Potential enhancement of degradation of the nematicides aldicarb,oxamyl and fosthiazate in UK agricultural soils through repeated applications

BACKGROUND: The potential for enhanced degradation of the carbamoyloxime nematicides aldicarb and oxamyl and the organophosphate fosthiazate was investigated in 35 UK agricultural soils. Under laboratory conditions, soil samples received three successive applications of nematicide at 25 day intervals. RESULTS: The second and third applications of aldicarb were degraded at a faster rate than the first application in six of the 15 aldicarb‐treated soils, and a further three soils demonstrated rapid degradation of all three applications. High organic matter content and low pH had an inhibitory effect on the rate of aldicarb degradation. Rapid degradation was observed in nine out of the ten soils treated with oxamyl. In contrast, none of the fosthiazate‐treated soils demonstrated enhanced degradation. CONCLUSION: The potential for enhanced degradation of aldicarb and oxamyl was demonstrated in nine out of 15 and nine out of ten soils respectively that had previously been treated with these active substances. Degradation of fosthiazate occurred at a much slower rate, with no evidence of enhanced degradation. Fosthiazate may provide a useful alternative in cases where the efficacy of aldicarb and oxamyl has been reduced as a result of enhanced degradation. Copyright © 2009 Society of Chemical Industry     

噻唑膦在西瓜及土壤中的残留动态研究

为评价噻唑膦在西瓜上的残留动态并制定合理的使用方法,在天津、南京两地同时进行了噻唑膦在西瓜上的残留动态试验。结果表明,在试验条件下,噻唑膦在西瓜中无明显消解规律,在土壤中的半衰期为8.9～9.3d;噻唑膦在西瓜(全果)中的最终残留量为未检出～0.020mg·kg-1,瓜皮中的最终残留量为未检出～0.030mg·kg-1,瓜肉中的最终残留量均为未检出。10%噻唑膦颗粒剂在西瓜上合理使用方法为:以2250～3000g(a.i.)·hm-2,土壤撒施1次,噻唑膦在西瓜中最高残留限量(MRL值)推荐值为0·5mg·kg-1。     

噻唑磷在甘蔗和土壤中的残留消解动态及风险评估

建立了噻唑磷在甘蔗和土壤中的残留分析方法,并在广东和广西2地进行了10%噻唑磷颗粒剂在甘蔗上残留的田间试验,研究了噻唑磷在甘蔗和土壤中的消解动态和最终残留量,并对甘蔗中噻唑磷可能产生的膳食摄入风险进行了评估。甘蔗样本用乙腈提取,氨基固相萃取小柱净化,采用气相色谱-火焰光度检测器 (GC-FPD) 检测。结果表明:在0.01、0.1和1 mg/kg添加水平下,噻唑磷在甘蔗中的平均回收率为83%～84%,相对标准偏差 (RSD) 为2.6%～3.4%;在土壤中的平均回收率为84%～86%,RSD为4.1%～6.7%。噻唑磷检出限 (LOD) 和定量限 (LOQ) 均为0.01 mg/kg。田间试验结果表明:10%噻唑磷颗粒剂在广东和广西甘蔗中的消解不符合一级反应动力学方程,没有显著的消解规律,呈现的特点是浓度由小到大再变小的趋势,施药后14～21 d甘蔗中噻唑磷的残留量达到最大值0.027 mg/kg;噻唑磷在土壤中消解符合一级反应动力学方程,半衰期为8.6～9.6 d,属易降解农药;噻唑磷在甘蔗和土壤中的最终残留量均小于0.01 mg/kg。膳食摄入风险评估结果表明:甘蔗中噻唑磷对人群的急性膳食摄入风险值为225%,急性膳食摄入风险较大,还需进一步结合噻唑磷在人体内的代谢行为等数据进行综合评估;慢性膳食摄入风险值为57%,表明按照推荐剂量施用10%噻唑磷颗粒剂,慢性膳食摄入风险较低,对消费者健康是安全的。     

土壤药剂处理结合阳光消毒防治番茄根结线虫技术评价

为了筛选安全、高效、实用的化学防治技术,对国内外生产的5种杀线虫剂(棉隆、1,3 二氯丙烯·氯化苦、威百亩、噻唑磷、溴甲烷)土壤处理结合阳光消毒防治番茄根结线虫的效果进行了评价。结果表明,使用98%棉隆微粒剂450 kg/hm2或10%噻唑磷颗粒剂30 kg/hm2防治番茄根结线虫(Meloidogyne incognita),结合夏季高温进行阳光消毒,能有效地降低番茄根结线虫的数量,减轻根结线虫的危害程度,节省农户的生产成本,提高番茄的产量和农户的经济效益,是夏季防治番茄根结线虫的有效措施。     

精异丙甲草胺对小麦药害及其安全剂解毒作用初步研究

为了探索精异丙甲草胺在小麦田的应用技术,室内研究了精异丙甲草胺对小麦的安全性,对安全剂进行筛选,并对安全剂作用机制进行初步研究。结果表明,精异丙甲草胺对小麦的生长抑制作用随着土壤含水量增大及温度的下降而上升。对4种安全剂进行筛选,结果表明,解草酮0.5、5g/kg种子处理能够显著降低精异丙甲草胺对小麦的药害,解草啶、二氯丙烯胺、苯叉酰胺在低剂量下能够一定程度缓解精异丙甲草胺药害,但高剂量无缓解作用。进一步研究表明,解草酮0.5~4g/kg种子处理能够有效降低精异丙甲草胺150~600g/hm2(有效成分含量)造成的小麦药害,缓解率均在20%以上,其中1g/kg解草酮种子处理缓解效果最好,提高小麦对精异丙甲草胺的耐药性可达4倍以上。生理指标测定结果表明,解草酮1g/kg种子处理可显著提高小麦出苗期(播后4~6d)GSTs比活力,而GSH含量与对照相当或降低。表明解草酮可能通过提高小麦GSTs活力来增强GSH对精异丙甲草胺的轭合代谢作用,而非通过增加GSH含量来提升精异丙甲草胺降解。     

光合细菌菌剂与噻唑膦协同使用对水稻根结线虫病防治研究

水稻根结线虫病近年来对我国的水稻生产造成了严重危害.探索低成本、高效安全的水稻根结线虫病防治方法对减少其危害具有极其重要的意义.本研究通过田间小区试验评价了光合细菌微生物菌剂与噻唑膦协同使用对水稻根结线虫病的防治效果及对水稻生产的影响.结果 显示,利用光合细菌微生物菌剂1 L/667m2与10％噻唑膦GR0.10 kg...     

防治黄瓜根结线虫的药剂筛选及防控技术研究

[目的]筛选能够有效防治黄瓜根结线虫的药剂。[方法]通过大田试验研究了10%噻唑膦GR、0.5%阿维菌素GR、10.5%阿维菌素·噻唑膦GR对黄瓜根结线虫的防治效果,并提出了黄瓜根结线虫的防控技术。[结果]按有效剂量计,10.5%阿维菌素·噻唑膦GR 2 756.25和3 150.00 g/hm2、10%噻唑膦GR 3 000.00 g/hm2、0.5%阿维菌素GR 225.00和262.50 g/hm2对黄瓜根结线虫的防效分别为75.5%、82.0%、78.0%、72.4%和79.5%,可有效防治黄瓜根结线虫的发生,且对黄瓜安全。黄瓜根结线虫的防治应以"化防为主、多种防治相结合"为原则。[结论]为根结线虫的防治提供了参考。     

The synergistic advantage of combining chloropicrin or dazomet with fosthiazate nematicide to control root-knot nematode in cucumber production

The highly-damaging root-knot nematode(Meloidogyne spp., RKN) cannot be reliably controlled using only a nematicide such as fosthiazate because of increasing pest resistance. In laboratory and greenhouse trials, we showed that chloropicrin(CP) or dazomet(DZ) synergized the efficacy of fosthiazate against RKN. The combination significantly extended the degradation half-life of fosthiazate by an average of about 1.25 times. CP or DZ with fosthiazate reduced the time for fosthiazate to penetrate the RKN cuticle compared to fosthiazate alone. CP or DZ combined with low or medium rate of fosthiazate increased the total cucumber yield, compared to the use of each product alone. A low-dose fosthiazate with DZ improved total yield more than a low dose fosthiazate with CP. Extending the half-life of fosthiazate and reducing the time for fosthiazate or fumigant to penetrate the RKN cuticle were the two features that gave the fumigant-fosthiazate combination its synergistic advantage over these products used singularly. This synergy provides the opportunity for farmers to use a low dose of fosthiazate which lowers the risk of RKN resistance. Farmers could combine DZ at 30 g m~(-2) with fosthiazate at a low rate of 0.375 g m~(-2) to control RKN and adequately control two major soil-borne diseases in cucumber greenhouses.     

Factors affecting the efficacy of non-fumigant nematicides for controlling root-knot nematodes

Second-stage juveniles (J2) and egg masses of root-knot nematodes as well as root debris heavily infected by the latter were exposed for different periods of time to six different doses of the nematicides cadusafos and fenamiphos. The efficacy of the nematicides increased significantly with increasing exposure time. Both nematicides were more effective against J2, although they could not provide acceptable control of J2 inside egg masses or heavily galled root debris. The effect of different application strategies on the efficacy and persistence of certain nematicides was also assessed in a field study. Cadusafos, fenamiphos, fosthiazate and oxamyl were applied in field micro-plots either as a single full dose at the time of crop establishment or as multiple reduced-rate applications at 14-day intervals throughout the cropping period, and their efficacy and persistence were determined using bioassays and analytical studies. Fosthiazate was the most efficient nematicide studied, and this was mainly attributed to its long soil persistence. Oxamyl also provided adequate nematode control for the first 48-56 days after its application, regardless of the application method used and its relatively rapid field dissipation. Fenamiphos and cadusafos failed to provide adequate nematode control, although cadusafos was the most persistent of the nematicides tested. The failure of fenamiphos to provide adequate nematode control was mainly attributed to its rapid degradation by soil micro-organisms, which were stimulated after its repeated low-rate application at 14-day intervals. In contrast cadusafos failure was attributed to the inability of the nematicide to reduce nematode populations even at relatively high concentrations in soil.