Prolonged exclusion of foraging ants (Hymenoptera: Formicidae) from citrus trees using controlled-release chlorpyrifos trunk bands

Abstract

Controlled-release chlorpyrifos trunk bands excluded foraging ants ( Iridomyrmex spp.) from citrus tree canopies for four growing seasons (182 and 211 weeks in two separate trials). The level of exclusion averaged 92.7% over the full period of the trials. Laboratory bioassays of weathered band material showed the bands were still toxic to ants (98 - 100% mortality) after 200 and 229 weeks. In contrast, trunk applications of lambda-cyhalothrin and a chlorpyrifos 'emulsion' were very short-lived (< 14 weeks) in their activity against foraging ants; levels of exclusion over 15 to 18 weeks averaged 46% for lambda-cyhalothrin and 23% for the chlorpyrifos 'emulsion'. The potential of controlled-release chlorpyrifos trunk bands as a practical management strategy for foraging ants in citrus groves is discussed.     

Decomposition of a Native Shrub,Piliostigma reticulatum,Litter in Soils of Semiarid Senegal

Developing effective management strategies that restore degraded soils requires an evaluation of the quality of the litter residues. This study relates the chemical composition of the biomass components to the decomposition rates for Piliostigma reticulatum (DC.) Hochst., a native shrub, under field and laboratory conditions. The rates were determined by mass loss. The changes in the specific surface area of the residue in relation to mass loss ranged from 15 X 10 -5 to 45 X 10 -5 which was similar to crop residues in other studies. At field conditions, P. reticulatum mass loss was higher (80% of the initial mass lost over eight months) than that under controlled conditions (50%). Such fast decomposition of residues offers the potential for farmers to stop burning these residues because high amounts of residues will not likely accumulate and cause interference with tillage and planting operations. Further studies are needed on the role of soil fauna on decomposition, mineralization of nutrients from these residues, and the potential for incorporating residues into the system without burning.     

小青菜对土壤中毒死蜱吸收移动特征研究

以小青菜为供试蔬菜,通过在土壤中添加毒死蜱,进行盆栽试验,研究毒死蜱对小青菜生长的影响、在土壤中的降解速度以及在小青菜中的吸收和转移规律,为蔬菜中农药残留风险评估和蔬菜安全生产提供理论依据。试验结果表明,与对照相比,含有高浓度(>50.0 mg kg-1)毒死蜱土壤对小青菜的生长有显著抑制作用;毒死蜱在不同处理土壤中的半衰期从23.03 d至77.43 d不等;残留于土壤中的毒死蜱能够被种植的小青菜根系吸收并转移至茎叶部分,随着土壤中处理浓度的增加,毒死蜱在小青菜根、茎和叶中的残留量也随之增加,且毒死蜱在小青菜根中的残留量最大,在叶中的残留量最小;土壤中毒死蜱残留量与小青菜根、茎和叶中毒死蜱的含量呈良好的线性关系,线性方程分别为:C根=0.025 1C土壤-0.235 8,C茎=0.012 3C土壤-0.051 7,C叶=0.000 7C土壤+0.011 5。为了实现蔬菜中农药残留从农田到餐桌的全程控制,保证无公害蔬菜的安全生产与供应,首先要对生产基地土壤中的农药残留进行检测,并从源头上进行控制。     

Soil and residue management effects on arable cropping conditions and nitrous oxide fluxes under controlled traffic in Scotland 1. Soil and crop responses

Soil compaction can affect crop growth and greenhouse gas emission and information is required of how both these aspects are affected by compaction intensity and weather. In this paper we describe treatments of compaction intensity and their effects on soil physical conditions and crop growth in loam to sandy loam cambisol soils. Soil conditions and crop performance were measured over three seasons in a field experiment on soil compacted by wheels on freshly ploughed seedbeds. Ploughing buried the chopped residues of the previous crop. After ploughing, traffic was controlled such that the experimental plots received wheel traffic only as treatments. The overall objective was to discover how the intensity and distribution of soil compaction just before sowing influenced crop performance, soil conditions and emissions of nitrous oxide. Compaction treatments were zero, light compaction by roller (up to 1 Mg m⁻¹) and heavy compaction by loaded tractor, (up to 4.2 Mg). The experiment was located at Boghall, near Edinburgh (860 mm average annual rainfall) for the first two seasons under spring and winter barley (Hordeum vulgare L.) and in a drier area at North Berwick (610 mm average annual rainfall) for the third season under winter oil-seed rape (Brassica napus L.). Heavy compaction in dry soil conditions had little effect on crop growth. However, in wet conditions heavy compaction reduced air porosity, air permeability and gas diffusivity, increased cone resistance and limited winter barley growth and grain yield. Heavy compaction in wet conditions reduced winter barley yields to 7.1 Mg ha⁻¹, in comparison to 8.8 Mg ha⁻¹ in the zero compaction treatment. The compaction status of the top 15 cm of soil seemed to be particularly important. Loosening of the top 10 cm of soil immediately after heavy compaction restored soil conditions for crop growth. However, zero seed bed compaction gave patchy and uneven crop emergence in dry conditions. Both zero and light compaction to a target depth of 10 cm gave similar crop productivity. Maintenance of a correct compaction level near the soil surface is particularly important for establishment and overwintering of barley and oil seed rape.     

Soil and residue management effects on cropping conditions and nitrous oxide fluxes under controlled traffic in Scotland2. Nitrous oxide, soil N status and weather

Nitrogen from fertilisers and crop residues can be lost as nitrous oxide (N₂O), a greenhouse gas that causes an increase in global warming and also depletes stratospheric ozone. Nitrous oxide emissions, soil chemical status, temperature and N₂O concentration in the soil atmosphere were measured in a field experiment on soil compaction in loam and sandy loam (cambisols) soils in south-east Scotland. The overall objective was to discover how the intensity and distribution of soil compaction by tractor wheels or by roller just before sowing influenced crop performance, soil conditions and production and emissions of N₂O under controlled traffic conditions. Compaction treatments were zero, light compaction by roller (up to 1 Mg per metre of length) and heavy compaction by loaded tractor (up to 4.2 Mg). In this paper we report the effects on production and emissions of N₂O and relate them to soil and crop conditions. Nitrous oxide fluxes were substantial only when the soil water content was high (>27 g per 100 g). Fertiliser application stimulated emissions in the spring whereas crop residues stimulated emissions in autumn and winter. Heavy compaction increased N₂O emissions after fertiliser application or residue incorporation more than light or zero compaction. The bulk densities of the heavily and lightly compacted soils were up to 89% and 82% of the theoretical (Proctor) maxima. Higher soil cone resistances, temperatures and nitrogen availability and lower gas diffusivities and air-filled porosities combined to make the heavily compacted soil more anaerobic and likely to denitrify than the zero or lightly compacted soil. Compaction sufficient to increase N₂O emissions significantly corresponded with adverse soil conditions for winter barley (Hordeum vulgare L.) growth. Soil tillage, which ensures that soil compaction is no greater than in our light treatment and is confined to near the soil surface, may help to mitigate both surface fluxes of N₂O and losses to the subsoil.     

高效液相色谱法检测鸡蛋中3种四环素类抗生素

建立了高效液相色谱分析法测定鸡蛋中四环素类抗生素的方法。采用色谱柱为C1(85μm,250mm×4.6mmi.d.)固相萃取小柱,流动相为乙腈/乙酸水溶液(pH值2.5)=35/65(V/V),流速1.0ml/min,检测波长为358nm,同时测定3种抗生素。该方法的最低检出浓度分别为:土霉素0.25μg/ml,金霉素0.11μg/ml,四环素0.52μg/ml,样品中土霉素、金霉素、四环素含量的相对标准偏差(RSD)分别为1.94%、1.20%、0.84%。     

9%毒死蜱·烯唑醇悬浮种衣剂对玉米地下害虫、丝黑穗病的防治效果

研究9%毒死蜱·烯唑醇悬浮种衣剂对玉米的安全性以及对地下害虫和玉米丝黑穗病的防治效果.2007-2008年在河南、黑龙江、吉林、内蒙古对该制剂进行药效对比试验.结果表明:9%毒死蜱·烯唑醇悬浮种衣剂在试验剂量范围内(药种比1∶50～70)对玉米无不良影响;在防治地下害虫方面,该药剂在药种比为1∶50和1∶60时的平均防效分别为79.85%和71.57%,与对照药剂48%毒死蜱乳油拌种、20%福·克悬浮种衣剂包衣差异不显著;药种比为1∶70时防效为60.08%,显著低于2个对照药剂.在防治丝黑穗病方面,该药剂在药种比为1∶50时防效为81.06%,略高于对照药剂5%烯唑醇干粉种衣剂包衣,显著高于20%福·克悬浮种衣剂包衣;药种比为1∶60时防效为72.65%,介于两个对照药剂之间,差异不显著;药种比为1∶70时防效为60.95%,显著低于2个对照药剂.因此,该种衣剂的最佳使用剂量为药种比1∶50～1∶60拌种包衣.     

6种有机磷农药分离及水中残留高效薄层析测定方法研究

[目的]比较有机磷农药的分离方法,用高效薄层色谱测定农药在水中残留。[方法]采用高效薄层析技术AMD和双槽展缸上行展开方式分离水中辛硫磷、毒死蜱、双硫磷、甲基异柳磷、喹硫磷和三唑磷6种有机磷农药,并对自来水中4种有机磷残留的测定方法进行研究。[结果]两种展开方式均能很好分离6种农药。AMD展开Rf值分布范围较窄（相差0.34）,双槽展缸上行展开Rf值分布范围较宽（相差0.76）;AMD多步展开检测灵敏度较双槽展缸上行展开低。采用双槽展缸上行展开薄层色谱法检测水中有机磷农药残留,添加回收率在86.05%-109.80%之间,添加回收率、变异系数均满足农药残留分析的要求。[结论]该研究中,双槽展缸上行展开表现出灵敏度较高、操作简便、分析速度快的特点。     

白蚁防治药剂在模拟房屋白蚁预防施工土壤中残留降解性动态研究

[目的]研究房屋白蚁预防药剂毒死蜱和联苯菊酯在合肥地区土壤中的降解动态。[方法]以毒死蜱和联苯菊酯为供试药剂,研究白蚁预防药剂在土壤中的残留降解性.[结果]添加浓度为50mg／kg时,毒死蜱和联苯菊酯的回收率分别为96．90％和93．25％,变异系数分剐为2．76％和4．02％、毒死蜱在土壤中的降解可以分为先快后慢2个阶段,而联苯菊酯在土壤中的降解符合一级动力学方程,、2种药剂的降解速度都较快,但联苯菊酯的降解速度比毒死蜱慢,毒死蜱的半衰期为79．68d,联苯菊酯的半衰期为94．96d。由2种药剂的降解方程计算得联苯菊酯的有效期为911d,毒死蜱的有效期为478d。[结论]该研究为白蚁防治药剂在房屋白蚁预防工程中的合理应用、安全性评价以及制定行业质量标准提供了理论依据。     

氯化苦在土壤中的消解动态和残留量检测研究

[目的]研究氯化苦在土壤上的残留分析方法及在土壤中的消解动态和最终残留量。[方法]采用气相色谱法测定氯化苦在土壤中的残留,用石油醚对土壤样品进行超声波提取,毛细管柱色谱分离,电子捕获检测器进行测定,进行了3种添加浓度的回收率试验并进行实际样品检测。[结果]氯化苦的的最低检出限（LOD）为0.008mg／kg,土壤中最低检出浓度（LOQ）为0.020mg／kg,回收率89.5％—111.1％,变异系数为3.6％—7.2％,均在农药残留测定所允许的范围内。同时在0.008—2.000mg／L浓度范围内峰面积值与氯化苦浓度线性关系良好,且线性范围较宽,适合测定土壤中不同浓度水平的氯化苦。氯化苦的消解很快,在土壤中的半衰期为5.5d。[结论]该分析方法操作简单、快速,定量准确,可有效地测定土壤中氯化苦含量。