甲酸乙酯熏蒸菜豆象的初步研究

本文利用广口瓶密闭熏蒸法,测定了不同浓度、时间和温度条件下甲酸乙酯对菜豆象的熏蒸效果。结果表明:选用浓度为45μL/L处理24 h或50μL/L处理12 h,均能使其成虫达到90%以上的死亡率,说明甲酸乙酯具有良好的速效性;菜豆象的熏蒸效果随熏蒸浓度的增加、温度的升高和时间的延长而逐渐增强;各虫态耐药性比较表明:甲酸乙酯浓度的高低对菜豆象各虫态耐药性影响较大,低浓度下卵的耐药性最差,而高浓度下成虫和卵的耐药性最差。     

甲酸乙酯对米象不同虫态的熏蒸作用

针对储粮害虫抗药性日趋严重、粮食熏蒸剂品种越来越少的现状,采用密闭熏蒸法,系统研究甲酸乙酯（EtF）在不同条件下对米象Sitophilus oryzae（L.）卵、低龄幼虫、高龄幼虫、蛹以及成虫的致死作用.在25℃条件下以40和45μL/L的药剂浓度处理米象成虫12h,其校正死亡率分别为90.541%和99.324%;以30μL/L的浓度在19、25和31℃下处理24h,校正死亡率分别为83.108%、62%和42%,表明甲酸乙酯具有良好的速效性,且在相对低温时比在相对高温时熏蒸效果好.在20、25和30℃条件下,熏蒸处理米象成虫24h,其LC50分别为25.094、28.650和30.875μL/L;处理48 h时则分别为23.101、25.805和27.316μL/L.30g/m^3的甲酸乙酯熏蒸处理米象卵、低龄幼虫、高龄幼虫和蛹24 h,对应死亡率为96.930%、99.333%、97.768%和93.386%,表明甲酸乙酯对米象低龄幼虫的熏蒸效果最好,蛹和卵对甲酸乙酯具有较高的耐药性.     

甲酸乙酯对面粉中赤拟谷盗的熏蒸效果

本文研究了甲酸乙酯对面粉中赤拟谷盗不同虫态的熏蒸作用。通过对熏蒸期间熏蒸剂浓度检测,计算浓度时间乘积(CT)计算不同时间下甲酸乙酯对赤拟谷盗各虫态达到99%控制的处理指标(Lct_(99))。结果表明甲酸乙酯熏蒸能有效防治面粉中的赤拟谷盗各虫态,赤拟谷盗不同虫态对甲酸乙酯的敏感性由强到弱依次为:卵>低龄幼虫>成虫>高龄幼虫>蛹。在23℃条件下处理6h和12h对面粉中赤拟谷盗的Lct_(99)分别为448.42和599.34mg·h/L     

甲酸乙酯对三种主要仓储害虫的熏蒸作用

为明确甲酸乙酯对仓储害虫的实际控制效果,避免二氧化碳对熏蒸作用的影响,该研究利用循环熏蒸系统(FTFS),测定甲酸乙酯对米象、赤拟谷盗、谷蠹三种主要仓储害虫混合虫态的熏蒸作用.结果表明:在25℃、70%RH条件下,甲酸乙酯43.34、80.72、99.08、117.74、146.49mg/L 熏蒸处理6 h,对赤拟谷盗和谷蠹混合虫态有很好的控制作用,死亡率大于95.96%;甲酸乙酯80.72、99.08、117.74、146.49mg/L处理对米象混合虫态的杀虫效果较好.甲酸乙酯对米象蛹的杀虫效果较差.     

甲酸乙酯对米象乙酰胆碱酯酶和羧酸酯酶的影响

报道了甲酸乙酯对米象[Sitophilus oryzae(Linnaeus)]乙酰胆碱酯酶(AChE)和羧酸酯酶(CarE)的活性影响,甲酸乙酯对米象表现出很高的毒力,25℃下熏蒸处理24 h的LC₅₀为28.65μL/L。亚致死剂量的甲酸乙酯可以使米象成虫体内AChE的比活力显著下降,用20μL/L的浓度处理24 h,AChE的比活力由15.684 nmol/mg.min下降至9.530 nmol/mg.min;酶动力学研究表明,甲酸乙酯可使米象成虫体内AChE的K_m值明显增加。对于羧酸酯酶,在活体条件下表现为先抑制后激活的规律,离体条件下则主要表现为抑制作用,且随着药剂浓度的增大抑制率也增大。     

氯甲酸乙酯尾气综合利用的研究

氯甲酸乙酯生产过程中,光气过量约5％～20％,使用氯甲酸乙酯和乙醇混合物吸收尾气,通过调节反应温度、氯甲酸乙酯与乙醇配比、反应时间,吸收尾气制得的氯甲酸乙酯含量在98％以上.     

甲酸乙酯对不同磷化氢抗性水平赤拟谷盗的毒力比较

参考FAO推荐的熏蒸剂毒力测定方法,测定了甲酸乙酯对4种不同磷化氢抗性水平的赤拟谷盗(Tribolium castaneum(Herbst))品系的毒力.主要结果为甲酸乙酯对4个磷化氢抗性系数分别为1、3、170和247倍的赤拟谷盗品系的LD50值相应地为17.354L/m3、18.776L/m3、20.464L/m3和21.470 mL/m3.结果表明,不同磷化氢抗性的赤拟谷盗品系对甲酸乙酯的敏感相似,对磷化氢具有明显抗性的赤拟谷盗对甲酸乙酯未表现出抗性.     

施药方法对草克星除稗效果的影响

草克星(Pyrazosulfuron—ethyl)在很低剂量下(1～2克/亩)就能很好地防除稻田多种杂草,但对稗草的防效低于其他杂草。实验采用盆栽法测定了影响药剂除稗的因素。     

豇豆闭花前后施药对防治蓟马效果的影响

蓟马是当前海南豇豆的头号害虫,防治主要依赖化学药剂。通过试验研究了分别在豇豆闭花前、后施药对于防治蓟马效果的影响,以确定施药适期。结果表明,豇豆闭花影响药剂的防治效果。与闭花后施药的防效相比,闭花前施用60 g/L乙基多杀菌素悬浮剂,药后第1、3天和7天的防效分别提高了4.76、4.30和3.03百分点;闭花前施用20%啶虫脒可溶性液剂,药后第1、3天和7天的防效分别提高了3.50、3.29和5.31百分点。两种药剂以乙基多杀菌素防效较高。     

不同时期施药对冬小麦田间杂草防除效果的影响

麦田杂草防除效果差是长期困扰江苏张家港地区小麦种植户的问题。笔者选取5种当地市售常用除草剂,比较在不同时期(播后封闭、冬前茎叶喷雾和春季茎叶喷雾)施用的除草效果。结果表明,使用封闭除草剂对田间杂草有明显的抑制作用,仅使用茎叶喷雾除草对杂草抑制效果有限,封闭配合茎叶喷雾处理,对麦田杂草的防除效果更显著。无论是否采用封闭除草,春季使用茎叶除草剂的效果都要优于冬季。除草剂的使用能显著提高小麦产量。因此,结合当地实际,"一封一杀"即小麦播后7 d内进行封闭除草,春季再进行1次茎叶除草具有除草效果好、经济、易操作等优点,值得在当地麦田大力推广应用。     

Efficacy of vaporised ethyl formate/carbon dioxide formulation against stored‐grain insects: effect of fumigant concentration,exposure time and two grain temperatures

BACKGROUND: The ethyl formate/carbon dioxide (CO₂) formulation Vapormate? is a rapid‐acting fumigant being developed for the control of stored‐grain insects. The effects have been investigated of concentration, exposure times of 1, 3, 24 and 72 h and two grain temperatures, 15 and 25 °C, on its efficacy against mixed‐stage cultures of Sitophilus oryzae (L.) Tribolium castaneum (Herbst) and strongly phosphine‐resistant Rhyzopertha dominica (F.) strain QRD569. RESULTS: High mortalities (≥92%) of mixed‐stage cultures of all three species were obtained when grain was fumigated with the formulation (193 g m^?3 ethyl formate) for 1 h. Complete control of R. dominica QRD569 and T. castaneum was achieved with 63 and 76 g m^?3 ethyl formate respectively, with exposure for 24 h, whereas mean mortality of S. oryzae was 86% under the same conditions. Mortalities of S. oryzae juvenile stages were significantly lower than adults under the conditions tested, which was due to pronounced tolerance of mid‐stage pupae to the fumigant. Reducing grain temperature from 25 to 15 °C had no effect on insect mortality. CONCLUSION: Ethyl formate/CO₂ formulation is highly effective against stored‐grain insects over a range of concentrations and exposure times. Efficacious fumigations were conducted in as little as 1 h, and a strongly phosphine‐resistant R. dominica strain was readily controlled with the fumigant. Copyright © 2009 CSIRO, Australia. Published by John Wiley & Sons, Ltd     

Detection and characterisation of strong resistance to phosphine in Brazilian Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae)

As failure to control Rhyzopertha dominica (F.) with phosphine is a common problem in the grain-growing regions of Brazil, a study was undertaken to investigate the frequency, distribution and strength of phosphine resistance in R. dominica in Brazil. Nineteen samples of R. dominica were collected between 1991 and 2003 from central storages where phosphine fumigation had failed to control this species. Insects were cultured without selection until testing in 2005. Each sample was tested for resistance to phosphine on the basis of the response of adults to discriminating concentrations of phosphine (20 and 48 h exposures) and full dose-response assays (48 h exposure). Responses of the Brazilian R. dominica samples were compared with reference susceptible, weak-resistance and strong-resistance strains from Australia in parallel assays. All Brazilian population samples showed resistance to phosphine: five were diagnosed with weak resistance and 14 with strong resistance. Five samples showed levels of resistance similar to the reference strong-resistance strain. A representative highly resistant sample was characterised by exposing mixed-age cultures to a range of constant concentrations of phosphine for various exposure periods. Time to population extinction (TPE) and time to 99.9% suppression of population (LT(99.9)) values of this sample were generally similar to those of the reference strong-resistance strain. For example, at 0.1, 0.5 and 1.0 mg L(-1), LT(99.9) values for BR33 and the reference strong-resistance strain were respectively 21, 6.4 and 3.7 days and 17, 6.2 and 3.8 days. With both strains, doubling phosphine concentrations to 2 mg L(-1) resulted in increased LT(99.9) and TPE. High level and frequency of resistance in all population samples, some of which had been cultured without selection for up to 12 years, suggest little or no fitness deficit associated with phosphine resistance. The present research indicates that widespread phosphine resistance may be developing in Brazil. Fumigation practices should be monitored and resistance management plans implemented to alleviate further resistance development.     

Gamma radiation susceptibility of strains of Tribolium castaneum (Herbst) resistant and susceptible to fenvalerate

Gamma radiation susceptibility of adults of the fenvalerateresistant strain of Tribolium castaneum (Herbst) (Coleoptera : Tenebrionidae) was studied under laboratory conditions. Selection for resistance to fenvalerate in adult beetles was carried out up to the sixth generation. In each generation of selection, adults of the fenvalerateresistant strain were evaluated for susceptibility to gamma radiation and compared with their fenvalerate-susceptible counterparts. Susceptibility to 60Co gamma radiation was evaluated on the basis of dosage-mortality (LD) and time-mortality (LT) responses. We found the LD values 50 50 50 for the fenvalerate-resistant and-susceptible strains to be 89.16 and 97.46 Gy respectively, showing no significant difference in susceptibility to gamma radiation. LT values were 7.58 and 17.20 days for the 50 fenvalerate-resistant and-susceptible strains respectively, showing that mortality in the resistant strain occurred markedly earlier than in the susceptible strain.     

Influence of grain type on the insecticidal efficacy of two diatomaceous earth formulations against Rhyzopertha dominica (F) (Coleoptera: Bostrychidae)

Laboratory bioassays were carried out in order to evaluate the effectiveness of two diatomaceous earth (DE) formulations, Insecto and SilicoSec, against adults of Rhyzopertha dominica (F) in eight different grain commodities. The adherence of the two DEs to each grain was also measured. The eight grains tested were wheat, whole barley, peeled barley, oats, rye, triticale, rice and maize. These commodities were treated with the DEs at three rates, 0.75, 1.0 and 1.5 g DE kg(-1) grain. The mortality of R dominica adults was measured after 24 h, 48 h, 7 days and 14 days of exposure in the treated grains at 26 degrees C and 55% RH. After the 14-day mortality count, all adults were removed and the treated grains retained under the same conditions for a further 60 days. The treated grains were subsequently examined for F1 progeny. Significant differences were recorded among the eight grain types as well as between the DE formulations tested. After 14 days of exposure, even at the lowest DE rate for both formulations, adult mortality was high (>90%) in wheat and triticale. In contrast, adult mortality was significantly lower in peeled barley. Increasing the rate improved the efficacy of the DEs significantly in only some of the grains tested. Reproductive capacity in all the treated grains was significantly suppressed when compared with untreated grains. Generally, more F1 individuals of R dominica were noted in the treated peeled barley than in the other commodities. Significant differences in the percentage of DE retention were noted among the eight grains. The highest retention level was noted in rice (>87%) and the lowest in maize (<6%). However, the degree of DE adherence to a given grain was not always indicative of the effectiveness of DE against R dominica.     

Efficacy of Artocarpus altilis (Parkinson) Fosberg extracts on contact mortality,repellency, oviposition deterrency and fumigant toxicity of Callosobruchus maculatus (F.) (Coleoptera:Bruchidae)

Callosobruchus maculatus (F.), a major pest of grain legumes, causes considerable losses worldwide. C. maculatus management relies on synthetic insecticides with their adverse environmental and health concerns. The current study investigated the use of Artocarpus altilis (breadfruit) extracts on contact and fumigant toxicity, repellency and oviposition deterrency of C. maculatus as a management strategy. Fumigant mortality (LC₅₀) of the dry inflorescence extract of A. altilis was 126.65 µL L^?1 air at 53.4 h. Fruit extract gave 73.3% repellency at 1000 ppm after 24 h. Percent repellency was dose and time dependent. Green inflorescence extract of A. altilis reduced egg laying with 50% oviposition occurring after 37.78 h at 1000 ppm. We conclude that extracts of leaf, fruit, green and dried inflorescence of A. altilis displayed contact mortality, repellency, deterred oviposition and had fumigant activity toward C. maculatus.     

水稻大螟施药技术的探讨

水稻大螟药剂防治协作研究的结果表明,杀虫双防治二代枯心,适宜在卵孵高峰后5d施药,防治三代白穗应在水稻破口5%～10%时施药。施药方法,以手动喷雾和泼浇的效果最好,施药时要适当加大用水量,田间应保持水层。     

Effect of exposure period on degree of dominance of phosphine resistance in adults of Rhyzopertha dominica (Coleoptera: Bostrychidae) and Sitophilus oryzae (Coleoptera: Curculionidae)

Degree of dominance of phosphine resistance was investigated in adults of Rhyzopertha dominica F and Sitophilus oryzae L. Efficacy of the grain fumigant phosphine depends on both concentration and exposure period, which raises the possibility that dominance levels vary with exposure period. New and published data were used to test this possibility in adults of R dominica and S oryzae fumigated for periods of up to 144 h. The concentrations required for control of homozygous resistant and susceptible strains and their F1 hybrids decreased with increasing exposure period. For both species the response lines for the homozygous resistant and susceptible strains and their F1 hybrids were parallel. Therefore, neither dominance level nor resistance factor was affected by exposure period. Resistance was incompletely recessive and the level of dominance, calculated at 50% mortality level, was -0.59 for R dominica and -0.65 for S oryzae. The resistant R dominica strain was 30.9 times more resistant than the susceptible strain, compared with 8.9 times for the resistant S oryzae strain. The results suggest that developing discriminating doses for detecting heterozygote adults of either species will be difficult.