Contribution of contact toxicity and wheat condition to mortality of stored-product insects exposed to spinosad

Spinosad, a reduced-risk commercial insecticide derived from a bacterial fermentation product, possesses both contact and oral toxicities against insects. Contact toxicity of spinosad to adults of Rhyzopertha dominica (F), Sitophilus oryzae (L), and Tribolium castaneum (Herbst) was evaluated by exposure for 24 or 48 h to treated glass Petri dishes. Adults were exposed to different deposits (0.001-0.79 mg cm(-2)) of spinosad in 24-h tests and to deposits of 0, 0.0016 and 0.016mg cm(-2) in 48-h tests. Rhyzopertha dominica was most susceptible to spinosad in 24- and 48-h tests, followed by S. oryzae, and T. castaneum. The 24-h LD50 values were 0.0004, 0.077 and 0.189mg cm(-2) for R. dominica, S. oryzae, and T. castaneum, respectively. All R. dominica adults were dead following 48 h exposure to both spinosad deposits, whereas mortality of S. oryzae and T. castaneum ranged from 10 to 85% and 12 to 48%, respectively. Rhyzopertha dominica, T. castaneum, and O. surinamensis adults were exposed for 14 days to whole wheat, cracked wheat and wheat flour treated with 0, 0.1 and 1.0 mg kg(-1) of spinosad. Rhyzopertha dominica adults were highly susceptible to spinosad, followed by O. surinamensis and T. castaneum. Immatures (eggs and larvae) of T. castaneum and O. surinamensis exposed for 14 days were more susceptible on spinosad-treated whole wheat than on treated cracked wheat and wheat flour. This is the first report documenting contact activity of spinosad, and the effect of grain condition on spinosad toxicity, to stored-product insects.     

Energy expenditure in Awassi sheep grazing wheat stubble in the northern Negev Desert of Israel

In semi-arid Mediterranean areas, small grain aftermath stubble represents an important summer source of food for grazing flocks of small ruminants. Wheat stubble is a mediocre source of forage and flocks are grazed in summer under harsh conditions of temperature and air dustiness. However, stubble grazing procedures are changing, water and shading are more frequently available between grazing sessions (“improved management”), and the biological soundness of this ancestral practice needs to be re-visited. The present study was aimed at evaluating the cost in energy of “improved” wheat stubble grazing, compared with feeding a similar diet indoors. The intake of stubble was first quantitatively and qualitatively evaluated in Awassi sheep. Ewes consumed daily 980 ± 100 g day^− 1 of wheat stubble. Ewes were then housed and fed diets consisting of wheat hay, straw and grain formulated to be iso-energetic and iso-nitrogenous to diets consumed from wheat stubble. The average intake of ME was similar during the confinement and the pasture periods (6.4 ± 0.5 and 7.6 ± 0.8 MJ day^− 1of ME, respectively). During 2 days of each period, animals were fitted with external electrodes and data loggers of heart rate and skin temperature. Energy expenditure (EE) was calculated from oxygen consumption estimated as the product of heart beats rate measured for the two days by the amount of oxygen delivered to body tissues at each heart beat (O₂ pulse). The O₂ pulse was determined by simultaneously measurement of oxygen consumption and HR twice daily on two occasions, while grazing stubble and indoors. Energy expenditure and energy balance were not different in sheep while grazing wheat stubble (11.1 and − 3.5 MJ day^− 1) or fed indoors (11.1 and − 4.8 MJ day^− 1). Our data show that stubble did not cover nitrogen and energy requirements for maintenance, and that the cost of summer stubble grazing carried out under conditions described here is less than thought before.     

吉林省主要粮食作物比较优势分析

根据比较优势理论，应用综合比较优势指数法对吉林省玉米、水稻、大豆三种主要粮食作物在1997-2005年间的比较优势变动趋势进行了分析，其结果表明：三种作物中，玉米具有明显的比较优势，大豆次之，水稻则处于劣势，但呈现出稳步上升的趋势；并在此基础上提出了吉林省主要粮食作物结构调整的建议。     

不同营养水平补饲对湘东黑山羊肥育羔羊生产性能的影响

采用80只3~4月龄的湘东黑山羊羔羊,研究3种不同营养水平补饲对肥育羔羊日增重、经济效益的影响。分别在冬、春两个季节进行为期2个月的补饲。试验按完全随机单因子设计,每个季节设4个处理,即3个精料补饲组与1个对照组,每个处理10头湘东黑山羊。参考NRC(1981)的山羊饲养标准设计补充饲料配方,每个季节的3个补饲试验组饲粮的精粗比分别按30∶70、40∶60、50∶50确定,平均补饲量依次按100、200、300g/(d.只)。结果表明冬季补饲试验1、2、3组平均日增重分别为62.75、80.00和85.92g,分别比对照组提高42.06%、81.12%、94.52%,差异显著(P<0.05)或极显著(P<0.01)。春季补饲试验1、2、3组平均日增重分别为85.33、93.50和100.83g,分别比对照组提高38.00%、51.22%、63.08%,差异均为极显著(P<0.01)。从季节对补饲效果来看,冬季的高精料补饲与低精料补饲(精粗比=30∶70)差异显著;春季的精料补饲量对增重影响不大。冬季补饲以精粗料比40∶60为好,春季以30∶70为好。冬季补饲使试验1、2、3组比对照组增加利润分别为5.14、9.23、4.49元/只;春季补饲使试验1、2、3组比对照组增加利润分别为8.97、5.98、2.35元/只。经济效益比较好的补饲量是,冬季187.5g/d,春季154.1g/d。     

西瓜成熟花粉的超微结构

为了解西瓜成熟花粉的超微结构特点,特别是营养细胞和生殖细胞之间的关系,选取刚开花的西瓜雄花采集花粉,2.5%戊二醛固定并制成超薄切片,透射电镜观察照相。结果表明,西瓜成熟花粉粒中营养细胞含丰富脂类储藏物质和内质网,内质网堆叠,周围和间隙中充满脂类物质;含丰富高尔基体和大量小泡;质体很少。营养核通常深度开裂,产生多数裂片,裂片伸向生殖细胞。生殖细胞流线型,细胞壁电子透明,细胞核伸长,细胞质含高尔基体、内质网,不含质体。生殖细胞表面产生波状突起,波峰背离营养核。生殖细胞一端伸入营养核裂片间隙,2者构成雄性生殖单位。     

多因素控制下渭北旱地小麦产量寻优的研究

在陕西渭北旱塬进行了连续三年定点小麦田间试验,通过栽培模式、氮肥水平、种植密度三因素的不同处理,研究多因素小麦栽培优化组合.结果表明:采用垄沟、覆膜、秸杆覆盖栽培模式对小麦穗数不产生影响;施用氮肥能极显著地影响小麦穗数,在施纯氮0～240 kg/hm2范围内,每增减纯氮1 kg,增减穗数4 288;增加播量,极明显地提高小麦穗数;不同的栽培模式、氮肥用量和小麦种植密度对小麦的穗粒数不产生影响;覆膜栽培与垄沟栽培之间千粒重差异显著,种植密度对小麦千粒重在不同的条件下影响明显,覆膜栽培条件下,高氮肥水平,低密度(播种量180 kg/hm2)的千粒重大于高密度(播种量225 kg/hm2),垄沟模式下,高氮水平(施纯氮240 kg/hm2)与中氮水平(施纯氮120 kg/hm2)之间差异不显著,但与不施氮肥相比,千粒重明显提高,秸秆覆盖模式下,高密度(播种量225 kg/hm2)与不施氮、高氮水平组合的平均千粒重最低,两者差异不显著,但与其它各组合差异显著.正常降水年份,旱地小麦采用一定的农业栽培模式,能够显著影响小麦的产量,尤其是覆膜下,产量显著高于对照;降水量多的年份,采用垄沟模式及秸秆覆盖模式对小麦产量甚至产生负效应.施用氮肥对小麦产量有极显著影响,在施纯氮0～240 kg/hm2范围内,每增减纯氮1 kg,增减籽粒产量5.7 kg;种植密度对小麦籽粒产量与生物产量的影响显著,秸秆覆盖栽培和常规栽培(对照)模式下籽粒产量差异显著,产量排列次序都为高密度(播种量225 kg/hm2)大于低密度(播种量180 kg/hm2),低氮和不施氮时,增加密度,可提高产量.     

金诺丰叶面肥对旱地冬小麦陕农981旗叶光合和灌浆特性及产量的影响

以冬小麦陕农981为材料,采用单因素随机区组设计,研究了不同时期喷施叶面肥金诺丰对陕农981灌浆期旗叶光合特性、籽粒灌浆特性和产量的影响.结果表明:金诺丰能够提高小麦灌浆期旗叶的光合速率和籽粒灌浆速率,分别较对照提高14.5%和10.7%;增加籽粒干物质的积累量,较对照增加2.6%;产量构成三要素都有不同程度提高,成穗数、穗粒数、千粒重分别平均提高8.0%、7.5%和2.6%.不同时期喷施对产量的影响大小依次是拔节期＞开花期＞灌浆期＞分蘖期＞返青期.     

风成沉积物环境敏感粒度指标的提取及意义

采用SPSS11.5软件中的主成分分析方法,对黄土高原西部末次冰期沉积的宁夏中卫冰沟剖面和兰州沙金坪剖面的粒度进行了环境敏感粒度指标的提取,沙金坪剖面和冰沟剖面的环境敏感粒级分别为24.70-27.90μm、62.47-68.97μm,冰沟剖面的阈值基本是砂粒级标准(>63μm),冰沟剖面由于距沙漠源区更近,受物源影响更大而使敏感组分更粗,不同地区的环境敏感粒度指标存在差异。另外,不同数学方法提取的指标也存在差异,数学方法的运用必须考虑其数值所表示的物理机制和环境意义。     

塔克拉玛干沙漠腹地纵向沙垅表面沙物质粒度特征

本文对塔克拉玛干沙漠腹地纵向沙垅表面沙粒、丘间地沙粒进行了粒度分析。结果表明,沙垅以极细沙为主,平均粒径３．０６Φ,沙粒从沙垅迎风侧到背风侧逐渐变细。沙丘沙比丘间地沙分选好,沙垅背风侧比迎风侧分选好。沙粒属极负偏,偏度－０．２２,丘间地沙比沙丘沙更趋向负偏。峰度１．３８,属尖峰态。粒径与偏度和峰度成正相关,分选和偏度成良好负相关。沙丘沙以单峰态为主,累积频率曲线为２～３段式,丘间地以双峰态为主,累积频率曲线为３～４段。大尺度地形对沙粒段式没有影响,对各段组分含量相对大小有影响。     

不同生态区藏山羊的产绒性能研究

选择青藏高原四个不同的生态区,对藏山羊的产绒性能进行了研究,结果表明：西藏两个产区藏山羊的产绒量和绒的主要品质指标均高于四川两个产区,尤其是西藏阿里地区藏山羊的产绒量和绒的品质明显优于其他产区,四川茂县藏山羊的产绒量和绒的品质较差;同时,西藏两产区藏山羊的产绒量从年龄上看以４岁较高,从毛色上看以白色个体较高;四个不同生态区内藏山羊的产绒性能差异较大,越严酷的高寒生态条件,其产绒量越高,绒的品质越好。今后应根据不同的生态区按不同的生产方向对藏山羊这一宝贵的基因库资源进行开发利用。