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Parasitism by the braconid wasp Dolichogenidia tasmanica of first instar larvae of the lightbrown apple moth Epiphyas postvittana, established on four different species of potted host plants, was assessed after 2 weeks of field exposure in an apple orchard. Parasitism varied significantly between larval host plants (apple 58%, broom 59%, clover 30%, poplar 19% ). Parasitism on potted apple seedlings of the co-evolutionary host, E. postvittana, was compared in a field trial with that of two native New Zealand leafroller species (to which D. tasmanica has had exposure for 5 decades only). Parasitism varied significantly with larval host (E. postvittana, 83%; Ctenopseustis herana, 58%;Planotortrix octo, 26% ). Larval collections were made from mature apple trees and identification of larvae was achieved by DNA analysis for the leafroller species using PCR-RFLP of ITS1 + ITS2, and for the parasitoid by specific PCR of partial 18S. Parasitism under natural field conditions on mature apple trees was not different between larval hosts (mean 32.5% ). In laboratory studies, more P. octo larvae departed in response to parasitoid probing behaviour than E. postvittana, which is likely to contribute to the difference in parasitism rates. This study conclusively shows that D. tasmanica parasitises native New Zealand leafrollers, despite their different evolutionary origins.

A theoretical investigation has been conducted for predicting the critical liquid height and the location of liquid entrainment during dual discharge from a stratified two-phase region through branches mounted on a vertical wall. The two branches are horizontal and their centrelines fall in a common inclined plane. Two models have been developed; a simplified point-sink model and a more-accurate finite-branch model. Predictions from the two models are shown to be in good agreement for the condition of high flow rates from the branches, while the finite-branch model is necessary for good predictions at low branch flow rates. Influences of the various independent parameters on the predicted onset are presented and discussed. Comparisons with experimental results are shown in Part 2 of this paper.

A RAPD-PCR technique was used to compare genetic material from three species (Naupactus leucoloma, N. peregrinus, and N. tucumanensis) of whitefringed weevil. N. peregrinus, N. tucumanensis andN. leucoloma were consistently distinguished from each other by the presence or absence of RAPD bands. The banding profiles obtained suggested that N. peregrinus is genetically more closely related to N. leucoloma thanN. tucumanensis. The technique distinguished between three “clones” in two N. leucoloma populations sampled from Australia and New Zealand. No differences were detected between individuals within N. tucumanensis or N. peregrinus populations. The potential for RAPD-PCR technique to provide useful genetic data at the population level is discussed.

The phenomenon of liquid entrainment is investigated theoretically for the condition of simultaneous discharge from two small slots located on the side of a large reservoir containing stratified layers of two immiscible fluids. A model is developed for predicting the critical height while simulating the small slots as two-dimensional line sinks. This model is expressed in terms of two simple algebraic equations suitable for hand calculations. Dependence of the critical height on the two discharge rates and the separating distance between the slots is formulated in terms of new dimensionless groups.

Light brown apple moth genotypes were sampled from the field by allowing wild males to cross with tethered females and by collecting mated wild females. The progeny were used to estimate the phenotypic frequency of azinphosmethyl resistance from the two sources: susceptible (laboratory) female × unknown genotype (wild) male and unknown genotype (wild) female × unknown genotype (wild) male. The crosses occurred within a known zone of azinphosmethyl resistance and the offspring were screened with diagnostic insecticide concentrations to determine the frequency of susceptible × susceptible crosses in the population. The frequency of resistant male parents within the population was estimated as 83% ( n = 18) from the first type of cross, while the frequency of resistant male and/or female parents was estimated as 100% ( n = 17) from the second type of cross. The offspring were also selected with azinphosmethyl at the LC 99 of susceptibles, and the survivors were compared with their unselected siblings for glutathione S -transferase activity. Adults, selected as larvae, had significantly higher glutathione S -transferase levels than their unselected siblings ( P S -transferase activity. This could not be explained by the removal of susceptible individuals with the insecticide or by induction of the enzyme by insecticide treatment. Insertion of the resistance into a susceptible genome through five generations of backcross and selection with azinphosmethyl resulted in significantly higher glutathione S -transferase activity in larvae of the resistant strain compared to the susceptible strain which shared a ca. 97% common genome.

Bioassay using diet incorporation of azinphosmethyl showed six strains of light brown apple moth to have varying levels of resistance to azinphosmethyl (3- to 15-fold) compared with three susceptible strains. Two of these strains were products of a selection and backcrossing program providing resistant insects that had a common genome with that of one of the susceptible strains. Individual male moths from each strain were tested for (i) glutathione S-transferase and (ii) non-specific esterase activity. Larvae were assayed for (iii) mixed function oxidase activity. Each enzyme group was assayed with two substrates. Significant positive regressions between LC50 and enzyme activity were observed for all three groups: (i) r2 = 0.84 for 3,4-dichloronitrobenzene conjugation, (ii) 0.64 for α-naphthyl acetate hydrolysis, 0.54 for α-naphthyl butyrate hydrolysis, and (iii) 0.88 for p-nitroanisole oxidation and 0.86 for aniline oxidation. No correlation with the LC50 was found for 1-chloro-2,4-dinitrobenzene conjugation (r2 = 0.001). Activities of all three groups were significantly higher in the two backcross resistant strains compared to the susceptible parent strain (P < 0.05). The gene(s) for high enzyme activity had thus been successfully transferred with the factor for resistance. The results suggest a close relationship between detoxication enzyme activity and azinphosmethyl resistance.

Target site and metabolic enzyme studies were carried out on azinphosmethyl susceptible and resistant strains of light brown apple moth, Epiphyas postvittana (Walker). Acetylcholinesterase from the two strains was inhibited in vitro to the same degree by azinphosmethyl oxon or by the carbamate eserine. There was also no difference between strains in the kinetics ( K m and V max ) of the reaction with acetylthiocholine iodide. The penetration and in vivo metabolism of topically applied [ 14 C]azinphosmethyl was greater by resistant moths after a 6-hr incubation. In vitro , metabolism of [ 14 C]azinphosmethyl was greater with homogenates of resistant moths and, for both strains, was influenced by the presence of glutathione but not NADPH. Assay for total nonspecific esterase activity showed significantly higher levels in resistant compared to susceptible strains for both field-collected and laboratory-reared samples. Electrophoretic analysis of esterases indicated that increased activity of many isoenzymes was involved. Assay for glutathione S -transferase activity, using 2,4-dichloronitrobenzene as substrate, also showed significantly higher levels in both field-collected and laboratory-reared resistant moths compared to the corresponding susceptibles. A kinetic study on laboratory-reared strains revealed that in the presence of independently varying concentrations of 2,4-dichloronitrobenzene and glutathione, the V max for both substrates was two fold higher in the resistant strain while the K m 's were similar to those of susceptible moths. High glutathione S -transferase activity in the resistant strain was, therefore, probably due to presence of a greater amount of the enzyme rather than due to a different form. In conclusion, modification of the target site was not a factor in resistance, but increased metabolism was involved.

Responses of resistant and susceptible strains of light brown apple moth, Epiphyas postvittana (Walker), to azinphosmethyl varied significantly depending upon the diet that larvae consumed. Responses of resistant larvae reared on blackberry and susceptible larvae reared on artificial (general purpose) diet were similar. Susceptible larvae on artificial diet were significantly more tolerant compared with susceptible larvae fed any of the natural host plants, whereas resistant larvae reared on blackberry were significantly less resistant than resistant larvae reared on any other diet. Activity of nonspecific esterases of resistant larvae fed blackberry was significantly lower than activities in resistant larvae fed general purpose diet, gorse, apple, or broom, and not significantly different from nonspecific esterase activities of susceptible larvae reared on general purpose diet, gorse, apple, blackberry, or broom. In the presence of high glutathione S-transferase activity that characterized all resistant larvae regardless of diet, depressed nonspecific esterase activity may be responsible for increased toxicity of azinphosmethyl to resistant larvae on blackberry. In resistant strains of other polyphagous species, responses of individuals tested with pesticide may reflect metabolic effects related to the host plant rather than to the magnitude of genetically based resistance to the pesticide.