The pyrethrins and related compounds. Part XXXVIII—optimisation of insecticidal activity in 3-[(alkoxyimino)methyl]-4-fluorobenzyl esters

Optimisation of activity in 3-[(alkoxyimino)methylbenzyl] esters has been investigated by introducing an α-cyano group and a fluorine atom in position 4 of the benzylic moiety in conjunction with varying the length and nature of the side chain. Of the five side-chain variations investigated, the 3-methoxyiminomethyl was more effective than others. Introduction of fluorine in position 4 of the benzylic moiety generally increased activity, particularly against mustard beetles, as in previous instances. Surprisingly, the effect on insecticidal activity of introducing an α-CN group ranged from positive to negative depending upon the nature of the alkoxyimino substituent, an effect not observed previously. The most effective esters were derived from α-cyano-4-fluoro-3-[(methoxyimino)methyl]benzyl alcohol, which was synthesised from 2-{4-fluoro-3-[(hydroxyimino)methyl]phenyl}-1,3-dioxolane.     

Chemical Control of Phalaris minor and Avena ludoviciana in Wheat

Abstract

In field experiments conducted at the Punjab Agricultural University, Ludhiana during 1973–74 and 1974–75, pre-emergence application (one day after sowing) of methabenzthiazuron (1.05 kg a.i./ha), metoxuron (1.6 kg a.i./ha) and chlortoluron (0.75 kg a.i./ha) gave effective control of Phalaris minor and Avena ludoviciana in wheat without any phytotoxic effect on the crop. Methabenzthiazuron, metoxuron and chlortoluron gave 1410, 1420 and 1090 kg/ha, respectively, more grain than the unweeded crop and 590, 600 and 270 kg/ha more than the crop hand-weeded twice. Nitrofen (1.25 kg a.i./ha) applied pre-emergence was effective against P. minor only and gave substantial increase in grain yield. Terbutryne, dichlormate and linuron, while effective against P. minor, also had a phytotoxic effect on the crop.     

Cotton whitefly (Bemisia tabaci) resistance to organophosphate and pyrethroid insecticides in Pakistan

Resistance to three organophosphate and four pyrethroid insecticides was monitored from 1992 to 2000 in field populations of adult whiteflies, Bemisia tabaci, from Pakistan using a leaf-dip method. There was generally a very high resistance to dimethoate and deltamethrin, and a moderate resistance to monocrotophos during 1992 to 1996. From 1997 to 2000, resistance to these insecticides dropped to low levels because of less reliance on them for whitefly control, and introduction of new chemistries with novel modes of action that had no cross-resistance to conventional insecticides. Concurrently, whitefly resistance to acephate, fenpropathrin, lambda-cyhalothrin and bifenthrin mostly remained low. An insecticide resistance management strategy is recommended that particularly emphasizes the rotation of still-effective insecticides from different chemical classes along with the use of novel chemicals and other tactics of integrated pest management.     

渔业水质中拟除虫菊酯农药残留的气相色谱分析

建立渔业水质中七氟菊酯、联苯菊酯、甲氰菊酯、三氟氯氰菊酯、氯菊酯、氟氯氰菊酯、氯氰菊酯、氰戊菊酯、氟胺氰菊酯、溴氰菊酯10种拟除虫菊酯残留的分析方法。样品以石油醚萃取、无水硫酸钠脱水、减压浓缩后用气相色谱-电子捕获检测器(GC-ECD)测定。七氟菊酯在2.5～100ng/mL、其它9种菊酯在5～200ng/mL内线性关系良好(r≥0.9954);0.05μg/L、0.5μg/L、1μg/L添加浓度水平的回收率在73.8%～100.2%之间,相对标准偏差(RSD)为2.53%～10.3%;检出限(LOD)为0.125～2.5ng/L,最低定量限(LOQ)为0.025～0.05μg/L。该方法简单快速、准确可靠,能满足渔业水质拟除虫菊酯污染的检测要求。     

不同抗性水平家蝇对有机磷、拟除虫菊酯等药剂的交互抗性研究

报道对辛硫磷和溴氰菊酯具有不同抗性水平的家蝇对有机磷、拟除虫菊酯及其他药剂的交互抗性情况和生化机制。处于高抗（R／S为625）和极高抗（R／S为547276）水平的抗溴氰菊酯家蝇、以及处于中抗（R／S为21．89）和高抗（R／S为310．72）水平的抗辛硫磷家蝇,对DDT及拟除虫菊酯类药剂均表现出明显的交互抗性;处于高抗和极高抗的抗溴氰菊酯家蝇以及处于中抗的抗干硫磷家蝇,对灭多威、abamectin及有机磷类药剂均不表现交互抗性;但处于高抗的抗辛硫磷家蝇则对有机磷类药剂表现出中等水平的交互抗性,对灭多威和abamectin无交互抗性。离休酶系分析结果表明,不同抗性水平家蝇的交互抗性情况不同,这与家蝇体内酯酶、多功能氧化酶、谷胱甘肽-S-转移酶和乙酸胆碱酯酶的酶活或特性存在差异有关。     

The Pyrethrins and Related Compounds. Part XLI. Structure–Activity Relationships in Non-ester Pyrethroids against Resistant Strains of Housefly (Musca domestica L.)

A series of pyrethroids, related to NRDC 200 and etofenprox (MTI500) in which the central region is represented by a non-ester link, have been tested against one susceptible and two resistant strains (kdr and super-kdr) of houseflies (Musca domestica L.). A range of structural variations in the central region have been examined. Resistance factors mostly fell within narrow ranges for both resistant strains i.e. 10–50-fold resistance against kdr and 50–150-fold against super-kdr; thus no correlation of resistance with structural features was detectable for this region. Other changes examined were the substituent on the phenyl ring in the ‘acid’ component and the bridging group in the ‘alcohol’ component where small variations in response were observed. Examination of the effect of varying the ‘alcohol’ side chain was limited by lack of active analogues.