PubMed Health⌕ Search

Biomedical subjects

P G Alderson

Publications and source records attributed to P G Alderson.

6 recordsLinked to original sources
PubMed2006

Effect of fungal infection on the reproductive potential of aphids and their progeny.

The effect of infection by Pandora neoaphidis and Beauveria bassiana on the reproductive potential of the pea aphid, Acyrthosiphon pisum, and their progeny was assessed. Infection by either P. neoaphidis or B. bassiana reduced the number of nymphs produced within 24 h of inoculation and over the entire infection period compared to uninfected aphids. However, infection by either P. neoaphidis or B. bassiana for 24 or 72 h did not alter the intrinsic rate of increase of the host aphid's progeny. Therefore, fungal infection appears to have no indirect effects on the fitness of the host's progeny.

Animals↗
PubMed2005

Pandora neoaphidis transmission and aphid foraging behaviour.

Pandora neoaphidis is an aphid-specific entomopathogen that produces infective conidia. As aphid movement increases, so does the likelihood of contact with conidia. Volatile distress signals released in response to aphid infestation as an indirect defence against herbivory may affect aphid foraging and, therefore, the fungus-aphid interaction. In this study, two different methods were used to investigate the effect of plant volatiles and P. neoaphidis-sporulating cadavers on (1) the colonisation of Vicia faba plants by Acyrthosiphon pisum and (2) P. neoaphidis transmission. This study indicates that A. pisum does not avoid bean plants containing P. neoaphidis and that transmission of conidia occurs during plant colonisation and, to a lesser extent, during in situ feeding. Although significantly more aphids were recovered from damaged plants compared to undamaged plants, the likelihood of infection was not affected by previous infestation by aphids.

Animals↗
PubMed2005

Response of the entomopathogenic fungus Pandora neoaphidis to aphid-induced plant volatiles.

We used a model plant-aphid system to investigate whether the aphid-specific entomopathogenic fungus Pandora neoaphidis responds to aphid-induced defence by the broad-bean plant, Vicia faba. Laboratory experiments indicated that neither in vivo sporulation, conidia size nor the in vitro growth of P. neoaphidis was affected by Acyrthosiphon pisum-induced V. faba volatiles. The proportion of conidia germinating on A. pisum feeding on previously damaged plants was significantly greater than on aphids feeding on undamaged plants, suggesting a direct functional effect of the plant volatiles on the fungus. However, there were no significant differences in the infectivity of P. neoaphidis towards A. pisum feeding on either undamaged V. faba plants or plants previously infested with A. pisum. Therefore, these results provide no evidence to suggest that P. neoaphidis contributes to plant indirect defence strategies.

Animals↗
PubMed2003

Effect of spatial heterogeneity on the role of Coccinella septempunctata as an intra-guild predator of the aphid pathogen Pandora neoaphidis.

The foraging behavior of starved and non-starved adult and larval Coccinella septempunctata on groups of plants in the presence of Pandora neoaphidis-infected Acyrthosiphon pisum, uninfected aphids or a mixture of these two prey types was compared. In general results of these studies confirmed the results of previous work comparing foraging behavior on a smaller spatial scale in Petri dishes. However, behaviors were modified in response to spatial complexity, prey quality, and the host plant. Starved C. septempunctata adults and larvae fed for longer and consumed more aphids than non-starved coccinellids. Both larvae and adults fed on infected aphids and in some cases entirely consumed them. This was thought to be due to the ease of capture of infected (dead) aphids and the feeding stimuli provided by the presence of the host plant and, where there was a choice of prey, uninfected aphids in the environment. Both larvae and adults spent the majority of the time foraging in the upper regions of plants and visited more plants when they were not starved or when they were in the presence of less suitable, infected aphid prey.

Animals↗
PubMed1998

Implications of predator foraging on aphid pathogen dynamics.

The foraging behavior of starved and nonstarved second and fourth instar Coccinella septempunctata larvae on dead Acyrthosiphon pisum aphids, either infected with the entomopathogenic fungus Erynia neoaphidis (sporulating) or uninfected, was examined. Larvae searched for longer and fed less when presented with infected rather than uninfected A. pisum. Although no sporulating infected aphids were completely consumed, both adult and larval ladybirds can still be considered as intraguild predators. In a further study, fourth instar larvae fed on dying infected, dead infected (not sporulating), and dead uninfected aphids for similar periods of time but again the infected aphids were seldom entirely consumed. Live uninfected aphids were fed upon for significantly longer than any other prey. Infected aphids which were damaged at an early stage of infection (0, 1, or 2 days after inoculation) did not sporulate, whereas damaged moribund aphids (3 days after inoculation) did subsequently sporulate. Damaged sporulating cadavers continued to sporulate. However, damage to moribund and sporulating infected aphids, both mechanical or due to C. septempunctata feeding, reduced the number of conidia subsequently produced. Larval feeding caused the most significant reduction. Under laboratory conditions, C. septempunctata foraging on infected aphids did, therefore, reduce the pathogen density. However, conidia produced from a damaged cadaver resulted in levels of transmission to healthy aphids comparable to that resulting from an intact cadaver. Furthermore, the presence of a foraging adult ladybird resulted in a significant increase in transmission of the fungus to healthy aphids. Preliminary studies to assess the potential of other aphid natural enemies as intraguild predators illustrated that adults of the generalist carabid, Pterostichus madidus, entirely consumed sporulating cadavers. Third instar lacewing, Chrysoperla carnea, and hoverfly, Episyrphus balteatus, larvae never fed on sporulating cadavers. The ecological implications of these results are discussed.

Animals↗