Showing papers on "Myzus persicae published in 1969"

The Ecology of Myzus persicae

Abstract: This review has been suggested by the Scientific Committee of the In­ ternational Biological Programme as part of a project on the population dy­ namics and biological control of Myzus persicae. In order to contain this review within a reasonable number of pages, information on transmission of virus diseases is virtually omitted; it could easily form a review of equal length. Work on other aphids which is relevant to the ecology of M. persi­ cae has been included in sections where knowledge of M. persicae is lacking or inadequate. A few insect species seem very well adapted to exploit the ephemeral crop environment. They include some aphid species of regional (Aphis fabae, A. gossypii, A. craccivora and Rhopalosiphon maidis as well as other grass aphids) or of almost world-wide importance (Brevicoryne brassicae, Macrosiphum euphorbiae, Myzus persicae) (2). M. persicae is outstanding in distribution, in host plant range (57, 67, 81, 103,148, 149,221,389,422,428,432,444, 525), and as a pest which causes not only direct damage but is able to transmit over 100 virus diseases of plants on about thirty different families including many major crops such as beans, sugar beet, sugar cane, brassicas, potatoes, tobacco and citrus (281). The use of chemical methods to prevent spread of viruses by controlling their aphid vectors has been either unsuccessful or only partially successful. Thus, there is a special need for the integrated control approach which will lower the numbers of the vector especially at times when viruses are spread. Control of the aphid by natural enemies in the noncrop or alternative crop habitat is therefore particularly important, but biological control by natural enemies and by manipulating the host plant could also be enhanced in the crop. Although there is a large background of knowledge on the biology of natural enemies of aphids, their significance in control in both the funda­ mental and applied senses is little understood, except perhaps for Thel'­ ioaphis maculata in California. Quantitative effects of natural enemies and of other factors which help to regulate numbers are partly understood for a few aphids (A. fabae, B. brassicae) during periods when they are pests on crops, but little relevant data is available for M. persicae. Even less atten-

A comparison of the reproduction of brevicoryne brassicae and myzus persicae in relation to soluble nitrogen concentration and leaf age (leaf position) in the brussels sprout plant

Abstract: Wide variations in total soluble nitrogen occurred in different leaves of Brussels sprout plants. These variations were partly the result of leaf age (leaf position) and partly the result of different fertiliser application to the plants. The fecundity of Brevicoryne brassicae and Myzus persicae caged on such leaves also varied greatly and was correlated with total soluble nitrogen within leaves of the same age, but not between leaves of different ages. The value of total soluble nitrogen concentrations, based on analysis of leaf tissue, for indicating plant suitability for aphids is discussed as well as the difference in response of the two aphid species to experimental conditions favouring proteolysis in the leaf. ZUSAMMENFASSUNG EIN VERGLEICH DER VERMEHRUNG VON BREVICORYNE BRASSICAE UND MYZUS PERSICAE IN BEZIEHUNG ZUM GEHALT LOSLICHEN STICKSTOFFS UND DEM BLATTALTER VON ROSENKOHLPFLANZEN Brevicoryne brassicae (L.) und Myzus persicae (Sulz.) wurden an Kohlblattern gekafigt, die infolge verschiedener physiologischer Ursachen sehr unterschiedliche Mengen loslichen Stickstoffs enthielten. Den Pflanzen wurden zwei Dungerstoffe ((NH4)2SO4 und KCL) verabreicht und die Blattlause auf jungen, mittelalten und alten Blattern gekafigt. Dadurch wurde der Gehalt loslichen Stickstoffs in den Blattern zwischen 0,543% und 1,286% variiert. Die Nachkommenzahl der Blattlause bei diesen Dungungen und auf verschiedenaltrigen Blattern war sehr unterschiedlich (zwischen 7,3 und 30,2 bei B. brassicae; 17,6 und 59,4 bei M. persicae) und konnte in jedem Blattalter mit dem Stickstoffgehalt korreliert werden. Der Befund, das die Korrelationen zwischen Blattlausnachkommenzahl und Stickstoffgehalt nicht unabhangig vom Blattalter waren, deutet darauf hin, das der Stickstoffgehalt in physiologisch aktiven Blattgeweben nicht relativ mit dem der Siebrohren ubereinstimmt. M. persicae vermochte in hoherem Mase als B. brassicae Blatter auszunutzen, in denen der Eiweisabbau durch Dungung oder Alter begunstigt war. Dieser Unterschied zwischen den beiden Arten steht moglicherweise mit ihren verschiedenen Nahrstoffbedurfnissen in Zusammenhang.

Plant resistance to myzus persicae induced by a plant regulator and measured by aphid relative growth rate

Abstract: Myzus persicae showed a reduced relative growth rate on plants given soil drenches of 1% CCC (a plant growth retardant), and a greater reduction when CCC was applied as a foliar spray. The use of the relative growth rate of aphids as a convenient measure of their performance in relation to plant resistance is discussed. ZUSAMMENFASSUNG RESISTENZ VON PFLANZEN GEGENUBER MYZUS PERSICAE, DIE DURCH EINEN REGULATOR DES PFLANZENWACHSTUMS INDUZIERT UND AN DER RELATIVEN WACHSTUMSRATE GEMESSEN WURDE Die Resistenz von Kohlpflanzen, die mit 1% CCC (einem Regulator des Pflanzenwachstums) behandelt worden waren, gegen Myzus persicae wurde mit Hilfe des Wachstumsquotienten der Blattlause (μg/μg/Tag) gemessen. Diese Methode arbeitet rasch und ergibt eine ziemlich geringe Variabilitat. Der Masstab scheint sinnvoll und ziemlich empfindlich zu sein. Mit CCC gedungte Pflanzen zeigten stets eine ziemlich starke Verminderung des Wachstumsquotienten von Myzus persicae. Wurde CCC auf die Pflanzen aufgespruht, so ergab sich ein noch geringerer Wachstumsquotient der Blattlause.

The stylets of the green peach aphid, myzus persicae (homoptera: aphididae)

Abstract: The morphology and fine structure of the maxillary and mandibular stylets of the green peach aphid, Myzus persicae (Sulzer), are described from sections, whole mounts, and two-stage replicas. The mechanisms of penetration of the host plant are discussed.

The potential of Chrysopa carnea as a biological control agent of Myzus persicae on glasshouse chrysanthemums

Abstract: SUMMARY Larvae of C. carnea lived for 13-4 days at 21·1°C and consumed an average of 385 second-instar Myzus persicae or 425 Aphis gossypii. At 15·5°C the larval lifespan was 29·5 days though the consumption of M. persicae was hardly affected. M. persicae developing on glasshouse chrysanthemum plants were eliminated by the introduction of 1-day-old larvae at aphid: chrysopid ratios up to 50:1; third-instar larvae achieved control at a ratio of 200:1. At very low aphid densities control was less effective. Control by C. carnea of aphid populations developing on glasshouse chrysanthemums can be predicted mathematically.

Preference of Green Peach Aphids for Virus-Infected Sugar beet Leaves

Abstract: In detached-leaf experiments, apterous Myzus persicae (Sulzer) preferred yellows-infected leaves to symptom less, mosaic-infected, or curly-top-infected leaves. However, apterous aphids appeared to move at random to healthy, mosaic-infected, or yellows-infected whole plants. Twice as many alate aphids were found on yellows-infected whole plants 24 hours after release as on healthy or mosaic-infected plants, but no marked differences were found in numbers of alate aphids on healthy, mosaic-infected, and yellows-infected whole plants 48–96 hours after release. In all tests aphids appeared to avoid curly top-infected leaves or plants.

Soybean Dwarf, a New Virus Disease

Abstract: A new virus disease, soybean dwarf, was first noticed on the Tsurunoko variety of soybean in southern areas of Hokkaido in about 1952. Since then it has been widely observed throughout Hokkaido, causing a considerable loss in soybean yields. Soybean plants infected with the virus show dwarfing (stunting), and downward curling, rugosity, and/or interveinal yellowing of the leaves.The virus was transmitted by grafting and by the aphid Aulacorthum solani (Kaltenbach), but not by juice inoculation or through seeds. Three species of aphids, Aphis glycines Matsumura, Aphis craccivora Koch and Myzus persicae (Sulzer), and two species of leafhoppers, Scleroracus flavopictus Ishihara, and Psammotettix striatus (Linne) failed to transmit the virus. The virus was retained in the vector A. solani for 20 days after leaving the source plants.It was found that red clovers and white clovers in the neighborhood of affected soybean fields were symptomless carriers of the virus.

Interplant movement of apterous aphids with special reference to Myzus persicae (Sulz.) (Hem., Aphididae)

Abstract: It is likely that under some conditions apterous aphids are significantly involved in the spread of plant viruses, most importantly by walking across soil from plant to plant. Various factors which affect their importance are considered in the paper.Figures are given for the frequency of movement of apterae of Myzus persicae (Sulz.) under settled conditions; this was found to vary with the species of host-plant that the aphid was on.Eourth-instar and adult apterae can walk proficiently on soil. The effect of soil condition on this is described. The walking speed of adult apterae on soil is 5.2 cm./min. at 18°C, and 1.2 cm./min. at 8.5°C. The walking speed of fourth-instar aphids on soil is 3.2 cm./min. at 18°C.Experiments showed that walking aphids are well able to locate a new host-plant, and that the attraction is visual.The significance of these observations is discussed, and it is concluded that apterae have a greater potential as virus vectors than has been generally realised.

Inherited resistance of sugar beet to aphid colonization

Abstract: SUMMARY Results of glasshouse experiments have confirmed that inbred lines of sugar beet differ in each of three types of resistance to Myzus persicae Sulz. and Aphis fabae Scop., namely: resistance to settling, resistance to multiplication, and tolerance. Resistance to multiplication was not invariably associated with resistance to settling, although plants of some lines showed both forms of resistance. Plants that were resistant to settling of alatae were not always resistant to apterae of the same species, and there was not a close relationship between resistance to M. persicae and to A. fabae. The mechanisms involved in resistance to aphids in sugar beet are not understood. Progenies of plants, selected for resistance to aphids from inbred lines, were often more resistant than progenies of unselected plants. Inheritance of each type of resistance is probably polygenic. The potential value of the different kinds of resistance, in reducing direct feeding damage and controlling the spread of virus yellows in the field, is discussed. The ultimate breeding objective is to produce commercial varieties in which appropriate kinds of resistance to aphids are combined with resistance to virus yellows. The use of such varieties would reduce the need to control aphids in the field by applications of chemicals.

Competition and other factors influencing the population dynamics of Aphis gossypii and Macrosiphoniella sanborni on greenhouse chrysanthemums

Abstract: Competition and other factors influencing the population dynamics of Aphis gossypii and Macrosiphoniella sanborni on greenhouse chrysanthemums were studied. Single- and mixed-species populations after an accelerated growth period, reached a moderately stable equilibrium phase. Removal of alate forms, which simulated dispersal, reduced the rate of population growth, but did not stabilize the populations. Because they were strongly influenced by aphid density, the main population regulating agents were aphid size (related to birth rate), and leaf mortality (related to death rate). Another indirect, regulating factor was high temperature, which killed more of the older leaves when they were infested with high aphid densities. Although Myzus persicae is the major aphid pest of greenhouse chrysanthemums in California, this study suggests that, in the absence of insecticides, M. sanborni and A. gossypii are better adapted to chrysanthemums.

Aphid transmission of tobacco mosaic virus

Abstract: Aphids (Myzus persicae Sulz.) can acquire tobacco mosaic virus from tobacco leaves coated with a virus suspension and inoculate it into healthy leaves. Transmission depends on virus concentration, period of acquisition, previous feeding history of the aphids, and time between acquisition and transmission feedings. Aphids whose stylets are cut do not transmit the virus.

Factors affecting aphid infestation of chrysanthemums

Abstract: SUMMARY Large differences exist between chrysanthemum cultivars in their susceptibility to attack by Myzus persicae (Sulz.). This is due to a repellent factor which increases in the leaves as they age, but which varies from one cultivar to another. Aphid population growth is retarded, or even prevented, on resistant cultivars. If susceptible and resistant plants are in contact, the rate of population increase will be the same on both, but numbers will remain proportionately lower on the resistant cultivars. For instance, aphid numbers are normally forty times as high on B.G.A. Tuneful as on Portrait. Aphids appear to select the cultivar or region of plant most suitable for reproduction (usually apical and basal leaves) but, as the plants and population grow, the aphids continually redistribute themselves. Within the limits of normal growing practice, cultural and environmental conditions have little effect on the aphids. Brachycaudus helichrysi (Kaltenbach) and Aphis fabae Scop, have similar varietal preferences but, unlike Myzus persicae, they avoid senescent leaves and only colonize the apex.

Resistance of rape (Brassica napus) to attack by the cabbage aphid (Brevicoryne brassicae L.)

Abstract: SUMMARY Resistance to Brevicoryne brassicae L. attacks in a New Zealand variety of forage rape resulted from a combination of host non–preference and antibiosis. Using clonal plant material obtained from cuttings, only half the numbers of immigrant alate cabbage aphids that settled to reproduce on the susceptible rape were to be found on the resistant rape. The reproduction rate of these alates was about 12 % slower on the resistant plants than on the susceptibles and the young took about 13% longer to mature. Antibiosis then shortened the reproductive life of the apterae by one-third, reduced their fecundity by nearly 50 % and caused 40% mortality in their progeny. The over-all effect of this was considerable and under conditions specified in the text could result in the population on the resistant plants being about one-eighth that on the susceptible plants in under 1 month. The resistant plants lost their resistance on flowering and became normally susceptible to cabbage aphid attack. With maturity, however, the B. brassicae-resistant plants became slightly resistant to Myzus persicae.

Plant Age in Relation to the Resistance of Nicotiana to the Green Peach Aphid

Abstract: Toxicity of resistant varieties of tobacco, Nicotiana tabacum L., and N. benthamiana Domin to Myzus persicae (Sulzer) increased as the plants matured. This paralleled an increase in the amount of the exudates on certain trichomes of these plants. Because of the lack of toxicity of seedling and young plants, older plants should be used in screening tests for this type of resistance to the green peach aphid.

The effect of potato leafroll virus on the biology of Myzus persicae

Abstract: Since potato leafroll virus multiplies in the green peach aphid,Myzus persicae, the effect of the virus on the biology of its vector was investigated. Observations were made regarding the longevity and the reproduction rate of viruliferous and non-viruliferous aphids on leafroll-diseased and healthy plants ofPhysalis floridana. The same matters were investigated for both viruliferous and non-viruliferous aphids on seedlings of Chinese cabbage (Brassica pekinensis). It was shown that on leafroll-diseased plants ofP. floridana the aphids produced more progeny than on healthy ones, although the average number of progeny produced per day in both cases was almost the same. On healthy Chinese cabbage seedlings there was no difference in average length of the larval and adult stages, number of progeny per aphid, and number of progeny per day, between viruliferous and non-viruliferous aphids. Evidence was obtained that the virus does not influence the development of its vector. Measurements of oxygen consumption of both viruliferous and non-viruliferous aphids point in the same direction.

Use of growth retardants on chrysanthemums: Effect on pest populations†

Abstract: Numbers of the aphid, Myzus persicae, and the spider mite, Tetranychus urticae, were compared on two chrysanthemum cultivars treated with commercial rates of B995, chlormequat chloride and chlorphonium chloride. The growth retardants did not give effective pest control on this host, but in some trials the populations were significantly lower where chlormequat chloride and chlorphonium chloride was used. They appear to act indirectly and reduced the survival rate of nymphal M. persicae.

The Repellency of Mature Citrus Leaves to Probing Aphids

Abstract: Individuals of the cowpea aphid, Aphis craccivora Koch; the melon aphid, A. gossypii Glover; the spirea aphid, A. spiraecola Patch; and the green peach aphid, Myzus persicae (Sulzer), were allowed to probe on leaves of bean, crotalaria, and citrus. The probing response of all 4 aphid species to the various leaves was similar. More than 65% of probes on upper or lower surfaces of mature citrus leaves were less than 15 seconds in duration, whereas, less than 35% of probes were of that duration on leaves of other hosts. Virus transmission from bean and crotalaria leaves was considerably lower from probes under 15 seconds in duration than from probes exceeding 15 seconds, suggesting that more than 15 seconds are usually necessary before aphid stylets are able to reach virus-containing regions in the epidermis. Frozen sections of leaves cut with a microtome failed to reveal any obvious anatomical differences that would account for the brevity of aphid probes on mature citrus leaves. We suggest that, upon maturity, the cuticle and/or cell walls of citrus leaves develop a condition that renders them repellent to aphids, and that this condition accounts for the brevity of probes by aphids placed on these leaves.

Effects of sucrose sprays and darkness on aphid colonization of sugar beet and on aphid transmission of yellowing viruses

Abstract: SUMMARY In the glasshouse, adult, apterous Myzus persicae (Sulz.) and Aphis fabae Scop, settled better and deposited more larvae on sucrose-sprayed sugar-beet plants than on water-sprayed plants. M. persicae settled badly and deposited few larvae on plants that were kept in the dark before or after infestation. The effects of darkness on aphids were reduced by spraying the host plants with 10% solutions of sucrose before infestation. Viruliferous M. persicae transmitted beet yellows virus (BYV) and beet mild yellowing virus (BMYV) less efficiently to dark-treated plants than to those grown in normal daylight. Spraying sugar beet with sucrose before inoculation with viruliferous M. persicae increased the proportion of successful BYV transmissions but only when the plants were dark-treated. The effects of sucrose and darkness on settling and larviposition of aphids and on virus transmission may be related to changes in the concentration of carbohydrates, particularly sugars, in the leaves.

Sexual forms of the pea aphid, acyrthosiphon pisum, produced on an artificial diet

Abstract: In recent years a number of aphid species have been successfully reared on chemically defined diets (Dadd & Mittler, 1966; Auclair, 1965; Dadd & Krieger, 1967; Ehrhardt, 1968). The development of such diets has offered an opportunity to study in detail several aspects of the physiology of these insects. In particular, the composition of the artificial diet has been shown to influence the production of winged forms by Myzus persicae (Sulzer) (Mittler & Dadd, 1966; Dadd, 1968). In all studies thus far, the aphids have been maintained in the parthenogenetic condition in order to accumulate data concerning the growth and fecundity of females of successive generations. However, it was clearly of interest to determine whether sexual forms could be produced by diet-reared aphids. If so, further information regarding the sexual reproduction of these insects would be forthcoming. Attempts to achieve this using local strains of Myzus persicae, Aphis fabae Scopoli and Acyrthosiphon pisum (Harris) were unsuccessful, presumably because these strains were anholocyclie (Kunkel, unpubl.). A clone of a green strain of A. pisum, previously found to be holocyclic (Sutherland, unpubl.), was then obtained from England and was cultured at 20° C in a photoperiodic regime of 16 hr light: 8 hr dark per day on young bean plants (Vicia faba). The artificial diet on which the experimental aphids were maintained was formulated according to Dadd (1967) and enclosed in sachets of stretched parafilm (Dadd, Krieger & Mittler, 1967). The aphids were provided with fresh sachets every 3–4 days. Adult apterous females taken from the plant culture were caged in groups of five, and exposed to a photoperiodic regime of 10 hr light: 14 hr dark per day at 15°. Successive batches of larvae deposited by these aphids were maintained in this environment until they were adult and had produced offspring for several days. These developed into oviparae and males. Compared to the sexual forms produced on host plants, these diet-reared individuals grew relatively poorly and mortality was high. Nevertheless, the surviving oviparae deposited numerous eggs, but these remained pale green whereas viable, fertilized eggs deposited by plant-reared oviparae rapidly become black. In the case of aphids reared on host plants in a short-day environment the possibility exists that the photoperiod may act indirectly via the plants and not directly on the insects themselves — a doubt which has been raised concerning Megoura viciae Buckton (von Dehn, 1967). However, our results with A. pisum reared on artificial diet demonstrate, as Lees did for M. viciae (Lees, 1960, 1967), that it is unnecessary to implicate the host plant in the determination of males and oviparae. This does not, of course, exclude the possibility that photoperiod-induced changes in a host plant may play a role as well. Nor have we ruled out the possibility that dietary composition may influence the aphids directly or their response to other environmental stimuli leading to the production of sexual forms.

A seed-transmitted strain of cucumber mosaic virus isolated from bean.

Abstract: Bean leaves with symptoms similar to those caused by bean common mosaic virus (BCMV) were obtained from a plant grown from seed of a plant introduction line growing in Puerto Rico. Differential seed transmission in two bean cultivars (Stringless Green Refugee and Topcrop) inoculated with leaf extracts revealed that the plant was infected with BCMV and cucumber mosaic virus (CMV), designated the PR strain. CMV-PR produced two types of symptoms on beans: mild vein banding on certain cultivars, or top necrosis on others. Host range included 8 genera and 12 species of legumes and 16 species of non-legumes. Physical properties are similar to major strains of CMV. Purified CMV-PR reacted serologically with CMV-C and CMV-S antisera in gel diffusion tests. Virions measured 25 to 27 nm. CMV-PR was transmitted by Myzus persicae to bean and cowpea, and in seed harvested from infected bean and cowpea plants. Survival of the virus in bean and cowpea seed stored for 6 months and 1 year, respectively, enhances the possibility of wide geographic distribution through movement of infected seed.

Relation of aphid populations to field spread of lettuce mosaic virus in New York.

Abstract: Aphid species migrating to and colonizing lettuce plantings were sampled to assess their importance in field spread of lettuce mosaic virus (LMV) under conditions existing in New York State. The studies were carried out in small-plot experiments and included an evaluation of various insecticides for regulation of field spread of LMV through reduction of numbers of aphids colonizing lettuce. The potato aphid, Macrosiphum euphorbiae (Thomas) was the predominant species colonizing lettuce, but high-level populations throughout the season were not correlated with significant field spread of LMV. Conversely, LMV infection of more than 90% was noted when plants were treated with oxydemetoumethyl and aphid numbers were very low. Large numbers of LMV-infected plants were detected only in late August and September, and this corresponded closely with peak numbers of alatae aphid populations captured in water-filled yellow pans (Moericke traps). A close correlation was found between incidence of LMV-infected plants and peak numbers of alatae of green peach aphid, Myzus persicae (Sulzer). Infected plants appeared in an apparent random pattern. Healthy plants protected from wandering apterae by sticky enclosures became infected with LMV as readily as plants not protected. These observations indicated that LMV was spread chiefly by the alatae. Oxydemetonmethyl was the most effective insecticide for reducing and maintaining low numbers of aphids on lettuce, but plants treated with a combination of DDT and malathion had more aphids than untreated plants. None of the insecticides was effective for preventing the spread of LMV.

Persistence and effectiveness of thionazin against potato aphids on three soils in Southern England

Abstract: Degradation curves were determined for thionazin applied to the soil in potato plots at three sites. Thionazin persisted longer in an acid, sandy soil than in an alkaline, clay soil, and residues were detected in the sandy soil a year after application. Results of residue analyses were confirmed by determining the kills of aphids (Myzus persicae Sulz.) ‘sleeved’ on to potato plants. Natural infestation by potato aphids was effectively decreased only on plots treated with thionazin at 40 Ib/acre (44.84 kg/ha) on the acid sandy soil.

Aphid Vectors of the Papaya Mosaic Viruses in Puerto Rico

Abstract: Two apparently related, aphid-transmitted virus diseases of papaya occur in Puerto Rico. These are the more severe, Distortion Mosaic (DM) and the more mild Papaya Mosaic (PM). Thirteen species of aphids were investigated as potential vectors of one or both viruses. The species Aphis nerii B. de F., Aphis gossypii Glover, Aphis spiraecola Patch, and Myzus persicae (Sulzer) were found capable of transmitting both virus types. In terms of efficiency of transmission in the laboratory, M. persicae appeared to be the most efficient vector. In addition, the species Carolinaia cyperi Ainslie and Dactynotus ambrosiae (Thomas) were found to be efficient vectors of Distortion Mosaic virus. No transmissions occurred with Aphis craccivora Koch, Toxoptera aurantiae (B. de F.), Aphis illinoisensis Shimmer, or Rhopalosiphum maidis (Fitch) all of which have been previously reported as vectors of papaya viruses. Negative results were also obtained with Hyperomyzus lactucae (L.), Rhopalosiphum nymphaeae (L.), and Sipha flava (Forbes).

Differential Transmission of Closely Related Strains of Potato Virus Y by the Green Peach Aphid and the Potato Aphid

Abstract: Comparative transmission trials were made with 2 strains of potato virus Y (MPVY and RPVY) using the green peach aphid, Myzus persicae (Sulzer). and the aphid, Macrosiphum euphorbiae (Thomas). RPVY inoculated by green peach aphids caused both mild and sever symptoms in ‘California Wonder’ pepper (CW) whereas inoculation by potato aphids and by sap of RPVY consistently caused severe symptoms in CW pepper. Symptoms of MPVY in CW pepper were always severe regardless of type of inoculation used. The mild syndrome of RPVY could be restored to the severe syndrome by serial sap inoculation in pepper. Fourteen days after inoculation, titrations by sap inoculation indicated concentrations of mild and severe symptom RPVY to be similar; whereas titrations by green peach aphid transmissions indicated concentration of the mild symptom RPVY to be significantly lower than concentration of the severe symptom type. Thirty-nine days after inoculation, titrations of these same plants by green peach aphid transmissions showed equal concentrations of both mild and severe symptom RPVY. MPVY was transmitted very efficiently by green peach and potato aphids in only 10–12 days after inoculation of virus source plants, irrespective of whether aphid-or sap-inoculated plants were used. Titrations by sap inoculation of MPVY correlated well with titrations by green peach aphid transmissions. In CW plants infected for 18–40 days, potato aphids transmitted both mild and severe symptom RPVY (both sap-inoculated and aphid-inoculated) with equal efficiency. Green peach aphids initially had difficulty in transmitting mild symptom RPVY where aphid-inoculated (either green peach or potato) virus inoculum source plants were used, but after 40 days these plants were equal as inocula to sap-inoculated plants. Rates of postacquisition feeding loss of RPVY in green peach aphids and potato aphids were determined for mild and severe symptom types of virus using both sap-inoculated RPVY. MPVY was tested similarly but only with green peach aphids. The half-life life of severe symptom RPVY (for both sap-and aphid-inoculated virus) was about 40 min in green peach and potato aphids. However, the half-life of mild symptom RPVY inoculated by green peach aphids was less (10 minutes) than when inoculated by sap or potao aphids (40–75 minutes). This was true for both green peach and potato aphids. The half-life of MPVY as determined for green peach aphids was (1) similar for both sap- and aphid-inoculated virus, and (2) was much longer than for RPVY (150–180 minutes). When vector efficiency was plotted against the half-life of virus, a linear relationship seemed evident.

Further Tests with Insecticides for the Control of Myzus persicae (Sulzer) on Year‐Round Chrysanthemums

Abstract: SUMMARY Eleven pesticides were compared for the control of a strain of Myzus persicae resistant to contact organophosphorus pesticides on year-round chrysanthemums growing in pots. The pesticides were applied as sprays, drenches or granules. Several of the pesticides were phytotoxic in varying degrees to the cultivar Heyday. Drenches of oxydemeton-methyl, demeton-S-methyl and demephion gave good results for several weeks but granules of the carbamates aldi-carb, PP062 and C13963 were more effective and more persistent.

Reproductive Capacity of the Green Peach Aphid on Maryland Tobacco

Abstract: When individual Myzus persicae (Sulzer) were reared for several generations in small cages on plotted tobacco, the first-born females lived longer than the last born. Nymphal development was about 8 days for both first-and last-born individuals but first-born aphids lived an average of 18 days as adults, while the last born lived an average of 11.5 days. First-born females gave birth to an average of 51.7 young, and last born an average of 28. Data obtained from individually caged aphids was used to construct a life table from which was calculated a net reproductive rate and the average length of 1 generation. Under the optimum conditions of this experiment a population of green peach aphids on Maryland tobacco has the potential to increase 26.7 times in each generation. The length of the average generation was calculated to be 12.6 days. At this rate of increase and with no environmental resistance, in 5 generations a single green peach aphid could give rise to a population of 13,552,028 aphids. Aphids colonized on tobacco leaves showed effects of crowding. The maximum density (534 aphids per square foot of leaf area) was attained in 30 days.