tetrabu-tylammonium sulphonates, when applied directly in the liquid medium supporting foliar dises. Several assumptions are considered to explain the results of the present investigation. 相似文献
12.
Semi-thin sectioning and transmission electron microscope techniques were employed to investigate the cuticle thickness, integument structure, and fat body of larvae from susceptible and resistant strains of Bactrocera dorsalis. The results showed that the cuticle of β-cypermethrin-resistant strains (25.96 ± 1.00 μm) was thicker than that of susceptible strains (19.36 ± 0.82 μm). The number of chitin layers in the endocuticle of β-cypermethrin-resistant strains (98.00 ± 3.61 layers) was more than that in susceptible strains (75.67 ± 2.40 layers). Compared with susceptible strains, the laminated structure of the chitin layers in the endocuticle of resistant strains revealed higher density and more distinctive structure, and the interspace of epidermal cells was thicker. Fat body in the resistant insects contained more fat granules than those in susceptible insects. Moreover, HPLC analysis showed that the cuticular penetration of β-cypermethrin into larvae of resistant strains was slower than that of susceptible strains. In addition, the metabolism of β-cypermethrin in resistant strains was faster than that in susceptible strains, indicating that the resistant strains could enhance detoxification metabolism. These results indicated that cuticle thickness, fat body, laminated structure of the chitin layers, and interspace of epidermal cells might be correlated with cuticular penetration between susceptible and resistant strains, suggesting that the resistant strains could decrease the rate of penetration of insecticide into the internal cavity. 相似文献
13.
In a topical bioassay with pupae and adults of the mealwormTenebrio molitor (Coleoptera: Tenebrionidae), an important pest in stored products worldwide, three insect growth inhibitors (IGRs) were tested:
the two chitin synthesis inhibitors diflubenzuron and flucycloxuron, and the ecdysone agonist halofenozide (RH-0345). To address
differences in toxicity, we determined with the use of a14C-labeled isotope, the pattern of absorption through the cuticle and then the distribution in the different body tissues of
gut, hemolymph, integument and reproductive organs (ovaries, testis). The rate of absorption through the cuticle was highest
for flucycloxuron, and this concurred with its high toxicity. In general, the patterns of absorption followed a similar trend
in young and old pupae and in the adult stage. Accumulation in the reproductive system of females and males was relatively
high, which may explain the strong reproductive effects of the IGRs tested. In addition, we recorded large differences in
the clearance of insecticide from the insect bodyvia the excrements, with the chitin synthesis inhibitors exhibiting higher rates than halofenozide. 相似文献
14.
亚洲玉米螟Ostrinia furnacalis是我国玉米最重要的害虫，了解亚洲玉米螟表皮形成的机制将有助于对其开展生物防治。表皮蛋白和几丁质是构成昆虫表皮的两种主要成分，因此研究两者的相互作用对于阐明昆虫表皮形成机制具有关键意义。CPR9是亚洲玉米螟体壁表皮转录组中相对丰度最高的表皮蛋白基因。序列分析发现CPR9属于CPR家族中RR-1亚家族的表皮蛋白，含有R&R结构域，可能是通过结合几丁质来发挥功能。为了研究CPR9与几丁质的相互作用，本研究利用pET-SUMO载体实现了SUMO-CPR9融合蛋白的可溶表达，并通过SUMO蛋白酶处理及两次金属螯合亲和层析纯化了CPR9，平均收率为5 mg/L。几丁质结合试验发现，CPR9对不同类型的几丁质的结合具有选择性。CPR9对α-几丁质结合能力很强，对胶体几丁质结合能力较强，但不与β-几丁质结合。脱乙酰几丁质（壳聚糖）结合试验发现，CPR9能与脱乙酰几丁质结合并使其发生团聚。圆二色光谱分析表明，CPR9在结合脱乙酰几丁质后，其二级结构中平行β折叠和β转角比例上升，反平行β折叠及无规卷曲比例下降。本研究发现了CPR家族表皮蛋白与不同类型几丁质的结合存在特异性，而且在结合过程中会发生结构变化，有助于进一步了解昆虫表皮的形成机制。 相似文献
15.
The increase in cuticle thickness with age of fifth instar larvae of Pieris brassicae (L.) was measured microscopically. The injection of a lethal dose of either Polyoxin D or diflubenzuron revealed total inhibition of cuticular growth and caused comparable abnormalities in the cuticles.In a further experiment [14C]glucose was injected along with Polyoxin D into Pieris brassicae and the incorporation of radioactivity into various tissue fractions was measured. This revealed that the impairment of cuticular growth was due to inhibition of chitin synthesis.With the methods used the effects of Polyoxin D and two benzoylphenylurea insecticides appeared to be the same. 相似文献
16.
Diflubenzuron was found to be effective on the pupae of Tenebrio molitor L. (Coleoptera, Tenebrionidae) when applied topically, by dipping, or by injection. Death occurred before or at adult ecdysis, or during the first few days after emergence. Its effectiveness decreases with increasing age of the pupa. Diflubenzuron delays adult ecdysis and decreases the longevity of normally ecdysed adults. After diflubenzuron had been applied topically or by dipping, the compound was determined, on the pupal cuticle, in the body and on the rearing tray, by highperformance liquid chromatography. The results showed that diflubenzuron penetrated rapidly into the body and was not degraded during the pupal life. The level of incorporation of the insecticide, in dipping experiments on pupae at the same stage, varied from one individual to another. Moreover, the mean amount of insecticide incorporated was lower after dipping of older pupae than of younger pupae. It is suggested that the lower efficacy of diflubenzuron on older pupae may be caused by the decrease both in the permeability of the cuticle and in the sensitivity of the target cells. 相似文献
17.
Housefly larvae of 2 days of age were allowed to grow in media containing 0, 0.4, 1.0, or 2.5 ppm TH 6040[1-(4-chlorophenyl)-3-(2,6-difluorobenzoyl)-urea] for 3 days prior to analysis of the cuticle for structural components (chitin and protein) or enzymes important in cuticle formation (chitinase and phenoloxidase). As the TH 6040 concentration is increased, the amount of chitin is progressively reduced such that, at 2.5 ppm TH 6040, the level is only 25% of normal. The amount of cuticle protein is unaffected so the protein: chitin ratio increases from 3.4 in the control larvae to 14.3 in 2.5 ppm-treated larvae, an alteration which probably affects the elasticity and firmness of the endocuticle. Dietary TH 6040 at 1.0 ppm increases the cuticle chitinase activity to about 180% and the cuticle phenoloxidase activity to 155% as compared with control larvae, with a further chitinase activity increase to 240% of normal at 2.5 ppm TH 6040. These enzyme changes are expected to hamper the build-up or maintenance of the cuticle chitin and enhance sclerotization of the exocuticle. 相似文献
18.
The mechanisms of resistance to the chitin synthesis inhibitor diflubenzuron were investigated in a diflubenzuron-selected strain of the house fly (Musca domestica L.) with > 1000 × resistance, and in an OMS-12-selected strain [O-ethyl O-(2,4-dichlorophenyl)phosphoramidothioate] with 380 × resistance to diflubenzuron. In agreement with the accepted mode of action of diflubenzuron, chitin synthesis was reduced less in larvae of the resistant (R) than of a susceptible (S) strain. Cuticular penetration of diflubenzuron into larvae of the R strains was about half that of the S. Both piperonyl butoxide and sesamex synergized diflubenzuron markedly in the R strains, indicating that mixed-function oxidase enzymes play a major role in resistance. Limited synergism by DEF (S,S,S-tributyl phosphorotrithioate) and diethylmaleate indicated that esterases and glutathione-dependent transferases play a relatively small role in resistance. Larvae of the S and R strains exhibited a similar pattern of in vivo cleavage of 3H- and 14C-labeled diflubenzuron at N1C2 and N1C1 bonds. However, there were marked differences in the amounts of major metabolites produced: R larvae metabolized diflubenzuron at considerably higher rates, resulting in 18-fold lower accumulation of unmetabolized diflubenzuron by comparison with S larvae. Polar metabolites were excreted at a 2-fold higher rate by R larvae. The high levels of resistance to diflubenzuron in R-Diflubenzuron and R-OMS-12 larvae are due to the combined effect of reduced cuticular penetration, increased metabolism, and rapid excretion of the chemical. 相似文献
19.
CME 134, a new benzoylphenyl urea chitin synthesis inhibitor, was less active than diflubenzuron and BAY SIR 8514, when tested againstSpodoptera littoralis eggs by a dipping method. AgainstS. littoralis larvae the compound was tested by feeding treated alfalfa, topical application and contact with crystalline residues on glass, followed by observation until the adult stage. With both 200–250 and 360–440-mg larvae 100% mortality was obtained by one-day feeding of alfalfa treated with 0.15 ppm a.i. Topical application to 100- and 200-mg larvae showed CME 134 to be about five and nine times more active than BAY SIR 8514 and diflubenzuron, respectively. These differences were even much greater in the contact tests. Cotton field plots were sprayed with either CME 134 or diflubenzuron formulations, leaves were collected at different intervals and fed for one day toS. littoralis larvae in the laboratory. 0.0009% a.i. CME 134 residues gave complete kill of 30–50-mg larvae after 5 and 20 days, and 86% kill after 28 days of aging. With 0.003 and 0.009% a.i., complete kill was obtained in 200–250-mg larvae until 50 days after spraying. 相似文献
20.
R.A. Leopold E.P. Marks J.K. Eaton J. Knoper 《Pesticide biochemistry and physiology》1985,24(2):267-283
The frequency and etiology of ecdysial failures occurring during the pupal-adult transformation of the cotton boll weevil, Anthonomus grandis, was studied after treatment with juvenile hormone (JH) and/or diflubenzuron (DFB). Failure at emergence was the result of inability of the adult insects to escape from their pupal exuviae. Teratogenic effects in the form of pupal-adult intermediates or adults with pupal characters were not obtained with JH or DFB treatment after the larval-pupal ecdysis. Combining JH with the DFB treatment yielded a synergistic response that increased the frequency of ecdysial failures about sevenfold when applied in the later pupal stages. The fine structure of the abdominal cuticle of adults experiencing ecdysial failure after treatment with JH as white-eyed pupae exhibited granular deposits within the lamellar region and interference with deposition of the nonlamellate endocuticle. DFB treatment of the earlier pupal stages interfered with deposition of the lamellate cuticle by eliminating or reducing the lamellar structure. It was concluded that the primary interaction of JH with DFB was that of extending or reinitiating DFB sensitivity in the later pharate adult. A secondary interaction may involve inhibition of cuticle hardening as both JH and DFB appear to inhibit the tanning process of adults treated as white-eyed pupae. 相似文献