Showing papers on "Aphid published in 1981"

An experimental investigation of inter-relationships between the wood-ant (formica rufa) and some tree-canopy herbivores

Abstract: SUMMARY (1) Previous work on interactions between F. rufa and some canopy herbivores is briefly reviewed. (2) In limestone woodland in N. England, populations of defoliators (illustrated by the Winter Moth, Operophtera brumata L.), a non-tended aphid species (Drepanosiphum platanoidis Schr.) and a tended aphid species (Periphyllus testudinaceus Fernie), are all affected by the presence of the ant. (3) Predation of D. platanoidis by F. rufa results in significant depression of the population compared with experimental conditions where ants were excluded from shoots. (4) Trees without ants have significantly higher populations of Lepidoptera larvae than do foraged trees. (5) On trees with ants an average of 1% of the leaf area had been removed by defoliators at the end of the season; without ants the total was nearly 8%. (6) Formica rufa tended eight aphid species and one psyllid in the woodland. The association of F. rufa with one of the aphids (P. testudinaceus) was studied. (7) Periphyllus testudinaceus populations were significantly increased in the presence of ants. When ants were excluded from colonies on shoots a significant fall in numbers occurred. There was probably also a reduction in the proportion of alatae. (8) The results are discussed in relation to previous work on aphid predation by ants and to the practice of introducing ants into woodland to protect trees from the effects of defoliators. It is concluded that this practice may be ill-founded.

The effect of cereal growth stage and feeding site on the reproductive activity of the bird‐cherry aphid, Rhopalosiphum padi

Abstract: SUMMARY Apterous Rhopalosiphum padi on the first leaf of cereal plants, developed faster and were more fecund at seedling to stem extension of barley, at tillering to earing of oats and at stem extension and earing of wheat. Feeding site on a mature plant also affected the rate of development and fecundity of the aphids; the largest and most fecund developed on the stems of oat and wheat plants. The consequences of these variations in reproductive performance are discussed in relation to the population dynamics of R. padi and its possible pest status in Britain.

Intraspecific variability in herbivore performance and host quality: a field study of Uroleucon caligatum (Homoptera: Aphididae) and its Solidago hosts (Asteraceae)

Abstract: . 1. Performances of two clones of Uroleucon caligatum on eleven clones of Solidago were measured by caging aphids on plants in the field. 2. Several measures were obtained, including developmental time from birth to adulthood, size of first instar nymphs, adult weight, and total colony weight. 3. All measures of performance were strongly affected by plant clone. 4. Effect of aphid clone-plant clone interaction was significant only for first instar size. 5. In a subsequent screenhouse experiment, plant clones were subjected to uniform conditions and still exhibited large differences in host quality.

Alate aphid (Homoptera: Aphididae) species and their relative importance as field vectors of soybean mosaic virus

Abstract: SUMMARY A technique was developed and deployed in central Illinois to trap and assay aphid alatae for incidence of soybean mosaic virus (SMV) transmission among naturally occurring transient aphid populations downwind of a field of infected soybean. In a 2-yr study, 1709 alate aphids were trapped alive and assayed, 4.2% of which transmitted SMV. Five species of aphids accounted for more than 93% of the transmissions: Aphis craccivora Koch, Macrosiphum euphorbiae (Thomas), Myzus persicae (Sulzer), Rhopalosiphum maidis (Fitch), and Rhopalosiphum padi (L.). At least 55 additional species were assayed, five of which transmitted only once. Others did not transmit. Because virus infection during the early growth stages of soybean increases the loss of yield and the percentage of seed-borne virus, vector species that tend to fly middle to late spring are, from an economic point of view, more important in the spread of SMV. R. maidis flew in mid- to late summer and in autumn. R. padi was not abundant at any time of year and its transmission efficiency was low. M. persicae tended to fly in mid summer. Two species (A. craccivora and M. euphorbiae) which had major flights in late spring and early summer and relatively high transmission efficiencies are potentially important in the economic spread of SMV in central Illinois. A third species, Aphis citricola Van der Goot, may also be important because it flies in late spring and laboratory data suggest it is a relatively efficient vector of SMV. A. citricola was not assayed by our technique because we trapped in the morning and this species appears to fly later in the day.

Quantitative studies on the uptake and retention of potato leafroll virus by aphids in laboratory and field conditions

Abstract: SUMMARY Enzyme-linked immunosorbent assay (ELISA) was adapted for the efficient detection and assay of potato leafroll virus (PLRV) in aphids. Best results were obtained when aphids were extracted in 0.05 M phosphate buffer, pH 7.0, and the extracts incubated at 37 °C for 1 h before starting the assay. Using batches of 20 green peach aphids (Myzus persicae), about 0.01 ng PLRV/aphid could be detected. The virus could also be detected in single aphids allowed a 1-day acquisition access period on infected potato leaves. The PLRV content of aphids depended on the age of potato source-plants and the position of source leaves on them. It increased with increase in acquisition access period up to 7 days but differed considerably between individual aphids. A maximum of 7 ng PLRV/aphid was recorded but aphids more usually accumulated about 0.2 ng PLRV per day. When aphids were allowed acquisition access periods of 1–3 days, and then caged singly on Physalis floridana seedlings for 3 days, the PLRV content of each aphid, measured subsequently, was not strongly correlated with the infection of P. floridana. The concentration of PLRV in leaf extracts differed only slightly when potato plants were kept at 15, 20, 25 or 30 °C for 1 or 2 wk, but the virus content of aphids kept on leaves at the different temperatures decreased with increase of temperature. PLRV was transmitted readily to P. floridana at all temperatures, but by a slightly smaller proportion of aphids, and after a longer latent period, at 15 °C than at 30 °C. The PLRV content of M. persicae fed on infected potato leaves decreased with increasing time after transfer to turnip (immune to PLRV). The decrease occurred in two phases, the first rapid and the second very slow. In the first phase the decrease was faster, briefer and greater at 25 and 30 °C than at 15 and 20 °C. No evidence was obtained that PLRV multiplies in M. persicae. These results are compatible with a model in which much of the PLRV in aphids during the second phase is in the haemocoele, and transmission is mainly limited by the rate of passage of virus particles from haemolymph to saliva. The potato aphid, Macrosiphum euphorbiae, transmitted PLRV much less efficiently than M. persicae. Its inefficiency as a vector could not be ascribed to failure to acquire or retain PLRV, or to the degradation of virus particles in the aphid. Probably only few PLRV particles pass from the haemolymph to saliva in this species. The virus content of M. euphorbiae collected from PLRV-infected potato plants in the field increased from early June to early July, and then decreased. PLRV was detected both in spring migrants collected from the plants and in summer migrants caught in yellow water-traps. PLRV was also detected in M. persicae collected from infected plants in July and August, and in trapped summer migrants, but their PLRV content was less than that of M. euphorbiae, and in some instances was too small for unequivocal detection.

The role of cereal growth stages and crowding in the induction of alatae in Sitobion avenae and its consequences for population growth

Abstract: . 1. Alatiform nymphs of Sitobion avenae were first recorded on wheat in 1977 and 1978 when there were 0.6 aphids per tiller and reached a maximum proportion of 0.9 of the population despite a seventeen-fold difference in aphid density between years. 2. At the same aphid density per tiller there was a higher proportion of alatiform nymphs on the tillers at an advanced than at an earlier stage of plant growth. 3. Both pre- and post-natal crowding, and late stages of plant growth, were important in inducing the development of alatae in the laboratory. 4. Changes in the quality of the host plant through its previously reported effect on reproductive and survival rates, and its effect on alate induction and emigration was important in shaping the population dynamics of S.avenae on cereals.

Defense Against the Green Peach Aphid and Potato Leafhopper by Glandular Trichomes of Solanum berthaultii

Abstract: The roles of type A and B gladular trichomes in defense of the wild potato species, Solanum berthaultii Hawkes, agamst the green peach aphid, Myzus persicae (Sulzer), and Potato leafhopper, Empoasca fabae (Harris), were assessed. Mortality of fourth-stadium M. persicae and encasement of tarsi and labia by type A exudate increased with a rise in density and volume of type A trichomes. Tarsi coated by type B exudate were highly adhesive and extremely effective in discharging type A trichomes. Immature stages of M. persicae and E. fabae were subject to greater mortality and encasement of body parts by trichome exudate than were adults.

Effect of Weedy Backgrounds on Colonization of Collards by Green Peach Aphid, Myzus persicae , and Its Major Predators

Abstract: Insect colonization of collards in contiguous weedy and weed-free plots was monitored in 1978 and 1979. Green peach aphids, Myzus persicae (Sulzer) preferentially invaded weed-free collards and developed higher densities thereon. Numbers of Chrysopa oculata (Say), Coccinellidae, and Syrphidae were higher in plots in which weeds were uncut, despite lower aphid densities. When weeds were trimmed to 10 cm maximum height, predators became more numerous on weedless collards. Predator response were generally inefficient, especially when overall aphid densities were low.

Host searching and oviposition behaviour of some parasitoids of aphidophagous Syrphidae

Abstract: 1 An analysis of host searching behaviour suggests that female parasitoids respond to aphid odours bringing them to the region of an aphid colony 2 Syrphid hosts are located within the aphid colony by response to contact chemicals on the larval integument 3 The behavioural mechanisms used by syrphid larvae to resist attacks and the subsequent responses made by parasitoids are described 4 Oviposition behaviour and host size preferences of parasitoids are described

Control of aphid density by a complex of predators.

Abstract: A series of field experiments using large field cages were used to evaluate the role of aphidophagous predators on the population dynamics of the pea aphid, Acyrthosiphon pisum (Harris), on alfalfa, Medicago sativa L. The pea aphid numbers increased rapidly in the cages to as much as 5 times the density in the adjacent fields. The difference between densities in the cage and field decreased as the season progressed. No significant differences in fecundity of the aphids were found either in clip cages in the field and cages, or in the laboratory using field-collected aphids that were allowed to larviposit for 24 h. We used an earlier simulation model of the aphid to show that if fecundity alone were responsible it would have to be 3 times the maximum rate we have ever observed. The return of the aphid density to the field value when one cage was removed and the aggregation of predators show the importance of predator movements in limiting prey numbers.

Growth, survival and reproduction of the bird‐cherry aphid, Rhopalosiphum padi, on its primary host

Abstract: SUMMARY Fundatrices died when caged on senescent leaves of bird cherry on which oviparae thrived. Fundatrigeniae had more ovarioles and a higher reproductive rate than fundatrices. Oviparae developed and matured eggs on unfurling leaves but they took longer to reach maturity and grew more slowly than when reared on senescent leaves. Fundatrices and oviparae in addition to having an intrinsic preference for bird cherry over other plants did better on particular growth stages of their primary host.

The influence of aphid prey consumption on searching behavior, weight increase, developmental time, and mortality of chrysopa carnea (neuroptera: chrysopidae) and hippodamia convergens (coleoptera: coccinellidae) larvae

Abstract: J . U. BAUMGAERTNER,' A. P. GUTIERREZ,' and C. G. SUMMERS^ University of California, Berkeley 94720 Abstract Can. Enr. 113: 1007-1014 (1981) The behavior of larval stages of the green lacewing, Chrysopa carnea Stephens, and of the ladybird beetle Hippodamia convergens G.-M. were studied in the laboratory. With increasing hunger level, only first instar H. convergens larvae spent more time searching in the upper part of alfalfa stems, where both prey aphids, Acyrthosiphon pisum (Harris) and Acyrthosiphon kondoi (Shinji), are found. All larval instars tested except first instar C. carnea visited more stems per unit time with increasing hunger level. The weight gain, the developmental time, and the mortality of all larvae were adversely influenced at low food levels, but differently for each predator size and species. C. carnea larvae had higher rates of fat body utilization and weight gain than coccinellid larvae.

Monitoring for cereal aphids in winter wheat

Abstract: A simple monitoring method for cereal aphids is described which diminishes observation time and can be used by farmers themselves. By repeated observations the farmers can follow the population upsurge of the aphids. A description of the yield decrease — aphid density relation is given which may help to decide whether control measures against cereal aphids are needed.

The role of Anthocoris species (Hemiptera: Anthocoridae) in the integrated control of the damson‐hop aphid (Phorodon humuli)

Abstract: SUMMARY Field studies in 1974, 1975 and 1976 investigated integrated control of the damson-hop aphid Phorodon humuli on hops. After the aphicidal effects of an early-season soil drench of mephosfolan had declined, natural enemies controlled the aphids for the remainder of the season. Anthocorid bugs, particularly Anthocoris nemoralis, were the most abundant predators. In each year a rapid decline in aphid numbers occurred in mid- to late-July, coinciding with the peak numbers of fourth and fifth instar larvae and adults, the most voracious anthocorid stages. Aphids in the cones remained under control for the rest of the season in 1974 and 1975, and increased in 1976 but damaging numbers did not develop. When predators were excluded by caging mephosfolan-treated bines, high aphid densities developed on the leaves, and the cones were heavily infested. Plants not treated with an insecticide were almost completely defoliated by late-July. Heavily infested ‘missed bines’, due to uneven uptake of mephosfolan, attracted large numbers of anthocorids, which later dispersed into the surrounding plants.

Effects of infection with the cabbage black ringspot strain of turnip mosaic virus on turnip as a host to Myzus persicae and Brevicoryne brassicae

Abstract: SUMMARY When turnip plants with 3–7 leaves were inoculated with cabbage black ringspot virus (CBRSV) on the 3rd rough-leaf, symptoms only appeared on leaves that had been less than 15 mm long at the time of inoculation, although infection decreased the area and both fresh and dry weight of all leaves. Leaves were ‘aged’ by their appearance and placed in Leaf Age Categories (LACs). Leaves with symptoms senesced (‘aged’) prematurely. CBRSV-infection of cv. Green Top White did not change the distribution of populations of Myzus persicae between LACs, but increased the proportion of the plant suitable for colonisation. All suitable LACs were quickly colonised by adult apterae and nymphs. On CBRSV-infected plants the nymphal period was shorter, F1 adults deposited larvae more frequently and the live body weight and tibial length of the F2 generation was greater, than on healthy plants. The distribution of Brevicoryne brassicae populations on cv. Green Top White differed from that of M. persicae but was also unchanged by CBRSV-infection. On healthy plants the largest colonies were on mature leaves, so that on virus-infected plants premature senescence shortened the life of the colony. On CBRSV-infected plants the nymphal period was prolonged and the live weight of F1 and F2 adult apterae was less than on healthy plants. The differences between the biology of M. persicae and B. brassicae on CBRSV-infected cv. Green Top White were associated with the accelerated senescence of CBRSV-infected leaves. The possibility that CBRSV-infection might reduce the resistance of turnips to aphid infestation was tested. M. persicae and B. brassicae were cultured on two favourable and two less favourable cultivars. No improvement in population growth rate was found when the less favourable host cultivars were infected with CBRSV, but both aphid species weighed less and/or had smaller nymphal populations on cultivars showing the severest symptoms. These results are discussed in relation to the evolution of non-persistent virus transmission by aphids.

Factors affecting egg survival in the bird cherry-oat aphid, Rhopalosiphum padi

Abstract: Adams, C. M. & Bernays, E. A. (1978). The effect of combinations of deterrents on the feeding behaviour of Locusta migratoria. Ent. exp. & appl. 23 : 101--109. Ascher, K. R. S. & Meisner, J. (1973). Evaluation of a method for assay of phagostimulants with Spodoptera littoralis larvae under various conditions. Ent. exp. & appl. 16 : 106~114. Clark, J. V. (1980). Changes in feeding rate and receptor sensitivity over the last instar of the African armyworm Spodoptera exempta (Wlk.) (Lepidoptera: Noctuidae). E n t . exp. & appl. 27 : 144--148.

The effect of temperature on the growth and reproduction of two closely related aphid species on sycamore

Abstract: . 1. Egg hatch in the two species of sycamore aphid was temporally separated: the median time to hatch was 30 days later in Drepanosiphum acerinum than in D.platanoidis. 2. D.platanoidis was larger at egg hatch than D.acerinum. Progeny of D.platanoidis adults were also larger than those of D.acerinum. 3. D.platanoidis was the larger of the two species as an adult, as a consequence of its greater birth weight. 4. Over a range of temperatures, development rates in the two species were the same, while the growth rate in D.acerinum was significantly higher at high temperatures. 5. The reproductive rate of the two species was significantly different at 6dC and 20dC.

The effect of introducing aphid‐pathogenic Entomophthoraceae into field populations of Aphis fabae

Abstract: SUMMARY During two warm, dry seasons (1975 and 1976) aphid-pathogenic species of Entomophthoraceae introduced into Aphis fabae populations on field beans established briefly but failed to spread. In cool moist seasons (1977 and 1978), the fungi, principally Erynia neoaphidis and Neozygites fresenii, spread more rapidly in treated than untreated plots. In 1977, the maximum aphid population in plots treated with fungi reached a mean of 9000/plant on 19 July compared with 16 000/plant 1 wk later in untreated plots. The corresponding yield of beans in treated plots was twice that in untreated plots though only half that in plots kept free of aphids with pirimicarb. In two experiments in 1978, the maximum aphid population in treated areas was 700/plant, half that in untreated areas and 1 to 2 wk earlier. Yields from treated plots, however, were not significantly different from those from untreated plots. In nature, the fungi attack A. fabae populations in England only after they have become damaging, partly because fungal inoculum is sparse when the aphid population is small.

Transmission of Cauliflower Mosaic Virus by the Green Peach, Turnip, Cabbage, and Pea Aphids

Abstract: The green peach aphid, Myzus persicae (Sulzer), and turnip aphid, Hyadaphis erysimi (Kaltenbach), transmitted cauliflower mosaic virus at a higher rate after single short acquisition probes than after a 6-h acquisition access period. The cabbage aphid, Brevicoryne brassicae (L.), transmitted the virus at a higher rate after a 6-h access period than after single short acquisitions probes. The pea aphid, Acyrthosiphon pisum (Harris), consistently transmitted at a high rate after prolonged access to the virus source but at a variable rate after single short probes. Retention of inoculativity of the virus by the cabbage aphid can be longer than 24 h, but this degree of retention did not occur with the other three vectors. Little difference occurred in the transmission rates of the virus between adults and 1st instars of the green peach or the pea aphid. However, adult cabbage aphids transmitted at about twice the rate of nymphs, whereas nymphs of the turnip aphid transmitted the virus at more than four times the rate of adults.

Response of Natural Enemies to the Green Peach Aphid in Different Plant Cultures

Abstract: In field tests in 1977 and 1978, both parasites and predators of the green peach aphid, Myzus persicae (Sulzer), displayed definite preferences for different host plants. Parasitic activity by Diaeretiella rapae (M'Intosh) was 6 and 10 × greater in broccoli plots than in either radish or sugarbeet plots, respectively, but predators were 2–5 × less active on broccoli. Some predators, including Geocoris bullatus (Say) and Coccinella transversoguttata Falderman, exhibited host plant preferences unrelated to prey density. Greenhouse tests with G. bullatus confirmed these findings.

Reducing the spread of aphid-transmitted viruses in peppers by coarse-net cover

Abstract: Spread of the aphid-transmitted cucumber mosaic virus (CMV) and potato virus Y (PVY) in pepper plots was markedly reduced by growing the plants under a white coarse-net cover permitting normal development of the plants. This net also reduced the winged aphid population on the plants by more than 40 times. Light grey and yellow nets also reduced virus spread and aphid populations, but were much less effective than white ones. The nets do not act as a mechanical barrier to aphids. It is suggested that under white and grey netting, aphid repellency and microclimatic conditions are the primary causes of virus check, while the controlling effect of the yellow nets may be explained by their being more attractive to aphids than the plants. A reduction of “background effect” and a limiting of the aphids’ vision range by nets are probably other factors involved in the protective mechanism.

Effects of vernalisation and aphid culture history on the relative susceptibilities of wheat cultivars to aphids

Abstract: SUMMARY The weight and embryo number of adults of the cereal aphid Metopolophium dirhodum were compared on vernalised and unvernalised seedlings of six winter wheat cultivars. Aphids were smaller when reared on vernalised plants and contained fewer embryos than those reared on unvernalised material. Resistance rankings of the cultivars also changed markedly; cultivars at the extremes of the resistance sequence when vernalised were not separable statistically when unvernalised. When Sitobion avenae was tested on five of the six unvernalised cultivars, results agreed with earlier work on this species but the ranking differed from that for M. dirhodum. The plant species on which the test aphid's parent had been reared markedly affected the level of resistance and this and the vernalisation effects are discussed in relation to earlier work on aphid resistance in cereals.

Establishment and dispersal of the introduced parasite Aphidius eadyi (Hymenoptera: Aphidiidae) in the North Island of New Zealand, and its initial effect on pea aphid

Abstract: Aphidius eadyi Stary, Gonzales, & Hall, an introduced parasite of Acyrthosiphon pisum, was recovered in the Helensville area in December 1977. It overwintered successfully, and in I year dispersed 120 km northward to Ruakaka and a similar distance southward to Hamilton. Parasitism was recorded in the field from September to May. The parasite was well synchronised with pea aphid populations, and parasitism rates frequently reached populations when the non-host species Acyrthosiphon kondoi was the dominant aphid. Comparison of areas with and without parasites, in space and time, indicated that A. eadyi had reduced pea aphid populations, possibly because of its ability to respond to increasing pea aphid densities.

Feeding by Selected Predators on Alfalfa Weevil 1 Larvae

Abstract: Twelve species of field-collected arthropod predators suspected of feeding on alfalfa weevil Hypera postica (Gyllenhal) (Coleoptera: Curculionidae) larvae were studied in the laboratory. Most experiments used weevil instars III and IV. In one type of test, weevil larvae were the only prey; the other type permitted a choice of weevil larvae, Lygus spp. nymphs and pea aphid adults Acyrthosiphon pisum (Harris). Hippodamia convergens (Guerin) (larvae and adults), Coccinella transversoguttata (Faldermann) (adults), Nabis spp. (adults), and Chrysopa oculata (Say) (larvae) preferred aphids. In the absence of aphids, the coccinellids were active weevil predators. The spiders Tibellus oblongus (Walckenaer) and Xysticus sp.; Collops vittatus (Say), Collops bipunctatus (Say) and Forficula auricularia Linn. (all adults), appeared to be opportunistic feeders. The latter ranked among the more effective weevil predators. Agulla sp. (adults) ate very few weevil larvae. Instar IV prey were too large for some smaller predators.