Laboratory evaluation of natural pyrethrins, pymetrozine and triflumuron as alternatives to controlCeratitis capitata adults

Three insecticides, pyrethrins + piperonil butoxide (PBO), pymetrozine and triflumuron, were tested as potential alternatives for controlling the Mediterranean fruit flyCeratitis capitata (Wiedemann) (Diptera: Tephritidae). The compounds were administered to adult flies in the laboratory by different uptake methods at the recommended rates currently used in fruit crops in Spain. Pyrethrins + PBO (80 + 320 ppm a.i.) exhibited a comparable knock-down effect to malathion (1,500 ppm a.i.) in the laboratory, irrespective of the method of application used. After these results were obtained, the number of concentrations tested was increased to carry out a dose-response analysis. Pymetrozine (300 ppm a.i.) and triflumuron (150 ppm a.i.) did not kill adults at the concentrations tested. However, pymetrozine diminished the fecundity, especially when adults were fed the insecticide; egg hatch was decreased by 59.3% compared with controls. Further experiments showed that increased period of ingestion and higher concentrations had a clear effect in reducing both fecundity and fertility. The possible use of pyrethrins + PBO and pymetrozine to reduce populations ofC. capitata is discussed. http://www.phytoparasitica.org posting July 22, 2006. Corresponding author     

Enhancement of thiazopyr bioefficacy by inhibitors of monooxygenases

The preceding paper described inhibition of thiazopyr metabolism in plant seedlings by inhibitors of cytochrome P450 monooxygenases, and the lack of inhibition by esterase inhibitors. We now describe greenhouse evaluation of the effects of these metabolic inhibitors on the bioefficacy of thiazopyr. Inhibitors of cytochrome P450 monooxygenases, piperonyl butoxide (PBO), 1-aminobenzotriazole (ABT), metyrapone (MET) and tetcyclacis (TET), all enhanced the bioefficacy of thiazopyr against pigweed and other plant species. In contrast, inhibitors of esterases, tributyl phosphate (TBP) and triphenyl phosphate (TPP), produced only slight enhancement of thiazopyr activity. The effect of PBO was dose-dependent and was demonstrated against barnyardgrass, grain sorghum, redroot pigweed, seedling johnsongrass, and giant foxtail. PBO demonstrated no enhancement of thiazopyr activity in velvetleaf, tall morningglory, cotton, or soybeans. Bioefficacy was most enhanced via exposure of seedling shoots to PBO and thiazopyr. The combination of results from the present and the preceding papers suggests that PBO enhances thiazopyr bioefficacy by effectively inhibiting thiazopyr metabolism in plants.     

Effect of binary combination of some plant-derived molluscicides with MGK-264 or piperonyl butoxide on the reproduction of the snail Lymnaea acuminata

The effects of sub-lethal treatments (20 and 60% of 24-h LC(50)) with plant-derived molluscicides Annona squamosa, acetogenins, Argemone mexicana seed and protopine, in combination (1 + 5) with MGK-264 (ENT 8184) or piperonyl butoxide on the reproduction of Lymnaea acuminata has been studied. The plant-derived molluscicides and their active molluscicidal components, protopine and acetogenins, in combination with ENT 8184 or piperonyl butoxide caused a significant reduction in the fecundity, hatchability and survival of young snails. Combination of A squamosa seed powder with piperonyl butoxide was very effective as it caused a complete arrest of snail fecundity within 24 h of treatment. Removal of the snails to fresh water after the 96-h treatments caused a significant recovery in the fecundity of L acuminata.     

Monooxygenase mediated pyrethroid detoxification in sea lice (Lepeophtheirus salmonis)

The role of monooxygenases in detoxification of the pyrethroids cypermethrin and deltamethrin was examined. Four strains of sea lice (Lepeophtheirus salmonis Krøyer) with normal or moderately reduced sensitivity towards the pyrethroids were tested in bioassays by exposure to the pyrethroid alone and in combination with an oxygenase inhibitor, piperonyl butoxide (PBO). The normal (baseline) sensitivity was considered as the sensitivity range for the two most sensitive strains. Pre‐treatment with PBO elevated the sensitivity (P < 0.01) compared with groups exposed to the pyrethroid only. A positive, but not statistically significant, correlation between the activity of haem peroxidases and the pyrethroid concentration immobilizing 50% of the parasites was demonstrated (ρ = 0.500 for deltamethrin and ρ = 0.310 for cypermethrin). The results indicate that cytochrome P450 monooxygenases are involved in detoxification of pyrethroids in sea lice. ¹⁴C‐Deltamethrin was absorbed in a lesser amount in a group of sea lice exposed to a mixture of the compound and PBO than in a group exposed to ¹⁴C‐deltamethrin alone. A significant difference could be demonstrated both immediately after exposure (P < 0.01) and 24 h after exposure (P < 0.05). No significant differences were found between groups pre‐treated with PBO and groups exposed to ¹⁴C‐deltamethrin only. ¹⁴C‐Deltamethrin was taken up mainly through the cuticle, especially the cuticle on the extremities of the ventral surface, and subsequently distributed throughout the body of the parasite. Copyright © 2005 Society of Chemical Industry     

增效剂胡椒基丁醚的气象色谱分析方法研究

 介绍一种菊酯类农药增效剂胡椒基丁醚的气相色谱定量分析方法。采用OV-101石英毛细管色谱柱，以邻苯二甲酸二丁酯为内标物，用氢火焰离子化检测器对胡椒基丁醚进行气相色谱内标法定量分析。方法的平均回收率为99.78%，标准差为0.12,变异系数为0.12%，线性相关系数为0.999 8。     

氟嘧磺隆与普杀特玉米田间除草效果比较

[目的]验证不同除草剂的除草效果，为玉米的杂草防除提供借鉴。[方法]设不同剂量氟嘧磺隆、普杀特单用处理，以及与增效醚混合处理，研究这2种除草剂对玉米Pioneer3751IR和Pioneer3751品种生长的影响，以及对杂草马唐和苘麻的防除效果。[结果]氟嘧磺隆与增效醚混合后产生药害促进效应，但普杀特无这种现象。氟嘧磺隆与增效醚混合处理对苘麻有药效促进效应，在0．040kg/hm^2浓度下呈现较好的除草效果，对马唐也呈现药效促进效应，但除草率较低。普杀特与增效醚混合处理苘麻时，在0．070kg／hm^2处理下有60％的除草效果，无药效促进效应，对马唐也无药效促进效应，但0．0175kg／hm^2下呈现90％以上的防除率。[结论]普杀特与增效醚混合可以更好地防除玉米田间杂草。     

Surface contact toxicity and synergism of several insecticides against different stages of the tropical bed bug, Cimex hemipterus (Hemiptera: Cimicidae)

BACKGROUND: Five formulated insecticides (lambda‐cyhalothrin at 10 mg m^?2, bifenthrin at 50 mg m^?2, fipronil at 10 mg m^?2, fenitrothion at 50 mg m^?2, imidacloprid at 5 mg m^?2) and one active ingredient (DDT at 500 mg m^?2) were evaluated using a surface contact method against early and late instars and adults of two strains of the tropical bed bug, Cimex hemipterus (F.). Synergism of lambda‐cyhalothrin and fipronil using piperonyl butoxide (PBO) was also assessed. RESULTS: The order of susceptibility of different stages of bed bugs was as follows: early stage ? lambda‐cyhalothrin > bifenthrin = imidacloprid > fipronil > fenitrothion > DDT; late stage—lambda‐cyhalothrin > bifenthrin > fenitrothion > imidacloprid > fipronil > DDT; adult—lambda‐cyhalothrin > imidacloprid > bifenthrin > fenitrothion > fipronil > DDT. The late instars exhibited significantly higher LT₅₀ among the life stages. The addition of PBO to fipronil increased the susceptibility of the insects. CONCLUSIONS: Lambda‐cyhalothrin, bifenthrin, fenitrothion and fipronil at the recommended application rates were effective against C. hemipterus. Although imidacloprid demonstrated good initial response against C. hemipterus, the insects showed substantial recovery 72 h post‐treatment. The late instars (fourth and fifth instars) should be used as the model for toxicological evaluation. Copyright © 2011 Society of Chemical Industry     

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.