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二化螟是水稻上的主要害虫之一．以幼虫为害水稻．初孵幼虫群集在叶鞘内为害．造成枯鞘．3龄以后幼虫蛀入稻株内为害,水稻分蘖期造成枯心苗,孕穗期造成枯孕穗．抽穗期造成白穗．成熟期造成虫伤株一般年份减产3％～5％．严重时减产30％以上。2013年崇阳县水稻二化螟发生面积10．4万hm2次,防治面积19．3万hm2次,挽回损失29454．7t．实际损失5875．4t。 相似文献
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2005年广西稻飞虱发生为害特点及成灾原因分析 总被引：3，自引：2，他引：3
稻飞虱是广西水稻的主要害虫,全区各稻区普遍遭受其危害,2005年全区达中等偏重局部大发生程度,部分稻区发生为害严重,个别田块出现了“落窝穿顶”现象。据统计,全区年发生面积达140·4万hm2次,占种植面积67·7%,防治面积154·8万hm2次,经防治后挽回损失63·5万t,实际损失6·6万t。与常年相比,稻飞虱迁入期属偏早年份,迁入峰次多,峰期长,迁入面广虫量多,田间主害期增多,虫口密度高,晚稻后期发生面积广、密度高,为近年所罕见。1稻飞虱发生为害特点1·1发生面积大、为害严重。广西稻飞虱年发生面积在20世纪90年代前期约为120万hm2次,90年代中后… 相似文献
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2001年水稻二化螟、三化螟大发生原因分析及综防对策 总被引：2，自引：0，他引：2
当阳市常年种植水稻面积 2 .8万 hm2 ,二化螟、三化螟分别是水稻生产中的主要害虫之一。近几年 ,由于农业结构的调整、作物品种、气候因素 ,以及防治规范化技术的差异 ,三化螟继 70年代之后 ,再次回升到猖獗为害 ,而二化螟的发生又居高不下 ,形成两螟同时大发生的局面。1 发生概况据历史资料分析 ,70年代 ,我市水稻生产以早稻、晚稻、中稻为主 ,二化螟仅为 1代大发生 ,2、3代为轻 ;三化螟猖獗为害 ,年度发生面积 6.7万hm2 ,三代平均 666.7m2 落卵量 2 37块 ,最高为 741块 ,平均被害率超过 1 .0 % ,高达 5 .3% ;1 995年前的 1 5年间是三化螟… 相似文献
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1重大病虫害发生特点据初步统计,2005年全国农作物病虫害总发生面积近3亿hm2次,比2004年增加3%左右。农作物重大病虫害发生特点:一是迁飞性害虫暴发频繁。2005年稻飞虱在南方稻区大发生,发生面积达0.23亿hm2次。其中,严重发生面积506.7万hm2次;东亚飞蝗在海南、广西严重发生,两地累计发生面积约13.3万hm2。二是大区域流行性病害发生加重。稻瘟病在西南及东北稻区发生严重,发生面积达580万hm2次,在东北部分稻区出现严重成灾现象;小麦条锈病在西北、鄂北、豫东等麦区冬前显病早、病点多、病情扩展快,发病中心形成早。三是经济作物病虫上升明显… 相似文献
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赤壁市水稻二化螟大发生原因及综合防治技术措施 总被引：1，自引：0，他引：1
赤壁市地处长江中游南岸,洞庭湖以北与湖南接壤,是湖北省产粮大县和优质稻板块基地,常年水稻种植面积3.3万hm2.水稻种植模式单、双季并存,一季稻桥梁田多,且插花种植,稻田生态环境适宜水稻二化螟为害.近几年来随着气候条件、种植结构和栽培制度等因素的变化,导致了水稻二化螟连续大发生,且发生量大、发生期早、发蛾峰次多、盛蛾期拉长和发育极不整齐等特点,已成为水稻重大生物灾害之一,严重影响水稻生产安全.为有效控制二化螟的为害,笔者根据近几年对水稻二化螟跟踪调查和综合防治实践情况,分析其大发生的原因并提出综合防治技术措施. 相似文献
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二化螟是全省水稻上的一个主要害虫，每年无论是早稻、中稻（一季晚）还是二晚，都是主要防治对象，特别是对第1代二化螟的防治，更为重要。1第1代二化螟发生特点1.1发生和为各时期长据我县1967～1987年测报灯下统计，第1代二化螟从见蛾至终蛾时间长达25～60d，平均32．8d。盛蛾期长达10～24d平均为14．5d，因此造成为害时期相就增长。1．2发生面积很大我县历年早稻面积约3000hm’，而第1代二化螟历年发生面积均达1666hm’以上，占早稻面积55％左右，占历年早稻害虫发生面积的35～90％，平均为60％左右。1．3防治使用高由于第1代二亿螟发生… 相似文献
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稻飞虱、稻纵卷叶螟是危害我国水稻生产的两大重要迁飞性害虫(简称水稻两迁害虫)。2005年,受"凉夏暖秋"气候和热带风暴活动频繁、雨水偏多等因素影响,水稻两迁害虫在江南大部、长江流域、江淮大部和华南稻区等地严重发生。据初步统计,全国稻飞虱发生面积2400万hm2,经防治,挽回稻谷损失100亿kg,实际仍造成稻谷损失20亿kg。田间发生表现为:迁入峰出现早、迁入峰次多、迁入量大、虫量上升迅猛、发生为害期延长等特点。稻纵卷叶螟已连续多年严重发生,2005年全国发生面积达1700万hm2,也造成了很大损失。为总结两迁害虫的发生概况、迁飞规律和暴发… 相似文献
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湘西自治州位于湖南西部,柑橘生产是本州的优势产业。近年来,本州柑橘上的一种次要害虫——柑橘粉虱[Dialeurodes citri(Ashmead)]为害逐年加重,局部地区橘园暴发成灾,给广大橘农造成了重大损失。为此,笔者对该虫在本州的发生为害现状及发生规律,进行了调查研究,分析其为害逐年加重原因,并提出相应的防治对策。1发生为害情况据调查,柑橘粉虱于1998年在吉首市开始零星发生,随后其为害逐年加重,目前已上升为柑橘主要害虫,到2002年,该虫已在湘西自治州范围内普遍发生,为害柑橘面积1.6万hm2。2005年为害严重,发生面积达2.1万hm2,局部约150hm2橘… 相似文献
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The Illinois soybean crop was monitored in 1965, 1966, 1967, 1971, and 1974 for dieldrin residues resulting from aldrin applied to corn in the years before soybean cultivation. Residue levels of dieldrin in soybeans increased between 1965 and 1974. The percent of fields which had soybeans with a dieldrin level above 0.03 ppm increased between 1965 and 1974. Dieldrin residue levels in soybeans grown in Illinois are expected to decline now that the use of aldrin has diminished and will soon cease. No significant correlation was evident between the dieldrin levels in soybeans and the area of the State where they had grown, the date of planting, or the variety. 相似文献
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W. D. Smilde M. van Nes H. D. Frinking 《European journal of plant pathology / European Foundation for Plant Pathology》1996,102(7):687-695
Cardinal temperatures for mycelial growth ofPhytophthora porri on corn-meal agar were <5 (minimum), 15–20 (optimum) and just above 25 °C (maximum). The number of infections after zoospore inoculation of young leaf plants was relatively low at supra-optimal temperatures, but was not affected by sub-optimal temperatures. Even at 0 °C plants were infected. The incubation periods needed for symptom formation were 36–57 d at 0 °C, 13–18 d at 5 °C, and 4–11 d at > 11 °C, and were fitted to temperature between 0 and 24 °C with a hyperbolical model (1/p=0.00812*T+0.0243). Oospore germination, reported for the first time forP. porri, was strongly reduced after 5 h at 45 °C, and totally absent after 5 h at 55 °C. Soil solarization for six weeks during an exceptionally warm period in May–June 1992 in The Netherlands raised the soil temperature at 5 cm depth for 17 h above 45 °C, but did not reduce the initial level of disease in August significantly. 相似文献
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Mercury, arsenic, and cadmium in fish, water, and sediment of American Falls Reservoir, Idaho, 1974.
Mercury and cadmium were found in fish, water, and sediment of American Falls Reservoir (AFR), Idaho. Mercury and cadmium levels in some fish exceeded human health standards set by the Food and Drug Administration, U.S. Department of Health, Education and Welfare, and the World Health Organization. Analyses performed on the flesh of rainbow trout showed mercury residues of up to 1.20 mg/kg, which were higher than residues previously reported in trout collected in 1970 and 1971 from AFR. Cadmium residue levels were as high as 0.80 mg/kg. Although arsenic was found in reservoir sediment at levels of 1.36-2.40 mg/kg, it was not detected in fish. 相似文献
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Joel R. Coats Robert L. Metcalf Inder P. Kapoor 《Pesticide biochemistry and physiology》1974,4(2):201-211
Dianisylneopentane or 1,1-bis(p-methoxyphenyl)-2,2-dimethylpropane was metabolized largely by O-demethylation to form mono- and diphenol derivatives. Only a small percentage was degraded by α-hydroxylation and rearrangement. In the model ecosystem, dianisylneopentane reacted very similarly to methoxychlor, accumulating in fish to about the same extent and yielding a slightly higher ratio of polar to nonpolar metabolites. The neopentyl group proved to be approximately as stable in biological systems as the isosterically equivalent trichloromethyl group. 相似文献
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ABSTRACT Monilinia fructicola, which causes brown rot in stone fruit, forms appressoria on plant and artificial surfaces. On nectarine, the frequency of appressoria produced by conidial germlings depends to a large degree on the stage of fruit development, with numerous appressoria formed on immature (stage II) nectarine fruit, and no appressoria observed on fully mature fruit (late stage III). On polystyrene surfaces, appressorium formation was increased from <10% of germinated conidia to >95% of germinated conidia when the conidia were washed to remove residual nutrients and self-inhibitors. M. fructicola appressorium formation also appears to be regulated by the topography of the plant surface. On fruit, appressoria formed on stomatal guard cell lips, on the grooves of lateral cells adjacent to stomata or between two epidermal cells, and on the convex surfaces of epidermal cells. Pharmacological effectors indicate that cyclic AMP-, MAP kinase-, and calcium/calmodulin-dependent signaling pathways are involved in the induction and development of appressoria. KN-93, an inhibitor of calmodulin-dependent protein kinase II, did not inhibit conidial germination but did inhibit appressorium formation and brown rot development on flower petals, suggesting that appressoria are required for full symptom development on Prunus spp. petals. 相似文献
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绝大多数啮齿动物种类为植食性的小型哺乳动物，其生物学特性导致了鼠类危害的复杂性。当前，面对日益提高的生态安全需求，粮食安全、人民健康和生物安全以及生态安全对鼠害控制需求的差异造成了中国鼠害防控策略制定及实施的困扰。尤其在草原地区，如何在应急性灭杀和长效缓控之间找到一个平衡点是目前鼠害防控面临的一个巨大挑战。针对这些矛盾和挑战，该文分析了我国鼠害监测防控的现状、主要瓶颈与短板，并从技术层面提出“精准监测指导精准防控”可能会是解决这些矛盾的有效途径，是在有效控制鼠害暴发对粮食生产和人民健康安全威胁的前提下，推进生态保护和修复的有效途径。 相似文献
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Organochlorine residues of TDE, DDE, and PCBs as high as 1.96, 2.79, and 28.74 microgram/kg, respectively, have been found in sediments of American Falls Reservoir, Idaho. Residues of TDE, DDE, and dieldrin in the flesh of sport fish were as high as 52.3, 67.2, and 160.4 microgram/kg, respectively. Maximum organochlorine residue levels found in sucker taken in the commercial fishery were 1.1 mg PCBs/kg, 781.7 microgram TDE/kg, and 82.1 microgram DDE/kg. 相似文献
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The rust fungus Maravalia cryptostegiae , from south-west Madagascar, was introduced into Australia in 1995 as a classical biological control agent against the highly invasive rubber-vine weed Cryptostegia grandiflora , a woody climber endemic to Madagascar. The rust was released at 69 sites between 1995 and 1997 and is now established throughout the plant's exotic range in Queensland, estimated at over 40 000 km2 . Dispersal was low in the first 3–4 months but was virtually linear thereafter, and the rust spread over 100 km within the first year; after 3 years it was recorded 550 km away from the nearest release site. Spraying both dry and aqueous inoculum of uredinioid teliospores from the ground using mist-blowers, as well as from the air by atomizing spore suspensions, resulted in rust-induced defoliation, producing an overall reduction in fecundity and biomass of the weed. In sites with low water tables, weed growth decreased markedly, with a reduction in plant volume from 9 m−3 to 1 m−3 over a 4-year period. Both rust- and drought-induced stress combined to cause up to 75% plant mortality at some sites, and at all monitored sites, seedling recruitment was virtually nil. Improved growth of indigenous grasses amongst rubber-vine thickets has increased fuel loads and created opportunities to use fire as a component of an integrated approach to the management of this economically and ecologically damaging weed. 相似文献
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Five soils with different organic matter contents ranging from 0.48 to 10.4% were used to study the adsorption and desorption of alachlor, metolachor, EPTC, chlorothalonil and pirimiphos-methyl in batch experiments. The isotherm shapes according to Giles classification were S-type for alachlor, metolachlor and chlorothalonil, changing to L-type for the latter as the level of soil organic matter increased, and L-type for EPTC and pirimiphos-methyl. The adsorption isotherms fitted the Freundlich equation x/m = KfCe1/n. The Kf values increased with the increase of organic matter content. The amounts of pesticides adsorbed over a range of concentrations of 0.1-20 mg litre-1 reached 63.1% for alachlor, 69.2% for metolachlor, 89.3% for EPTC, 98.4% for chlorothalonil and 96.3% for pirimiphos-methyl. The increase of the amounts desorbed with acetone indicated that the sorption of organic compounds onto organic matter occurred principally via weak London-type induction forces, or dispersion forces which are characteristics of the physical adsorption process. 相似文献