Residual toxicity of two insecticides on three field populations of Lygus lineolaris (Hemiptera: Miridae) collected along the St Lawrence valley in eastern Canada

Insecticides are still the single main pest control method employed today by most growers to mitigate damage done by the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois) (Hemiptera: Miridae). In eastern Canada, the complex agricultural ecosystem, which may be described as a mosaic of farmlands dispersed among natural habitats (forest, prairies), allows tarnished plant bug adults to fly and move from sprayed to non-sprayed areas. In 2004 (late August to early September), three populations of L. lineolaris were collected from three mixed vegetation strips adjacent to orchards and vineyards along the St Lawrence valley: the Niagara Peninsula (Ontario), Dunham (Quebec) and La Pocatière (Quebec). Assays were done in the laboratory by confining adults in glass vials coated with dried residues. The estimated LC(50) values for the three populations varied from 11.2 to 16.8 x 10(-5) g L(-1) for azinphos-methyl and from 0.8 to 1.4 x 10(-5) g L(-1) for cypermethrin. In contrast to the Mississippi delta, no tolerance to insecticides was found in the populations collected. Possible explanations for this non-tolerance to insecticides includes a very low selection pressure as a result of the reduced number of insecticide treatments done in the context of the diversified agricultural landscapes encountered in eastern Canada which allow movements of adults from treated to non-treated areas.     

Water balance,respiration and immobilisation in relation to deltamethrin poisoning and physical conditions in the epigeal spider Oedothorax apicatus

The effect of a pyrethroid insecticide, deltamethrin, on water loss, metabolic rate and immobilisation was studied, using the epigeal spider Oedothorax apicatus (Blackwall) (Linyphiidae) as a test species. Water loss was measured gravimetrically at different temperatures, air humidities, and doses of deltamethrin. Metabolic rate and immobilisation were measured at different temperatures and doses. Immobilisation was measured at different relative humidities and temperatures. Water loss due to evaporation increased linearly with vapour pressure deficit. The slope of the latter relationship increased with temperature, indicating an increase in cuticle permeability with temperature. In addition to water loss by evaporation, deltamethrin treatment induced water excretion. This was positively related to dose and temperature, but independent of air humidity. Metabolic rate increased with temperature and dose. Immobilisation was highest at low temperatures in combination with low air humidity. The consequences of pesticide-induced water excretion are discussed with respect to field- and laboratory-based dose-effect relationships for pyrethroids presented in the literature. The present results seem to offer an explanation for hitherto unexplained minima in temperature-response curves in pyrethroid toxicity in some arthropod species. It is concluded that simultaneous measurements of metabolic rate, water-loss rate and pesticide effects are a prerequisite for an understanding of the effects of pesticides on arthropods.     

The pyrethrins and related compounds part XL— structure-activity relationships of pyrethroidal esters with acyclic side chains in the alcohol component against resistant strains of housefly (Musca domestica)

Activities of a range of pyrethroidal esters, incorporating structural variations in all regions of the acid and alcohol components, have been measured against two fully characterised and homozygous resistant strains of Musca domestica (kdr and super-kdr). The results, limited in this paper to esters of alcohols with acyclic side chains, show the same level of uniform resistance as the kdr strain observed previously, across a range of acid and alcohol variations. Against the super-kdr strain, in contrast to the cyclic side chain set, resistance factors are barely higher than for the kdr strain. Against super-kdr flies, some dependence of resistance factor on the position of the side chain substituent was detected. Polyfluorobenzyl esters confer particularly low resistance factors.     

棉铃虫对拟除虫菊酯的抗性稳定性研究

应用生物测定的方法研究了棉铃虫Ｈｅｌｉｃｏｖｅｒｐａａｒｍｉｇｅｒａ（Ｈüｂｎｅｒ）对溴氰菊酯高抗（１３６．７３倍）、对三氟氯氰菊酯（９．５０倍）和凯明二号（３．４０倍）低抗的３个种群的抗性稳定性。结果发现，无论棉铃虫的抗药性是高或低，在连续几代不接触药剂的情况下，都表现为抗性不断下降；第８代后３个种群都表现为抗性基本稳定，变化不大。停药后第８代分出部分种群作抗性再恢复试验，经６代连续点滴筛选后，３个种群抗性都有所回升。而且，棉铃虫对单剂抗药性衰退明显，但再恢复较快；对混剂的抗性衰退慢，再恢复也慢。     

The pyrethrins and related compounds. Part XLII:Structure–activity relationships in fluoro-olefin non-ester pyrethroids

A series of compounds containing fluorine atoms in place of hydrogen in olefinic non-ester pyrethroids has been synthesised using a route based on novel intermediates, ie 2-fluoroallyl acetates, which are coupled with aryl Grignard reagents, and tested against several insect species. In most cases, after introduction of fluorine at the olefinic position, the activity remains high in both the 1-aryl-1-(3-arylprop-2-enyl)cyclopropane and the (1-aryl-4-arylbut-2-enyl)cyclopropane series. In particular, the former series have potential as soil insecticides, because in tests against Diabrotica balteata, activities were high, and dose-transferability factors were increased by the introduction of fluorine. © 1999 Society of Chemical Industry     

Thermal behaviour and biological activity of pyrethroids in smoke-generating formulations

Smoke-generating insecticide formulations are nowadays very important for the control of Chagas' disease vectors. In this work, the thermal decomposition of different pyrethroid insecticides in smoke-generating formulations has been studied. Their recovery from the smoke has been determined, and the effect on this of the addition of foaming agents such as cyanoguanidine (CNG) or azodicarbonamide (ADC), or antioxidant agents such as butylated hydroxytoluene (BHT) or butylated hydroxyanisole (BHA) has been assessed. In each case the best smoke-generating formulation was established. Calorimetric studies were done to justify the behaviour of the smoke-generating mixtures. The isomerization process for different pyrethroids was also studied, to establish the influence of the foaming agents in inhibiting isomerization to less active pyrethroids. Smoke-generating mixtures containing β-cypermethrin and cis-permethrin as insecticides and CNG or ADC as foaming agents were evaluated for their insecticidal activity against nymphs I of Triatoma infestans, vector of Chagas' disease. The best effect was found with β-cypermethrin formulated with ADC, with LT₅₀ values lower than 5 min. © 1999 Society of Chemical Industry     

Seasonal Dynamics of Metabolic Mechanisms Mediating Pyrethroid Resistance in Helicoverpa armigera in Central India

Very high cypermethrin and fenvalerate resistance frequencies were recorded in Helicoverpa armigera (Hübner) populations in central India during the 1993–94, 1994–95 and 1995–96 cropping seasons. Synergism assays and biochemical analyses of detoxification enzyme levels indicated that mono-oxygenases and esterases were important metabolic mechanisms mediating pyrethroid resistance. Piperonyl butoxide- (PBO) and profenofos-suppressible pyrethroid resistance were correlated with enhanced levels of cytochrome P450 and general esterases respectively. Enzyme assay data indicated that high cytochrome P450 levels generally coincided with low esterase activity and vice versa. Similarly, synergist bioassays showed that PBO-insensitive resistance was frequently associated with profenofos-sensitive resistance and vice versa. Oxidase- and esterase-mediated mechanisms evidently alternated in a reciprocal manner, with perceptible shifts in relative importance occurring during mid-October in all three seasons and in late January in 1995. Apart from metabolic mechanisms, a synergist-insensitive resistance mechanism (believed to be nerve insensitivity), accounted for an average of 51, 30 and 28% of cypermethrin resistance during the 1993–94, 1994–95 and 1995–96 seasons respectively. © 1997 SCI.     

Nerve Insensitivity to cis-Cypermethrin is Expressed in Adult Heliothis virescens

Adult and third-instar larval Heliothis virescens were examined for nerve insensitivity to cis-cypermethrin using a rapid and robust neurophysiological method. Three laboratory strains, BRC susceptible, PEG-87 resistant and MS2 metabolic resistant, were compared with a series of pyrethroid-resistant strains collected from a field site in Louisiana, USA, during the 1992 cotton season. Nerve insensitivity was present in a proportion of the individuals in both the PEG-87 and the field strains, at both life stages, minimal in the MS2 strain and absent in the BRC strain. Frequencies of nerve-sensitive and nerve-insensitive individuals in each strain were not significantly different at the two life stages examined.