The effect of piperonyl butoxide on pyrethroid-resistance-associated esterases in Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

Pyrethroid resistance in field populations of Australian Helicoverpa armigera (Hübner) is primarily a consequence of the overproduction of esterase isoenzymes which metabolise and sequester pyrethroid insecticides. Biochemical studies have shown that pyrethroid-resistance-associated esterases in H armigera are inhibited by the insecticide synergist piperonyl butoxide (PBO). Esterase inhibition by PBO did not occur immediately after dosing, but exhibited maximum inhibition 3-4 h after dosage. Esterase activity subsequently recovered until full activity was restored by 24 h. Topical bioassays using a pre-treatment of PBO showed that maximum H armigera mortality was achieved with pre-treatment times corresponding to maximum esterase inhibition. These results demonstrated that, with correct temporal application, PBO can restore pyrethroid efficacy against H armigera. It would also be expected that restoration of efficacy with other conventional insecticides, currently compromised by esterase-based resistance mechanisms, would occur.     

Inhibition of thiazopyr metabolism in plant seedlings by inhibitors of monooxygenases

Metabolism of the herbicide thiazopyr [methyl 2-(difluoromethyl)-5-(4, 5-dihydroO-lhiazo!vt)-4-(2-methylpropy!)-6-(trinuorornethyl)-3-pyridinecarboxy-late] was examined in young seedlings of redroot pigweed, grain sorghum, sunflower, corn and soybean. As previously observed with rat liver microsomes plants predominantly metabolized thiazopyr via oxidation reactions. Sulfur and carbon atoms in the thiazoline ring were the primary sites of plant oxygenases. De-esterification was also identified as an important pathway of transformations in plants. Although similar pathways of thiazopyr metabolism were observed among plants, our data indicated species differences in rates of thiazopyr degradation. Among species examined, pigweed (Amaranthus retroflexus L.) showed the fastest metabolism. Thiazopyr metabolism in pigweed was significantly inhibited by several cytochrome P450 monooxygenase inhibitors, among which tetcyclacis (TET) and piperonyl butoxide (PBO) were the most inhibitory. Thiazopyr metabolism in pigweed was not inhibited by organophosphates, known inhibitors of esterases. The results suggest that thiazopyr metabolism in plants is predominantly mediated via plant mono-oxygenases.     

70%增效型吡虫啉水分散粒剂的制备及其性能评价

采用滚动式挤压造粒法,通过配方筛选成功制备了70%增效型吡虫啉水分散粒剂(WG),并考察了增效剂胡椒基丁醚(PB)对制剂的热贮稳定性、表面张力及杀虫活性等性能的影响。优化配方(以质量分数计)为:吡虫啉原药(71.9%),增效剂PB(1.0%),分散剂MORWET-EFW(2.5%)、MORWET D-425或Tesperse 2700(5.0%),崩解剂硫酸铵(3.0%),粘结剂聚乙二醇(2.0%)和载体[m(白炭黑):m(高岭土)=1:4] 14.6%。所制备的70%增效型吡虫啉WG热贮(54℃±2 ℃)14 d后有效成分降解率为1.27%(≤1.5%);其表面张力无明显改变;润湿分散性良好,悬浮率≥90%。对蚜虫的室内毒力测定结果显示,含有PB的70%吡虫啉WG的毒力是不含PB成品的6～7倍,表明PB具有极显著的增效作用。     

Effects of piperonyl butoxide on Bemisia tabaci Genn. (Homoptera: Aleyrodidae): mortality, development, parasitism and predation in Israeli cotton fields

In field trials in Israel, piperonyl butoxide (PB) alone, at concentrations of 2000 and 5000 ppm exerted good control over nymphal Bemisia tabaci populations on cotton. Weekly doses of these concentrations exerted greater control than a recommended oil and were as effective as the standard single application of buprofezin. Cypermethrin caused marked resurgence within the plots, probably as a consequence of its detrimental effects on natural enemies. Neither PB, buprofezin nor the oil reduced the incidence of natural enemies. Treatment with 2000 or 5000 ppm PB resulted in a shift in age structure toward a greater proportion of young instars than in other treatments. There was some evidence that these effects facilitated a greater level of parasitism in PB-treated plots.     

细胞色素P450抑制剂对白腐菌Phlebia lindtneri降解氯丹的影响

为确定细胞色素P450酶系在白腐菌Phlebia lindtneri降解有机氯类农药氯丹中的作用,在液体培养条件下,以胡椒基丁醚和1-氨基苯并三唑作为细胞色素P450的抑制剂,分析了不同浓度抑制剂对氯丹的降解、代谢产物的生成以及中间代谢物降解的影响。结果表明:与对照相比,高浓度(1.0 mmol/L)胡椒基丁醚或1-氨基苯并三唑处理15 d后氯丹的降解率均下降了约60%,且其代谢产物中除七氯和二氯代六氯的检出量显著增加外,其余环氧化及羟基化代谢产物均未检出;此外,添加高浓度的抑制剂可导致白腐菌降解中间代谢产物七氯及二氯代六氯的降解率下降90%以上,氧化氯丹的降解率下降70%以上,但不影响环氧七氯的降解。表明细胞色素P450可能是氯丹降解的主要酶系,其参与催化了氯丹的初始羟基化和水解、七氯和二氯代六氯的环氧化及氧化氯丹的水解等多个反应过程。     

Molecular response of Musca domestica L. to Mintostachys verticillata essential oil, (4R)+-pulegone and menthone

Intense applications of synthetic insecticides for the control of adult Musca domestica have led to the insects developing resistance to most of them. In consequence, there is interest in new active ingredients as alternatives to conventional insecticides. Essential oils (EO) are potential tools for controlling M. domestica because of their effectiveness and their minimal environmental effects. In a fumigant assay, M. domestica adults treated with Minthostachys verticillata EO [LC(50)=0.5 mg/dm(3); majority components by SPME-GC: (4R)(+)-pulegone (67.5%), menthone (22.3%) and (4R)(+)-limonene (3.8%)], died within 15 min or less. The terpenes absorbed by the flies and their metabolites, analyzed using SPME fiber, were (4R)(+)-limonene (LC(50)=6.2 mg/dm(3)), menthone (LC(50)=1.9 mg/dm(3)), (4R)(+)-pulegone (LC(50)=1.7 mg/dm(3)) and a new component, menthofuran (LC(50)=0.3 mg/dm(3)), in a relative proportion of 12.4, 6.5, 35.9 and 44.2% respectively. Menthofuran was formed by oxidation of either (4R)(+)-pulegone or menthone mediated by cytochrome P450, as demonstrated by a fumigation assay on flies previously treated with piperonyl butoxide, a P450 inhibitor, which showed a decrease in toxicity of the EO, (4R)(+)-pulegone and of menthone, supporting the participation of the P450 oxidizing system in the formation of menthofuran. The enzymatic reaction of isolated fly microsomes with the EO or the (4R)(+)-pulegone produced menthofuran in both cases. Contrary to expectations, the insect detoxification system contributed to enhance the toxicity of the M. verticillata EO. Consequently, resistant strains overexpressing P450 genes will be more susceptible to either M. verticillata EO or (4R)(+)-pulegone and menthone.     

Temporal synergism can enhance carbamate and neonicotinoid insecticidal activity against resistant crop pests

BACKGROUND: Piperonyl butoxide (PBO) effectively synergises synthetic pyrethroids, rendering even very resistant insect pests susceptible, provided a temporal element is included between exposure to synergist and insecticide. This concept is now applied to carbamates and neonicotinoids. RESULTS: A microencapsulated formulation of PBO and pirimicarb reduced the resistance factor in a clone of Myzus persicae (Sulzer) from >19 000- to 100-fold and in Aphis gossypii (Glover) from >48 000- to 30-fold. Similar results were obtained for a strain of Bemisia tabaci Gennadius resistant to imidacloprid and acetamiprid, although a second resistant strain did not exhibit such a dramatic reduction, presumably owing to the presence of target-site insensitivity and the absence of metabolic resistance. Synergism was also observed in laboratory susceptible insects, suggesting that, even when detoxification is not enhanced, there is degradation of insecticides by the background enzymes. Use of an analogue of PBO, which inhibits esterases but has reduced potency against microsomal oxidases, suggests that acetamiprid resistance in whiteflies is largely oxidase based. CONCLUSION: Temporal synergism can effectively enhance the activity of carbamates and neonicotinoids against resistant insect pests. Although the extent of this enhancement is dependent upon the resistance mechanisms present, inhibition of background enzymes can confer increased sensitivity against target-site resistance as well as increased metabolism. .     

Temporal synergism by microencapsulation of piperonyl butoxide and alpha-cypermethrin overcomes insecticide resistance in crop pests

A microencapsulated formulation that gives a burst release of piperonyl butoxide (PBO) several hours before a burst release of a conventional pyrethroid can effectively overcome metabolic resistance in Bemisia tabaci Gennadius, Helicoverpa armigera (Hübner), Aphis gossypii Glover and Myzus persicae Sulzer. This increase in efficacy against resistant pests was reflected in a field trial against B. tabaci on cotton, eliminating the need for two treatments. The ratio between the active insecticide and the synergist was found to be crucial in reducing resistance factors.     

The effect of single, binary, and tertiary combination of few plant derived molluscicides alone or in combination with synergist on different enzymes in the nervous tissues of the freshwater snail Lymnaea (Radix) acuminata (Lamark)

The effect of single, binary, and tertiary combination of few plant derived molluscicides alone or in combination with synergist on different enzymes (acetylcholinesterase—AChE, lactic dehydrogenase—LDH, and acid/alkaline phosphatase—ACP/ALP in the nervous tissue of the freshwater snail Lymnaea acuminata were studied. Sublethal in vivo 24 h exposure to 40 and 80% of LC₅₀ of Azadirachta indica oil (AI), oleoresin of Zingiber officinale (OL), Cedrus deodara oil (CD), Allium sativum (AS), and Polianthes tuberosa (PT) bulb powder singly, their binary combination of AI + OL, AS + CD, AS + PT, CD + OL, CD + PT, OL + PT, and tertiary combination of these binary combinations with the synergist piperonyl butoxide (PB) or MGK-264 significantly altered the activity of these enzymes. Tertiary combination with PB or MGK was very effective. Combination of CD + PT + MGK was more effective against AChE whereas, the combination of CD + OL + PB, CD + AS + PB, and CD + PT + PB were more effective against LDH, ACP, and ALP, respectively.     

应用短程蒸馏技术提纯胡椒基丁醚

应用刮膜式短程蒸馏装置对胡椒基丁醚(piperonyl butoxide, PB)的提纯进行了研究。考察了进料速率、进料温度和蒸发温度等因素对胡椒基丁醚分离效果的影响。通过试验，初步得到了工艺参数的范围：进料温度70～92℃，进料速率50～70 mL/h，脱除轻组分杂质阶段蒸发温度I为90～94℃，脱除重组分杂质阶段蒸发温度II为98～107℃，操作压力0.1 Pa，刮膜转子转速130～150 r/min，得到的胡椒基丁醚产品纯度96%以上，分离过程总得率大于70%，并为今后工艺参数优化奠定了基础。