The Validation of Pesticide Leaching Models     

Adrian C. Armstrong  Andrew M. Portwood  Peter B. Leeds-Harrison  Graham L. Harris  John A Catt 《Pest management science》1996,48(1):47-55

The validation of pesticide leaching models presents particular problems where the number of model predictions is far in excess of the observed data. Normally, however, there are more frequent field observations for other parameters (notably the site hydrology) than for pesticide concentrations in either water or soil. A five-stage validation procedure which takes advantage of the most frequently available observations and which tests each of the components of the model in a cumulative way, is thus advocated: Stage 1: Parameterisation of the model using only independently measured parameters. Stage 2: Hydrological validation: the validation of the predictions of water movement and water content of the soil. Stage 3: Solute movement validation: where field data are available for solutes other than pesticide, the model should first be validated for them, especially if they are more abundant than the pesticide observations. Conserved solutes such as chloride or bromide are preferred, although nitrate may be used for short periods. Stage 4: Pesticide fate in the soil: models should use parameters of pesticide fate derived from independent studies. Stage 5: Pesticide leaching: only in the last stage are the relatively small number of pesticide observations compared with the model predictions with respect to patterns and orders of magnitude of occurrence. With this scheme, the results of each stage are carried forward to the next, and confidence in the model is built with each stage. This is illustrated using the CRACK-P model and hydrological, nitrate and pesticide data from the Brimstone Farm Experiment Oxfordshire, UK.  相似文献   

Synthesis and Anthelmintic Activity of 7-Hydroxy- 5-oxo-5H-thieno[3,2-b]pyran-6-carboxanilides and -6-thiocarboxanilides     

Andrew Plant  Achim Harder  Norbert Mencke  Heinz-Jürgen Bertram 《Pest management science》1996,48(4):351-358

7-Hydroxy-5-oxo-5H-thieno[3,2-b]pyran-6-carboxanilides and -6-thio-carboxanilides represent a novel series of anthelmintic compounds, with broad-spectrum activity against important parasitic nematodes in sheep and dogs. In particular, an improved efficacy against Trichostrongylus colubriformis in sheep over the related 3-carbamoyl-4-hydroxycoumarins has been noted. New synthetic routes to the key intermediate, 7-hydroxythieno[3,2-b]pyran-5-one, have been developed.  相似文献   

Simulation modelling of potato virus Y spread in relation to initial inoculum and vector activity          下载免费PDF全文

Andrew GALIMBERTI  rei ALYOKHIN  Hongchun QU  Jason ROSE 《农业科学学报》2020,19(2):376-388

Potato virus Y(PVY) is a non-persistent virus that is transmitted by many aphid species and causes significant damage to potato production. We constructed a spatially-explicit model simulating PVY spread in a potato field and used it to investigate possible effects of transmission efficiency, initial inoculum levels, vector behavior, vector abundance, and timing of peak vector activity on PVY incidence at the end of a simulated growing season. Lower PVY incidence in planted seed resulted in lower virus infection at the end of the season. However, when populations of efficient PVY vectors were high, significant PVY spread occurred even when initial virus inoculum was low. Non-colonizing aphids were more important for PVY spread compared to colonizing aphids, particularly at high densities. An early-season peak in the numbers of noncolonizing aphids resulted in the highest number of infected plants in the end of the season, while mid-and late-season peaks caused relatively little virus spread. Our results highlight the importance of integrating different techniques to prevent the number of PVY-infected plants from exceeding economically acceptable levels instead of trying to control aphids within potato fields. Such management plans should be implemented very early in a growing season.  相似文献   

Evaluation of cultural control and resistance‐breeding strategies for suppression of whitefly infestation of cassava at the landscape scale: a simulation modeling approach     

Hazel Parry  Andrew Kalyebi  Felix Bianchi  Peter Sseruwagi  John Colvin  Nancy Schellhorn  Sarina Macfadyen 《Pest management science》2020,76(8):2699-2710

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Use of Dried Fermented Biomass as a Fish Meal Replacement in Practical Diets of Florida Pompano,Trachinotus carolinus     

Melanie A. Rhodes  Yangen Zhou  D. Allen Davis 《Journal Of Applied Aquaculture》2013,25(1):29-39

Substitution of fish meal (FM) as a protein source in aquaculture diets is required to reduce cost and promote a sustainable industry. Potential protein sources include a range of traditional products from agricultural production such as plant or animal proteins. However, there are also a number of manufacturing coproducts, including bacterial dried fermented biomass (DFB,) for which there is an increased interest. Hence, the objective of this study was to evaluate DFB as a replacement for FM in practical diets for Florida pompano, Trachinotus carolinus. Four diets were prepared in which different levels of FM (15%, 10%, 5%, and 0% of the diet) were replaced with DFB (0%, 4.27%, 8.54%, and 12.82%) on an iso-nitrogenous and iso-lipidic basis, to contain 40% crude protein and 10% lipid. A 10-week growth trial was conducted in a recirculating system consisting of 12 indoor 1.0 m³ tanks, stocked with 20 juvenile pompano (mean initial weight 8.1 g) per tank. There were no significant differences in final weight (64.5 g?79.5 g), survival (81.7%–96.7%), percent weight gain (711.6%–879.0%), FCR (2.1–2.0), or thermal-unit growth coefficient (0.1013?0.1149), regardless of the levels of dietary FM or DFB tested. Based on these results, it is recommended that DFB can be included up to 12.8% in practical diets for Florida pompano without significantly reducing growth performance. The response to higher levels of DFB inclusion should be evaluated.  相似文献   

Evaluation of a 4‐h static copper sulphate treatment against experimental infection of Flavobacterium columnare in channel catfish (Ictalurus punctatus)     

Ahmed M Darwish  Andrew Mitchell  David L Straus 《Aquaculture Research》2012,43(5):688-695

The efficacy of copper sulphate (CuSO₄) against the early stages of an experimental acute infection of Flavobacterium columnare in channel catfish (Ictalurus punctatus) was evaluated. Fish were challenged, by waterborne exposure to F. columnare in an ultra‐low flow‐through water delivery system, and treated with CuSO₄ at 4.2 and 2.1 mg L^?1 at 5.5 h post challenge for 4 h. Bacterial challenged non‐treated fish acted as a positive control and non‐challenged non‐treated fish acted as a negative control. Fish challenged with F. columnare and treated with CuSO₄ at 4.2 and 2.1 mg L^?1 post challenge had mortalities of 6.4% and 18.3%, respectively, compared with the positive control, which had 90.2% mortality. The mortality of challenged fish treated with CuSO₄ at 4.2 and 2.1 mg L^?1 was significantly different from the positive control. There was no significant difference between the mortalities of the 4.2 and 2.1 mg L^?1 treatments. The results suggest that CuSO₄ has clear therapeutic value against columnaris infections.  相似文献   

Thirty years of change and the future of Alaskan fisheries: Shifts in fishing participation and diversification in response to environmental,regulatory and economic pressures     

Anne H. Beaudreau  Eric J. Ward  Richard E. Brenner  Andrew O. Shelton  Jordan T. Watson  Jennifer C. Womack  Sean C. Anderson  Alan C. Haynie  Kristin N. Marshall  Benjamin C. Williams 《Fish and Fisheries》2019,20(4):601-619

Heterogeneity in human responses and decision‐making can contribute to the resilience of social–ecological systems in the face of environmental, political and economic pressures. In fishery systems worldwide, the ability of harvesters to maintain a diverse portfolio of fishing strategies is important for building adaptive capacity. We used a case‐study approach to examine the complexity of factors that inhibit or promote diversification in fisheries of Alaska, one of the major fishing regions of the world. Through a combination of harvest records and literature review, we explored shifts in participation and portfolio diversity in Alaskan fisheries over three decades. The four case‐studies examined the responses of fishers, fleets and communities to multiple, intersecting pressures, including biological declines, market and price dynamics, fishery privatization and the 1989 Exxon Valdez oil spill. These cases illustrate how stressors acting at multiple scales can encourage or constrain opportunities for diversification, and that these opportunities may be spread inequitably across participants. Overall, we found evidence for reduced participation and increasing specialization in Alaskan commercial fisheries. While numerous factors explain these trends, policies like individual quota systems and the increasing cost of entry into fisheries are forcing consolidation at local to regional scales. A portfolio approach to managing fisheries that reduces barriers to diversification and includes broad representation of resource users and communities in management may help to maintain opportunity and choice for fishers.  相似文献   

Shrimp (Litopenaeus vannamei) production and stable isotope dynamics in clear‐water recirculating aquaculture systems versus biofloc systems          下载免费PDF全文

Andrew J Ray  Jeffrey M Lotz 《Aquaculture Research》2017,48(8):4390-4398

Closed recirculating aquaculture systems (RAS) offer advantages over traditional culture methods including enhanced biosecurity, the possibility of indoor, inland culture of marine species year‐round and potential marketing opportunities for fresh, never‐frozen seafood. Questions still remain regarding what type of aquaculture system may be best suited for the closed‐system culture of marine shrimp. In this study, shrimp (Litopenaeus vannamei) were grown in clear‐water RAS and in biofloc‐based systems. Comparisons were made between the system types with respect to water quality, shrimp production and stable isotope dynamics used to determine the biofloc contribution to shrimp nutrition. Ammonia and nitrite concentrations were higher, and shrimp survival was lower in the biofloc systems. Although stable isotope levels indicated that biofloc material may have contributed 28% of the carbon and 59% of the nitrogen in shrimp tissues, this did not correspond with improved shrimp production. Overall, the water column microbial communities in biofloc systems may be more difficult to manage than clear‐water RAS which have external filters to control water quality. Biofloc does seem to offer some nutritional contributions, but exactly how to take advantage of that and ensure improved production remains unclear.  相似文献   

Patterns and impacts of fish bycatch in a scallop dredge fishery     

Helen R. Craven  Andrew R. Brand  Bryce D. Stewart 《水产资源保护:海洋与淡水生态系统》2013,23(1):152-170

大豆疫霉根腐病菌游动孢子侵染野生大豆下胚轴的透射电镜观察     

徐鹏飞  吴俊江  Allen G.Xue  靳立梅  王金生  张小明  李文滨  张淑珍 《大豆科学》2012,31(3):462-465

用大豆疫霉根腐病菌的游动孢子悬浮液处理抗感性不同的野生大豆下胚轴,接种后3～72 h,用透射电镜观察野生大豆与大豆疫霉菌的亲和性与非亲和性互作中细胞超微结构的变化。结果表明:接种后3～36 h,感病野生大豆随接种时间延长下胚轴细胞器结构破坏严重,而抗病野生大豆细胞结构基本完整;接种后48 h,抗病野生大豆的细胞壁物质累加,出现胞壁沉积物,而感病野生大豆细胞壁出现部分降解;接种后72 h,抗病野生大豆细胞质壁分离,但细胞器结构基本完整,感病野生大豆细胞器几乎无完整的结构。  相似文献