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.

Effects of predator specialization, host plant and climate on biological control of aphids by natural enemies: a meta-analysis

Abstract: Aphids are among the most severe invertebrate pests of crops and cause high economic losses. The control of aphids by natural enemies is an essential ecosystem service with high relevance to management strategies applied in agricultural plant production and horticulture. However, the current knowledge on the effectiveness of specialist and generalist predators in aphid control with respect to host plants and climatic conditions has not yet been summarized in a meta-analytical approach. We collected 60 studies providing 168 independent cases of predator exclusion experiments to analyse how predator and host plant group and climatic conditions affect aphid control by natural enemies. Effects of natural enemies on aphid populations were strongest in assemblages that included specialist predators, either alone or with generalist predators. Generalists alone also reduced aphid numbers significantly, but not to the same extent as specialists. Effects of natural enemies were weaker on aphid populations feeding on legumes compared with aphids on grasses or herbs. The percentage reduction of aphids feeding on grasses, herbs or legumes was higher in treatments with assemblages or specialists alone compared with generalists with the largest difference on grasses. According to all field studies from the temperate zone, effects of natural enemies on aphid populations were strongest in areas with high precipitation seasonality. A relationship between predator effects and temperature seasonality was only found for the USA. Synthesis and applications. Specialist predators alone or assemblages of specialists and generalists had the strongest effect on aphid populations, especially when either feeding on grasses and herbs or when exposed to extreme weather events. The control of aphids by natural enemies is most promising in grass and herb crops, whereas it is less suited for controlling aphids in legume crops. Facing climate change, the effect of extreme weather events on aphid control by natural enemies will have further implications for developing management strategies for aphid control in the future. (Less)

Control of whitefly, Trialeurodes vaporariorum and cotton aphid, Aphis gossypii in glasshouses by two isolates of the fungus, Verticillium lecanii.

Abstract: SUMMARY The abilities of two isoiates of the entomopathogenic fungus, Verticillium lecanii (one isolated from whitefly and one from aphids), to control both aphids and whitefly on glasshouse cucumbers was investigated. Control of homologous hosts was better than that of heterologous hosts. A single spray of a commercial substrate-containing formulation of the ‘whitefly’ isolate controlled established whitefly populations satisfactorily on sprayed foliage and also when the whitefly moved up to younger untreated foliage. In addition, because the substrate permitted growth and sporulation of the fungus on leaf surfaces, whitefly populations introduced after a V. lecanii application were also controlled. Control of whitefly by the ‘aphid’ isolate alone was unsatisfactory although control could be obtained in conjunction with the hymenopterous parasite Encarsia formosa. Control of Aphis gossypii by the ‘aphid’ isolate was obtained by spraying a commercial formulation containing a substrate but not by spraying pure spore suspensions. The ‘whitefly’ isolate did not control aphids satisfactorily. The difference between the two isolates in pathogenicity for aphids and whitefly was supported by laboratory infectivity experiments.

Silicon influence on the tritrophic interaction: wheat plants, the greenbug Schizaphis graminum (Rondani) (Hemiptera: Aphididae), and its natural enemies, Chrysoperla externa (Hagen) (Neuroptera: Chrysopidae) and Aphidius colemani viereck (Hymenoptera: Aphidiidae)

Abstract: We studied the tritrophic interaction: wheat, greenbug Schizaphis graminum (Rondani) and its key natural enemies, Chrysoperla externa (Hagen) and Aphidius colemani Viereck, in plants with or without silicon fertilization. Treatments consisted of: 1) silicon application via the leaves; 2) silicon application in the soil 3) control (no application). The evaluations consisted of: a) free-choice aphid preference test in the laboratory, from the 35th day after plant emergence, and b) biological aspects of the immature stages of predator C. externa, feeding on aphids reared on plants from the different treatments. Two treatments were tried in the bioassays involving A. colemani: 1) silicon application in the soil, and 2) control (no application). The biological traits evaluated were: duration of the immature stage, longevity, sex ratio, total developmental time, and percentage parasitism. Silicon application increased the degree of resistance in wheat plants, decreasing greenbug preference in relation to the control. This result could be related to the mechanical barrier provided by silica deposition in the cell wall, which would make it difficult for the stylet to penetrate the plant tissue, as well as an increase in the synthesis of plant defense compounds. However, no indirect effect of silicon application was observed on the biological traits of either the predator or the parasitoid.

A consideration about the origin of aphid intracellular symbiont in connection with gut bacterial flora

Abstract: In an attempt to investigate the origin of the intracellular symbiont of the aphid (Buchnera), aphid gut aerobic bacteria were isolated, and their phylogenetic relations to other prokaryotes were examined based on nucleotide sequences of 16S rDNA. It turned out that there are seven aerobic bacterial groups which constitute major flora of the aphid's gut. As three of the isolated bacteria were identified as members of the family Enterobacteriaceae, and share the common ancestor with the intracellular symbiont, the nucleotide sequences of 16S rDNA were determined for 15 representative strains of the family Enterobacteriaceae. One of the gut microbes belonging to the family Enterobacteriaceae was identified as Erwinia herbicola that is found mainly on plant surfaces. This fact may suggest that the intracellular symbiont of aphid is derived from a habitant of plant on which host insects feed.

BYDV PREDICTOR: a simulation model to predict aphid arrival, epidemics of Barley yellow dwarf virus and yield losses in wheat crops in a Mediterranean‐type environment

Abstract: BYDV PREDICTOR, a simulation model, was developed to forecast aphid outbreaks and Barley yellow dwarf virus (BYDV) epidemics in wheat crops in the grainbelt region of southwest Australia, which has a Mediterranean-type climate. The model used daily rainfall and mean temperature to predict aphid (Rhopalosiphum padi) buildup in each locality before the commencement of the cereal-growing season in late autumn, and to forecast the timing of aphid immigration into crops. The introduction of BYDV by aphid immigrants, aphid buildup within the crop, spread of BYDV, and yield losses were predicted for different sowing dates. The model simulations were validated with 10 years’ field data from five different sites in the grainbelt, representing a wide range of scenarios. When first aphid arrival dates ranging from 1 June to 2 September were compared with predictions, 65% of the variation between sites and years was explained. Progress curves for the predicted percentage of plants infected with the serotype BYDV-PAV closely resembled the starting point and shape of those recorded in 14 out of 18 scenarios. Sensitivity analysis confirmed that the combination of a high proportion of immigrants vectoring BYDV, early sowing of crops and early start to aphid arrival relative to sowing date led to the most BYDV spread and greatest yield loss. The model was incorporated into a decision support system used by farmers in targeting sprays against aphids to prevent virus spread in autumn and winter. BYDV PREDICTOR could serve as a template for modelling similar virus/aphid vector pathosystems in other regions of the world, especially those with Mediterranean-type climates.