Robert Bues

Deltamethrin resistance in the codling moth (Lepidoptera: Tortricidae): inheritance and number of genes involved.

The inheritance of deltamethrin resistance in Cydia pomonella (L.) has been investigated by crossing a resistant (Rv) and a susceptible (Sv) strain, derived from a population collected in south-eastern France in 1995. Deltamethrin resistance was suspected to be under the control of a kdr-type allele and an enhanced mixed-function oxidase (mfo). F1 and F2 progenies were therefore tested through dose–response and enzyme assays. Dose–response relationships indicated that resistance was inherited as an autosomal incompletely recessive (D=−0.199) character, involving at least two genes. Enzyme measures suggested the contribution of 1.2 genes to the expression of mfo, with incomplete dominance (D=0.460). Our results support the hypothesis of a polygenic response to deltamethrin selection in the Rv strain, including a major kdr-type allele with a minor effect of mfos. In the light of these findings, we consider the resistance in codling moth populations in south-eastern France as a product of an adaptive sequential selection process, occurring through the sequential addition of resistance genes.

Field attraction ofAgrotis segetum males in four european countries to mixtures containing three homologous acetates

Abstract(Z)-5-Decenyl, (Z)-7-dodecenyl, and (Z)-9-tetradecenyl acetate were tested as single compounds and blends for field attraction to the turnip moth in Denmark, France, Hungary, and Switzerland. Best attraction was obtained when all three components were present. Attractants for other noctuids are described, e.g.,Meristis trigrammica, Hoplodrina alsines, Erastria trabealis, Euxoa nigricans, Axylia putris, andAutographa gamma, which were caught with some of the components and their blends.

Allozyme polymorphism in the cotton bollworm Helicoverpa armigera (Lepidoptera: Noctuidae): comparison of African and European populations

Genetic variability of 22 populations of Helicoverpa armigera (Hübner) (Lepidoptera, Noctuidae) was studied by comparison of allozyme frequencies at 15 loci. Seven loci were polymorphic at the 99% level. Populations originated from the south of France, Portugal, Morocco, Tunisia, Burkina Faso and Ivory Coast. Few significant deviations from Hardy–Weinberg equilibrium occurred, except for the Acp locus. Overall comparison of allele frequencies revealed significant differences for four loci, although the value of θ was low (0.007). At a lower geographical scale, two situations were observed. Populations from France and Portugal showed significant differences when comparing allele frequencies, although θ was low (0.0099). On the other hand, in northern and western Africa, no significant difference exists even when comparing populations located on either side of the Sahara desert. Results are discussed in relation to the migratory abilities of the species.

Resistance of pear psylla (Cacopsylla pyri L.; Hom., Psyllidae) to deltamethrin and synergism with piperonyl butoxide

Abstract: Topical application bioassays, conducted on French populations of Cacopsylla pyri, showed resistance rates to deltamethrin ranging from 31‐fold at the adult stage to 135‐fold at the last larval stage. Synergism studies between deltamethrin and piperonyl butoxide (PBO), applied either topically or by tarsal contact with PBO, showed (i) that the rates of synergism were more than 10‐fold in all the populations and that they could increase to a thousand‐fold in some populations, (ii) that the synergistic effect was present to a similar extent at both the larval and adult stages, (iii) that there was no correlation between the synergistic effect and the resistance rates, and (iv) that no correlation was observed between the dates of collection and the rates of synergism. The results makes it impossible to determine whether resistance to deltamethrin is of genetic origin or results only from the induction of monooxygenases by allelochemical substances present in the food ingested by the species.

Geographic and seasonal variability of resistance to insecticides in Cacopsylla pyri L. (Hom., Psyllidae)

Pear psylla (Cacopsylla pyri L.) resistance to insecticides was studied in adults using the topical application method. In the Avignon population, the winter forms tested (diapausing generation) showed a greater tolerance to insecticide than the summer forms. High resistance rates, ranging from 25‐ to 180‐fold, were observed for three organo‐phosphorous insecticides. Resistance rates were seven times lower for pyrethrinoids and amitraz and practically nil for carbamates. Inter‐population resistance rates, for an identical period, were different for the three organo‐phosphorous insecticides and for deltamethrin in two localities. However, it was difficult to make comparisons in time due to seasonal variations.

Genetic analysis of resistance to azinphosmethyl in the pear psylla Cacopsylla pyri

Laboratory selection with azinphosmethyl had little effect on the chemical resistance in Cacopsylla pyri strains, in comparison to the original wild populations. The resistance ratio relative to a susceptible strain varied from 10‐ to 40‐fold depending on the generation studied. Crosses between two resistant strains and the susceptible strain show resistance to be autosomally inherited and semi‐dominant in expression. Backcrosses between F1 and the susceptible strain were unable to distinguish unabigously between monogenic and polygenic inheritance. In the majority of experiments, however, the overall dose‐response relationship for backcross progeny was consistent with a single gene hypothesis. Additional bioassays showed azinphosmethyl‐resistant strain to cross‐resistant monocrotophos and phosmet, but not carbamates, pyrethroids, amitraz or the organophosphates chlorpyrifos and mevinphos.

Genetic structure and dispersal of pear psylla (Cacopsylla pyri L.) populations

Abstract The electrophoretic analysis of eight polymorphic enzyme loci in one Italian and 14 French psylla populations showed no significant differences between the genotype frequencies and the Hardy-Weinberg equilibrium. Gene differentiation was low ( Fst = 0.0111) and gene flow was high ( Nm = 22.3). Populations from western France presented higher gene differentiation than those from eastern France. Separately studying two genes coding for esterases revealed a high level of structuring. Each locus was independent and characterized by a null allele and an expressed allele with the same mobility. The geographical distribution of each locus and the existence of confluence zones suggest that the exchanges between sub-populations preferentially occur via the north and the south of the Massif Central. The possible involvement of esterase genes in resistance to insecticides is discussed in relation with their known role of detoxification.