Showing papers on "Aphid published in 1968"

The relationship between aphid infestations and oviposition by aphidophagous Syrphidae (Diptera)

Abstract: SUMMARY Oviposition by aphidophagous Syrphidae varies with the size of aphid infestations and different syrphid species have different optimum aphid population sizes for oviposition. In one experiment using potted brussels sprout plants infested with Brevicoryne brassicae L., Platycheirus manicatus (Meig.) preferred about 100 aphids per plant, P. scutatus (Meig.) about 1000 aphids per plant and Syrphus ribesii (L.) about 2000 aphids per plant. These preferences were less clear in certain Platycheirus species (e.g. P. peltatus (Meig.)), than in Syrphus species (e.g. S. luniger Meig.). Once a plant has been selected for oviposition there may still be selection of suitable colonies on that plant. For a given aphid population, S. luniger preferred a small number of large aggregates to a larger number of smaller ones, whereas S. balteatus (Deg.) preferred the opposite. The tendency of the different species to select aphid populations of different sizes and distributions is likely to decrease interspecific competition.

Probing Behavior of the Pea Aphid, Acyrthosiphon pisum. II. Comparisons of Salivation and Ingestion in Host and Non-Host Plant Leaves

Abstract: Differences in probing behavior of the Chualar pea aphid biotype of Acyrthosiphon pisum (Harris) became evident when salivation and ingestion activities in host and nonhost plants were electronically recorded on strip charts. Leaves of healthy broadbean, Vicia faba L., and V. faba plants infected with the Geneva 2 strain of bean yellow mosaic virus were used as hosts. Cowpea, Vigna sinensis Endl., and lettuce, Lactuca saliva L., were used as the non-host plants. Lettuce and cowpea were judged to be non-host plants when young adult pea aphids confined to leaves of these plants were unable to survive for more than 5 days. During this period, these aphids produced about 20 times fewer offspring than did aphids of comparable age on the V. faba plants. Specimens from 1 group of pea aphids were allowed to ingest for 10 minutes. Waveform sequences and the study of histological preparations showed that 70% of the aphids ingested fluid during their first probe regardless of whether the leaf was from a host or a non-host. Of the aphids probing host plant leaves, 78% ingested sap from the sieve elements during their first probe. Sixty-one percent of the aphids probing V. sinensis and 53% probing L. sativa ingested sap from epidermal or sulxjpidermal cells during their first ingestion probes. None of the aphids probing non-host plants ingested sap from the sieve elements during the first probe. Salivation and ingestion activities of another test group of aphids were continuously recorded for 24 hours. Twelve activity parameters were analyzed statistically. Significant differences in probing behavior occurred between aphids on host and non-host plants. Some differences in ingestion behavior were evident between aphids on lettuce and aphids on cowpea. There were some statistical differences in probing behavior between aphids on healthy V. faba and those on diseased V. faba. Aphid probing behavior is discussed in light of the results and some hypotheses are presented in explanation of these phenomena.

Role of Aphids in the Ecology of Plant Viruses

Abstract: Ecology attempts, among other things, to account for the numbers and spatial distribution of organisms. The ecology of viruses has usually been considered in terms of the number and spatial distribution of infected hosts (22, 114, 122). Although viruses cannot be regarded as small cells or micro­ organisms (85) , like other parasites, they must maintain their populations by a dependable means of transfer among susceptible hosts. The continued sur­ vival of a virus requires that the number of sources of virus shall never fall so low that transfer to other susceptible hosts becomes unlikely (22). The characteristics of a virus that permit or enhance natural transfer are thus undoubtedly subject to selective pressures. The relationships of a virus with its vectors must ensure the necessary frequency of transfers. Vectors must have a consistent relationship with host plants, although it may be only a matter of alighting by one or another noncolonizing species during migration. It is not surprising, therefore, that so many viruses are aphid-borne. Most species of angiosperms and gymno­ sperms, and some lower plants such as ferns, in the Northern Temperate Zone are hosts for at least one aphid species. The enormous reproductive potential and the behavioral patterns of aphids ensure their wide dispersal among populations of virus host plants. The numbers and distribution of plants infected with aphid-borne viruses reflect the numbers and activity of the aphid vectors. There is the added condition that the extent to which aphid populations may be important vectors depends on the sources of virus which are available. Under natural conditions and in many agricultural situations, these virus sources are plants infected by aphid transmission in previous years.

Outbreaks of Two-Spotted Spider-Mites and Cotton Aphids Following Pesticide Treatment. I. Pest Stimulation vs. Natural Enemy Destruction as the Cause of Outbreaks

Abstract: Numerous pesticides are known to provoke outbreaks of a variety of mites and aphids. Some of the conditions surrounding-these upsets are reviewed, and the capabilities of 59 different pesticides to induce increases of mites and/or aphids are examined in relation to their individual effects on some of the major natural enemies of mites and aphids. When critical examination is made of the arguments for either of the 2 suspected causes of such pesticide-induced outbreaks, i.e., (a) natural enemy destruction and (b) pest fecundity stimulation, it appears that neither by itself offers a completely adequate explanation. Since one of the methods now commonly used for evaluating natural enemy effectiveness relies on measurement of host increases in insecticidal check plots, this technique may credit the natural enemies with undeserved efficiency if the insecticide stimulates the pest’s fecundity. In this first of a series of experimental programs designed to resolve the problem of whether abnormal mite or aphid increases can be generated by pesticidal stimulation of the fecundity of mites or aphids, 59 different materials were examined for their effect on the reproductivity of the two-spotted spider mite, Tetranychus urticae Koch, and the cotton aphid, Aphis gossypii Glover. Following treatment with the different materials, population fold increases of each pest were measured weekly on the potted cotton plants held in the greenhouse and outdoors in the complete absence of natural enemies. The period of retention of toxicity of each material to mites and aphids (or the period during which any stimulation effect might be masked) is presented. Some anomalous conditions of treatment which caused abnormal increases in these tests could be explained by elimination of either pest when competing with the other. Some other abnormal increases of both mites and aphids were found which were difficult to explain other than as a pest-stimulation effect. For these cases no common denominator could be found. A few of the stimulatory responses obtained appeared in-consistent with the recorded performance of the materials in inducing upsets in the field.

Population studies on the active stages of the black bean aphid, Aphis fabae Scop., on its winter host Euonymus europaeus L

Abstract: SUMMARY Autumn populations of Aphis fabae Scop, on the primary host Euonymus europaeus L. were little affected by natural enemies, most of which had begun to hibernate before the aphid populations developed. The size of the population in spring was usually determined by the number of overwintering eggs on a bush. The fundatrices hatched about 3–6 weeks before natural enemies became common. The growth of large A. fabae populations was first halted by the effects of intra-specinc competition, notably by the production and departure of emigrant alatae and by adult apterae reproducing more slowly. Later, natural enemies, especially Adalia 2-punctata (L.), Syrphidae and the parasite Trioxys sp. (near angelicae), multiplied and accelerated the decline in the aphid populations, which usually disappeared in June leaving many immature natural enemies. Larval A. 2-punctata began to eat parasitized aphids and cannibalized other larvae and pupae. The small populations of A. fabae that develop from few overwintering eggs are at greater risk from natural enemies than are large ones. Intraspecific competition still slowed population increase, because most aphids remained crowded on the few originally colonized twigs. Such populations produced very few emigrant alatae before they were exterminated by the combination of T. angelicae with specific and non-specific predators. Adult Cantharidae killed many of the aphids, especially in hedgerow habitats, where they were abundant. Coccinellidae, Anthocoridae and syrphid larvae, and the adults of nonspecific predators, notably Cantharidae, prevented recolonization of E. europaeus throughout July and August. Leaves of E. europaeus may remain physiologically suitable for A. fabae throughout July but begin to deteriorate in August when A. fabae kept on them become less fecund. Experiments using exclusion techniques provided evidence that natural enemies which attack A. fabae on E. europaeus and on summer hosts cause the common 2-year cycle of aphid abundance. Individual E. europaeus differ consistently in the extent to which they are colonized by A. fabae. Conditions are discussed that should govern the choice of E. europaeus bushes on which the A. fabae populations can be used as sensitive indicators of later crop infestations.

Resistance in Lycopersicon and Solanum Species to the Potato Aphid

Abstract: Solunum Pennellii Correll and segregates of 5 accessions of Lycopersicon peruvianum (L.) Mul. were resistant to Macrosiphum euphorbiae (Thomas) in the greenhouse at Beltsville, Maryland. The entanglement of the aphids in the heavy vesture of glandular hairs prevented colonization of S. pennellii , but physiological incompatibility appeared to be the reason that aphids failed to colonize the segregates of L. peruvianum , which have a sparse vesture of glandular hairs.

Nachweis einer durch symbiontische Mikroorganismen bewirkten Sterinsynthese in künstlich ernährten Aphiden (Homoptera, Rhynchota, Insecta)

Abstract: Up to now the aphid,Neomyzus circumflexus Bckt., has been reared on a synthetic, sterile diet for 11 successive generations. The culture is still going. The defined diet contains no sterol or any other lipid. Nevertheless the sterol content of the artificially fed aphids remains constant over 8 generations. Ingestion of sodium acetate-1-C14 with the diet by the aphids leads to the appearance of a labelled sterol in the tissues of the insects. Incorporation of radioactivity into sterols was not found in aphids free of symbionts.

A new biotype of cabbage aphid (Brevicoryne brassicae (L.)) on Aphid Resistant rape (Brassica napus L.)

Abstract: The reaction of young plants of five varieties of Brassica napus L. to Brevicoryne brassicae (L.) from two sources was investigated in a glasshouse. Source I was a normal crop of Aphid Resistant rape carrying a small aphid population; source II was a severely-attacked crop of Aphid Resistant rape. Aphids from both sources caused severe leaf curling in Broad Leaf Essex rape, and those from source II caused medium to severe leaf curling in the varieties Aphid Resistant and Rangi rape, and Calder and Sensation swede. Some plants of an open-pollinated progeny of a naturalised rape plant were resistant to leaf curling caused by aphids from source II. The aphids from the two sources have been designated biotype NZ-1 and biotype NZ-2; the latter is the first biotype of B. brassicae to attack Aphid Resistant rape severely.

Migration in aphids: response to current adversity.

Abstract: Johnson1–3, Kennedy4 and Southwood5 state that migration occurs in alate aphids whether the alate population is large or small, and this behaviour of the alatae is not due to population pressure or to current lack of food; in other words, the migration of alatae is an evolved adaptation rather than a response to current adversity. This hypothesis does not apply to the sycamore aphid, Drepanosiphum platanoides (Schr.), in which migration is more marked in conditions of over-population (unpublished results of A. F. G. D.). The sycamore aphid, however, which is a tree dwelling aphid and therefore occupies a permanent habitat5, does not show the same degree of polymorphism as polyphagous aphids. It could be regarded as an exception to this hypothesis, which has been developed to explain migratory activity in aphids occupying temporary habitats.

The Spray Warning Scheme for Control of Sugar Beet Yellows in England Summary of Results between 1959–66

Abstract: SUMMARY Sugar beet growers in England have been advised since 1959 to spray their crops with systemic insecticide to control spread of yellows viruses when infestation with the vector aphids (mainly Myzus persicae Sulz.) in May and June reaches 0.25 aphids/plant. The data collected up to 1966 show that aphid infestation at any one time is not proportionally related to eventual yellows incidence. Graphs of mean aphid infestation and yellows incidence in different areas are presented, which are a guide to issuing spray warnings.

Bands on Peach Trees as Shelters for Predators of the Green Peach Aphid

Abstract: When bands on peach trees were evaluated as artificial overwintering sites for beneficial arthropods over a 2-yr period, predaceous Hemiptera, Syrphidae, Neuroptera, Acarina, Araneida, and parasitic Hymenoptera successfully overwintered in moderate to large numbers under the bands. More than 90% of the arthropods using the bands were beneficial. The ratio of overwintering phytophagous mites to predaceous mites was 3:1 in December 1966, but it changed by mid-February 1967 to 11:1 in favor of predaceous mites. When the temperature and relative humidity under and around a black band was monitored, a wide range of temperature (16.7-26.7 and relative humidity (28-58%) was measured at the time of highest air temperature. When arthropod movement was restricted to a limited area of the band, high mortality occurred; when they were allowed to move around the band, the rate of survival was high for most of the species. The spring emergence of the species of parasites, hyperparasites, and syrphids overwintering under the bands was also studied.

Probing Behavior of the Pea Aphid, Acyrthosiphon pisum. III. Effect of Temperature Differences on Certain Probing Activities

Abstract: Groups of 10 Acyrthosiphon pisum (Harris), adults were exposed to each of the following temperatures for 24 hours: 5, 10, 15, 20, 25, 30, and 35°C. Ten parameters of probing behavior were analyzed for the 10 groups at each temperature. Results showed that certain probing activities were significantly affected by temperature. Aphids exposed to the 2 temperature extremes (5 and 35°C) ingested fluid from sieve element cells less frequently than aphids exposed to the other temperatures. It was concluded that some temperature between 25 and 30°C was probably environmentally optimal for the pea aphid. Aphids at these temperatures ingested fluid from sieve elements for longer periods, probed for longer times, and produced more offspring than aphids at the other 5 temperatures.

Testing for pea leafroll virus and inheritance of resistance in peas

Abstract: Different aspects of pea leafroll, the most important virus disease of peas and Vicia-beans in The Netherlands, are discussed. These aspects include the spread of the virus, the damage done by the disease, the symptoms, the nature of the virus, the vectors and the host plants. Pea leafroll virus (PLRV) is a persistent virus which is invariably transmitted by aphids. The most important vector is the pea aphid, Acyrthosiphon pisumHarris. Lucerne actas as a winter host for the virus and the pea aphid. The pea aphids are reared on diseased lucerne plants and are used in a glass-house experiment to test cross populations for resistance. In view of its importance for that test it is necessary to discuss the biology of the pea aphid in some detail. Besides the glasshouse test some field test methods are mentioned.

Yellow Dwarf of Pea and Broadbean Caused by Milk-Vetch Dwarf Virus

Abstract: The occurrence of yellow dwarf disease of pea and broadbean was noticed in Wakayama, Aichi, and Okayama Prefectures since 1963. In general, the outbreak was sporadic, but was observed to be epidemic in occasional fields.The virus causes yellowing, leaf-curling or rolling, and dwarfing in various leguminous plants, such as pea, broadbean, bean, azuki-bean, soybean, milk-vetch, crimson clover, and subterranean clover, and also in Datura stramonium. In tobacco (Samsun and White Burley), N. glutinosa, N. rustica, and spinach leaf-curling and stunting are observed as well, although the virus is not yet recovered. The causal virus is not transmitted by plant juice. It is transmitted by Aphis craccivora, but not by Myzus persicae, Acrythosiphon pisum, and Megoura viciae japonica. In the dip-preparation from diseased plants, no elongated virus particles are detected under the electron microscope. No inclusion body is demonstrated in epidermal cells of infected pea and broadbean. Aphis craccivora could acquire the virus in as short time as 5 minutes. Efficiency of transmission, however, increased with more time than 4 hours on the source plants. The aphids which had received sufficient acquiring feed, transmitted the virus to about 7 per-cent of plants if fed for inoculation for 5 minutes on test plants, but infection increased to above 30 percent when aphids fed for 4hr. or more. Latent period invector aphid was found to be at least 36 hours at alternating temperatures of 24°C (day) and 18°C (night). As a result of daily serial transfers, individual aphids seemed to transmit the virus as long as they lived, although not every plant in a series was infected. In one case, a single aphid was able to infect all the test plants during a period of successive 15 days. Thus, the virus can be considered a persistent virus. By reference to the literature, the virus in the present work is apparently distinct in symptoms and agents of transmission from such persistent aphid-borne viruses as pea ena-tion mosaic virus, pea leaf roll virus, groundnut rosette virus and subterranean clover stunt virus, but identical with milk-vetch dwarf virus (MDV) which was described in Japan by Matsuura in 1953 and by Hino et al. in 1967.

Aphid Sampling Efficiency of Möericke Traps Affected by Height and Background

Abstract: Alate aphids were trapped in studies of the field spread of lettuce mosaic virus. The effectiveness of yellow-painted water pans (MOericke traps) at different heights and backgrounds was compared in determining the seasonal abundance of alate aphid populations. Pans 15 inches above bare soil were most effective; pans at the same height surrounded by plants were less effective; and pans 8 feet above bare soil were least effective. Sixty-eight species of aphids in 37 genera were identified. Myzus persicae (Sulzer), green peach aphid, comprised 28% of the total. Brevicoryne brassicae (L.), cabbage aphid; Rhopalosiphum maidis (Fitch), corn leaf aphid; and Hyalopterus atriplicis (L.) contributed 37% of the total.

Alate aphids trapped over 8 years at two sites in Canterbury, New Zealand

Abstract: Trapping of alate aphids at two sites with grease traps over 8 years yielded a total of 51 species, 9 of which flew regularly in high numbers and are referred to as primary species. Six others occasionally occurred in high numbers The validity of likely inferences from information collected by this method is discussed, as is also the application of the knowledge of flights to problems of aphid control.

Effects of Soil Fertility on Abundance of Green Peach Aphids on Maryland Tobacco

Abstract: Experiments were conducted to determine the effect of soil fertility on the fecundity and longevity of the green peach aphid, Myzus persicae (Sulzer), on Southern Maryland (Type 32) tobacco. Studies of aphids caged individually on tobacco grown in soil with varying amounts of nitrogen, phosphorous, and potassium showed that as the amount of nitrogen or potassium was increased in the soil, fecundity of aphids increased. Observations of population growth rates on confined portions of tobacco plants indicated that medium levels of nitrogen and phosphorous fertilization (90 lb per acre each) resulted in the most rapid population increase and the highest population density. Population growth rate and density were positively correlated with potassium fertilization. By varying the amount of 4-8-12 fertilizer applied to field plots of tobacco, it was possible to demonstrate a positive correlation between amount of fertilizer and the number of aphids on tobacco.

Nitrogen fertilization of the host tree and population growth of the balsam woolly aphid, adelges piceae (homoptera: adelgidae)

Abstract: The relationship between nutrition of the host tree, Abies amabilis (Dougl.) Forbes, as influenced by nitrogen fertilizers, and the growth of populations of the balsam woolly aphid, Adelges piceae (Ratz.), was investigated. Sixty trees, growing in a greenhouse in two soil types, a nutrient-deficient mineral soil and an enriched humic soil, were infested with woolly aphid larvae. Subsequently, groups of 10 trees received foliar treatments of various concentrations of ammonium nitrate and urea. The following year, 32 young trees in Seymour Valley, B.C., were studied to determine the effect of fertilization of uninfested trees on establishment of aphid larvae.In the greenhouse, foliar sprays of 1% ammonium nitrate solution resulted in a 23% decrease in population in 10 weeks, as contrasted with a 31% increase in the control population. In the field, larval establishment was 31% to 37% lower on the ammonium nitrate-treated trees than on the control trees. Inasmuch as there was no evidence of increased mortality of aphids in situ, we infer that the fertilizer acts primarily by inhibiting initial settling of larvae on the host trees.

Survival of the balsam woolly aphid on abies logs

Abstract: Survival of the balsam woolly aphid on Abies grandis logs was observed to evaluate the danger of spreading the pest while moving logs. Active stages of the aphid survived submergence in sea water for 7 days and periodic sprinkling with sea water for 3 weeks. Dormant stages survived submergence up to 28 days. Active aphids survived on logs in the forest as long as 5 months. Crawlers frequently re-established on logs and completed a second generation there. Dormant neosistentes on autumn-felled trees persisted over winter and resumed development in the spring. Recommendations for moving infested logs through uninfested areas are made.

Studies on the transmission of pea leaf roll virus by Myzus persicae (Sulz.)

Abstract: Factors affecting transmission of pea leaf roll virus by the aphid Myzus persicae (Sulz.) were studied. Results indicated that this virus exhibits properties consistent with those described for circulative viruses. The minimum feeding period for acquisition of the virus from infected leaves was from four to six hours, and for transmission to healthy plants between six and 24 hours. Aphids could infect plants for at least eight days after acquiring the virus. Approximately 25 aphids per pea plant during transmission were needed to infect 100% of the test plants. The number of test plants which became infected was directly correlated with the number of viruliferous aphids feeding on them. However, the number of aphids had no effect on the severity of infection. Young leaves of infected plants were the best site for acquisition of virus. The percentage of plants becoming infected decreased as the size of the test plants (when inoculated) increased.

Use of Chemical Defoliants on Peach Trees in Integrated Program to Suppress Populations of Green Peach Aphids

Abstract: When peach trees were sprayed with chemical defoliants to control green peach aphids, Myzus persicae (Sulzer), the number of aphids per leaf was higher on leaves remaining on the sprayed trees, but the number of aphids per tree was higher on the unsprayed trees. The high density of aphids per leaf in the foliage still present on sprayed trees was associated with an increase in deposition of syrphid eggs per leaf. Also, the number of aphid eggs was significantly fewer on the sprayed trees than on the unsprayed trees. The decrease in deposition of aphid eggs in 1966 compared with 1965 was correlated with the differences in trends of aphid population, temperatures, and syrphid activities.

Factors Affecting Transmission of Tristeza Virus by Melon Aphids

Abstract: A study of the transmission of tristeza virus by the melon aphid, Aphis gossypii Glover, revealed very small differences in transmission rate when infected source plants (orange seedlings) and Key lime indicator plants, Citrus aurantifolia (Christm.) Swingle, were held in an air-conditioned greenhouse or in an insectary, but the development of symptoms in the indicator plants was accentuated and speeded up in the insectary where temperatures ranged up to 15°C higher in the summer and 10°C lower in the winter than temperatures in the greenhouse. Young 2 to 6-inch Key lime plants were as good virus indicators as older 8 to 12-inch plants. The efficiency of the melon aphid as a vector of tristeza varied from 1 population to another. Numbers of transmissions were higher with 200 aphids per plant than with 10 to 50 aphids per plant, but the rate of transmission was not proportional to the number of aphids per plant. Mixed populations of nymphs and adult aphids transmitted tristeza virus as well as populations of adult aphids. Starvation of aphids for 2 and 4 hours before feeding did not increase the transmission of tristeza virus. Transmission of the virus to indicator plants by aphids feeding on thorns and on mature or immature leaves of infected plants was not significantly different, and transmission of the virus by aphids reared on cotton, Gossypium hirsutum L., was not significantly different from transmission by aphids reared on kenaf, Hibiscus cannabinus L.

The incidence of parasitism and disease in some populations of the cabbage aphid (Brevicoryne brassicae L.) in New Zealand

Abstract: The incidence of parasitism in field populations of the cabbage aphid (Brevicoryne brassicae L.) over several seasons wa:.; frequently low. Rearing of field-collected material showed that three secondary parasites, Charips brassicae (Ashm.), Lygocerus niger (How.), and Pachyneuron sp. (?siphonophorae (Ashm.)), were associated, at various levels, with the primary parasite Diaeretiella rapae (M'Intosh). Incidence of the entomophagous fungus Entomophthora aphidis Hoffman reached a significant level only during the autumn population peak of the aphid.