Biomedical subjects

Barry J Pye

Publications and source records attributed to Barry J Pye.

4 recordsLinked to original sources

PubMed2006

Chemically mediated intraguild predator avoidance by aphid parasitoids: interspecific variability in sensitivity to semiochemical trails of ladybird predators.

The avoidance responses of aphid parasitoids with varying host ranges (Aphidius eadyi, Aphidius ervi, and Praon volucre) to chemical trails deposited by intraguild predatory ladybirds, Coccinella septempunctata and Adalia bipunctata, were investigated. Females of all three parasitoid species avoided leaves previously visited by C. septempunctata or A. bipunctata adults. The avoidance responses shown by the two Aphidius species were stronger to trails of C. septempunctata than to those of A. bipunctata. However, P. volucre avoided trails of both ladybird species to a similar degree. Dose responses of these three parasitoid species to the hydrocarbons n-tricosane (C23H48), n-pentacosane (C25H52), and n-heptacosane (C27H56), which are components of the trails of both C. septempunctata and A. bipunctata, were evaluated. Dual-choice bioassays indicated the following: (1) A. eadyi showed more sensitive avoidance responses to n-tricosane than did the other two parasitoid species, (2) all three species showed similar responses to n-pentacosane across a range of doses, and (3) only P. volucre showed avoidance responses to n-heptacosane. Quantitative analyses of each hydrocarbon in the trails of the two ladybird species showed that n-pentacosane and n-heptacosane occur in significantly greater amounts in C. septempunctata trails than in those of A. bipunctata. The trails of the two species also differ qualitatively in the other hydrocarbons present.

Alkanes↗

PubMed2004

The role of semiochemicals in the avoidance of the seven-spot ladybird, Coccinella septempunctata, by the aphid parasitoid, Aphidius ervi.

The role of semiochemicals in mediating intraguild interactions between the seven-spot ladybird, Coccinella septempunctata, and the aphid parasitoid, Aphidius ervi, was investigated. Female parasitoids avoided leaves visited by C. septempunctata adults and larvae during the previous 24 hr. Ethanol extracts of C. septempuntata adults and larvae also induced avoidance responses by A. ervi. Two of the hydrocarbons identified by gas chromatography (GC) and coupled GC-mass spectrometry (GC-MS), n-tricosane (C23H48), and n-pentacosane (C25H52), when tested individually at levels found in the adult extract, induced avoidance by A. ervi. Further investigation of the larvae extract, and footprint chemicals deposited by adults in glass Petri dishes, confirmed the presence of the hydrocarbons. Parasitism rates of the pea aphid, Acyrthosiphon pisum, on broad bean plants, Vicia faba, which had been sprayed with a mixture of the chemicals, were lower than those on control plants. The effect, however, was no longer evident if parasitoid foraging was delayed by 24 hr after the plants were treated. The ecological significance of intraguild avoidance behavior and implications for possible use of the semiochemicals involved in future biological control programs are discussed.

Alkanes↗

PubMed2003

Laboratory evaluation of temperature effects on the germination and growth of entomopathogenic fungi and on their pathogenicity to two aphid species.

As part of an approach to select potential mycoinsecticides for aphid biocontrol, we investigated the effects of temperature on the growth, germination and pathogenicity of some hyphomycete fungi. Commercially available mycoinsecticides (based on Beauveria bassiana (Balsamo) Vuillemin and Verticillium lecanii (Zimmermann) Viegas) and other isolates of B bassiana, V lecanii, Metarhizium anisopliae (Metschnikoff) Sorokin and Paecilomyces fumosoroseus (Wize) Brown & Smith were evaluated. The rate of in vitro conidial germination of all isolates was slower at 10 and 15 degrees C than at 20 and 25 degrees C. Similarly, in vitro growth of most isolates was adversely affected at 10 and 15 degrees C. The greatest reduction at 10 degrees C in rates of conidial germination and colony growth, compared with other temperatures, was for M anisopliae isolates. Germination of V lecanii (isolate HRI 1.72) was fastest at 10 degrees C compared with the other fungi. It was also the most pathogenic of three isolates tested against Aphis fabae Scopoli and Myzus persicae Sulzer at 10, 18 and 23 degrees C. Generally, A fabae was more susceptible than M persicae to infection by the fungal isolates tested. A significant interaction between aphid species and temperature indicated that the pathogenic nature of an isolate was dependent not only on the target aphid species but also the temperature conditions of the bioassay. The series of studies, detailed above, allowed a temperature profile to be formed for the different isolates. Verticillium lecanii isolate HRI 1.72 (commercialised as Vertalec) was the most promising isolate selected from results of the series of experiments. Temperature profiles in conjunction with infectivity assays can be useful in selecting appropriate isolates for a particular thermal environment.

Animals↗

PubMed2003

cis-Jasmone treatment induces resistance in wheat plants against the grain aphid, Sitobion avenae (Fabricius) (Homoptera: Aphididae).

cis-Jasmone is a plant volatile known to have roles as an insect semiochemical and in inducing plant defence. It was evaluated in laboratory and field trials for control of cereal aphids. In an olfactometer bioassay cis-jasmone was repellent to alatae of the grain aphid, Sitobion avenae (Fabricius) (Homoptera: Aphididae). Moreover, wheat, Triticum aestivum (L), seedlings sprayed with formulated cis-jasmone 24 h previously were less susceptible to attack by S. avenae than control plants. In field simulator studies, significantly fewer alate S. avenae settled on cis-jasmone-treated plants over a 24-h period. In addition, the intrinsic rate of population increase, r(m), of S. avenae apterae was reduced on cis-jasmone treated seedlings. In a series of small-plot experiments conducted over four years, cis-jasmone applications reduced cereal aphid populations infesting wheat in the field.

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