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1.
Earthworms, Eisenia fetida, were treated by surface exposure to the fungicide benomyl at various stages of posterior segmental regeneration. Teratogenic effects of benomyl were observed when worms were treated 7–11 days after amputation (i.e. during the normal period of segmental replication), but not during days 1–5, 13–17, or 19–23. Teratogenic effects included a reduction in the number of regenerated segments, an increased frequency of segmental groove anomalies, and a variety of monstrosities. The effects of benomyl treatment on the number of regenerated segments and frequency of anomalies were dose-dependent within a narrow concentration range (approximately 0.2–5.0 mg litre?1); at higher concentrations (e.g. 25 mg litre?1) teratogenic effects were less frequent because the onset of segmental delineation was delayed until well after exposure. Non-invasive electrophysiological recordings from treated worms indicated that functional integrity of giant nerve fibre conduction pathways was established in all anomalously regenerated tail segments, except in a two-tailed monstrosity. The evidence supports the hypothesis that these teratogenic effects derive from an antimitotic mode of action of benomyl on segmental regeneration.  相似文献   

2.
The antifeedant effect of five organotin compounds (fentin acetate, fentin hydroxide, fentin chloride, cyhexatin and fenbutatin oxide) and of three other compounds known to possess antifeeding activity (guazatine triacetate, 4′-chloroacetophenone isobutyrylhydrazone and thiram) was investigated by feeding treated alfalfa to larvae of Boarmia selenaria. The three fentins and cyhexatin were highly active at 0.1 g litre?1, the order of activity at this concentration being fentin chloride > fentin hydroxide > fentin acetate ? cyhexatin, whereas the other compounds were practically inactive at either this or a somewhat higher concentration (0.5 g litre?1). Guazatine triacetate had a concentration-independent antifeedant effect at much higher concentrations (5–20 g litre?1).  相似文献   

3.
Seventeen field isolates of Botrytis cinerea were compared by determining their radial growth on synthetic media containing various amounts of 21 antifungal compounds. Twelve of these compounds were fungicides that are recommended for the control of Botrytis infections. There were marked differences between the isolates in their sensitivity to the compounds. Individual isolates displayed high levels of resistance to some of the fungicides, including benomyl, carbendazim, iprodione, thiabendazole, thiophanate-methyl, vinclozolin and zineb. The most potent growth inhibitors were benomyl and carbendazim (ED95 values for most isolates <0.1 μg fungicide ml?1 media), dichlofluanid, iprodione, nystatin, thiabendazole, thiophanatemethyl and vinclozolin (ED95 values for most isolates < 1.0 μg ml?1), and captan, chlorothalonil, dicloran and thiram (ED95 values for most isolates < 6.0 μg ml?1). Zineb was much less potent than the other recommended anti-Botrytis fungicides; it was no more effective than carboxin, dinocap and mancozeb (ED95 values for most isolates > 25 μg ml?1).  相似文献   

4.
Earthworm populations in apple orchard plots sprayed with benomyl and thiophanate-methyl were greatly reduced. Lumbricus terrestris, a surface-feeding species, was not found in the treated plots. Captive worms would not feed on leaf material with spray deposits of benomyl, MBC and thiophanate-methyl at 1.75 μg/cm2, and feeding was significantly reduced when deposits were 0.87 μg/cm2. There was 100 % kill of worms in pots of soil within 14 days following a benomyl drench at the rate of 7.75 kg/ha, and a 60 % kill following a drench at the rate of 1.55 kg/ha. Worms immersed for 1 min in benomyl suspensions of 0.05 or 0.5 % died within 27 and 13 days respectively; those immersed in lower concentrations would not feed for 2 weeks but eventually did so. It is suggested that the lethal effects of benomyl may be due to anti-cholinesterase activity of the carbamate moiety of the molecule.  相似文献   

5.
Uptake of aminotriazole (3-amino-1,2,4-triazole) by bean leaves (Phaseolus vulgaris var. Canadian Wonder) was not greatly influenced by the addition to the spray solution of dimethylformamide (DMF), ethylene glycol and polypropylene glycol 400 (PPG 400) over the concentration range 1.0–50.0 ml litre?1. However, the addition of polyoxyethylene 20 sorbitan monolaurate (polysorbate 20) (0.2–1.0 g litre?1) to spray solutions of the above additives and glycerol (5.0 ml litre?1; except for DMF, 50.0 ml litre?1) substantially increased uptake to 80–100% in all cases at 50 ± 10% relative humidity (r.h.). Similar penetration figures were recorded when a range of polysorbate surfactants (polysorbate 20, 40, 60, 80 and 85; 0.2 g litre?1) were applied to spray solutions containing either dimethyl sulphoxide (DMSO) or glycerol (5.0 ml litre?1). Humidity was found to have a critical effect upon the humectant-surfactant combinations tested, i.e. DMSO + polysorbate 20, ethylene glycol+ polysorbate 20 and PPG + 400-polysorbate 20 (5.0 ml litre?1+0.2 g litre?1). With DMSO + polysorbate 20 the following uptake figures were recorded: < 30% r.h., 3.1 %; 45 ± 10% r.h., 86.8%; 55–65% r.h., 48.2 % and 100% r.h., 0.3%. Similar trends were recorded with all three humectant-surfactant combinations. Further studies revealed that the adverse effect of humidity on DMSO-polysorbate mixtures could be at least overcome partially by regulating the DMSO concentration.  相似文献   

6.
Feeding the last instar larvae of Nephantis serinopa, the coconut black-headed caterpillar, on coconut leaves that had been dipped in diflubenzuron suspensions (0.2-4.0 g litre?1) and dried, inhibited the moulting process and caused morphogenetic deformities of their pupae. The inhibition of moulting ranged from 27.5 to 75% The maximum effect was produced by suspensions of 4.0 g litre?1 when only 5% of the larvae survived to become adults against 97.5% of untreated larvae.  相似文献   

7.
A technique is described for testing isolates of Septoria tritici from winter wheat for resistance to benzimidazole fungicides. Secondary spores from 23 isolates were tested on Czapek Dox V-8 agar amended with benomyl at 1–10 μg ml. Twenty-one isolates were recovered from eight crops in England in 1984 and two (PBI isolates) were obtained in 1973. Thirteen isolates, including both PBI isolates, were sensitive to benomyl at 1 μg ml?1 and nine were resistant at 10 μg ml?1. The remaining isolate had a low proportion (1:3.7 x 104) of resistant spores. The minimum inhibitory concentration for sensitive isolates was 0.2–0.4 μg ml 1 benomyl and for resistant isolates was more than 1000 μg ml 1. Benomyl-resistant isolates were cross-resistant to carbendazim, thiabendazole and thiophanate-methyl, but not to 12 other fungicides with different modes of action. The implications of these findings are discussed.  相似文献   

8.
Warehouse moth (Ephestia elutella) larvae in diapause were exposed at 15°C to methyl bromide at 8 mg litre?1 for 14.5 h and then immediately exposed at a lower concentration. The exposure at 8 mg litre?1 killed 44–69% of the larvae treated. Subsequent concentrations down to 1.1 mg litre?1 obeyed Haber's rule (concentration × time= k, a constant for mortality), but a higher concentration-time product (ct) was required for over 90% kill at 0.8 mg litre?1. Only concentrations down to 1.9 mg litre?1 obey Haber's rule if there is no prior exposure at a higher concentration. Although minimum effective concentrations are lower at 15°C than at 25°C, exposure at a higher concentration depresses the subsequent level to a similar extent at each temperature. The contribution to the efficacy of a treatment, of low concentrations persisting at the end of fumigation, is thus likely to be even greater at moderate to low temperatures than at 25°C. The implications for the development of resistance to methyl bromide are discussed.  相似文献   

9.
Pyriproxyfen, a novel juvenile hormone mimic, is a potent suppressor of embryogenesis and adult formation of the sweetpotato whitefly, Bemisia tabaci (Gennadius), and the greenhouse whitefly, Trialeurodes vaporariorum (Westwood). Dipping of cotton or tomato seedlings infested with 0 to 1-day-old eggs in 0.1 mg litre?1 resulted in over 90% suppression of egg hatch of both B. tabaci and T. vaporariorum. Older eggs were affected to a lesser extent. Exposure of whitefly females to cotton or tomato seedlings treated with pyriproxyfen resulted in oviposition of non-viable eggs. The LC90 values for egg viability of B. tabaci and T. vaporariorum exposed to treated plants were 0.05 and 0.2 mg litre?1, respectively. Treatment of whitefly larvae with 0.04–5 mg litre?1 resulted in normal development until the pupal stage; however, adult emergence was totally suppressed. Second instars of B. tabaci exposed to 5 mg litre?1 pyriproxyfen, excreted honeydew at a level similar to the control level until the fourth instar (pupation), after which a strong reduction was observed. Inhibition of egg-hatch on the lower surface of cotton leaves was observed when their upper surface was treated with 1–25 mg litre?1, indicating a pronounced translaminar effect. These findings indicate that pyriproxyfen is an efficient control agent of both B. tabaci and T. vaporariorum. The compound has been used successfully for controlling whiteflies in Israeli cotton fields since 1991. Adults of B. tabaci collected from a rose greenhouse and from adjacent cotton fields were monitored during 1991–1993 for their susceptibility to pyriproxyfen. A high level of resistance was recorded in whiteflies collected from a greenhouse after three successive applications of pyriproxyfen. Based on LC50 values, the resistance ratio for egg-hatch suppression was 554-fold and, for adult emergence failure, 10-fold. However, a single treatment of pyriproxyfen in cotton fields during the summer season (according to an insecticide resistance management (IRM) strategy) did not alter appreciably the susceptibility of B. tabaci to this compound. In order to prevent development of resistance, an attempt should be made to restrict its use to one treatment per crop season applied during the peak activity of the pest. Pyriproxyfen can be alternated with other novel compounds such as buprofezin and diafenthiuron for controlling whiteflies in cotton, vegetables and ornamentals as part of integrated pest management (IPM) and IRM strategies. In pyriproxyfen- or buprofezin-resistant strains of B. tabaci or T. vaporariorum, no appreciable cross-resistance was observed among pyriproxyfen, buprofezin and diafenthiuron.  相似文献   

10.
The toxicity of cyromazine and a commercial formulation, ‘Vetrazin’®, to Chironomus zealandicus (thummi) Hudson and Deleatidium sp. was investigated. Under acute test conditions, the LC50 values for each species were quite comparable. For C. zealandicus, the value varied according to instar, 100–400 mg litre?1 for second- and third-instar to 1000–10000 mg litre?1 for older fourth-instars. For the one size class of Deleatidium tested (c.10 mm long), the value was 300–400 mg litre?1. High control mortalities of C. zealandicus limit that species' usefulness as an acute bioassay candidate. Under chronic test conditions, cyromazine showed a high toxicity to eggs or early-instar larvae of C. zealandicus. The maximum acceptable toxicant concentration for cyromazine against C. zealandicus was approximately 17.5 μg litre?1. The possibility of water contamination at this level is discussed. Whole-of-life chronic tests with C. zealandicus indicated that the most susceptible stage was in the egg or soon after larval emergence. These results highlight the dangers of using short-term acute toxicity results to formulate environmental exposure limits for modern pesticides that do not have dysfunction of the nervous system as their mode of action.  相似文献   

11.
The effects of DPX-MP062 [methyl 7-chloro-2,3,4a,5-tetrahydro-2-[methoxycarbonyl(4-trifluoromethoxyphenyl)carbamoyl] indeno[1,2-e][1,3,4] oxadiazine-4a-carboxylate] a broad-spectrum insecticide with a novel mode of action, on the Egyptian cotton leafworm, Spodoptera littoralis, were studied in laboratory experiments. Egg hatch was affected by high concentrations (125 mg AI litre-1) of DPX-MP062. Larvae that hatched from treated eggs were significantly affected at concentrations of 12·5 mg AI litre-1 and greater. Larvae were fed castor bean leaves treated with DPX-MP062; 1st-instar larvae were the most susceptible development stage. Pupation and adult formation were determined in assays with 5th-instar larvae. There was strong suppression of adult formation; 65 and 91% at 0·5 and 0·75 mg AI litre-1, respectively. Highly affected larvae died before pupation; slightly affected ones reached pupation 2–4 days later, were smaller than larvae in the untreated control, and were sometimes unable to develop into normal adults. Comparatively high concentrations (50 and 100 mg AI litre-1) of the test compound were necessary to affect adults by ingestion, but no effects from contact application could be determined at a concentration of 100 mg AI litre-1. © 1998 Society of Chemical Industry  相似文献   

12.
Earthworms Eisenia fetida were treated by surface contact exposure for 4 days with the fungicide benomyl. Non-invasive electrophysiological recordings after treatment with sublethal concentrations of 0.2-25 mg benomyl litre?1 of water (=0.003?0.435 μg benomyl cm?2 of filter paper) indicated concentration-dependent decreases in conduction velocity for the medial and lateral giant nerve fibres. Threshold concentration for these effects was approximately two orders of magnitude less than the LC50. The effects on velocity were not accompanied by alterations in refractory period or impairment of locomotory reflexes, but persisted for at least several weeks after treatment. Morphometric analysis of treated animals revealed a disruption of the myelin-like sheath surrounding giant fibres but no change in fibre diameters. It is concluded that benomyl had subtle and sublethal neurotoxic effects on earthworm giant nerve fibres. The data indicate that giant fibre conduction velocity is a particularly sensitive parameter for detecting these effects in intact worms.  相似文献   

13.
Diflubenzuron, 1-(4-chlorophenyl)-3-(2,6-difluorobenzoyl)urea, possesses larvicidal and ovicidal activities. On larvae it acts mainly as a stomach poison, yet it sometimes exhibits important contact activity. Though all instars can be controlled, older instars are generally less susceptible than younger ones. Histological inspections of Leptinotarsa decemlineata larvae revealed that after ending exposure to the compound, distortions in newly deposited cuticular layers decreased gradually. Ovicidal effects resulted from direct contact of diflubenzuron with eggs or from contamination of females by contact or feeding. Electron microscopic observations of embryos of Leptinotarsa decemlineata, contaminated via the female, also showed disturbed cuticule formation, suggesting a similar activity of the compound in larvae and in eggs. Spraying the eggs of Leucoptera scitella shows the compound to be mainly ovidical at a rate of 100 mg litre?1, whilst with lower concentrations (10 and 1 mg litre?1) the young larval instar will be killed. The levels of cross-resistance to diflubenzuron as a larvicide are low and the compound can be used effectively in the field against populations that are highly resistant to conventional insecticides. Laboratory and field results, based on larvicidal and ovicidal activities of diflubenzuron, are discussed in respect of species belonging to the Diptera, Lepidoptera, Coleoptera, Acarina (Phyllocoptruta oleivora) and Hemiptera (Eurydema oleraceum and Psylla piri).  相似文献   

14.
Ephestia elutella larvae in diapause were exposed at 25°C to methyl bromide at 12 mg litre?1 for 3.5 or 7.5 h and then immediately exposed to a lower concentration. The minimum effective concentration (that at which Haber's rule, concentration × time = k, a constant for mortality, still applied) was about 3 mg litre?1 in tests with no previous exposure toa high concentration, but it was about 2.5 mg litre?1 for individuals surviving a 3.5 h exposure to 12 mg litre?1, and was about 1.6 mg litre?1 for those surviving a 7.5 h exposure to 12 mg litre?1. These exposures to 12 mg litre?1, respectively, killed 2–20% and 50–75% of larvae exposed, and hence the smaller the proportion of survivors of exposure to a high concentration, the lower the minimum effective concentration needed against them. Thus the low concentration persisting at the end of a practical fumigation should contribute significantly to the success of the treatment and be much more effective than any similar low concentration present soon after the introduction of gas.  相似文献   

15.
The effectiveness of aqueous solutions of sodium chloride and potassium chloride as wood preservatives was tested against larvae of the house longhorn beetle Hylotrupes bajulus (L.). Immersion of pine (Pinus sylvestris L.) blocks for 24 h provided only a shallow protective layer. In a test series according to EN 46 a concentration of 200 g litre-1 potassium chloride was required for complete larval mortality within 12 weeks; 200 g litre-1 sodium chloride failed to achieve this. With vacuum impregnation in tests according to EN 47 a concentration of 100 g litre-1 sodium chloride achieved complete mortality of larvae within four weeks. Vacuum impregnation of 100 g litre-1 potassium chloride attained complete mortality only after 12 weeks. Ovipositing female beetles did not avoid wooden blocks treated with either salt. © 1997 SCI.  相似文献   

16.
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.  相似文献   

17.
In order to determine the effect of pH and temperature on post-harvest dip solutions of dimethoate (500 mg litre?1), the half-lives and pseudo first-order rate constants were calculated from measurements at pH 4, 6, 8, 10, 11.5, and at two temperatures 25 and 52°C. The half-lives ranged from 206 days to 39.3 min at 25°C, and from 5.6 days to 205s at 52°C; the rate constants ranged from 3.9 × 10?8 s?1 to 2.9 × 10?4 s?1 at 25°C, and from 1.4 × 10?6 s?1 to 3.4 × 10?3 s?1 at 52°C. The results show that the water used in dips should have a pH≤7. The addition of benomyl to the dip solutions at two concentrations (0.5 and 1.0 g litre?1) had no effect on the half-lives and rate constants. The use of hard and salted waters in dips also showed no major effect. A formula was developed that gives the half-life of the dimethoate as a function of the pH and temperature.  相似文献   

18.
The effects of two herbicides, glyphosate (as a 359 g litre?1 SL) and hexazinone (as a 50gkg?1 granule) on soil microbial population, carbon dioxide evolution, and in-vitro growth of five species of ectomycorrhizal fungi were investigated. Glyphosate at 0–54 and 3.23 kg a.i. ha?1 and hexazinone at 1. 2 and 8 kg a.i. ha?1 did not reduce soil microbial population or carbon dioxide evolution in the long term (6 months). However, there was a significant short-term (2 months) effect of glyphosate on both fungal and bacterial counts at the 0.54 kg ha?1 treatment. In in-vitro tests, Cenococcum graniforme. Hebeloma crustuliniforme and Laccaria laccata were more susceptible to both herbicides than was Suillus tomentosus. which was, in turn, more susceptible than Paxillus involutus. The growth of all five ectomycorrhizal fungi was significantly reduced when subjected to concentrations above 50 μl formulation litre?1 (glyphosate) or 50 μg formulation litre?1 (hexazinone).  相似文献   

19.
The toxicities of five systemic fungicides [benomyl, carbendazim, methyl 4-(2- aminophenyl)-3-thioallophanate (NF48), thiabendazole and thiophanate-methyl] and of two non-systemic fungicides (guazatine and phenylmercury acetate) against Fusarium culmorum were compared on agar plates; their performance as seed treatments was measured by inoculating the shoot bases of wheat seedlings with F. culmorum in pot experiments. The two most effective compounds, benomyl and thiabendazole, and the less effective thiophanate-methyl, were evaluated in further seed treatment experiments in which leaf sheaths and roots of slightly older plants were infected. The three fungicides protected the first leaf sheath for more than 5 weeks, but thiophanate-methyl was least effective. Against root disease, they were effective when infection was mild, but only thiabendazole significantly controlled severe infection. Bioautography confirmed that fungicide levels in shoots were greater after benomyl and thiabendazole, than after carbendazim and thiophanate-methyl treatments, and that concentrations of fungicide after benomyl, carbendazim and thiophanate-methyl treatments generally declined between 5-13 weeks after treatment. Thiabendazole produced a second fungitoxic component detectable in plants after 34 days.  相似文献   

20.
The performance of low concentrations of methyl bromide against diapausing larvae of Ephestia elutella at 15 and 25°C was assessed in extended exposure periods. At concentrations of 1.9 mg litre?1 and below, test batches required higher concentration-time (ct) products for 100% kill at 25°C than at 15°C. The minimum concentration at which the concentration: time relationship still applied was between 1.3 and 1.9 mg litre?1 at 15°C, whereas at 25°C it was between 2.7 and 4.0 mg litre?1. For many individuals within each population sample, however, lower concentrations at moderate dosage levels remained lethal. At 25°C, a ct product of about 90 mg litre?1 h gave between 53 and 77% kill at 6.1, 4.0, 2.7 and 1.9 mg litre?1. The trends observed suggest that the most tolerant members of the population have an enhanced ability to detoxify methyl bromide at the higher temperature. The implications of the results for the build-up of resistance and for practical control measures are discussed.  相似文献   

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