Selection for pesticide resistance in Aphytis

Abstract

Field-collected populations of Aphytis holoxanthus DeBach (Hymenoptera: Aphelinidae) and of A. lingnanensis Compere were selected for malathion and azinphosmethyl resistance, respectively, utilizing the male selection method. In preliminary experiments, fertility of virgin females was not significantly lower than that of mated females, and the rate of development of their progeny was similar. Males proved more susceptible to pesticides than females, and among them the sons of virgins were more susceptible than the sons of mated females. Some after-effects of sublethal exposure to pesticides were noted in both species. A mating ratio of 1 selected male: 2.0-2.5 females was optimal. Cold storage of female pupae proved feasible for synchronizing availability.Resistance of A. holoxanthus to malathion was not increased by 25 male selection cycles. Resistance of A. lingnanensis to azinphosmethyl, which had already been improved by mass selection, was further increased by 7 cycles of male selection.The different outcomes of the two projects are discussed in relation to the variability of the original field populations, and the results of male selection are compared with those of mass selection of identical populations.

Does experimental evolution produce better biological control agents? A critical review of the evidence

“…This is not surprising, as the insecticides used to control pests are a great threat to natural enemies. Some studies, however, failed to obtain a response to insecticides in natural enemies (Adams & Cross, 1967;Croft & Meyer, 1973;Schulten et al, 1976;Hoy & Knop, 1979;Markwick, 1986;Hamamura, 1987;Havron et al, 1991;Javier et al, 1991). In almost all studies, resistance against the applied insecticide increased, from as low as 1.8-fold (Kostiainen & Hoy, 1994) to ca.…”

“…40-fold (Roush & Hoy, 1981a;Grafton-Cardwell & Hoy, 1986), 65-fold (Zhu et al, 1996), 71-fold (Balanza et al, 2019) and even several hundred-fold (Croft & Meyer, 1973). Some studies, however, failed to obtain a response to insecticides in natural enemies (Adams & Cross, 1967;Croft & Meyer, 1973;Schulten et al, 1976;Hoy & Knop, 1979;Markwick, 1986;Hamamura, 1987;Havron et al, 1991;Javier et al, 1991). In others, insecticide resistance did not increase because the source population was already resistant Strickler & Croft, 1982;Baker, 1995).…”

Selection for pesticide resistance in Aphytis

“…Conspecificity of the selection line with the ref- erence (Riverside) strain was tested by reciprocal crosses, and scoring the sex ratio of ensuing offspring. Pupae of both strains were sexed (see Javier et al, 1991) and held for emergence. Females of each strain were placed individually with 2 males of the other strain in small test tubes.…”

“…Under the assumption that a small proportion of highly resistant individuals was nevertheless available in the population, the selection program was continued. At the same time, a putatively more discriminating male selection project was launched with the same population (Javier et al, 1991).…”

“…A small, residual population of the California red scale (CRS), Aonidiella aurantii (Maskell) (Homoptera: Diaspididae), was observed to be parasitized. A sample was collected, and the emerging parasites were evaluated for our program of improving pesticide resistance in Aphytis (see Havron et al, 1991;Javier et al, 1991). Several species of Aphytis parasitize CRS in Israel, including A. lingnanensis and A. coheni De-Bach which are sibling species (Rosen & De-Bach, 1979).…”