Selection for pesticide resistance in Aphytis

Abstract

Field‐collected populations of Aphytis holoxanthus DeBach (Hymenoptera: Aphelinidae), a parasite of Chrysomphalus aonidum (L.) (Homoptera: Diaspididae), were tested for malathion and for azinphosmethyl tolerance, and selected for increased resistance. Initial tolerance for malathion was not significantly different between populations, and could not be significantly increased by 30 selection cycles. Two field populations showed relatively high levels of azinphosmethyl tolerance, which were further increased by selection to 24–48 times that of a susceptible laboratory population. The differences in response to the two organophosphorus insecticides are discussed in relation to differences in their modes of application, detoxification by insects and the genetic bottleneck experienced by an imported species.

Evaluation of an endosulfan tolerant strain of Trichogramma chilonis on cotton

“…The fact that the parasitising abilities of the tolerant and susceptible strains were on par in a pesticide-free environment indicates that the normal parasitising ability of the tolerant strain remained unaffected. Similar observations were made by Havron et al (1991) and Baker and Thorne (1995), who reported that the biological parameters of insecticide resistant strains of parasitoids Aphytis lingnanensis Compere and Anisopteromalus calandrae (Howard) were not affected by exposure to insecticides. However, Caprio and Hoy (1995) reported that certain biological parameters of insecticide tolerant strains could be affected in the process of selection, thus reducing their efficacy in the field.…”

PLANT CHEMISTRY AND NATURAL ENEMY FITNESS: Effects on Herbivore and Natural Enemy Interactions

“…A single base pair substitution (thymine in the susceptible strain is replaced with guanine in the resistant strain) leads to an amino acid change from tryptophan to glycine in the encoded protein; this mutation is inherited in a Mendelian fashion and is linked to malathion resistance (170, 171). Furthermore, successful attempts to artificially select for increased resistance to pesticides in several parasitoid species indicate the presence of additive genetic variance for detoxification abilities in parasitoid populations (73, 85, 116). Likewise, that fieldcollected populations of several parasitoid species become increasingly susceptible to pesticides when reared for several generations in the absence of selective pressure from pesticides (131, 166) might indicate a fitness cost for resistance.…”