Aphid

About: Aphid is a research topic. Over the lifetime, 11380 publications have been published within this topic receiving 229721 citations. The topic is also known as: Aphidoidea & plant lice.

Molecular analysis of predation on parasitized hosts.

Abstract: Predation on parasitized hosts can significantly affect natural enemy communities, and such intraguild predation may indirectly affect control of herbivore populations. However, the methodological challenges for studying these often complex trophic interactions are formidable. Here, we evaluate a DNA-based approach to track parasitism and predation on parasitized hosts in model herbivore-parasitoid-predator systems. Using singleplex polymerase chain reaction (SP-PCR) to target mtDNA of the parasitoid only, and multiplex PCR (MP-PCR) to additionally target host DNA as an internal amplification control, we found that detection of DNA from the parasitoid, Lysiphlebus testaceipes, in its aphid host, Aphis fabae, was possible as early as 5 min. post parasitism. Up to 24 h post parasitism SP-PCR proved to be more sensitive than MP-PCR in amplifying parasitoid DNA. In the carabid beetles Demetrias atricapillus and Erigone sp. spiders, fed with aphids containing five-day-old parasitoids, parasitoid and aphid DNA were equally detectable in both predator groups. However, when hosts containing two-day-old parasitoids were fed to the predators, detection of parasitoid prey was possible only at 0 h (immediately after consumption) and up to 8 h post consumption in carabids and spiders, respectively. Over longer periods of time, post-feeding prey detection success was significantly higher in spiders than in carabid beetles. MP-PCR, in which parasitoid and aphid DNA were simultaneously amplified, proved to be less sensitive at amplifying prey DNA than SP-PCR. In conclusion, our study demonstrates that PCR-based parasitoid and prey detection offers an exciting approach to further our understanding of host-parasitoid-predator interactions.

Comparisons of Salivary Proteins From Five Aphid (Hemiptera: Aphididae) Species

Abstract: Aphid (Hemiptera: Aphididae) saliva, when injected into host plants during feeding, causes physiological changes in hosts that facilitate aphid feeding and cause injury to plants. Comparing salivary constituents among aphid species could help identify which salivary products are universally important for general aphid feeding processes, which products are involved with specific host associations, or which products elicit visible injury to hosts. We compared the salivary proteins from five aphid species, namely, Diuraphis noxia (Kurdjumov), D. tritici (Gillette), D. mexicana (Baker), Schizaphis graminum (Rondani), and Acyrthosiphon pisum (Harris). A 132-kDa protein band was detected from the saliva of all five species using sodium dodecyl sulfate polyacrylamide gel electrophoresis. Alkaline phosphatase activity was detected from the saliva of all five species and may have a universal role in the feeding process of aphids. The Diuraphis species cause similar visible injury to grass hosts, and nine electrophoretic bands were unique to the saliva of these three species. S. graminum shares mutual hosts with the Diuraphis species, but visible injury to hosts caused by S. graminum feeding differs from that of Diuraphis feeding. Only two mutual electrophoretic bands were visualized in the saliva of Diuraphis and S. graminum. Ten unique products were detected from the saliva of A. pisum, which feeds on dicotyledonous hosts. Our comparisons of aphid salivary proteins revealed similarities among species which cause similar injury on mutual hosts, fewer similarities among species that cause different injury on mutual hosts, and little similarity among species which feed on unrelated hosts.

Mortality of coccinellid (Coleoptera: Coccinellidae) larvae and pupae when prey become scarce

Abstract: Coccinellid larvae are known to prey upon conspecific and heterospecific eggs, larvae, prepupae, and pupae. This behavior may depend on both the aggregation and intensive search of potential cannibals and predators near aphid colonies and the disappearance of aphids before coccinellid larvae have completed their development. We examined how coccinellid density and prey availability influence cannibalism and interspecific predation of larvae and pupae of 4 species of coccinellids. We determined whether coccinellid mortality and dispersal were density-dependent when prey become scarce, and estimated the leaving rates of Coleomegilla maculata (DeGeer), Adalia bipunctata (L.), and Hippodamia convergens (Guerin) larvae from plants with aphids and plants without aphids. Our results show that larval and pupal cannibalism and interspecific predation occur more frequently when aphid populations crash, but we found no evidence of coccinellid density-dependent mortality or density-dependent larval dispersal among species. However, A. bipunctata and H. convergens were significantly more aggressive and more likely to leave a plant without aphids than was C. maculata. These results suggest that the decision to stay on a plant is not strongly aphid- or pollen-mediated for C. maculata, but the decision to stay or leave does appear to be aphid-mediated for H. convergens and to some extent A. bipunctata. Whether a coccinellid larva stays or leaves and its tendency to cannibalize can affect larval and pupal survival and the population dynamics of each species.

The spread of beet yellows and beet mosaic viruses in the sugar-beet root crop. II. The effects of aphid numbers on disease incidence

Abstract: Multiple regression analysis of the data described in a previous paper identified alate Myzus persicae of the spring and summer migrations as the most important factor affecting spread of beet yellows virus in the sugar-beet root crop in England. Apterae of M. persicae spread little virus, and the contribution of alatae and apterae of Aphis fabae was negligible. A simple mathematical model of the spread of infection was developed. Assuming that the crop is visited by N aphids at a time when the proportion of plants infected is k0, the predicted proportion of infection for a time 3–4 weeks later (k1) is k1=k0+ 100(1-k0) (1-e-N1), where I=p[(1-k0)t+k0t-1]/k0. This formula adequately accounts for the observed spread of infection when N=1/10 sticky trap count for the 3–4 weeks preceding the time when k0 infection is observed; p= probability of infection by a single aphid =½; t= number of movements per aphid effective for spreading beet yellows virus = 5. The good fit of this formula to the observed data supports the results of the regression analyses in showing that alate M. persicae were mainly responsible for spreading beet yellows virus. Once infection had been introduced into the root crops in the spring spread was mainly within fields, or between fields in the same neighbourhood. In areas where beet and mangold seed crops were grown intensively some infection was spread to the root crops by summer migrants from infected seed crops. Apart from this, the greater prevalence of yellows in seed crop areas was caused by the greater development of M. persicae infestation of the root crops which occurs in these areas. The proportion of plants infected by spring migrants entering the root crops before the end of June was small and variable. It did not vary significantly between seed and non-seed areas. This implies either that initial infection came equally from sources other than seed crops, or that, if the seed crops were the main sources of infection, winged aphids acquired infectivity by visiting them during migration, and later became very widely dispersed. In contrast to yellows, mosaic virus spread mainly in the neighbourhood of seed crops within the seed-crop areas. No significant relation between aphid numbers and increase of infection was established, but there is a strong suggestion that alatae of M. persicae and A. fabae spread the virus, and that the contributions of both species are equal. This suggests that mosaic virus is not spread by movement of aphids within the root crops, but only by infective migrants coming from outside sources. As the virus is non-persistent the sources must be near to the root crops, and as there is little internal spread many infective migrants are needed to cause a high level of infection. The seed crops fulfil these conditions as they are often severely infected with mosaic, and both vector species breed on them. The irregularity of the data relating aphid numbers to mosaic incidence is probably caused mainly by individual variation in the intensity of infection of seed crops, and in the proportion of migrants caught on the traps which actually derive from them.

Testing the importance of jasmonate signalling in induction of plant defences upon cabbage aphid (Brevicoryne brassicae) attack

Abstract: Background Phloem-feeding aphids deprive plants of assimilates, but mostly manage to avoid causing the mechanical tissue damage inflicted by chewing insects. Nevertheless, jasmonate signalling that is induced by infestation is important in mediating resistance to phloem feeders. Aphid attack induces the jasmonic acid signalling pathway, but very little is known about the specific impact jasmonates have on the expression of genes that respond to aphid attack.