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1.
Four groups of Indian buffaloes were fed daily with 25 mg of p,p′-DDT p,p′-TDE p,p′-DDE or o,p′-DDT for 100 days. Milk was analysed for organochlorine residues during this period and also for 100 days after pesticide administration had been discontinued. For the period showing ‘plateau level’ residues, 17.2% of p,p′-DDE, 17% of p,p′-TDE, 14% of p,p′-DDT as p,p′-DDT (3.5%); p,p′-TDE (10.5%); 3.2% of p,p′-DDT as o,p′-DDT (1.3%) and o,p'-TDE (1.9%) of their administered amounts were excreted in the milk. Since these compounds were excreted at different rates, the residue levels in the milk expected from a given feed would depend on their concentration and proportional distribution in the feed. The maximum tolerable content of DDT analogues in feed was derived to be 0.1 mg kg?1 (dry weight basis) by using the maximum accumulation coefficient and incorporation of the necessary safety margin. It is concluded that Indian buffaloes fed with rations contaminated with a total of DDT analogues below this limit will yield milk of acceptable quality. Following the termination of feeding with contaminated rations, the elimination of p,p′-DDE in the milk took the longest time and that of o,p′-DDT the shortest. These results suggest that the time required for the initial high residue concentration to decline to less than the legal limit would be determined by the relative amounts of DDE, TDE and DDT in the milk, after elimination of the potent source of contamination.  相似文献   

2.
DDT residues in or on the roots and leaves of the herbage and the roots, bark, leaves and fruit of the trees are given for an apple orchard sprayed annually (1953–1969). The distribution of DDT in both the grass and the grass roots was in circular areas of residues, with maximum values at each trunk and decreasing radially to each alley. Of the spray applied at the green cluster stage 80% was deposited on the grass sward and very little, if any, directly on the soil surface. The pp′-DDT content of the grass fell rapidly with successive mowings (from which the cuttings remained in situ) from 400 μg/g at spraying to 2 μg/g after nine months. 33 g/ha pp′-DDT was found in the herbage roots (0.87% of the total residues in the soil). The residues in the bark (87.5 g/ha) were much lower than expected after 13 years spray application. There were increased amounts of pp′-DDE, pp′-TDE and pp′-TDEE relative to pp′-DDT, indicating some breakdown on the bark, but the chief losses were attributed to volatilisation and to removal by wind and rain. The residue content of root bark varied from 3 μg/g near the emerging trunk to 0.05 μg/g at a depth of 90 cm. The pp′-DDT content of leaves at leaf fall rose from <1 ng/g after a single spring spray to 8.33 μg/g following an additional spray in late June. There was a large loss of DDT from the canopy between the June spray and leaf fall (440–480 g/ha down to 25 g/ha), attributed to volatilisation. The amount of pp′-DDT on the fruit, after a single spray, was 3 ng/g fresh weight (80.9 mg/ha out of a total of 1.0–1.5 kg/ha used).  相似文献   

3.
Lactating cows fed 0.05 part/million aldrin, 0.2 part/million γ-BHC and 2.0 parts/million pp'-DDT in their concentrate ration gave detectable residues of dieldrin, γ-BHC, pp'-DDE, pp'-TDE and pp'-DDT in the milk and also aldrin in the butter and cheese. The levels found after 28 days of feeding were not significantly greater than those after 14 days. Subsequent increase of the pesticide content of the feed increased the residue content of the milk, butter and cheese. Only a small percentage of pesticide residue was found in the buttermilk, separated milk and the whey.  相似文献   

4.
Twenty-eight specimens representing five types of fish and five types of birds from the Gezira Research Farm, Wad Medani, Sudan, were analysed for residues of organochlorine insecticides. All fish muscle samples were found to contain pp′-DDE, pp′-TDE and pp′-DDT in total concentrations ranging from 0.27 to 16.0 mg/kg. In addition to DDT-type residues, dieldrin (HEOD) was also found in the majority of bird samples. Concentrations in bird breast muscle ranged from 0.07 to 5.5 mg/kg. When bird liver samples were examined they were found to contain higher residues than the breast muscle in nearly all cases.  相似文献   

5.
Twelve strains of Aedes aegypti have been compared for resistance to pp′-DDT, uptake of pp′-DDT, and dehydrochlorination of pp′-DDT to pp′-DDE in vivo and in vitro both at the larval and adult stages. Resistant larvae were shown to contain significantly more pp′-DDE than susceptible larvae after a standard exposure to pp′-DDT but also substantially more pp′-DDT in an unmetabolised state. There was a small increase in the percentage dehydrochlorinated in vivo in the resistant strains compared with the susceptible strains, but this was not correlated with the level of resistance nor with dehydrochlorination in vitro. However, dehydrochlorination in vitro was correlated with resistance. Adult resistance was correlated positively with dehydrochlorination, both in vivo and in vitro, but the resistant adults did not contain increased levels of unmetabolised DDT. By comparing resistance levels at the two stages, it was found that there were two kinds of resistant strain: four strains of Asian origin and one from West Africa were highly resistant as larvae but showed almost no resistance as adults; five strains from Central and South America were highly resistant at both stages. The different mechanisms of resistance in adults and larvae are discussed in relation to genetic studies.  相似文献   

6.
Soils from an orchard sprayed annually (1953-1969) with technical DDT (77% pp′DDT and 22 % pp′DDT) were analysed for residues from 1964 until 1969. The amount of DDT found after 17 years was 21 %pp′DDTout of 27.1 kg/ha applied, and 7 % of pp′DDT out of 7.6 kg/ha. The vertical distribution of residues (pp′DDT, pp′DDE, pp′TDE and pp′DDT) showed a linear relationship between log amount and depth, with approximately 80% in the top 10 cm of soil. At depths from 50 to 210 cm, residue values were too small to be determined (i.e. < 1 ng/g dry wt). The surface distribution in the orchard showed a systematic pattern of circular areas of residues, with maximum values centred at each trunk (7.5 μg/g) and decreasing rapidly to each alley (1.9 ug/g). The levels of pp′DDT had reached a steady state (3-4 kg/ha) and the half-life time was calculated as 3.0 j′ears. pp′DDE (1.8 kg/ha) was the main metabolite of pp′DDT. Small amounts of pp′TDE were also found, pp′DDT was less persistent than pp′DDT, with a half-life time of 1.5 years.  相似文献   

7.
DDT at 1.12 and 2.24 kg/ha a.i. and Torbidan at 5 and 10 litre formulation/ha (1 and 2 kg DDT/ha) were sprayed five times on cotton over a period of 15 weeks. Seeds from the first pick of the crop were found to contain as residues pp′-DDT and pp′-DDE [1,1-dichloro-2,2-di- (4-chlorophenyl)ethylene]. The highest residue level (0.783 parts/106) was found in seeds from Torbidan 10 litre/ha treatment.  相似文献   

8.
Amounts of DDT and its breakdown products were determined in soil in an apple orchard in Herefordshire. Samples were taken for a number of years (1972–79) after use of the insecticide in the orchard had ceased in 1969. The results were compared with those obtained in an investigation of the same orchard in 1968. From 1968 to 1979, soil residues of pp′-DDT, p′--DDT and pp′--TDE decreased gradually whereas those of pp′--DDE increased, and there were linear relationships between log (concentration) and time. The calculated time for 50% decrease in concentration (Dt50) was 11.7 years for pp′--DDT, 3.3 years for pp′--TDE and 7.1 years for op′--DDT; the time for doubling the concentration for pp′--DDE was 9.1 years. Regression analysis on the two major components (pp′--DDT+pp′--DDE) indicated that the total amount (2.7 mg kg?1) was not decreasing with time. It was concluded that during a post-spray era, the breakdown of pp′--DDT to pp′--DDE was a significant feature of the persistence of DDT, and that, in contrast to the findings of other workers who sampled when DDT was being used, there were no losses by volatilisation. There was an exponential decrease in the amount of DDT residues with increasing soil depth and approximately 90% was found in the top 10 cm of the undisturbed soil profile.  相似文献   

9.
Three groups of buffaloes were fed with 20, 100 and 400 mg of p,p′-DDT in their daily rations. The DDT residues in the milk fat of the treated animals showed an initial rapid rise but soon attained a dose-dependent equilibrium. The transfer coefficient of DDT residues in milk at ‘plateau’ levels showed an average value of about 12%. Half-life values for the rate of decline of DDT residues during the post-dosing period were computed according to a two-open-compartment model. Dermal application of p,p′-DDT to buffaloes also resulted in excretion of a significant amount of its residues in milk. TDE was the predominant compound present in milk when buffaloes had ingested p,p′-DDT, whilst p,p′-DDT itself was present in greater quantity than its metabolites when animals were treated dermally.  相似文献   

10.
为研究不同苹果种植模式下土壤养分变化情况,在陕西省千阳县2种不同种植模式(矮化和乔化种植)的苹果园区采集土样,通过测定0~100 cm土层土壤中的全氮、全磷和有效磷含量,分析和比较其土壤氮磷养分含量差异及剖面分布特征。结果表明：在0~100 cm深度的土层中,除全磷外,矮化苹果园土壤各养分含量显著低于乔化苹果园(P<0.05),矮化富士、嘎啦苹果园和乔化富士苹果园全氮含量分别为0.60、0.63、0.76 g·kg-1,全磷含量分别为0.58、0.56、0.63 g·kg-1,有效磷含量分别为6.98、3.48、51.00 mg·kg-1;矮化苹果园全氮、全磷以及有效磷含量主要在0~10 cm的表层土壤中聚集显著(P<0.05);土壤养分含量与土层深度相关性显著(P<0.05),矮化苹果园和乔化苹果园土壤养分含量与土层深度的变化过程分别符合幂函数和对数函数的变化趋势。  相似文献   

11.
Botrytis cinerea isolates from pear blossoms (Pyrus communis) in South Africa were collected from four orchards in two production areas in the Western Cape. The cryptic species status based on vegetative‐incompatibility alleles of the Bc‐hch gene indicated that all the isolates belonged to B. cinerea. A microsatellite analysis of B. cinerea populations was performed to assess the genetic population structure. Total gene diversity (H) was high, with a mean of 0.69 across all populations. Some genotype flow was evident between orchards as indicated by the spread of microsatellite multilocus genotypes, in agreement with the moderate, but significant population differentiation among orchards (mean φPT = 0.118, P = 0.001). Index of association analyses (IA and r?d) suggest that the populations reproduce mostly asexually, even though mating type distribution did not differ significantly from a 1:1 ratio, suggesting frequency‐dependent selection. Isolates resistant to benomyl were evident in one orchard only. This orchard was also significantly differentiated from all other populations, suggesting infrequent localized selection for benomyl resistance. Overall, the findings of this study highlight the dangers of a mixed reproduction system, and stress the importance of regularly monitoring fungicide resistance levels towards developing more efficient management practices.  相似文献   

12.
Selection with pp'-DDT was applied to fourth-stage larvae of Aedes aegypti along four lines, starting with larvae of the F2 generation from crosses between a susceptible strain and each of four resistant strains (two of Trinidad origin and two of Bangkok origin). Larval resistance increased substantially along each line but there was little or no change in the percentage breakdown of DDT to 1,1-dichloro-2,2-bis(4-chloro-phenyl)ethylene (pp'-DDE) in vivo and in no line were these two variables significantly correlated. Percentage breakdown was generally higher at 10 mg than at 50 mg litre?1. DDT uptake (defined as content of DDT+pp'-DDE) was generally higher after exposure to 50 mg than to 10 mg litre?1. It increased significantly with selection in the TE×NS line; it remained unchanged in the T8 × NS line; and in the other two lines (BSJ × NS and B51 × NS), it increased initially but dropped as selection progressed, the reduction being highly significant in the second of these lines. The amount of internal residual (unmetabolised) DDT tolerated by larvae of the TE × NS line also increased significantly with resistance. The levels in the other lines followed the pattern of uptake, remaining steady in T8 × NS despite the increase in survival, rising at first and then declining in the two Bangkok lines. Thus selection produced a higher tolerance to internal unmetabolised DDT in the two Trinidad lines but led ultimately to a lower content of DDT+pp'-DDE in the two Bangkok lines. The reasons for this behaviour are discussed.  相似文献   

13.
Larvae of eight strains of Aedes aegypti were exposed to DDT and compared for resistance, DDT uptake, in-vivo breakdown of DDT and residual unmetabolised DDT. Resistance varied widely between strains, three being fully susceptible, two almost immune and three of intermediate resistance. Breakdown of DDT by dehydrochlorination to 1,1-dichloro-2,2-bis(4-chlorophenyl)ethylene (pp'-DDE) occurred in all strains and was greater in the five resistant types, but there was no significant correlation between the extent of breakdown in the resistant strains and the level of resistance. Moreover the overall difference between susceptible and resistant strains disappeared when they were compared at a low, almost sublethal, concentration of DDT. Larvae of resistant strains carried a greater absolute quantity of unmetabolised DDT in the body and were able to tolerate levels of DDT that were lethal to susceptible larvae. However the two most resistant strains (T8 and B51) contained significantly less DDT plus pp'-DDE than strains of intermediate resistance (T30 and BSJ) from which they had been derived. Addition of the synergist chlorfenethol to DDT increased its knockdown effect on all resistant strains, suggesting that dehydrochlorination was a factor in resistance. Three strains, two DDT-resistant and one DDT-susceptible, were tested with 1,1-bis(4-ethoxyphenyl)-2,2-dimethylpropane (I), an insecticide that cannot be dehydrochlorinated. All the strains were relatively tolerant to it although the DDT-susceptible strains were less tolerant. Addition of the synergist sesamex decreased the level of tolerance to I in all strains which suggested that microsomal oxidation made some contribution to it. It is concluded that three factors contribute to larval DDT resistance in A. aegypti; (a) increased metabolism to pp'-DDE; (b) increased tolerance to unmetabolised internal DDT; and (c) reduced content of DDT+pp'-DDE (only in the most resistant strains and due either to reduced absorption or increased excretion). These factors are discussed in relation to known larval resistance genes RDDT1 and y.  相似文献   

14.
利用叶绿素荧光仪测定了26份青贮玉米自交系和105个组合的叶绿素含量及荧光动力学参数,对其生理性状关键耐旱指标进行主成分及相关分析,并进行配合力及遗传参数分析。青贮玉米Fv/Fm的影响因素大 小依次为：叶片Fv>叶片Fm>叶片Fo>叶片Area>叶片SPAD>苞叶Fv/Fm>苞叶SPAD。筛选出了5个关键指 标(叶片Fm、叶片Fv、叶片Area、叶片Fv/Fm、叶片SPAD)及一般配合力(GCA)较高的9份自交系和特殊配合力(SCA)较高的19个组合。在F1吐丝期,叶片Fo、叶片Area主要受基因加性效应支配;叶片Fm、叶片Fv的加性与 非加性效应相当;叶片Fv/Fm、叶片SPAD主要受基因非加性效应支配。狭义遗传力(h2N,)大小依次为：叶片SPAD>叶片Area>叶片Fo>叶片Fv>叶片Fm>叶片Fv/Fm。通过对叶片Fv的早代正向直接选择、叶片Fo的早代 负向直接选择,以及对叶片Fv/Fm的杂种优势利用,可提高旱区青贮玉米单位面积生物产量。叶绿素含量及荧光 动力学参数可用于青贮玉米的耐旱性筛选。  相似文献   

15.
以25个不同青贮玉米品种为试验材料，在宁夏银川北部盐碱地，通过测定不同品种大喇叭口期和成熟期的表型性状和光合气体交换参数进行耐盐碱性鉴定，并利用主成分分析和模糊隶属函数法对不同青贮玉米的耐盐碱强弱进行综合评价。结果表明：各青贮玉米品种处于不同生育期时对盐碱的敏感程度不同（发育阶段性），同一时期不同品种之间耐盐碱性也存在着差异（品种特异性）。根据综合评价值（D值）大小，将耐盐碱性分为三级：D值大于0.6为强耐盐碱性材料；D值在0.2~0.6之间为中耐盐碱性材料；D值低于0.2为对盐碱敏感的材料。其中，在大喇叭口期时具有强耐盐碱性的材料有：科多8号、桂青贮1号和133-2/1528，D值分别为0.770、0.705和0.614；在成熟期时具有强耐盐碱性的材料有：H14/A18和桂青贮1号，D值分别为0.761和0.728；而表现为敏盐性的材料为H14/1528，D值在大喇叭口期和成熟期时分别为0.140和0.155；其余品种均属于中度耐盐碱材料，D值处于0.2~0.6之间。  相似文献   

16.
Toxins produced by Penicillium species are reported in maize silage and have been associated with health problems in cattle. Our objectives were to evaluate the prevalence and dynamics of patulin (PAT), mycophenolic acid (MPA), cyclopiazonic acid (CPA), and roquefortine C (ROC) in fresh and ensiled maize. To achieve these objectives we developed a high-performance liquid chromatography method coupled with mass spectrometry to detect all four toxins simultaneously in silage. In addition we collected weather data, information on agronomic practices, and silage fermentation characteristics for each study site. Silage was collected at harvest and after ensiling in 2001 and 2002 from 30 Pennsylvania dairies. The average concentration of toxins (range in parentheses) was: PAT 0.08 microg/g (0.01 to 1.21), MPA 0.16 microg/g (0.02 to 1.30), CPA 0.12 microg/g (0.02 to 1.43), and ROC 0.38 microg/g (0.01 to 5.71). ROC was the most frequently detected toxin (60%), followed by MPA (42%), CPA (37%), and PAT (23%). Of 120 samples tested, 15% contained no detectible levels of toxin, 25% were contaminated with one toxin, 32% with two, 18% with three, and 10% with all four toxins. All four mycotoxins were found in freshly harvested material, contradicting the belief that Penicillium toxin formation occurs exclusively during storage. We observed that weather conditions during specific growth stages of the crop affected the final concentration of toxins in freshly harvested maize. In ensiled material, PAT levels were affected by concentrations of propionic and isobutyric acids. Based on our data, Penicillium mycotoxins can form while the crop is in the field and after ensiling, suggesting that preventative measures should begin prior to ensiling.  相似文献   

17.
In order to understand the degradation of different residual pesticides of white clover silage and their influence on silage quality, three commonly used orchard pesticides with different concentrations were added to the white clover and fermented for 90 days. The results showed that the degradation rate of cypermethrin and its toxic degradation product 3-phenoxybenzoic acid (3-PBA) was the highest after silage, at different concentrations, both were 100%. The degradation rate of Tebuconazole and chloropyridine was 72.47–80.27% and 47.76–64.82%, of which 3,5,6-trichloro-2-pyridinol (TCP) content, poisonous toxic degradation product, increased 0.0525–0.253 mg·kg−1. The residues of beta-cypermethrin and tebuconazole had reached safety standards after silage. As compared with the control, the contents of lactic acid, acetic acid, and propionic acid increased in the treated samples. The higher concentrations of three pesticides all significantly reduced the lactic acid content of silage (p<0.05). Pesticides had different effects on the nutritional components of white clover silage. Conclusively, silage is a potential way to expand the utilization of covering plants in orchards.  相似文献   

18.
Three nurseries produced apple rootstocks (M9) and budwood (cv. Royal Gala), which they exchanged at the end of the first year. Each nursery then budded its own budwood onto the rootstocks it had produced and that from the other two nurseries. Budded trees were grown on for a further year before being planted at HRI, East Malling in southern England; NIHPBS, Loughgall in Northern Ireland; and ADAS, Rosemaund in the West Midlands of England. Canker development was monitored twice a year. The position of the infected trees within the orchard was recorded, as was the position of the canker on each tree (main-stem or peripheral). Nectria galligena was isolated from representative cankers and analysed using molecular techniques. At the sites in Northern Ireland and HRI there was a strong positional effect, especially of peripheral cankers, indicating that most of the inoculum was external and had been spread from neighbouring orchards. There was little or no positional effect on main-stem cankers at any of the three sites. The proportions of different isolates taken from peripheral cankers was different in Northern Ireland from that in England, suggesting different populations associated with the geographic areas. In contrast, the populations of N. galligena obtained from main-stem cankers were very similar in England and Northern Ireland. It was concluded that a small proportion of trees developing canker were infected during propagation, with no symptom development until after planting. In a second trial it was demonstrated that trees infected during the propagation phase, and particularly at budding and heading back, could develop canker up to 3 years later. While it is clear that some canker developing in the orchard can be associated with the nursery of production, in climatic conditions conducive to the formation and dissemination of conidia, inoculum from surrounding infected orchards is the primary source of the pathogen. Aerial spread is therefore an essential element of the epidemiology of N. galligena, and its control is a crucial part of any canker-control programme.  相似文献   

19.
Effects of irrigation on the dynamics of soil populations of Phytophthora citrophthora have been studied in three citrus orchards in East Sicily (Italy). Significant increases of inoculum levels were detected 24 h after irrigation. In one orchard throughout summer, population of P. citrophthora beneath the tree canopy was more than 15 propagules g-1 soil, a value which is considered a threshold level for root rot infections.  相似文献   

20.
The use of the fungicides benomyl and thiophanate-methyl on experimental orchard plots for 3 years and of benomyl on a commercial orchard for 1 year resulted in a drastic reduction of earthworm populations. The species of earthworms affected were Lumbricus terrestris, L. castaneus, L. festivus, L. rubellus, Allolobophora caliginosa, A. chlorotica, A., longa, A. rosea, A. tuberculata and Octolasium cyaneum. L. terrestris and A. chlorotica were more affected than the other species, both being virtually eliminated after 2 years' spraying. The depleted populations of species other than L. terrestris and A. chlorotica recovered to normal levels after a 2-year rest period following a single year's treatment with benomyl (1.40 kg/ha). The role of the surface-feeding L. terrestris is discussed in relation to the spray fall-out on the sward and to grass management.  相似文献   

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