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1.

Toxicities of indoxacarb on eggs and 5-day-old larvae of diamondback moth, Plutella xylostella L., on cabbage and those of field-aged leaf residues on 5-day-old larvae were determined in the laboratory. The persistence and efficacies of indoxacarb and two other newer insecticides (spinosad and emamectin benzoate) to P. xylostella were tested under field conditions. Results from laboratory bioassays indicate that indoxacarb was highly toxic to P. xylostella larvae through food ingestion, with LC50 and LC90 values of 24.1 and 90.1 mg AI l - 1, respectively. However, indoxacarb had no significant effects on eggs and larvae through direct contact compared with water control. The toxicity of field-aged leaf residues of indoxacarb (0-, 3-, 5-, 7-, 10-, 14-, 17- and 21-day-old residues) declined slowly and gradually under the field conditions in South Texas. Almost all larvae died on day 5 after feeding on the leaves with 0 - 14-day residue, and the mortalities were as high as 94 and 78% for the 14- and 17-day-old leaf residues. With one application, indoxacarb suppressed P. xylostella larvae below the economic threshold for 14 - 21 days. Two field trials showed that indoxacarb at 0.05 - 0.07 kg AI ha - 1 was effective against P. xylostella, providing marketable cabbage with three applications per season. In addition, indoxacarb was as effective as spinosad, and significantly more effective than emamectin benzoate.  相似文献   

2.

The objectives of this study were to investigate Piliostigma reticulatum (shrub) and Cordyla pinnata (tree) residues for chemical composition, and C, N, and P mineralizationin Senegalese soils. Soil samples (Sols ferrugineux tropicaux) were collected from a native agroforestry system beneath and outside a C. pinnata canopy. Soils were incubated for 11 weeks with P. reticulatum (leaves), C. pinnata (stem, leaves or stem + leaves), peanut (Arachis hypogea), or pearl millet (Pennisetum glaucum) residues. Nitrogen and P mineralization for the soil-plant mixtures was determined by periodic leaching with a 0.01 M CaCl 2 solution. An additional separate incubation was conducted to investigate C mineralization. The results showed that only peanut residues caused net N mineralization, while N immobilization occurred in the remaining treatments in both the soils derived from beneath or outside the canopy. This indicates that, at least in the short-term, these agroforestry residues would not likely be a source of N for crops. Net P mineralization varied among plant residues and soils sites but P. reticulatum amended soils increased soluble PO in both soils. This suggested that it could be useful for improving P avail4 ability. Peanut residues had the highest CO evolution in both soils suggesting a 2 probable relationship between C and N mineralization.  相似文献   

3.
The movement and persistence of imazaquin, oxyfluorfen, flurochloridone and terbacil residues were studied using a bioassay based on the shoot growth of Raphanus sativus L. var, radicula DC (radish) in a sandy loam soil under field conditions in 1992 and 1993. Imazaquin (0.3 kg a.i. ha-1) was more mobile in the soil than the other three compounds. In 1992, under heavy rainfall conditions, the herbicide was distributed down to 60 cm in amounts of about 0.01 mg kg-1. Conversely, in the dry year of 1993, the maximum depth of penetration was 20 cm and persistence in the surface soil layer (0-5 cm) was greater. After the first month in 1992, residues of terbacil were distributed in the 0-20 cm layer, and after 2, 3 and 5 months the herbicide had penetrated to a depth of 40 cm. In 1993, terbacil residues were distributed in the 0-10 cm layer only. In both years, residues of flurochloridone (1.0 kg a.i. ha-1) were located mainly in the 0-5 cm layer, but there was some penetration to 10 cm. Oxy-fluorfen (1.2 kg a.i, ha-1) showed least mobility in the soil profile. It was retained in the 0-5 cm layer throughout the experimental period in both. years.  相似文献   

4.
Summary. Electron-capture gas chromatography was used to detect dicamba residues in three prairie soils, and the breakdown under different moisture conditions was studied. At rates equivalent to 1·1 kg/ha degradation was rapid in all soils at 25°C and at moisture levels in excess of the wilting point, with over 50% of the applied dicamba being dissipated in 2 weeks. Negligible breakdown occurred in the sterile soils, over a 4–week period, indicating that microbial decomposition could be an important factor contributing to dicamba degradation.
The persistence of dicamba was investigated under field conditions at three locations using small plots. Applications equivalent to 1·1 kg/ha were made in October 1971 for analysis in May 1972, and in May 1972 for analysis in August 1972. At both sampling dates no dicamha residues were detected in any of the treatments at the 0–5, 5–10 or 10–15 cm soil levels.
Degradation du dicamba dans les sots de prairies  相似文献   

5.
Residual effects of chlorotriazine herbicides in soil at three Rumanian sites. I. Prediction of the persistence of simazine and atrazine Persistence of simazine and atrazine in the top 10 cm soil was measured at three sites in Rumania with variations in climate and soil conditions. Both herbicides were applied at 1 and 3 kg ai ha?1 to uncropped plots and to plots cropped with maize (Zea mays L.). Rates of residue decline were independent of application rate and crop cover but varied between sites. The time for 50% loss of atrazine varied from 36 to 68 days and that of simazine from 48 to 70 days. Laboratory studies were made with atrazine to characterize degradation rates under standard conditions and to measure adsorption and leaching behaviour in the different soils. Weather records for the periods of the field experiments were used in conjunction with appropriate constants derived from the laboratory results, or from data in the literature, in a computer program to simulate persistence in the field. Results from the model were in reasonable agreement with the observed soil residues although there was a tendency to overestimate rates of loss on some occasions. The results suggest that the model of persistence was sufficiently accurate for practical purposes, and that its use could preclude the need for extensive analytical measurements of residues.  相似文献   

6.
Persistence as affected by rate of application and moisture regimes and leaching of beta-cyfluthrin was studied in alluvial soil under laboratory conditions. The effects of rate of application and moisture regimes on persistence were studied by incubating fortified soil at 0.1, 1.0 and 10.0 mg kg(-1) under air-dry, field capacity and submerged moisture regimes. The initial deposits of 0.09, 1.11 and 10.1 mg kg(-1) dissipated with time and 78.4-100% loss was recorded at 90 days. The half-life values varied from 7.8 to 41.8 days. The rate of dissipation decreased as the rate of application increased under field capacity and submerged conditions. However, under air-dry conditions, the effect was less pronounced, and half-life values showed a reverse trend. Persistence of beta-cyfluthrin under different moisture regimes followed the trend: air-dry > field capacity > submerged. The trend could be attributed to the effect of moisture on number and type of microbes. Leaching was studied in a packed soil column under saturated flow conditions. beta-Cyfluthrin was found to be highly immobile in alluvial soil. No residues were detected in any leachate fraction under the experimental conditions. In column soil, residues were detected at 0-10 cm depth and the major amount (>99%) was recovered from 0-5 cm depth. Although beta-cyfluthrin showed moderate persistence in alluvial soil, the possibility of its leaching to ground water is negligible as a result of its immobility.  相似文献   

7.
The susceptibility of 11 species of terrestrial gastropods to the infection with Varestrongylus sagittatus has been studied under laboratory conditions. The gastropods Zenobiella umbrosa, Monachoides incarnata. Deroceras reticulatum, Cepaea nemoralis, Cepaea hortensis, Arion rufus, and Trichia hispida are new potential intermediate hosts of V. sagittatus. The highest susceptibility and the shortest period of development of the V. sagittatus larvae occurred in Succinea putris. The development of V. sagittatus larvae inside S. putris did not proceed at the temperature of 5 degrees C, but at 10 degrees C, 15 degrees C, 20 degrees C, and 25 degrees C, the period of development became shorter with increasing temperature of environment. The length of V. sagittatus larvae reached the following values: 0.302-0.327 mm in first-stage larvae, 0.385-0.550 mm in second-stage larvae, and 0.484-0.590 mm in third-stage larvae. At the temperature of 25 degrees C, the larvae of V. sagittatus did not reach the third stage if the course of the experiment only in Helicigona arbustorum.  相似文献   

8.
In growth room studies, total recoverable 2, 4-D residues on or in turfgrass (Kentucky bluegrass, Poa pratensis) declined from 92% of that originally applied, to less than 66% by day 15. Although a high proportion of the applied chemical remained associated with the leaf surface under growth room conditions, only 10% was dislodged by vigorous mechanical wiping of the leaf surfaces with moistened cheese-cloth. In field studies with 1 kg acid equivalent (a.e.) ha−1, less than 5% of the chemical originally applied could be dislodged with a cheese-cloth wipe at day 0. Disappearance of dislodgeable residues was very rapid. Less than 0.01% of the applied chemical was dislodgeable after 1 day in turf that received 18 mm of rainfall 1 h after spraying. Residues in turfgrass that received no rainfall required 7 days to dissipate to the same level. In a study in which the clippings were not removed, the disappearance of dislodgeable residues, when the turf was mowed at 3, 7, and 11 days after application, was nearly as rapid as in unmowed turf. In turf treated with 2.24 kg a.e. ha−1 of liquid or granular formulations, dislodgeable residues were less than 1% by days 5 and 3, respectively.  相似文献   

9.
Summary Germination of Phalaris minor declined with the increase in duration of imbibition in water from 30 min to 72 h at temperatures above 22 °C . Germination was reduced down to 10 cm and 2 cm soil depth by wheat straw burning in puddled and non-puddled soil, respectively, with maximum reduction near the soil surface. The dormancy of P . minor seed was not more than 60 days under field conditions. In puddled soil, 38–60% of the viable seeds of P. minor remained concentrated in the upper 5-cm layer. Germination decreased with an increase in soil depth. In total, 15% of seeds stored in the laboratory emerged from 10-cm depth, whereas seeds did not germinate below 4.2-cm depth under field conditions. Depth of emergence of P . minor was shallower in zero tillage compared with the conventional method of wheat sowing. The seeds retrieved from rice soils kept under continuous submergence for 60 days exhibited 26% and 57% loss of germination over semi-submergence and semi-wet conditions respectively. There was 100% loss of germination in 10-month-old seeds retrieved from the soil under rice-growing conditions. Plant density of P. minor was lower in zero tillage than with the conventional method of wheat sowing. Cross-ploughing in the upper 2–5 cm of soil (shallow tillage) and drill-sowing of wheat 1 week after shallow tillage reduced germination of P. minor by 44% and 37% and increased grain yield by 21% and 47% over zero-tillage and conventional methods respectively.  相似文献   

10.
Apples treated with tetrachlorvinphos (Gardona, trans-isomer of dimethyl 1-(2′,4′,5′-trichloropheny1)-2-chlorovinyl phosphate) insecticide under field conditions in several countries in 1965, 1966 and 1967 have been analysed at intervals after treatment for residues of tetrachlorvinphos itself, its cis-isomer and seven potential breakdown products. Residues of up to 10 ppm of tetrachlorvinphos were detected immediately after the last of three applications of tetrachlorvinphos (diluted to 0.16% active material). The initial half-life of the tetrachlorvinphos was on average about 0.5 weeks under U.K. conditions and only 10% of the tetrachlorvinphos remained unchanged at 2 weeks after application. The overall chemical persistence of the wettable powder formulation was not significantly different from that of the emulsifiable concentrate formulation. Within 8 weeks of the application the residues were mainly of tetrachlorvinphos itself, its cis-isomer and the alcohol 1-(2′,4′-5′-trichlorophenyl)ethan-l-ol, in free and sugar-conjugated forms. The residues of the conjugates of this alcohol (up to 0.92 ppm) were generally present in higher concentration at 6-8 weeks after the application than were the residues of the other components. Whilst residues of other breakdown products were detected on the apples their individual residues were below 0.05 ppm and generally below 0.01 ppm at 6 weeks or more after the last of several applications of tetrachlorvinphos.  相似文献   

11.
典型荒漠植物凋落物分解及养分动态研究   总被引：1，自引：0，他引：1  
采用分解网袋法,对古尔班通古特沙漠南缘粗柄独尾草(Eremurus inderiensis)、尖喙牻牛儿苗(Erodium oxyrrhynchum)和沙漠绢蒿(Seriphidium santolinum)3种荒漠植物叶、茎和根的分解、养分释放特性进行了研究。结果表明：叶片、茎、根系的质量损失过程均符合指数衰减模型。经过364 d的分解,粗柄独尾草叶、粗柄独尾草根、尖喙牻牛儿苗叶、尖喙牻牛儿苗茎、尖喙牻牛儿苗根、沙漠绢蒿茎、沙漠绢蒿根的失重率分别为41.96%、81.94%、42.18%、29.32%、47.02%、20.66%和20.71%;3种植物根、茎、叶的分解速率存在显著差异,分解速率依次为：粗柄独尾草根>叶;尖喙牻牛儿苗根>叶>茎;沙漠绢蒿根>茎。在整个分解过程中,N和P含量总的趋势表现为释放,叶、根凋落物质量损失与初始N、P含量显著负相关,非生物因素对其分解有重要影响。  相似文献   

12.
Chlorpyrifos [O,O-diethyl O-(3,5,6-trichloro-2-pyridyl) phosphorothioate] is an organophosphorus insecticide applied to soil to control pests both in agricultural and in urban developments. Typical agricultural soil applications (0.56 to 5.6 kg ha?1) result in initial soil surface residues of 0.3 to 32 μg g?1. In contrast, termiticidal soil barrier treatments, a common urban use pattern, often result in initial soil residues of 1000 μg g?1 or greater. The purpose of the present investigation was to understand better the degradation of chlorpyrifos in soil at termiticidal application rates and factors affecting its behaviour. Therefore, studies with [14C]chlorpyrifos were conducted under a variety of conditions in the laboratory. Initially, the degradation of chlorpyrifos at 1000 μg g?1 initial concentration was examined in five different soils from termite-infested regions (Arizona, Florida, Hawaii, Texas) under standard conditions (25°C, field moisture capacity, darkness). Degradation half-lives in these soils ranged from 175 to 1576 days. The major metabolite formed in chlorpyrifos-treated soils was 3,5,6-trichloro-2-pyrid-inol, which represented up to 61% of applied radiocarbon after 13 months of incubation. Minor quantities of [14C]carbon dioxide (< 5%) and soil-bound residues (? 12%) were also present at that time. Subsequently, a factorial experiment examining chlorpyrifos degradation as affected by initial concentration (10, 100, 1000 μg g?1), soil moisture (field moisture capacity, 1.5 MPa, air dry), and temperature 15, 25, 35°C) was conducted in the two soils which had displayed the most (Texas) and least (Florida) rapid rates of degradation. Chlorpyrifos degradation was significantly retarded at the 1000 μg g?1 rate as compared to the 10 μg g?1 rate. Temperature also had a dramatic effect on degradation rate, which approximately doubled with each 10°C increase in temperature. Results suggest that the extended (3–24 + years) termiticidal efficacy of chlorpyrifos observed in the field may be due both to the high initial concentrations employed (termite LC 50 = 0.2– 2 μg g?1) and the extended persistence which results from employment of these rates. The study also highlights the importance of investigating the behaviour of a pesticide under the diversity of agricultural and urban use scenarios in which it is employed.  相似文献   

13.
为了揭示还田玉米秸秆在不同施氮水平下的腐解及养分释放特征,在马铃薯田间定位试验中,设置了6个不同施氮水平(T1:0 kg·hm~(-2);T2:75 kg·hm~(-2);T3:150 kg·hm~(-2);T4:225 kg·hm~(-2);T5:300 kg·hm~(-2); T6:375 kg·hm~(-2)),研究其对还田玉米秸秆腐解及养分释放特征的影响。研究表明:还田玉米秸秆的腐解主要发生在前90 d,在此期间玉米秸秆腐解较快,T1～T6处理的玉米秸秆腐解率分别为37.3%、40.3%、44.8%、45.0%、50.8%、48.4%,以T5处理为最高,处理间差异显著(P0.05);同时,T1～T6处理的玉米秸秆碳、氮释放率分别为48.2%～56.6%、33.8%～44.4%,T5处理下秸秆的碳、氮释放率均显著高于其他处理(P0.05),而秸秆磷、钾的释放率分别为43.1%～49.2%、90.5%～93.0%,处理间无显著性差异。还田150 d后,玉米秸秆的腐解率为52.7%～55.8%,养分释放表现为KCPN。综上所述,连续施氮可以显著促进还田玉米秸秆前期的腐解及碳氮的释放,但对磷钾的释放无明显影响,当施氮量为300 kg·hm~(-2)时还田玉米秸秆的腐解效果最好。  相似文献   

14.
A field tracer experiment, simulating point source contamination, was conducted to investigate attenuation and transport of atrazine, hexazinone and procymidone in a volcanic pumice sand aquifer. Preliminary laboratory incubation tests were also carried out to determine degradation rates. Field transport of the pesticides was observed to be significant under non‐equilibrium conditions. Therefore, a two‐region/two‐site non‐equilibrium transport model, N3DADE, was used for analysis of the field data. A lump reduction rate constant was used in this paper to encompass all the irreversible reduction processes (eg degradation, irreversible adsorption, complexation and filtration for the pesticides adsorbed into particles and colloids) which are assumed to follow a first‐order rate law. Results from the field experiment suggest that (a) hexazinone was the most mobile (retardation factor R = 1.4) and underwent least mass reduction; (b) procymidone was the least mobile (R = 9.26) and underwent the greatest mass reduction; (c) the mobility of atrazine (R = 4.45) was similar to that of rhodamine WT (R = 4.10). Hence, rhodamine WT can be used to delimit the appearance of atrazine in pumice sand groundwater. Results from the incubation tests suggest that (a) hexazinone was degraded only in the mixture of groundwater and aquifer material (degradation rate constant = 4.36 × 10?3 day?1); (b) procymidone was degraded not only in the mixture of groundwater and aquifer material (rate constant = 1.12 × 10?2 day?1) but also in the groundwater alone (rate constant = 2.79 × 10?2 day?1); (c) atrazine was not degraded over 57 days incubation in either the mixture of aquifer material and groundwater or the groundwater alone. Degradation rates measured in the batch tests were much lower than the total reduction rates. This suggests that not only degradation but also other irreversible processes are important in attenuating pesticides under field conditions. Hence, the use of laboratory‐determined degradation rates could underestimate reduction of pesticides in field conditions. © 2001 Society of Chemical Industry  相似文献   

15.
A 5-year field study was conducted on the effect of plant residue management on soil erosion, runoff, bulk density, penetration resistance, and organic carbon. There were three treatments: burning residues on field (BR), returning residues unto the soil surface after harvesting (TR), and removing residues from soil surface (RR) (control treatment). At the end of the 5-year treatment, a rainfall simulation at 90?mm?h?1 was applied to each plot. After rainfall simulation started, the runoff volume and soil loss amount in samples were collected at four sampling times. The results showed that the runoff volume for BR (from 145.5?±?12.2 to 190.0?±?11.8?mL) differed significantly (p?≤?0.01) from that of RR (from 32.3?±?5.5 to 67.5?±?11.1?mL) and TR (from 10.0?±?0.7 to 16.7?±?3.3?mL). A significant difference (p?≤?0.01) was also observed between RR and TR regarding runoff volume and soil loss amount in different sampling times, except for the first sampling time (2–4?min). The runoff volume in BR and TR was 215% higher and 294% lower than that of the control (RR), respectively. As compared to the control (RR), soil loss decreased by 96.5% in TR but increased by 192% in BR. The BR increased soil bulk density and penetration resistance by 4.9% and 12.4%, whereas TR reduced them by 2.1% and 15.8%, respectively, as compared to the control (RR). The results indicated that the highest (0.35) and lowest (0.03) runoff coefficients were obtained for BR and TR treatments, respectively. It is concluded that returning plant residues to soil is the best residue management practice in decreasing soil runoff volume and controlling soil erosion in semi-arid regions.  相似文献   

16.
Chlorpyrifos is an organophosphorus insecticide used to control insect pests in soil. The fate of chlorpyrifos in soils under different moisture regimes is of interest because application directions specify soil-surface treatments for a number of agricultural and urban pests. Chlorpyrifos was degraded rapidly in all air-dry soils and slightly more slowly in soils at field capacity and/or under submerged conditions. Degradation rates were influenced by clay-catalysed hydrolysis under air-dry conditions and neutral or alkaline hydrolysis under submerged conditions. Degradation was faster in Bellary soil (chromic haplustert) and slower in Chettalli soil (ustic palehumult) under all three moisture regimes. The calculated half-lives ranged from 1·6 to 10·0, 5·2 to 22·0 and 8·7 to 25·1 days under air-dry, field capacity and submergence respectively at an application rate of 10 mg kg-1. © 1997 SCI.  相似文献   

17.
Magnaporthe oryzae is the fungal plant pathogen that causes rice blast. The sources of primary inoculum and overwintering mode of the fungus remain largely unknown. The effect of rice residues on the onset of blast epidemics and the potential for survival of M. oryzae in the residues were studied in upland conditions in Madagascar. Blast disease was observed in a 3‐year field experiment in three treatments: with either infected or uninfected rice residues on the soil surface, or without rice residues. Leaf blast incidence was significantly higher in the treatment with infected rice residues than in the two other treatments at the early stages of the epidemic. In a second set of trials, the survival of M. oryzae on rice residues was monitored. Infected rice stems were placed by lots in three places: on the mulch of rice residues, under the mulch, and buried at a depth of 10 cm in the soil. Each month, samples were taken from the field and tested for sporulation. The survival of the blast fungus decreased rapidly on the stems buried in the soil but remained high for the other conditions. Sporulation of the fungus was observed on stems left on the mulch for up to 18 months. It is concluded that under field conditions, the presence of infected rice residues could initiate an epidemic of blast. The results of this study may help in designing effective management strategies for rice residues infected by M. oryzae.  相似文献   

18.
Slugs are major pests of many crops in the UK, including winter wheat, yet current methods of control are often unreliable. This study investigates the potential use of red clover, as an alternative food source, to reduce the amount of damage caused to winter wheat by the field slug, Deroceras reticulatum (Müller). Two laboratory-based studies, each conducted over a 7-day period, investigated the effects of red clover seedlings and commercial metaldehyde pellets on damage to winter wheat seeds and seedlings. The results indicate that metaldehyde applications, in the form of commercially available pellets, resulted in significantly greater protection to wheat seeds compared with red clover, whereas metaldehyde and red clover were equally as effective in reducing damage to wheat seedlings. A further laboratory experiment investigated the effect of two slug population densities (48 and 16 adults m(-2)) and high and low red clover seed rates (125% and 75% of a standard rate) on damage to wheat seeds. Results showed that, at the highest slug population density, red clover sown at 125% of the standard rate gave 99% protection to wheat seeds, compared with the 75% seed rate which gave 55%. At the lower slug population density, both seed rates of red clover resulted in similar levels of protection. Implications for the potential use of red clover as an alternative food source for reducing damage to winter wheat in field conditions are discussed.  相似文献   

19.
The persistence of [14C]sethoxydim (2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexene-1-one) at the 2 μg g?1 level was studied under laboratory conditions in three soils at 20°C and 85% of their field capacity moistures. Following extraction of the soils with methanol, the herbicide remaining was determined using radiochemical techniques. Loss of radioactivity was more rapid on moist clay loam and sandy loam, where the half-lives were 12 days, than on heavy clay in which the half-life was 26 days. Loss of radioactivity from air-dried soils (15% of field capacity) was negligible with over 94% of the applied activity being recovered after 28 days. The persistence of sethoxydim at a rate of 1 kg ha?1 was investigated under field conditions using small plots at three prairie locations for 3 successive years. Using an oat-root bioassay procedure, no residues were detected in the 0–10 cm depths of any soils, any year, in September following May treatments.  相似文献   

20.
燕麦孢囊线虫对山东地区小麦产量的影响   总被引：2，自引：2，他引：0  
为评估燕麦孢囊线虫Heterodera avenae发生对小麦产量损失的影响,采用室内盆栽和田间试验相结合的方法,测定了燕麦孢囊线虫不同初始接种密度下对山东省小麦主栽品种的为害损失。结果表明：盆栽条件下,燕麦孢囊线虫为害小麦,影响小麦农艺性状,每克土壤中初始接种卵量为5~30个时,小麦叶绿素含量、根干重、茎干重、有效分蘖数、穗粒数、千粒重、穗重与未接种线虫处理的小麦相比分别降低了10.89%~34.46%、30.65%~73.95%、13.93%~58.68%、30.48%~53.33%、3.97%~36.93%、-3.73%~1.28%、-0.72%~35.08%;而在田间肥水充足条件下,燕麦孢囊线虫对小麦的各项产量指标无显著影响;繁殖系数与线虫初始密度呈负相关。试验表明,燕麦孢囊线虫发生对小麦产量存在潜在威胁,在制定防治措施时,应充分考虑水肥条件,重视对中低产田的影响。  相似文献   

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