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.

The distribution of aphid infestation in relation to leaf age

Abstract: The leaf-by-leaf distributions of free infestations of viviparous Myzus persicae (Sulz.) and Aphis fabae Scop, were recorded on sugar-beet plants and spindle bushes in pots in the greenhouse, and the distributions of the various seasonal forms of A. fabae were recorded on the same plants growing naturally outdoors. The aphid distributions were related to the ages of the leaves estimated on an arbitrary scale of ten types of leaf distinguished by degree of unfurling and colour. The diverse types of distribution recorded were all reducible to a common general pattern: growing and senescing leaves were more susceptible to colonization than maturing, mature and dying leaves. The resultant two-peaked curve of aphid density on a series of leaves at successive stages of development was found in its entirety on certain sugar-beet plants, but part only of the complete curve was usually found, owing to the incomplete range of leaf ages present on any one plant, particularly on the spindle tree. Fundatrigeniae were found colonizing sugar beet, and spring and summer migrants were found starting colonies on the spindle tree. The normal association of each seasonal form of the aphid either with the ‘primary’ winter host, or with a ‘secondary’ summer host, but not with both, is therefore not obligatory. It is attributed to the normal inaccessibility of summer hosts to fundatrigeniae and the normal unsuitability of the winter host when the ‘alienicolae’ are migrating and its leaves are mature. When M. persicae and A. fabae were infesting the same plant at the same time, their distributions were broadly alike, but M. persicae extended on to both younger and older leaves than did A. fabae and more strictly avoided the more mature leaves. Hence it is suggested that the degree of adaptation of a given aphid to a given plant may be gauged by the extent to which the aphid can colonize the plant's leaves not only when they are growing and senescing but also when they are mature and fully functional.

The natural occurrence of secondary bacterial symbionts in aphids

Abstract: 1. Many insects host secondary bacterial symbionts that are known to have wide-ranging effects on their hosts, from host-plant use to resistance against natural enemies. This has been most widely studied in aphids, which have become a model system to study insect–bacteria interactions. 2. While there is an increasing understanding of the role of symbionts in aphids from controlled laboratory studies, we are only beginning to explore the impact of hosting these symbionts on eco-evolutionary dynamics in natural systems. To date, many research groups have identified bacterial symbionts from various aphid species, providing us with a bank of literature on aphid–symbiont associations in natural populations. 3. The role of secondary symbionts in aphids is discussed, and the taxonomic and geographical distribution of symbionts among aphids are summarised, and the potential reasons for the patterns observed. The need to test for multiple symbiont species (and co-infections) across many individuals and the whole distribution range of an aphid is highlighted, including sampling on all known host-plant species. 4. It is further important also to consider variation within the symbiont, the aphid-host and the surrounding community, e.g. host-plants or the natural enemies, to understand how these have the potential to mediate aphid–symbiont interactions. 5. Finally, the knowledge gained from experimental work should now be used to understand the role of aphid secondary symbionts in field systems, to fully understand the potentially far-reaching consequences of aphid endosymbionts on community and ecosystem processes.

Indirect Interactions in Biological Control of Insects: Pests and Natural Enemies in Alfalfa

Abstract: The population dynamics of insect pests in agroecosystems may often be linked to those of other phytophagous species through the foraging activities of natural enemies; these indirect interactions provide both opportunities and challenges for biological control. We conducted field experiments to explore indirect interactions in the biological control of the alfalfa weevil (Hypera postica) in northern Utah. Honeydew produced by pea aphids (Acyrthosiphon pisum) in alfalfa fields may be important as a source of nutrition for adults of the wasp Bathyplectes curculionis and may thereby enhance parasitism of the wasp's host, the alfalfa weevil. The presence of aphids may also promote aggregation of lady beetles, which consume weevil larvae in alfalfa. But by feeding heavily on pea aphids as well, these predators could indirectly enhance weevil survivorship by undercutting the wasp's capacity to parasitize its host. In one field experiment, we added pea aphids and/or adults of the lady beetle Coccinella septempunctata to caged field plots of alfalfa during the first (spring) hay crop. Adding aphids increased levels of parasitism among late-maturing alfalfa weevil larvae. Adding lady beetles decreased numbers of late-maturing weevil larvae, but also decreased levels of parasitism among these larvae. In another experiment, repeated application of artificial honeydew to caged alfalfa plots during the first crop increased levels of parasitism among weevil larvae. In a third experiment, a single application of artificial honeydew to open (uncaged) alfalfa plots in mid-May also had a direct positive effect on rates of parasitism among larvae. However, this application had an indirect negative effect on parasitism as well: the presence of artificial honeydew caused aggregation of lady beetles and thus led to decreased aphid abundance. Consequently, provision of artificial honeydew as a food source for parasitoid adults was neutralized by a subsequent reduction in naturally occurring honeydew. These field experiments illustrate the complexity with which indirect interactions can affect exploiter-victim relationships in biological control. They also raise questions con- cerning the long-term consequences that may result from the purposeful introduction of the Old World lady beetle C. septempunctata to alfalfa and other crops in North America. Artificial honeydew may prove useful in enhancing parasitism of the alfalfa weevil, but frequent applications may be required to compensate for associated reductions in availability of naturally occurring aphid honeydew. The effects of honeydew producers on other her- bivores through natural enemies fall under the general concepts of short-term apparent competition and related ecological relationships among species, and highlight the impor- tance of temporal and spatial factors in indirect interactions.

Genetic linkage mapping of the soybean aphid resistance gene in PI 243540.

Abstract: The soybean aphid (Aphis glycines Matsumura) is a pest of soybean [Glycine max (L.) Merr.] in many soybean growing countries of the world, mainly in Asia and North America. A single dominant gene in PI 243540 confers resistance to the soybean aphid. The objectives of this study were to identify simple sequence repeat (SSR) markers closely linked to the gene in PI 243540 and to position the gene on the consensus soybean genetic map. One hundred eighty-four F2 plants and their F2:3 families from a cross between the susceptible cultivar Wyandot and PI 243540, and the two parental lines were screened with the Ohio biotype of soybean aphid using greenhouse choice tests. A SSR marker from each 10-cM section of the consensus soybean map was selected for bulked segregant analysis (BSA) to identify the tentative genomic location of the gene. The BSA technique was useful to localize the gene to a genomic region in soybean linkage group (LG) F. The entire F2 population was then screened with polymorphic SSR markers from this genomic region and a linkage map with nine SSR markers flanking the gene was constructed. The aphid resistance gene was positioned in the interval between SSR markers Satt334 and Sct_033 on LG F. These SSR markers will be useful for marker assisted selection of this gene. The aphid resistance gene from PI 243540 mapped to a different linkage group than the only named soybean aphid resistance gene, Rag1, from 'Dowling'. Also, the responses of the two known biotypes of the soybean aphid to the gene from PI 243540 and Rag1 were different. Thus, the aphid resistance gene from PI 243540 was determined to be a new and independent gene that has been named Rag2.