Insecticide‐based management programmes targeting codling moth, Cydia pomonella L. (Lepidoptera: Tortricidae: Olethreutinae), in apple orchards in southern France have incurred increasing levels of fruit injury in recent years. An alternative programme incorporating the use of exclusion netting named Alt'carpo has been developed. This study aimed at studying its efficiency and gaining more insight into its mode of action. This was achieved through laboratory and field behavioural tests and observations in a network of commercial orchards in southern France. The moths were able to lay eggs through the nets and escape from net cages in the laboratory. Male moths released in the netted rows were poorly recaptured using sexual pheromone trapping, whereas over 20% of the released males were recaptured in unprotected rows. The netting reduced fruit injury by up to 91% compared to the unprotected rows in the experimental orchard. The efficacy of this netting was even higher in commercial orchards in which fruit injury did not exceed 0.1% without any application of specific insecticide. These results lead us to assume that netting alters the reproduction of the pest, mainly by preventing it from flying over the canopy to find mates.
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 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 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.
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.
Rates of synergism by S,S,S‐tributyl phosphorotrithioate (DEF) and piperonyl butoxide (PBO) were low when applied 4 h before the insecticide (0.3‐ to 3.3‐fold), except for deltamethrin with PBO (>60‐fold). The presence of mixed‐function oxidases in winter forms is discussed with regard to bibliographical data concerning another psylla species from North America (Psylla pyricola Foerster).
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