Showing papers on "Aphid published in 1987"
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01 May 1987
TL;DR: Control of Aphid Behaviour and Damage: Principles and Results.
Abstract: 10. Damage by Aphids. The Responses of Plants to the Feeding of Aphidoidea: Principles. The Responses of Plants to the Feeding of Aphidoidea: Specific Responses and Damage (P.W. Miles). Crop Loss Assessment (P.W. Wellings et al.). Viruses Transmitted by Aphids (E.S. Sylvester). 11. Control of Aphids. Chemical Control: Introduction. Chemical Control to Reduce Damage. Chemical Control to Reduce Virus Diseases (A. Schepers). Aphid Resistance to Insecticides (A.L. Devonshire, A.D. Rice). Biological Control: Introduction (M. Carver). Biological Control in the Open Field (R.D. Hughes). Biological Control in Greenhouses (P.M.J. Ramakers). Modifying Aphid Behaviour (R.W. Gibson, A.D. Rice). Host Plant Resistance (J.L. Auclair). Integrated Control (P. Harrewijn et al.).
747 citations
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TL;DR: It is concluded that aphid control by polyphagous predators is likely to be widely based.
Abstract: (1) Enzyme-linked immunosorbent assay (ELISA) was used to detect aphid consumption by predators collected from three fields of winter wheat. (2) A total of 7781 predators belonging to 105 species was tested and 81 species were found to have eaten aphids at some time during the study. (3) An unexpectedly high percentage of many species had eaten aphids when aphid density was low, early in the season. (4) The relative efficiencies of ELISA and gut dissection for detecting prey remains varied according to the species of predator tested, and secondary predation was a potential problem, especially in the former technique. (5) In general, staphylinid beetles and beetle larvae digested their aphid meal much more rapidly than carabid beetles and spiders. (6) Field data on percentage of predators positive in ELISA and on predator density were combined with laboratory data on digestion rates to give predation indices which enabled comparison of species in terms of some aspects of their probable value as aphid predators. Spiders usually had the highest predation indices, but mites and adult and larval beetles were also of significance as aphid predators. It is concluded that aphid control by polyphagous predators is likely to be widely based.
240 citations
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TL;DR: Several key predators which are abundant in spring cereal fields at a time when R. padi emigrants arrive in the crop and which feed on R.padi during the aphids' establishment phase, are identified and are suggested to be faster at higher temperatures than the rate of elimination of prey solids from the guts.
Abstract: SUMMARY
Polyphagous predators (e.g. Araneae, Carabidae and Staphylinidae), collected from spring barley fields during 1981-85, were examined by either gut dissection or a R. padi-specific antiserum in enzyme linked immunosorbent assay (ELISA) in order to detect predation of Rhopalosiphum padi during the aphids' establishment and exponential growth phases.
Overall 18% of c. 3000 carabids dissected were shown to feed on R. padi during the aphids' pre-peak period. No overall relationship was found between percentage carabids with R. padi in the diet and peak R. padi densities. Relatively high proportions of Bembidion spp. (particularly B. lampros) and Pterostichus cupreus fed on R. padi during the aphids' establishment phase, and proportions of those predator taxa containing R. padi increased with increasing R. padi densities in both high and low aphid density years. P. melanarius and Harpalus rufipes mainly fed on R. padi during the aphids' exponential growth phase.
Overall 11% of c. 1350 predators examined in ELISA gave positive reactions to the R. padi antiserum. Relatively high proportions of linyphiid and lycosid spiders were positive throughout the aphid pre-peak period. Several Acari, Opiliones, Trechus spp. (Carabidae), Philonthus spp. (Staphylinidae), Cantharidae and Chilopoda were positive mainly during the aphids' exponential growth phase. Sample sizes were small, however.
Very few of the Bembidion spp. tested in ELISA were positive compared with those examined by gut dissection. The maximum period of R. padi protein (antigen) detection in B. lampros was related to temperature, i.e. 8.5 h at 30°C, 20.5 h at 20°C and 34.5 h at 10°C, respectively. It is suggested that the rate of R. padi protein digestion in B. lampros is faster at higher temperatures than the rate of elimination of prey solids from the guts.
Several key predators (in this case B. lampros, P. cupreus and linyphiid spiders) which are abundant in spring cereal fields at a time when R. padi emigrants arrive in the crop and which feed on R. padi during the aphids' establishment phase, are identified. The results are compared with those from similar investigations elsewhere with predators of Sitobion avenae and Metopolophium dirhodum.
144 citations
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TL;DR: Parallels between the mechanism of aphid-plant and pathogen-plant attack are pointed out and how aphid bacterial endo-symbiotes play a central role in host-plant selection.
Abstract: The importance of host-plant resistance of crop plants in the biological control of aphids and the formation of aphid biotypes is discussed. The rapid response of plant breeders to the formation of new aphid biotypes requires detailed knowledge on the mechanism of host-plant resistance. Current knowledge on the chemical basis of host-plant resistance to aphids is summarized. Of central importance to this relationship is the aphid-pectinase plant-pectin interdependence. Parallels between the mechanism of aphid-plant and pathogen-plant attack are pointed out and how aphid bacterial endo-symbiotes play a central role in host-plant selection.
142 citations
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01 Jan 1987
TL;DR: Aphids are ideally suited for transferring plant-infecting viruses from host to host because of the piercing-sucking mouthparts, mode of dispersal, and prolific reproductive behavior of aphids.
Abstract: Aphids are ideally suited for transferring plant-infecting viruses from host to host. The piercing-sucking mouthparts, mode of dispersal, and prolific reproductive behavior of aphids facilitate survival and spread of plant viruses over large areas. Two general mechanisms have been described to explain how aphids transmit plant viruses. One mechanism involves aphid acquisition of virus during brief probes of the aphid’s stylet into epidermal cells of virus infected plants. During these exploratory test probes the stylets penetrate epidermal cells and the aphid ingests cell contents into the fore gut, especially the maxillary food canal, cibarial pump, and pharynx. During ingestion some viruses suspended in the plant cytoplasm are believed to adhere to the lining of the fore gut (27, 28, 55). Adherence of virus to the chitin-lined fore gut may involve an interaction between the virus and other compounds (helper factor) produced in the infected cell (4). If the aphid completes a test probe on an infected plant and then moves immediately to another plant and initiates a second test probe, it is believed that some of the virions in the lumen are adhering to the lining of the fore gut may detach and be expelled or egested into the newly penetrated epidermal cell being sampled (27, 28). For unknown reasons aphids lose the ability to transmit viruses by this mechanism within minutes or hours. This type of transmission is, therefore, described as non-persistent transmission. Other types of viruses are probably transmitted by a similar mechanism; however, aphids retain the ability to transmit these viruses for up to several days. This type of transmission has been described as semipersistent (27, 28, 46).
95 citations
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TL;DR: This information should prove very useful to county, state, and federal personnel involved with surveys of grain aphids, particularly those surveys for D. noxia as it spreads into other grain-growing areas of the United States.
Abstract: In the United States, Diuraphis noxia (Mordvilko), variously called the “Russian wheat aphid,” the “Russian grain aphid,” and the “barley aphid,” was first collected and identified in March 1986, near Muleshoe, Bailey County, Tex. By the end of 1986, D. noxia had been collected in Colorado, Kansas, Nebraska, New Mexico, Oklahoma, Texas, and Wyoming on wheat, barley, oats, rye, triticale, and several grasses. Damage to wheat and barley during 1986 was extensive in some fields in Texas, New Mexico, and Colorado; crop losses were heavy in these areas. In addition to D. noxia , 12 other aphid species are known to colonize leaves of wheat, barley, and other small grains and some related grasses in the United States. A brief summary of taxonomic characteristics, usual hosts, and known distribution within the United States is given here for each species along with a couplet key and pictorial plates. This information should prove very useful to county, state, and federal personnel involved with surveys of grain aphids, particularly those surveys for D. noxia as it spreads into other grain-growing areas of the United States.
93 citations
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TL;DR: It is suggested that mycetocyte loss may represent an important means by which the symbiont population is regulated and can be interpreted as evidence for substantial variation in the characteristics of nutritional interactions between the aphid and its symbionts with age and morph of the aphids.
88 citations
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TL;DR: Phloem sap of oats and barley showed similar patterns in their composition of free amino acids at the seedling stage, but as the plants grew older the patterns became increasingly different, and the relative growth rates of R. padi nymphs were low when amino acid content was low and vice versa.
Abstract: SUMMARY
The concentrations and composition of free amino acids in phloem sap from two cultivars of oats and barley, both susceptible to the aphid Rhopalosiphum padi, were determined by means of high performance liquid chromatography Sap was collected from excised aphid stylets at three developmental stages (seedlings, tillering plants and plants undergoing stem elongation) from plants given or not given fertiliser and grown outdoors In connection, the growth of individual R padi nymphs was estimated at the same phenological stages on plants grown in the greenhouse
The content of free amino acids was consistently higher in seedlings than in plants at the early tillering stage Only in seedlings did the addition of fertiliser increase amino acid levels Barley phloem sap contained more free amino acids than that of oats when fertiliser was added and at later developmental stages
Phloem sap of oats and barley showed similar patterns in their composition of free amino acids at the seedling stage, but as the plants grew older the patterns became increasingly different Plants given fertiliser had higher amounts of dicarboxylic amino acids (glutamic and aspartic acid) than unfertilised plants The concentrations of γ-amino butyric acid, glycine, histidine, and methionine were very low in all treatments
The relative growth rates of R padi nymphs were low when amino acid content was low and vice versa The results are discussed in relation to host plant suitability and plant resistance mechanisms
85 citations
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TL;DR: The turnip aphid, Lipaphis (Hyadaphis) erysimi, responds weakly to (E)-β-farnesene, but the response is substantially increased by incorporating plant-derived isothiocyanates, identified in aphid volatiles by coupled gas chromatography-single-cell recording.
Abstract: The turnip aphid,Lipaphis (Hyadaphis) erysimi, responds weakly to (E)-β-farnesene, the main component of the alarm pheromone, but the response is substantially increased by incorporating plant-derived isothiocyanates, identified in aphid volatiles by coupled gas chromatography-single-cell recording.
81 citations
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TL;DR: Aphid dispersion was manipulated in the field to determine how the different spatial patterns of the two species influenced reproduction and mortality, and hence the relative tendencies of their populations to irrupt, and found that feeding in large colonies provided no reproductive advantage to either species.
Abstract: Two aphid species, Uroleucon nigrotuberculatum and U. caligatum, that feed on the goldenrod Solidago altissima, are similar in life histories and feeding habits, but differ markedly in their spatial distribution and temporal variability. In this study, U. caligatum typically occurred in small colonies scattered throughout goldenrod fields, and its numbers remained relatively constant through time, whereas U. nigrotuberculatum occurred in dense colonies and exhibited greater fluctuations in population size. The aggregated spatial pattern of U. nigrotuberculatum resulted from both active aggregation of alates and lack of dispersal by apterae and nymphs. Field experiments in which colony size was held constant revealed that U. nigrotuberculatum enjoyed no clear reproductive advantage that might explain its greater tendency to outbreak. In addition, U. nigrotubercultatum was more susceptible to generalist predators (such as cantharid beetles, mirid bugs, and mites) than U. Caligatum. Aphid dispersion was then manipulated in the field to determine how the different spatial patterns of the two species influenced reproduction and mortality, and hence the relative tendencies of their populations to irrupt. Feeding in large colonies provided no reproductive advantage to either species. Aggregation did, however, enhance aphid survivorship when generalist predators were the main mortality agents. The advantage was reversed later in the season when the aphids' fungal pathogen was present; aggregation then led to a decrease in survivorship. Thus, aggregation allowed a numerical escape from generalist predators but also promoted fungal epidemics, so that the temporal variability in U. nigrotuberculatum populations was largely a consequence of its spatial distribution.
72 citations
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TL;DR: The dose-response curve is discussed in relation to reported changes in the nitrogen metabolism of plants subject to air pollution, the response of aphids to host plant nitrogen and possible toxic effects of high concentrations of SO(2) on the aphid.
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TL;DR: The dynamics of migration of the parasitoids Aphidius spp. between grassland and cereal fields of varying sowing dates was investigated in southern England in 1980 and 1981 as mentioned in this paper.
Abstract: The dynamics of migration of the parasitoids Aphidius spp. between grassland and cereal fields of varying sowing dates was investigated in southern England in 1980 and 1981. Using baffled water traps, direct evidence of migration of A. rhopalosiphi De Stefani Perez females from grassland to winter wheat was obtained in June 1980, suggesting that the early-maturing grassland aphid Metopolophium festucae (Theobald) can act as a reservoir of cereal aphid parasitoids. In 1981, estimates of parasitoid production in cereal fields containing the aphids Sitobion avenae (F.), M. dirhodum (Walker) and Rhopalosiphum padi (L.) were compared with actual numbers to calculate net immigration and emigration. Barley and early-sown wheat (drilled before 14 October) proved to be significant sources of Aphidius spp., with one wheat field generating sufficient parasitoids in May to account for immigration into about 25 late-sown fields. Parasitoid migration as larvae inside aphid alatae was apparently of considerably less significance than that by adults, which were predominantly female. The advantages of early drilling of cereals to form ‘semi perennial’ reservoirs of beneficial insects is discussed and weighed against the corresponding disadvantages, especially an increased risk of barley yellow dwarf virus (BYDV).
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TL;DR: It is predicted that honeydews are important in the development of Leishmania infantum Nicolle in the gut of P.ariasi, and tests on females caught in a house showed that, having taken blood, the females stop taking sugar until the bloodmeal is completely digested.
Abstract: Wild-caught Phlebotomus ariasi Tonnoir, starved until their sugar meals had been digested, were caged for 24 h with plants or plants infested with aphids and then tested for fructose, a constituent of plant sap. No evidence was found that the flies took sap directly from nine types of plants present in their habitat. About two-thirds of flies caged with oak (Quercus ilex L.) infested with an aphid [Lachnus roboris (L.)] and about a fifth kept with leaves of the french bean (Phaseolus vulgaris L.) infested with an aphid took honeydew. Experiments with three other aphid species gave negative results. Of sandflies caught in an oak tree infested with aphids, half of the females and three-quarters of the males contained fructose. Tests on females caught in a house and grouped according to state of engorgement showed that, having taken blood, the females stop taking sugar until the bloodmeal is completely digested. It is predicted that honeydews are important in the development of Leishmania infantum Nicolle in the gut of P. ariasi.
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TL;DR: There was no difference in the level of infection between the native and introduced species that were represented, but the Arundinoideae and Panicoideae were predominantly infected with RPV types, while the Pooideae, with the exception of Dactylis glomerata and Poa pratensis, were mainly infected with PAV types.
Abstract: Samples of 2077 grasses and cereal plants representative of the Poaceae found in Tasmania were collected from a wide range of habitats throughout the State. Each sample was examined for infestation with aphids and then checked for infection with viruses causing barley yellow dwarf by both aphid transmission and serological tests. Aphid species found among the samples were Hyalopterus pruni, Rhopalosiphum maidis, R. padi and Sitobion fragariae. R. padi transmitted a vector non-specific type of barley yellow dwarf (PAV) and a vector specific type (RPV), either alone or together, while S. fragariae transmitted PAV alone and occasionally RPV when present in plants together with PAV. The other aphid species did not transmit. A total of 189 samples contained virus. Incidence was greatest in samples from the Bambusoideae subfamily (31%) and least in the Arundinoideae (4%). There was no difference in the level of infection between the native and introduced species that were represented. The Arundinoideae and Panicoideae were predominantly infected with RPV types, while the Pooideae, with the exception of Dactylis glomerata and Poa pratensis, were predominantly infected with PAV types. Many more infected plants contained both PAV and RPV (11.9%) than would have been expected had the two types of virus infected independently (2.5%). No infected plants were found among samples from 25 of the 56 species tested, and some of these may prove useful in breeding for resistance to barley yellow dwarf viruses.
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TL;DR: It is suggested that the observed niche partitioning cannot be the result of interspecific competition in variable environments such as maize monocultures.
Abstract: Principal components analysis was used to assess niche partitioning between four aphid predators on the basis of oviposition strategies. The study was conducted by sampling abundance and position of the eggs of these predators in corn monocultures in two locations of southern Quebec. The results indicated that the chrysopid Chrysopa occulata Say laid its eggs on corn leaves usually without aphid colonies, and late in the season. All other predators reacted to aphid concentrations. The syrphid Sphaerophoria philanthus (Mg.) oviposited close to the ground, early in the season, and among colonies of the aphid Rhopalosiphum padi (L.). The two coccinellids laid their eggs during July and August with a maximum during tasseling for Coleomegilla maculata lengi (Timberlake) and after pollination for Hippodamia tredecimpunctata tibialis Say. Of these two species, the latter one selected sites at higher levels on the plant, and was more abundant at the edges of the field. It is suggested that the observed niche partitioning cannot be the result of interspecific competition in variable environments such as maize monocultures.
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TL;DR: There was only a weak association between the total number of alates and the proportion of PVYo-infected progeny tubers infected by potato virus Yo, and the association became stronger when only known PVYo vectors were considered and the effect of mature-plant resistance was also taken into account.
Abstract: The relationship between the occurrence of alate aphids and the proportion of progeny tubers infected by potato virus Yo (PVYo) was studied in 7 regions of Sweden from 1976 until 1984. The importance of mature-plant resistance and the proportion of PVYo diseased potato source plants were also considered.
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TL;DR: The demographic statistics and the temperature requirements for development of Ephedrus californicus Baker were determined under constant laboratory conditions and the potential use of E. califORNicus in the biological control of the lupine aphid, Macrosiphum albifrons Essig, in England is considered.
Abstract: Can. Ent. 119: 231-237 (1987) The demographic statistics and the temperature requirements for development of Ephedrus californicus Baker were determined under constant laboratory conditions. At 23"C, females provided each day with forty 2nd-instar pea aphids, Acyrthosiphonpisum (Harris), lived for 13.4 days and laid 1193 eggs on average; the highest fecundity of any female was 1762 eggs. For an assumed population sex ratio of 1: 1 males to females, the intrinsic rate of increase, r, was 0.371 females.female-l.day-L when all eggs laid were counted. The lower temperature-threshold for development, t, was estimated as 6.83"C, and the time-to-adult, K, as 228.9 degree-days. The potential use of E. californicus in the biological control of the lupine aphid, Macrosiphum albifrons Essig, in England is considered.
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TL;DR: A relationship was found by both methods between the density of aphid on the plants and the numbers of aphids on the soil that indicated that a higher proportion of the aphid population was on the soils surface at the lower densities on the plant.
Abstract: SUMMARY
The numbers of cereal aphids on the soil surface was assessed by soil samples and by counting the numbers captured in pitfall traps. A relationship was found by both methods between the density of aphids on the plants and the numbers of aphids on the soil. This relationship indicated that a higher proportion of the aphid population was on the soil surface at the lower densities on the plant. Reasons for this relationship are suggested and discussed.
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TL;DR: The results indicated that resistance to BYDV infection occurs in several Agropyron species, and infection might be avoided in cereal cul tivan by resistance to phloem contact and ingestion.
Abstract: Shukle, R. H .• Lampe, D. J ., Lister, R. M .• and Foster, J. E. 1987. Aphid feeding behavior: Relationship to barley yellow dwarf vi rus resistance in Agropyron species. Phytopathology 77: 725-729. The infectibility of various Agropyron species (wheatgrasses) was examined with respect to thl\"« isotates of barley yellow dwarf virus (BYDV) by infl:$ting them with appropriate vector aphids, followed by testing by enzyme-linked immunosorbent assay. Feeding behavior of the VCi:tors Rhopalosiphum padi and SilObion avenoe was also electronically monitored to determine their abi lity to inoculate phloem. The results indicated that resistance to BYDV infection occurs in several Agrop>'n}n species. For most species tested. resistance seemed due to failure in virus increase. but in $Orne species a major constraint on infection \\\\'as the inability ofvcctors 10 locate phloem. Two potential approaches to breeding for reduced BYDV in wheat by crossing with Agropyron species may thus be: incorporating facto rs reducing or preventing virus production and incorporating factors reducing the ability of \"ectors to inoculate plants successfully. Addirlonal kry words: 8 YDV-resistant germ plasm.luteoviru.ses, wheat improvement. The term barley yellow dwarf virus (BYDV) includes at least five variously interrelated types of luteovirusts (9. 18) that are appa rently res t ricted to gramineou5 plants. They cause yellowdwarf diseases in cereals that affect the su pply of whcat, oats, and barley throughout the world (6, 18). Like the other luteovirusts, Th. publlc'!ion COlt. of !ht •• nlcle wer. def,.yed In p.,t by p.~ chl'g. p.yment This .,Uct. mu\" lI,or.r.,..o be horoby mlrked \" • .,.. ... ,; ..... .\",In _,,.nco wllh t8 U.S.C. t 11304 s
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TL;DR: The drought, which developed concurrently with the decline and may have reduced source populations on non-irrigated lucerne plants thus lowering immigration rates into irrigated crops, broke in 1983 with no indication of aphid resurgence since.
Abstract: SUMMARY satisfactorily account for it. The capacity of the aphid to infest and increase on susceptible lucerne remains unchanged. The drought, which developed concurrently with the decline and may have reduced source populations on non-irrigated lucerne plants thus lowering immigration rates into irrigated crops, broke in 1983 with no indication of aphid resurgence since. Insecticide use, although high at first, decreased rapidly with the reduction in infestations. Relative to the rate of decline, the replacement of aphid- susceptible lucerne with aphid-resistant varieties proceeded slowly to reach only 10%/o in 1981 and 26%/o in 1984. The majority of lucerne grown in Australia is still susceptible to the aphid. Although native predatory insects became numerous in aphid-infested crops, they did not reduce aphid numbers sufficiently consistently to account for the decline. (4) Of the hymenopterous parasites, only one, Trioxys cornplanatus, became generally widespread and numerous throughout the lucerne-growing areas of Australia. (5) Parasitization by T. complanatus increased from one lucerne growth cycle to the next and higher levels were associated with aphid infestations that did not increase to damaging levels. (6) Observed reductions in the proportion of apterous adult female aphids in field populations were consistent with estimates of parasitization by T. complanatus. (7) When the properties of the aphid and parasite, as measured in the laboratory, were assembled into a simulation model of their interacting life systems on irrigated lucerne crops, outputs from the model closely matched the observed field data. Furthermore, the simulated population at harvest from initial lucerne growth cycles, when used as input for other runs of the model, resulted in good simulations of aphid and parasite populations in subsequent cycles in the same season. (8) It is concluded that Therioaphis trifolii on irrigated lucerne crops was biologically controlled by the introduced hymenopterous parasite Trioxys complanatus. (9) The short-term (say 5-year) value of the biological control, in terms of the reduction in the cost of insecticide applications needed to prevent loss and spoilage of the N.S.W. lucerne-hay crop, has probably been of the order of 1 million dollars a year. In terms of reduced urgency for replanting with aphid-resistant varieties, the value was similar. Over the whole of Australia, the value would be proportionally greater. (10) Although T. complanatus was known to be less effective at high summer temperatures, this did not prevent an overall reduction in immigration rates, although some alates still infest many crops.
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TL;DR: Infestation of the aphid altered the amino acid balance of Sitka spruce foliage but not the concentration of total amino acids, and the effect was more pronounced on Sitka than on Norway spruce.
Abstract: SUMMARY
The effect of chlorosis induced in needles of Sitka and Norway spruce by the green spruce aphid on growth of the aphid is investigated, and the effect of infestation of the aphid on amino acid levels in Sitka spruce foliage is reported.
On both Sitka and Norway spruce green spruce aphids were heavier when reared on chlorotic (previously infested) needles than when reared on green (previously uninfested) needles. The effect was more pronounced on Sitka than on Norway spruce. Infestation of the aphid altered the amino acid balance of Sitka spruce foliage but not the concentration of total amino acids. Possible causes of chlorosis, the influence of individual amino acids on aphid growth, the potential effect of chlorosis on outbreaks of the aphid and the differences in susceptibility of Sitka and Norway spruce to damage by the aphid are discussed.
01 Jan 1987
TL;DR: Besides the slower penetration of organophosphorus insecticides into the aphids of resistant populations, the use of synergists including methyl iodide, SV1 and piperonyl bul oxide has given evidence whether mixed function oxidases (MFO), carboxylcsterase and glutathion S-transferase are involved in the formation of resistance.
Abstract: The cotton aphid Aphis gossypii Glover is oue of the most important pests infesting cotton in the cotton areas of North China. Since 1953 organophosphorus insecticides have been used to-control the aphid for keeping up good yield of cotton. At present, resistance of the aphid to insecticides has become a vital probl閙 in cotton production. This has prompted us to investi-gata the mechanism of resistance to organophosphorus insecticides and to search for the strategy to control the resistant aphids.All experiments were performed on apterous viviparous female aphids and topical applica-tion was adopted for testing the effct of insecticides on the aphids. Three populations of cot-ton aphids (B-Beijing, Q = Qing Dao, and G = Gao Mi) were compared. The LD50 values of parthion and paraoxon on aphids of population B, Q and G were 38 and 4, 59 and 9, and 93,5 and 21 ng/aphid respectively. Besides the slower penetration of organophosphorus insecticides into the aphids of resistant populations, the use of synergists including methyl iodide, SV1 (O, O-diethyl O-phenyl phosphorothionate) and piperonyl bul oxide has given evidence indica-ting whether mixed function oxidases (MFO), carboxylcsterase and glutathion S-transferase are involved in the formation of resistance. MFO seems to be one of the factors causing resistance, but the cotton aphid homogenates in v韙ro are found to contain endogenous inhibitors of MFO. The results also showed that the sensitivity of AChE to paraoxon in resistant population G was 1.9 and 14.2 times lowcr than that in populations Q and B. The activities of L-Na este-rases and L-NA carboxylesterases in population G were respectively 2.3-15.4 and 18.0-70.0 times higher than that in populations Q and B. The activities of esterases showed rnore conspi-cuous difference in the three populations.
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TL;DR: In this article, a field cage in southern England enclosing single rows of potatoes and infested with differing initial proportions of S (susceptible), R1 (moderately insecticide resistant) and R2 (very resistant) clones of Myzus persicae (Sulzer) were sprayed three times, at 14-day intervals, with pirimicarb (carbamate), demeton-S-methyl (organophosphorus) or a mixture of deltamethrin and heptenophos (pyrethroid and organoph
Abstract: Field cages in southern England enclosing single rows of potatoes and infested with differing initial proportions of S (susceptible), R1 (moderately insecticide resistant) and R2 (very resistant) clones of Myzus persicae (Sulzer) were sprayed three times, at 14-day intervals, with pirimicarb (carbamate), demeton-S-methyl (organophosphorus) or a mixture of deltamethrin and heptenophos (pyrethroid and organophosphorus insecticides). The numbers of aphids on top, middle and basal leaves were counted, pre-treatment and one and eight days after each of the three sprays. The resistance genotype frequencies of the three variants were determined by an immunoplate assay which measures the amount of the carboxylesterase E4, the enzyme conferring resistance, in individual aphids. All three chemicals selected strongly for the very resistant variant. After three sprays, R2 aphid frequencies approached or equalled fixation (1·00) for both starting frequencies. However, the deltamethrin-heptenophos mixture selected for R2 aphids more rapidly than the other chemical treatments. Increasing the initial starting frequency of R2 aphids from 0·02 to 0·20 led to a more rapid increase of their frequencies towards 1·00 for all chemicals. The numbers of aphids on all treated plots were less than on the control. However, the more rapid increase in the proportion of R2's on plots treated with deltamethrin plus heptenophos, coupled with enhanced nymph production, resulted in a smaller reduction in numbers than was achieved by the other chemical treatments. The need for novel control methods is discussed in the light of the strong selection for R2 aphids exerted by all three insecticide classes.
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TL;DR: In this paper, a distributed delay age structure model is presented for plants and insects that describes the dynamics of per capita energy (dry matter) acquisition and allocation patterns, and the within-organism subunit (e.g. leaves, fruit, ova) number dynamics that occur during growth, reproduction, and development.
Abstract: A distributed delay age structure model is presented for plants and insects that describes the dynamics of per capita energy (dry matter) acquisition and allocation patterns, and the within-organism subunit (e.g. leaves, fruit, ova) number dynamics that occur during growth, reproduction, and development. Four species of plants (common bean, cassava, cotton, and tomato) and two species of insects (pea aphid and a ladybird beetle) are modeled. A common acquisition (i.e. functional response) submodel is used to estimate the daily photosynthetic rates in plants and consumption rates in pea aphid and the ladybird beetle. The focus of this work is to capture the essence of the common attributes between trophic levels across this wide range of taxa. The models are compared with field or laboratory data. A hypothesis is proposed for the observed patterns of reproduction in pea aphid and in a ladybird beetle.
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TL;DR: It is shown that the rate at which aphids lose MDMV inoculativity is lower when solid surface probing behaviour is denied, and thatMDMV retention times are longer than those previously published.
Abstract: SUMMARY
In total, 17 589 aphids were assayed for rate of loss of inoculativity and maximum retention times of maize dwarf mosaic (MDMV). The Standard-treatment, involved acquisition access to MDMV-infected tissue followed by confinement of active aphids in Petri dishes. In addition various aphid immobilisation treatments were used to prevent probing on solid surfaces after acquisition access to simulate conditions experienced by wind-borne aphids when aloft. Immobilisation treatments, using nitrogen or argon gases at 25°C, or cold treatments at 6°C after acquisition access greatly increased the efficiency of MDMV transmission by greenbugs, Schizaphis graminum, in an experimental design where insects were individually assayed for transmission over a 7 h period.
Further tests in which groups of greenbugs were assayed for MDMV transmission revealed that MDMV strains may be retained for over 21 h, regardless of post-acquisition access treatment. Experiments with other aphid vectors of MDMV (Dactynotus ambrosiae, Macrosiphum euphorbiae, Rhopalosiphum maidis and Myzus persicae) also demonstrated MDMV retention times exceeding 18 h.
These results show that the rate at which aphids lose MDMV inoculativity is lower when solid surface probing behaviour is denied, and that MDMV retention times are longer than those previously published. The findings are discussed in relation to the epidemiology of nonpersistent viruses and their dispersal over great distances.
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TL;DR: The reproduction of aphids on acid-treated birches was enhanced when precipitation was below long term average, suggesting an interaction between the stress caused by acid treatment and dry periods.
Abstract: The effect of artificial acid rain on the reproduction and survival of the aphid Euceraphis betulae on silver birch was studied in Turku, southern Finland. Eight bioassays were done during 1984-1986. In four of the bioassays the aphids produced 40% to over 100% more progeny on birches watered with dilute sulphuric acid (pH 3.5) than on control trees. In four other cases the performance of aphids did not differ between the treatments. An index of aphid reproduction pooled over the whole study was significantly higher on acid-treated than on control birches. The reproduction of aphids on acid-treated birches was enhanced when precipitation was below long term average, suggesting an interaction between the stress caused by acid treatment and dry periods.
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TL;DR: Foliar insecticide treatments were applied at various stages of plant growth to control natural infestations of two cereal aphids, the English grain aphid, Sitobion avenae (F.), and the rose-grass Aphid, Metopolophium dirhodum (Walker), in field plots of spring wheat.
Abstract: Foliar insecticide treatments were applied at various stages of plant growth to control natural infestations of two cereal aphids, the English grain aphid, Sitobion avenae (F.), and the rose-grass aphid, Metopolophium dirhodum (Walker), in field plots of spring wheat. Yield increases of 2.7 t/ha (36.5%) and 1.2 t/ha (29.3%) were obtained when sprays were applied at flowering in 1984 and 1985, respectively. Lower but significant yield increases were also obtained when sprays were applied at the milky ripe and early dough stages. Depending on the cost of chemical treatment and price received per kilogram of wheat, the economic injury level was calculated to be 15 and 10 aphids per tiller in 1984 and 1985, respectively. Based on the plant growth stage and the rate of aphid population growth, economic thresholds were calculated to be 2–4 aphids per tiller at flowering, 6–10 aphids per tiller up to the milky ripe stage, and 10 or more aphids per tiller from the milky ripe to medium-dough stage. After the medium-dough stage, treatment cannot be justified.
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TL;DR: Twenty-seven accessions of Hordeum species and interspecific hybrids were screened in a growth chamber for resistance against the aphid Rhopalosiphum padi and the most resistant species were all diploids.
Abstract: Twenty-seven accessions of Hordeum species and interspecific hybrids were screened in a growth chamber for resistance against the aphid Rhopalosiphum padi. Resistance measurement was based on the aphids' population growth during a 16-day period. The mean number of nymphs produced per female was only about 14% of that on the control cv. Tellus. H. bogdani was the most resistant accession. As a group, interspecific F1-hybrids with common barley (H. vulgare × H. sp.) held an intermediate position. Differences in resistance between hybrids as well as between species (H. jubatum and H. lechleri) were observed. The most resistant species were all diploids. No effects of the host plant on formation of alatae or on the within-plant distribution of aphids were found.