Showing papers on "Aphid published in 1980"

Aphid feeding by some polyphagous predators in relation to aphid density in cereal fields.

Abstract: (1) Samples of aphids and predators were taken from ten spring barley and winter wheat fields between May and September 1972-77. (2) The guts of c. 12 000 predators were dissected and the presence or absence of aphid remains recorded. Sixteen species of Carabidae, three species of Staphylinidae and one species of earwig were shown to have fed on aphids. (3) No overall relationship was found between the amount of feeding and aphid densities in the different years. But, when the species were considered separately, it was found that the proportion containing aphid remains increased with aphid density, though the form of this relationship varied between species. (4) Tachyporus spp. had a limited response to aphid density and Amara plebeja, A. aenea and Notiophilus biguttatus ate aphids only at higher aphid densities. Forficula auricularia, Agonum dorsale and Demetrias atricapillus were the most important, both in terms of the overall percentage containing aphid remains, and the predation index (proportion containing aphid remains during the aphid increase phase multiplied by the mean density of the predator at this time). These three species should be the most valuable in restricting build up of aphids. (5) Successful aphid predation at low aphid density may be partly related to the climbing ability of the predator.

Numerical response of coccinellids to aphids in corn in southern Ontario.

Abstract: Populations of two abundant coccinellid species, Coleomegilla maculata lengi Timberlake and Hippodamia tredecimpunctata tibialis Say, responded rapidly to corn leaf aphid populations [ Rhopalosiphum maidis (Fitch)] once the aphids became exposed to predation when the plants tasselled. Coleomegilla m . lengi oviposited at lower densities of aphids than did H . t . tibialis but H . t . tibialis was shown to have a greater numerical response than C . m . lengi at high densities of aphids due to its greater fecundity. The numerical response of the coccinellids by oviposition was linear with a lag of 1/2 week behind the aphid population.

Increased Production of Alatae by Aphids Reared on Oats Infected with Barley Yellow Dwarf Virus

Abstract: Morphological development of parthenogenetic viviparous Sitobion avenae (F.) and Rhopalosiphum padi (L.) (Hemiptera: Aphidae) was influenced by the condition of a host plant, Avena byzantina (Koch). Aphids reared on oats infected with various isolates of barley yellow dwarf virus (BYDV) were much more likely to mature as winged adults (alatae), than were aphids reared on healthy oats. In 15 experiments during a 2-yr period, 75% of 2670 aphids reared on BYDV-infected oats developed as alatae; 36% of 2470 reared in parallel on healthy oats developed as alate forms. A greater percentage of winged progeny was consistently produced on infected oats in all experiments, regardless of aphid species, morphology of parent aphid, or the BYDV isolate used. Results of one experiment indicated that BYDV-infected plants could influence aphids during 1st instar development to mature as alatae. Alatae production was also favored by senescing oat tissues. Differences in nitrogen metabolism, resulting in increased amino acid concentration in diseased or senescing plants, could explain increased alatae production. The possible importance of these observations in spread of plant luteoviruses by aphids is discussed.

Pirimicarb resistance in the melon and cotton aphid, Aphis gossypii Glover

Abstract: SUMMARY The resistance to pirimicarb of populations of Aphis gossypii Glover from several glasshouses in England was studied in the laboratory by topical applications of insecticide and by electrophoresis and isoelectric focusing of aphid esterases. When compared with a known susceptible population, the aphids were found to be resistant to pirimicarb. Esterase patterns produced from resistant populations by poly-acrylamide gel and starch gel electrophoresis and by isoelectric focusing consistently differed in both numbers of bands and migration rates from the susceptible type. Resistant A. gossypii were found infesting only chrysanthemums and would not transfer to cucumber, the host of the susceptible population.

Egg survival in the bird cherry-oat aphid, Rhopalosiphum padi.

Abstract: The number of aphids that survive winter is important in determining the number of aphids present in any year. The numbers of Rhopalosiphum padi L. and other cereal aphids are affected by meteorological and biological factors, (Jones & Dean, 1975, Rautap~t~i, 1976). This paper reports egg mortality and hatch rates in R. padi. Methods. Eggs of R. padi laid around the buds on seven Prunus padus saplings were counted after egg laying had ceased. They were then counted at weekly intervals and classified as mature, infertile or eaten. Mature eggs are shiny and black, infertile eggs remain green and those eaten by predators have a dull crumpled appearance or are absent. When the fundatrices started to hatch in March, the buds were inspected daily and the number of newly born fundatrices noted.

Studies on Entomophthora in populations of Aphis fabae on field beans

Abstract: SUMMARY The population of Aphis fabae on field beans at a site in Highfield, Rothamsted in 1973 reached its peak 1 wk earlier than that at an equivalent site in Mill Dam Close, Woburn, 29 km NW of Rothamsted. Epizootics of Entomophthora caused weekly maximum mortalities of adult apterae of 71% at Highfield and 67% at Mill Dam Close. These epizootics and the periodicity of Entomophthora conidia in the air closely paralleled the development of the aphid population. There was little evidence of a consistent relationship between Entomophthora infection and any of the weather factors considered. At both sites most mortality was caused by E. planchoniana though many aphids were killed by E. aphidis and E. obscura. E. fresenii and E. virulenta killed very few aphids. Most conidia in the air were of the E. aphidis-type. Up to 44% of alatae emigrating from bean crops were infected with Entomophthora, confirming that aphid migration is an important means of distributing the fungi. Aphid numbers rose to more than 1600/plant at both sites, in spite of the action of Entomophthora, and would probably have been less had the fungi been more abundant earlier in the season.

Enzyme variability in populations of aphids.

Abstract: From 1976 to 1978 nine aphid species were investigated electrophoretically. A low degree of polymorphism was found. Only 5 of the species were polymorphic, and only at most in 3 enzyme systems out of 19.

Population density of aphids at the time of settling and ovariole maturation inCoccinella septempunctata [Col.: Coccinellidae]

Abstract: In 1978 and 1979 in Central Bohemia the census of aphid populations on bean, sugar beet, cereals, maize, and alfalfa were taken at the time when overwinteredCoccinella septempunctata L. (1) settled and (2) the ovarioles of females ripened. Settling occurred immediately after aphid immigration. Minimum aphid density required for settling was estimated to about 10 aphids per 1 m2 of field area. The aphid density at the time of ovariole ripening equaled 1 aphid per 200–400 cm2 of leaf area.

Pathogens (Phycomycetes: Entomophthoraceae) of the blue-green aphid Acyrthosiphon kondoi Shinji and other aphids in Australia

Abstract: Aphid pathogens were collected in Australia, mainly from June 1977 until September 1979. A brief description is given of each of the six species of Entomophthora found; E. aphidis, E. exitialis, E. obscura. E. phalloides, E. planchoniana and E. virulenta. A key to these species is provided. The principal host aphids studied were two exotic legume aphids. Acyrthosiphon kondoi and Therioaphis trfolii f. maculata. In addition, pathogens were identified from Aphis craccivoua, Brevicoryne brassicae, Cliaetosiphon tetraihodum, Hyperoniyzus lactucae, Macrosiphum rosae, M. euplzorbiae, Myzus ornatus, M. persicae, Sitobion miscanthi, Rhopalosiphum rujabdorninalis, Acyrthosiphon pisum 'Broom-biotype' from Tasmania, Capitophorus elaeragni and three unidentified species. Three pathogens (E. exitialis, E. obscura and E. planchoniana) have been found causing epizootics in A. kondoi. Only one pathogen, E. obscura, occurs regularly in populations of T. trifolii f. maculata. The potential for introducing Entomophthora species for microbial control of aphids in Australia is discussed.

Energy and Nitrogen Relation for a Macrosiphum Liriodendri (Homoptera: Aphididae) Population in an East Tennessee Liriodendron Tulipifera Stand

Abstract: Biomass and density of all instars of a Liriodendron aphid population on three mature trees in an east Tennessee yellow "poplar" stand were determined for the 1971 growing season. Concurrently, laboratory studies were carried out to ascertain rates of each aphid instar's metabolism, growth, reproduction, and honeydew production. Similarly, whole body caloric content and concentrations of N were determined for each instar. Results from these studies were utilized in estimating ingestion of sap by the aphid population, and in developing a mathematical model of aphid population dynamics. These estimates were used in preparing annual budgets of dry matter, energy, and N for the population. Maximum aphid biomass of 169 mg dry mass/m2 ground area (Leaf Area Index = 4.7) occurred in early June coincident with maximum nitrogen concentrations in phloem sap and favorable canopy temperature. There was a second peak in population biomass in September, just prior to leaf abscission when nitrogen compounds were again mobile in the phloem streams. Reproduction and honeydew production were functions of temperature and followed a Q10 = 2 relationship. Metabolism and growth were also functions of temperature but increased exponentially (Q10 relationship) up to an optimum temperature, °22°C, and them declined rapidly. Values observed for these parameters were well within ranges reported in the literature for numerous aphid species. Energy budgets calculated for both laboratory and field populations of this aphid species indicate that M. liriodendri consumes ca. 400% of its dry body mass per day, or 185 kcal/m2 annually. Of this ingestion, 65% goes into honeydew production (egestion), 6% into respiration, and 27% into production of biomass. Similar budgets prepared for nitrogen indicate that 970 mg N/m2 are consumed annually, and of this, 27% goes into honeydew and 73% is incorporated into aphid biomass. Comparison of these data with standing pools of energy and nitrogen in the Liriodendron stand shows that this aphid population consumes 1% of annual photosynthate production and an amount equivalent to 17% of the annual standing crop of foliar N. The impact of this consumption on primary production is not presently known.

Barley yellow dwarf virus infectivity of alate aphid vectors in west Wales

Abstract: SUMMARY Live trapping at 0.9 m of alate aphid vectors of barley yellow dwarf virus (BYDV) at Aberystwyth from 1970 to 1979 showed that ten species transmitted the virus to oat test plants. Conversion of percentage infective at 0.9 m to numbers infective based on continuous trapping at 1.2 m showed Rhopalosiphum padi and R. insertum to be the main vector species in most years, whilst Metopolophium dirhodum and Sitobion auenae were normally of minor importance. The data obtained suggest that epiphytotics of BYDV in autumn-sown cereals were caused by numerous infective vectors flying late in the year and transmitting severe strains of the virus. Evidence is presented that gynoparae and males of R. padi are involved in the autumn spread of BYDV and that three further aphid species, Anoecia corni, Metopolophium albidum and M. frisicum are BYDV vectors. The use of live and continuous trapping techniques in forecasting BYDV epiphytotics is discussed.

The phenology and distribution of aphids in California alfalfa as modified by ladybird beetle predation (Coleoptera: Coccinellidae).

Abstract: The phenologies and distributions of pea aphid (Acyrthosiphon pisum (Harris)), blue alfalfa aphid (A. kondoi (Shinji)), and spotted alfalfa aphid (Therioaphis maculata (Buckton)) were intensively studied in California alfalfa. The results showed, as expected, that aphid populations across all densities were aggregated; but that ladybird beetle (Hippodamia convergens (G.-M.)) predation increased the degree of aggregation. The distribution parameters of the aphids were estimated using methods developed by Iwao and Kuno (1971).

Intergall migration in the aphid genus Pemphigus.

Abstract: Aphids of the gall-forming species Pemphigus populitransversus (Hemiptera: Aphidae) exhibit surprising amounts of within-gall diversity for allozyme phenotypes. The patterns are inconsistent with meiotically produced variation. Lack of variation within galls wrapped in cloth bags indicates that the variation is the result of among-gall dispersal by immature aphids.

Effect of Mineral Oil and a Systemic Insecticide on Field Spread of Aphid-Borne Maize Dwarf Mosaic Virus in Sweet Corn

Abstract: The percentage of field grown sweet corn plants infected by maize dwarf mosaic virus (MDMV) was significantly less for plants receiving applications of mineral oil (mineral oil = 15.4% and mineral oil and aphicide = 16.7%) than plants untreated (23.2%) and plants having only an aphicide treatment (27.7%). The mineral oil had no adverse affect on aphid population growth. The mineral oil caused no phytoxicity. Alates of the following species of aphids, known to transmit MDMV, were trapped: corn leaf aphid, Rhopalosiphum maidis (Fitch); English grain aphid, Macrosiphum avenae (F.); green peach aphid Myzus persicae (Sulzer); and potato aphid, Macrosiphum euphorbiae (Thomas).

An association between resistance to root aphid ( Pemphigus bursarius L.) and downy mildew ( Bremia lactucae Regel ) in lettuce

Abstract: Many lettuce cultivars (Lactuca sativa L.) with high resistance to lettuce root aphid (Pemphigus bursarius L.) also carried the gene Dm-6 for specific resistance to downy mildew (Bremia lactucae Regel). This suggests the possibility of linkage between this gene and root aphid resistance. The origin of this association is discussed.

Aphidius eadyi n.sp. (Hymenoptera: Aphidiidae), a widely distributed parasitoid of the pea aphid, Acyrthosiphon pisum (Harris) in the Palearctic.

Abstract: Aphidius eadyi n. sp., a parasitoid of Acyrthosiphon pisum in the west Palearctic is described. Its distribution and interspecific relations (crossing experiments) to a related species, Aphidius smithi, are elucidated. The new species has been found to be a promising agent in biocontrol of the pea aphid, Acyrthosiphon pisum, whereas it does not parasitize the blue alfalfa aphid, A. kondoi.

Effect of pea aphid and bluegreen lucerne aphid (Acyrthosiphon spp.) on coumestrol levels in herbage of lucerne (Medicago sativa)

Abstract: Field and glasshouse studies showed that infestations of pea aphid (Acyrthosiphon pisum Harris) and bluegreen lucerne aphid (A. kondoi Shinji) (BGA) caused increased coumestrol levels in herbage of lucerne (Medicago sativa cv. “Wairau”). Under field conditions log coumestrol concentration (ppm) was linearly related to aphid numbers and a reduction in stem length was associated largely with aphid damage. The coumestrol levels in severely aphid-damaged herbage were high enough to impair ewe fecundity. Glasshouse studies showed that similar levels of coumestrol were found in leaf and stem tissue of aphid damaged plants and that BGA infestations caused higher coumestrol levels than similar population levels of pea aphid.

Morphometric variation between populations of the balsam woolly aphid, Adelges piceae (Ratzeburg) (Homoptera: Adelgidae), in North America

Abstract: Morphological variation in characters of the first-instar and the adult stage of the balsam woolly aphid, Adelges piceae (Ratzeburg) (Homoptera: Adelgidae), were studied. Multiple discriminant anal...

Virus diseases of annual legume crops

Abstract: An increase in incidence and diversity of virus diseases of peas (Pisum sativum L.) dwarf beans (Phaseolus vulgaris L.) broad beans (Vicia faba L.) and field beans (V. faba L. minor) has followed the arrival in New Zealand of blue­ green lucerne aphid (BGLA) (Acyrthosiphon kondoi Shinji) and pea aphid (A. pisum Harris). Crop -surveys showed that alfalfa mosaic virus (AMY) has become prevalent and damaging in peas. Bean yellow mosaic (BYMV), cucumber mosaic and pea seed-borne mosaic viruses were also isolated from pea crops. Bean common mosaic virus was detected in dwarf bean crops for the first time in many years. BYMV and AMY were also isolated from this crop, from field beans and from broad beans. The incidence of subtenanean clover red leaf virus (SCRL V) was low probably due to use of resistant peas and the manipulation of sowing dates of beans to avoid aphid flights. A bait plant study showed that lucerne and white clover were good sources of AMY and the period during which this virus was most frequently isolated corresponded with the peak flight activity of BGLA but not with that of pea aphid. The bait-plant study also showed that although not a problem in the legume, crops, SCRLV was prevalent and that white clover was the main source of this virus and of its vector Aulacorthum so/ani Kltb. BGLA is a nonvector of SCRL V and pea aphid appeared to l!e of only minor importance as a vector of this virus.

Evaluation of six insect pests for transmission of potato spindle tuber viroid

Abstract: Six insect pests of potato, green peach aphid,Myzus persicae (Sulzer); potato leafhopper,Empoasca fabae (Harris); Colorado potato beetle,Leptinotarsa decemlineata (Say); tarnished plant bug,Lygus lineolaris (Palisot de Beauvois); red-legged grasshopper,Melanoplus femurrubrum (DeGeer); and southern army worm,Prodenia eridania (Cramer), were tested for their ability to transmit potato spindle tuber viroid (PSTV). PSTV infection was determined by a gel electrophoretic assay made 6 weeks after transfer of insects from infected to non-infected plants of the cultivar, ‘Katahdin.’ Plants grown from tubers of the original non-infected hosts were also assayed. PSTV was detected in only 2 of 183 test plants; these 2 plants had been infested with the tarnished plant bug. These results suggest that the insect species studied are relatively insignificant as vectors of PSTV.

Effects of aphids on seedling growth of lucerne lines. 2. Spotted alfalfa aphid (Therioaphis trifolii f. maculata (Monell)) in field conditions

Abstract: Seedlings of 23 lucerne lines introduced from the USA, and 2 Australian cultivars (Hunter River and Falkiner), were screened for resistance to the spotqed alfalfa aphid (Therioaphis trifolii f. maculata (Monell) (SAA) under field conditions during summer. This was assessed by measuring changes in plant mortality and yields from surviving plants in plots infested with SAA at the unifoliate leaf stage, compared, over a period of 19 days, with controls sprayed with insecticide. Cultivar Hunter River was extremely susceptible to SAA. It was the only line in which all seedlings died. Cultivar Falkiner was relatively susceptible, but no more so than 12 imported lines. Seven imported lines (WL 508, WL 512, WL 514, WL 600, CUF 101, UC Cargo and PS 572, all of which are known to be winter-active) exhibited greater resistance than the others. There was no association between the total number of SAA carried and their seedling resistance among the imported lines.

The Median Latent Periods for Three Isolates of Barley Yellow Dwarf Virus in Aphid Vectors

Abstract: VAN DER BROEK, L. J., and C. C. GILL. 1980. The median latent periods for three isolates of barley yellow dwarf virus in aphid vectors. Phytopathology 70:644-646. The median latent periods (LP 50) were determined for three isolates of Rhopalosiphum padi with R. padi-specific isolate 6524 the values were 50.1 barley yellow dwarf virus in their specific vector or most efficient vector at hr and 35.0 hr, and for R. padi with R. padi nonspecific isolate 7410 the two temperatures. The latent period per aphid was defined as the time lapse values were 62.4 and 35.2 hr, respectively. A decrease equivalent to 50% in from the start of the acquisition feeding period to the middle of the the median latent periods for a 10 C increase in temperature was found with inoculation day during which transmission of an infectious dose of virus the two aphid-specific isolates, but the decrease was more than 50% with first occurred. At 15 C and 20 C, the median latent periods for Sitobion the R. padi-nonspecific isolate. avenae with S. avenae-specific isolate 6407 were 65.5 hr and 44.5 hr, for Barley yellow dwarf virus (BYDV) is a luteovirus which is missions) were transformed to log-probits. The resulting curve was transmitted in a circulative manner by its aphid vectors. Currently rendered linear by a correction factor designed to compensate there is no evidence that this virus multiplies in the aphid (10) and for the excluded potential first transmissions by aphids that may multiplication that occurs in its host plants is limited to phloem have transmitted very late. A median latent period (LP 50) was cells (3,7,8). estimated. The method entailed the use of a short acquisition Viruses that are circulative in the vector, are characterized by a feeding period followed by a series of inoculation feeding periods of latent period which may be defined as the time that elapses between equal length on healthy test seedlings. Although empirical in nature, acquisition of the virus and the ability of the vector to first transmit this method appears to be well suited to persistent viruses especially the virus. The virus, therefore, is presumed to progress from the gut those with rather short latent periods. To enable adequate to the haemolymph, to the salivary glands and then into the plant comparisons to be made between virus isolates, this method was via the saliva. Determination of the length of the latent period is adopted to estimate the LP 50 with three variants of BYDV. The important for experimental work and also may be of value in effect of temperature on the latent periods was also examined. estimating whether the virus multiplies in the vector. Early estimations of the latent period of BYDV in its aphid MATERIALS AND METHODS vectors produced various results that reflected the different methods used by the investigators. Toko and Bruehl (16) using The aphids used were from one clone each of S. avenae and R. Sitobion avenae (Fabricius) (= Macrosiphum granarium [Kirby])- padi. Each clone was derived from a single adult aphid collected in specific and Rhopalosiphum insertum (Walker) (= R. fitchii the field in southern Manitoba in 1964. The aphids were reared on [Sand.])- specific isolates reported that after an acquisition feeding caged barley, Hordeum vulgare L. 'Parkland', in separate growth period of 24 hr, an inoculation feeding period of 4 hr was necessary cabinets at 18 ± 1 C with mixed incandescent and cool white before transmission occurred. Aphid nomenclature is according to fluorescent illumination for a daily 18-hr photoperiod. Aphids Eastop and Hille Ris Lambers (2). No transmission resulted from these colonies were tested weekly to ensure that they were free following an acquisition feeding period of 16 hr or less, even with an from BYDV. inoculation feeding period of 72 hr. Watson and Mulligan (18) The BYDV isolates were 6407, an isolate transmitted specifically working with a Rhopalosiphum padi (L.)-specific and an aphid- by S. avenae (4); 6524, transmitted specifically by R. padi; and nonspecific isolate reported that, of the R. padi individuals that 7410, an aphid-nonspecific isolate transmitted most efficiently by eventually transmitted virus, 32 hr of acquisition feeding was R. padi (6), called R. padi-nonspecific. These virus isolates were required for approximately 50% of the aphids to transmit. Orlob et maintained in oats, Avena byzantina C. Koch 'Coast Black', in a al (9) reported a minimum latent period of 6 hr for R. insertum (= growth cabinet at 17 ± 1 C. Individuals of S. avenae were used as R. fitchii) to transmit a Wisconsin strain of BYDV. Finally, vectors with isolate 6407, and individuals of R. padiwere used with Rochow (12) demonstrated that R. padi and S. avenae (= M. isolates 6524 and 7410. granarium) with their specific virus variants required about 5 days The method used for determining the median latent periods was to attain maximum transmission ability after acquisition feeding that of Sylvester (13) but with some modifications. Infected Coast periods of 12 hr or less. These results indicated the presence of at Black oat seedlings were prepared as follows for use as virus source least a short latent period for BYDV in the aphid, but the length of plants. Leaves were detached from oat plants in which virus isolates the period for a population of aphids was not well defined, were maintained, and placed with the basal end in moist sand in a In 1965, Sylvester (13) published an improved method for petridish. Virus-free aphids were placed in the dish and allowed an determining the latent period of pea enation mosaic virus in its acquisition feeding period of 2 days at 15 ± 0.5 C in the dark. Then aphid vector, based on an estimation of the time when 50% of the 10 feeding aphids were transferred in the morning to each of several aphids that eventually transmitted virus had achieved a first individually caged Coast Black oat seedlings at the one-leaf stage. transmission. These data (hours/percentage cumulative first trans- After a 30 hr inoculation feeding period the plants were sprayed with insecticide and were placed in a growth cabinet at 18 ± 1 C.

Effects of aphids on seedling growth of lucerne lines. I. Blue-green aphid in field conditions (Acyrthosiphon kondoi Shinji)

Abstract: Twenty-three lucerne lines introduced into Australia from the United States of America and two Australian cultivars (Hunter River and Falkiner) were screened for resistance to the blue-green aphid (Acyrthosiphon kondoi Shinji) (BGA), in the seedling stage under rain grown field conditions. Considerable tolerance to BGA was shown by seedlings of all lines infested at the 2-3 trifoliate leaf stage, as no seedling mortality occurred in the presence of high aphid populations. Using the suppression of both plant height and dry matter production as indices, six imported lines exhibited greater resistance than the others. These were DK 167, AS 49, WL 31 8, AS 13, WL 51 4 and CUF 101. There was no relation between the resistance expressed and the aphid population carried.