Enzymatic systems of insecticide detoxication in a population of Colorado beetles resistant to permethrin

The activity of enzymes providing for permetrin detoxication in the imago resistant natural population of the Colorado potato beetle Leptinotarsa decemlineata was studied with the view of elucidating the biochemical mechanisms of resistance to the insecticide. It was demonstrated that the activity of the main enzymes of insect detoxication, i.e., microsomal monooxygenases, nonspecific esterases and glutathione-S-transferases in the permetrin-resistant population of L-decemlineata is enhanced as compared with the permetrin-sensitive population. It was demonstrated that the inhibitors of microsomal monooxygenases, piperonyl butoxide, and of nonspecific esterases, butifos, significantly increase the sensitivity of the resistant population to permetrin. The experimental results suggest that the activity of microsomal monooxygenases and nonspecific esterases is the main factor which determines the resistance of the Colorado potato beetle to permetrin.     

Triangular fecundity function and ageing in ladybird beetles

Abstract 1. In insects, the age schedules of fecundity tend to be triangular and this has been attributed more to temporal patterns of mortality than to fecundity. The objective of the work reported here was to test the assumption that senescence shapes the fecundity function in ladybird beetles, and in particular that the production function declines with age.
2. The results of a laboratory study on three species of predatory ladybird beetle indicated that the efficiency with which these insects acquire and process food declined with age. Although supplied with the same amount of food each day, after the onset of reproduction, these beetles ate less and less with increasing age. Egg production mirrored the decline in aphid consumption. Associated with this was a decline in fertility, assimilation, and speed of locomotion with age.
3. This study indicates that production declined with age and that this shaped the fecundity schedules in these ladybird beetles. In addition, the results indicated that ladybirds are income breeders and, as predicted, the reproductive effort of the small species was greater than that of the large species used in this study.     

Effect of diet on the fecundity of three carabid beetles

Abstract In the present study, the importance of diet in terms of fecundity is compared for three species of the carabid genus Amara (Coleoptera: Carabidae), using an insect diet, two types of seed diet (Capsella bursa‐pastoris, Stellaria media) and a mixed diet. It is expected that the species of carabid studied have different food requirements for reproduction. Diet affects reproduction performance and egg production significantly. A mixed diet and both single‐seed diets are suitable for reproduction in Amara aenea (DeGeer) because a higher proportion of the females reproduce and lay significantly more eggs than on a purely insect diet. Females of Amara familiaris (Duftschmid) do not reproduce unless provided with seeds of S. media. Seeds of C. bursa‐pastoris or a mixed diet are equally suitable diets for reproduction of Amara similata (Gyllenhal); a diet of insects or seeds of S. media is unsuitable. The results support the hypothesis that the species under investigation have specific food requirements, suggesting that seed feeding has evolved to different degrees in particular species: A. aenea is omnivorous, whereas A. familiaris and A. similata specialize on the seed of a particular plant species or family. This resource partitioning facilitates co‐occurrence of carabid species.     

Diet, fecundity and egg size in some polyphagous predatory carabid beetles

Egg size was measured at different rates of egg laying in three polyphagous carabid species, known to be useful predators of cereal aphids; the small Bembidion lampros Herbst and the medium-sized Pterostichus cupreus L. and P. melanarius Illiger. Variations in fecundity, as well as the ability of the medium-sized species to also build up fat reserves, were obtained when beetles were subjected to different dietary regimes consisting of aphids, or foods with a lower or higher protein content. Egg size was found to be dependent on the rate of egg laying within a species. A diet of cereal aphids appeared to be adequate for egg production in these polyphagous carabids, but female P. cupreus were unable to build up fat reserves when they ingested aphids contaminated with the aphicide pirimicarb. Beetles were able to devote resources to more and larger eggs (B. lampros), or to larger eggs and/or fat reserves (P. melanarius/P. cupreus) when given access to a carbohydrate-rich food with low protein content. The highest rate of egg laying was obtained when female P. cupreus and P. melanarius were given a more varied diet at frequent intervals; including regular shifts between unsprayed aphids, carbohydrate-rich food and protein-rich maggots. Within the varied diet treatment a negative relationship was obtained between egg size and egg number among similar-sized individuals of P. cupreus and P. melanarius; females producing the largest number also laid the smallest eggs. Egg size affected larval survival, since first instars hatching from large eggs were found to survive longer than those hatching from small eggs. The influence of differences in food intake on reproduction, maintenance metabolism, and survival of fieldinhabiting carabids is discussed.     

Fitness consequences of malathion-specific resistance in red flour beetle (Coleoptera: Tenebrionidae) and selection for resistance in the absence of malathion

Malathion resistance in the red flour beetle, Tribolium castaneum (Herbst), is a worldwide problem and is very stable once it becomes widespread in natural populations. In the absence of insecticide the proportion of resistant phenotypes may rapidly decline but the development of resistance does not always involve reduced fitness. Malathion-specific resistance in T. castaneum seems not to involve any loss of fitness in laboratory or field conditions. Susceptible beetles were in competition with resistant beetles at different initial frequencies and modifications of susceptible gene frequency were estimated in these laboratory populations over 10 generations. A significant decrease in susceptible gene frequency was observed in Tribolium populations over time. The selection coefficient of the susceptible allele was estimated and the fitness of susceptible alleles in all tests was observed to range from 0.89 to 0.93 compared with the fitness of resistant genotypes, which was assumed to be 1. Data provided evidence that the resistant strains exhibited fitness advantages in the absence of malathion. We also compared the biotic potential (fecundity and developmental time) of the susceptible strain, the homozygous malathion-specific resistant strain, and their hybrids. Malathion-specific resistant strains showed an 8 -23% increase in biotic potential relative to the susceptible strain. These findings are consistent with those of malathion-specific resistance in T. castaneum; the fitness of the insects seems independent of the genetic background and the fitness of the resistant insects is not affected by this resistance mechanism.     

Behaviour and fitness of γHCH/dieldrin resistant and susceptible female Anopheles gambiae and An.stephensi mosquitoes in the absence of insecticide

The effects of gamma HCH/dieldrin resistance genes on various fitness components of mosquito larvae and adult females in the absence of insecticide were investigated in backcrossed strains of Anopheles gambiae Giles and An.stephensi Liston. Among larvae, heterozygotes (RS) developed slightly but significantly faster than homozygotes for resistance (RR) or susceptibility (SS). The lifetime fecundity of RR females in population cages was only half to two-thirds that of SS and RS females despite similar longevities; several reasons were identified: RR gravid females were less responsive to oviposition-site stimuli, their spontaneous activity--as measured in an acoustic actograph--was only half that of SS or RS females, and RR females produced fewer eggs per unit bloodmeal. When inseminated females were recorded in LD 12:12, RR were again less active than SS or RS. When the lighting was switched to a regime simulating full-moonlight, the activity pattern of SS and RS changed and they flew for longer periods. In contrast, the activity of RR females was the same in LD 12:12 as in 'moonlight'. In a test simulation of potential predation, RR mosquitoes took to flight least readily. All component tests on adult females therefore point to RR as being the least fit of the three genotypes. The behavioural tests suggest that resistance has raised the response threshold of RR females to diverse stimuli. A possible physiological mechanism underlying RR behaviour is that a change in the cyclodiene receptor on the chloride channels has increased their permeability to chloride ions, causing hyper-inhibition of the nervous system.     

Increased accuracy of batch fecundity estimates using oocyte stage ratios in Plectropomus leopardus

Using the ratio of the number of migratory nuclei to hydrated oocytes to estimate batch fecundity of common coral trout Plectropomus leopardus increases the time over which samples can be collected and, therefore, increases the sample size available and reduces biases in batch fecundity estimates.     

Mutation in ace1 associated with an insecticide resistant population of Plutella xylostella

Insensitive acetylcholinesterase (AChE) was determined to be involved in an EPN-resistant (ER) strain and a contaminated susceptible (CS) strain of diamondback moth (DBM, Plutella xylostella L.), as estimated by AChE inhibition assay using DDVP as a inhibitor in a nondenaturing electrophoresis gel. The ER strain exhibited very high AChE insensitivity, high resistance ratio, and two point mutations (G324A, A298S) in ace1-type AChE gene (Pxace1). The CS strain showed low AChE insensitivity, low resistance ratio, and it has only one point mutation (G324A). These findings suggest that the A298S mutation, along with reported G324A mutation (Baek et al, 2005), can be important in the development of organophosphate resistance. These results also suggest that the A298S mutation could be a good candidate for a molecular diagnosis marker for resistance monitoring. Three molecular diagnosis methods (Quantitative Sequencing; QS, PCR amplification of specific alleles; PASA and restriction fragment length polymorphism; RFLP) were developed which successfully detected specific resistance associated point mutations. Seven local population DBMs were surveyed and showed high insecticide resistance levels and a A298S mutation in Pxace1. These methods can be used to monitor the resistance allele in field population of DBMs and resistance management strategy.     

Increased openness around retained oaks increases species richness of saproxylic beetles

The decrease of old deciduous trees in northern Europe is a threat to the saproxylic fauna. In northern Europe, oak sustains the highest richness of saproxylic invertebrates, among which beetles is a large group. In order to preserve species associated with old trees, it has become common practice in commercial forestry to retain such trees at final felling. However, to create beneficial conditions for species associated with retained trees, the surrounding plantation has to be managed with regard to their specific demands. In the case of oak-associated species, including many red-listed species, several studies have shown that light is an important factor. The aim of this study was to analyze the effects of increased openness around oaks (Quercus robur) in spruce plantations (Picea abies) on species richness and abundance of oak-associated saproxylic beetles. The study was performed in nine spruce plantations located in southern Sweden, with mature oaks standing in a gradient of canopy openness. Beetles were collected from 54 oaks from May to September during two seasons, using window traps. The analyses revealed that increased openness around oaks increases species richness and abundance of oak-associated beetles. By including insolation angle in the analysis, we found that it is mainly the degree of openness directed south from the oak that has positive effects on beetle richness. These findings imply that it is desirable to maintain an open area around retained oaks, and that this area should be placed on the southern side of the oak to maximize the biodiversity benefit in relation to costs for the forest owner.     

Effects of temperature on baseline susceptibility and stability of insecticide resistance against Plutella xylostella (Lepidoptera: Plutellidae) in the absence of selection pressure

Plutella xylostella L. (Lepidoptera: Plutellidae) is an important pest causing significant losses to vegetables worldwide. Insecticides resistance in P. xylostella is a serious issue for scientists since last 30 years. However, deltamethrin and Bt Cry1Ac are commonly used insecticides against P. xylostella but studies involving development of resistance in P. xylostella against these two insecticides at different temperatures are lacking. The current study was aimed to find out the toxicity of deltamethrin and Bt Cry1Ac, and resistance development in P. xylostella. Results showed that the positive correlation between the temperature and toxicities of deltamethrin and Bt Cry1Ac. The results indicated −0.051, −0.049, −0.047, and −0.046 folds of deltamethrin resistance at 15 °C, 20 °C, 25 °C, and 30 °C temperatures, respectively from 1^st to 12^th generations. The toxicity of Bt Cry1Ac after 24 h was 2.2 and 4.8 folds on 1^st generation at 20 °C and 25 °C temperatures, respectively compared to the toxicity recorded at 15 °C (non-overlapping of 95% confidence limits). Based on the results of this study, it is concluded that the temperature has a positive correlation with the toxicity of deltamethrin and Bt Cry1Ac against the larvae of P. xylostella. This study suggests that deltamethrin and Bt Cry1Ac can be included in the management program of P. xylostella on many vegetable crops. The baseline susceptibility data might be helpful to understand the resistance mechanisms in P. xylostella.     

Response of insecticide-resistant and susceptible Colorado potato beetles, Leptinotarsa decemlineata to 2-tridecanone and resistant tomato foliage: the absence of cross resistance

Insecticide-resistant Colorado potato beetles (CPB), Leptinotarsa decemlineata, from Long Island, New York and susceptible beetles from North Carolina were tested for response to 2-tridecanone and foliage of the CPB resistant wild tomato, Lycopersicon hirsutum f. glabratum C. H. Mull, PI 134417. Populations did not differ in their response to 2-tridecanone or PI 134417 foliage. Exposure of beetles to sublethal doses of 2-tridecanone did not increase tolerance of either population to subsequent exposures to 2-tridecanone. It was also found that the New York beetles suffered higher mortality than North Carolina beetles on CPB susceptible L. esculentum foliage and PI 134417 foliage from which the glandular trichomes, which contain 2-tridecanone, were removed. Survival of North Carolina beetles was lower on PI 134417 foliage without trichomes than on L. esculentum foliage.

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Résumé La lutte contre Leptinotarsa decemlineata, sur la tomate et des autres récoltes, compte ordinairement sur les insecticides. Cette confiance a causé plusieurs populations de cette espèce à développer une résistance aux insecticides. Accession PI 134417 de la tomate sauvage, Lycopersicon hirsutum f. glabratum C. H. Mull, est résistant à L. decemlineata, en grande partie à cause de la presence de 2-tridécanone dans les éxtremités des poils glandulaires du feuillage. Notre étude entreprendait à rechercher la possibilité d'une résistance croisée aux insecticides et au 2-tridécanone.Les coléoptères de Long Island, New York, ceux qui sont résistants aux insecticides et ceux susceptibles de North Carolina, éprouvaient pour une réponse au 2-tridécanone et au feuillage résistant.Les deux populations de coléoptères ne diffèrent pas dans sa réponse au 2-tridécanone ou au feuillage résistant. Nous ne trouvons pas d'évidence d'une résistance croisée.Aussi, nous trouvons que les coléoptères de New York ne survivaient pas aussi bien que ceux de North Carolina au feuillage résistant sans les éxtremités des poils glandulaires et au feuillage susceptible. La survivance était plus basse sur le feuillage résistant sans les éxtremités des poils glandulaires que le feuillage susceptible seulement avec les coléoptères de North Carolina.

     

Correlated insecticide cross-resistance in azinphosmethyl resistant codling moth (Lepidoptera: Tortricidae)

Resistance to several classes of insecticides was correlated with azinphosmethyl resistance in codling moth, Cydia pomonella (L.), in California. In tests of laboratory and field populations, cross-resistance was positively correlated with azinphosmethyl and two organophosphates (diazinon, phosmet), a carbamate (carbaryl), a chlorinated hydrocarbon (DDT), and two pyrethroids (esfenvalerate and fenpropathrin). Additionally, negatively correlated cross-resistance was identified between azinphosmethyl and two other organophosphates, chlorpyrifos and methyl parathion. Patterns of resistance observed in laboratory colonies were confirmed with field bioassays. In bioassays of field populations, azinphosmethyl resistance was observed to increase from 1991 to 1993, although levels of resistance remained < 13-fold. Because orchards with azinphosmethyl resistance have had difficulties with suppression of codling moth, and cross-resistance was found for all tested classes of insecticides, strategies for managing resistance will need to be developed so as to protect current and future control tactics. The two insecticides with negatively correlated cross-resistance are discussed as potential tools for resistance management.     

温度对抗性朱砂叶螨发育和繁殖的影响

比较了朱砂叶螨Tetranychus cinnabarinus (Boiduval)敏感品系（S）、阿维菌素抗性品系（AR）和甲氰菊酯抗性品系（FR）在不同温度下的发育和繁殖情况,用王-兰-丁模型拟合了各品系发育速率与温度的关系。结果表明,在36℃下,S品系和FR品系卵均不能孵化,而AR品系却能完成世代发育。15℃下,AR和FR品系的世代历期分别比S品系延长8.0和6.2天,产卵前期均比S品系缩短约2.0天。在20～28℃下,S品系繁殖力大于抗性品系; 在34℃下, AR品系的产卵量显著大于S和FR品系。S、FR和AR品系发育临界高温分别为36.0℃、36.1℃和42.4℃。结果提示AR品系对高温的适应能力较S和FR品系明显增强。     

The occurrence of translocations in insecticide resistant and susceptible field-collected strains of the German cockroach

Insecticide resistant and susceptible field-collected strains of the German cockroach were surveyed for the occurrence of chromosome polymorphisms. Analyses were on meiotic cells of males that hatched from oothecae with unusual numbers (>5) of incompletely developed eggs (aberrant oothecae). Three males were reciprocal translocation heterozygotes. A spontaneous translocation was noted in one cell of a fourth male. The males were from insecticide resistant strains. Partially developed eggs in oothecae from outcrosses of two of the translocation herozygotes ceased development in early stages and were characterized by gross morphologic abnormalities. Chromosome abnormalities other than translocations occurred in a low percentage of males from aberrant oothecae in both resistant and susceptible strains. The only general differences between susceptible and resistant strains were that, in pooled data, the frequencies of unhatched oothecae and of aberrant oothecae were higher in the resistant than susceptible strains.     

Molecular characterization of the amplified aldehyde oxidase from insecticide resistant Culex quinquefasciatus.

Primary structural information including the complete nucleotide sequence of the first insect aldehyde oxidase (AO) was obtained from the common house mosquito Culex quinquefasciatus (Say) through cloning and sequencing of both genomic DNA and cDNA. The deduced amino-acid sequence encodes a 150-kDa protein of 1266 amino-acid residues, which is consistent with the expected monomeric subunit size of AO. The Culex AO sequence contains a molybdopterin cofactor binding domain and two iron-sulfur centres. A comparison of the partial sequences of AO from insecticide resistant and susceptible strains of C. quinquefasciatus shows two distinct alleles of this enzyme, one of which is amplified in the insecticide resistant strain on a 30-kb DNA amplicon alongside two resistance-associated esterases. The amplified AO gene results in elevated AO activity in all life stages, but activity is highest in 3rd instar larvae. The elevated enzyme can be seen as a separate band on polyacrylamide gel electrophoresis. The role of AO in xenobiotic oxidation in mammals and the partial inhibition of elevated AO activity by a range of insecticides in Culex, suggest that this AO may play a role in insecticide resistance.     

Biochemistry of phosphine uptake in susceptible and resistant strains of two species of stored product beetles

1. Uptake of phosphine by resistant strains of Rhyzopertha dominica and Tribolium castaneum was lower than by susceptible ones.2. There was no active uptake of phosphine in vitro by insect fractions and gel filtration of R. dominica cytosol showed no evidence of the presence of a phosphine-binding factor.3. Phosphine appeared to be converted mainly to hypophosphite in insects and the difference in accumulation by resistant and susceptible insects is postulated to be due to differences in the rate of oxidation of phosphine in vivo.     

Efficacy of etofenprox against insecticide susceptible and resistant mosquito strains containing characterized resistance mechanisms

tofenprox is a non-ester pyrethroid insecticide with comparable toxicity and a similar mode of action to other pyrethroids. Cross-resistance studies on mosquitoes showed no effect of carboxylesterase, elevated esterase, altered acetylcholinesterase or glutathione S -transferase-based resistance mechanisms on etofenprox toxicity, when compared to standard susceptible strains of Anopheles and Culex . Cross-resistance to etofenprox occurred in a pyrethroid-resistant strain of Culex quinquefasciatus with both oxidase and 'kdr'-like resistance mechanisms.
Dose–response data for susceptible mosquito strains suggest that, in standard W.H.O. susceptibility tests of adult mosquitoes, appropriate discriminating concentrations of etofenprox for detection of resistance would be 0.1% for Culex and 0.25% for Anopheles .