Alate Aphids Research Articles

Seed Systemics for Control of Aphids on Oats and Barley 1

Eleven organophosphorous compounds in carbon formulation were tested as seed systemics for phytotoxicity to barley and oats, and control of aphids on oats. Ph orate, Bayer 25198 ( O, O -dimethyl- O-p -(methylsulfinyl)phenyl phosphorothioate), Di-Syston ® ( O, O -diethyl S -2 (ethylthio)ethyl phosphorodithio-ate), dimethoate, and phosphamidon were promising. Phorate and Di-Syston did not. prevent transmission of barley yellow-dwarf virus to small plots of oats by migrating alate aphids.

Aphid Transmission of Bean Viruses in Field Beans in Central Washington1

Epidemiology studies of bean mosaic diseases in central Washington were made from 1955 to 1959. Surveys of aphid populations and mosaic disease symptoms were made in plots of field beans. Aphids rarely colonized the bean plants, but moderate to large populations of alate aphids were present from late June until sometime in August. The majority were green peach aphids, Myzus persicae (Sulzer). The bulk of the remainder consisted of pea aphids, Macrosiphum pisi (Harris), and English grain aphids, Macrosiphum granarium (Kirby). Possible arthropod vectors other than aphids were very few. Mosaic symptoms began appearing in the bean plots in July and were well distributed by early August. A number of different nonpersistent viruses were isolated and subjected to greenhouse tests. All were readily transmissible by the green peach aphid and somewhat less so by the clover aphid, Anuraphis bakeri (Cowen). None were transmitted by the English grain aphid. The pea aphid transmitted these viruses only from broad bean. It was concluded that virus spread in the bean fields was due to migrant aphids, especially the green peach aphid, and, because of the short transmission feeding times, vector control methods would likely be of little value in controlling the mosaic diseases.

Studies on the Seed Potato Growing in Warmer District in Japan : I. Seasonal variation in the parasitic activity and the flight of potato aphids in relation to the transmission of virus disease in potato fields grown twice in a year in spring and autumn.

I. Fluctuations in population of the alatae and the apterae of Myzus persicae (SULZER), Aphis gossypii GLOVER and Aulacorthum solani (KALTENBACH) were Surveyed, sticky traps of BROADBENT style being used with regard to their flight, in experimental potato-field-blocks which were planted at nine different times successively throughout from spring to autumn in Himeji from 1955 to 1958. The results are as follows: (1) The appearance of those aphids has three seasons, marked off by the disappearance and the diminution periods on host and flight, which are relatively stable but without connection with plant growth. (2) M. persicae appears most abundantly in the early and middle part of the first season (from April to June), and also in the middle and late part of the third season (from Octover to December), but scarcely in the second season (from July to mid September); A. gossypii exceedingly in the second season, and also in the middle and late part of the first season, and in the early and middle of the third season; the counts of A. solani is always the smallest. (3) Though the aphid population varies markedly with dats of potato sprouting, the seasonal fluctuation curve of parasitic activity in each species is obtainable by the line connecting the highest value of the aphid population among blocks of each planting date. Such fluctuation curves in different years and aphid species were discussed with regard to flight fluctuation. II. On a virus free potato row planted in a victoria lawn tunnel, adjacent to an alternate open row of diseased poatoes infected with virus Y and leafroll virus, was allowed natural inoculation by opening the tunnel for one week at definite time, in Himeji from 1955 to 1957. The results are: (1) the fluctuation observed in virus transmission in years, seasons and with the dates of sprouting revealed close connection with activities, especially with flight, of the aphids which inoculated the diseases, i.e. virus Y being associated with A. gossypii or plus M. persicae, and leafroll virus with M. persicae or plus A. solani. However, in un-caged blocks, transmission of leafrall and virus Y were rather correlated with the index-value for the whole season infestation of alate aphids, with the relation of M. parsicae plus A. solani to leafroll and A. gossypii plus A. solani to virus Y, the index-value being obtainable by summing up all countings made on every tenth day by the line of parasitic activity. The reason for the affecting of A. solani to the transmission of virus Y must be owing to the abnormal appearance of the species in autumn 1956. (2) The number of days for virus diseases to flow down from inoculated leaves to tubers varied in connection with the aphid population; in relatively shorter period of time the tubers seemed to be infected, if much of inoculations have been occured by many aphids.

Studies on the degeneration of the flight muscles of alate aphids—II Histology and control of muscle breakdown

Within a few days of settling down on a host plant, alate aphids of most species undergo a change in metabolism which becomes manifest in breakdown of the flight muscles, resumption of embryo development in the ovarioles, and hypertrophy of the fat body. In this paper an account is given of the histology of flight muscle breakdown, and experimental evidence is presented which suggests that the change in metabolism in the aphid is brought about by the secretion of a hormone. Muscle breakdown and fat body hypertrophy could be initiated in aphids in response to abnormal afferent stimuli, as when aphids were tied down on inert surfaces.

Factors affecting the locomotor and settling responses of alate aphids

In suitable environmental conditions for flight, alate aphids typically fly from their parent host plants and they can not normally be brought to settle down on those or other plants until after they have engaged in flight or other activity. In unsuitable flight conditions they remain on the plants but do not respond to them by feeding and reproducing. Aphids alighting on plants after flight normally spend some time wandering and probing and they may settle down. By allowing young alatae of Aphis fabae Scop, short tethered and untethered flights of a minimum of 10–20 seconds and then putting them on a leaf surface, it was possible to induce wandering and probing behaviour. There is evidence that aphids do not normally alight and show this behaviour after being airborne for such a short time, and the behaviour of the aphids in the experiments was probably due to the composite effect of flight and some part of the experimental procedure. Wandering and probing behaviour could also be produced by giving aphids a knockdown dose of CO 2, and by allowing them an extensive period of activity other than flight. The length of time aphids spent wandering on plants before they took off again, and whether or not they settled down to feed and reproduce, was influenced by the length of flight they had engaged in, the nature of the surface they were released on, and the physical environment. Aphids flown for five minutes or less and put on mature host leaves in the light wandered and probed but soon took off again; aphids released on host seedlings or on mature leaves which were then put in darkness, after short flights of a few seconds, and on mature leaves kept in the light after long flights of 30 minutes to 8 hours, frequently settled down to feed and reproduce. The effect of both short and long flights was soon lost and in the absence of strong contralocomotory stimuli such as darkness or a very suitable host, the aphids reverted to typical locomotory behaviour after showing some degree of the settling response (i.e. wandering and probing or settling down for some time). Much of the behaviour of alate aphids can be grouped under two opposing general responses: the locomotor response and the settling response; it is suggested that the stimuli determining the type and strength of response of aphids at any time are principally of the same kinds as those which were shown in the experiments to affect the strength of the settling response.

THE ANALYSIS AND RECONSTRUCTION OF DIURNAL FLIGHT CURVES IN ALIENICOLAE OF APHIS FABAE SCOP.

Experiments, in which alate aphids were marked immediately after eclosion from the last nymphal instar and observed until they took flight, gave information which, together with the measured rate of moulting and a continuous record of temperature, has been used to construct theoretical daily curves for numbers flying from a bean crop. These curves have been matched against the observed curves for the same days.The differences between curves so constructed for a period of 17 days and the observed curves for the same period are of the same order and kind as the differences between two measured curves in different sites at the same time.The different types of daily flight curve can thus be accounted for in terms of the rate of production of alatae by moulting, the effect of temperature on the teneral (‘drying out’) period and the effect of low light intensity and temperature on take‐off behaviour.

Studies on the degeneration of the flight muscles of alate aphids—I: A comparative study of the occurrence of muscle breakdown in relation to reproduction in several species

When alate aphids of several species were allowed to settle down on their host plants, their flight muscles began to break down within a few days. The onset of muscle degeneration could be delayed by preventing the aphids from settling down, either by denying them their host altogether or by leaving them on a poor host in darkness for several days. The reproductive capacity of alatae before they lost the ability to fly varied for different species. Embryo development was arrested in alatae of all the species that were studied after the end of the teneral condition following the final ecdysis, and was resumed when they settled down on a new host. Some species of aphids contained a number of fully formed embryos at the time embryo development was arrested, and these plus a few additional embryos whose development had been completed after the aphids settled down were born before the ability to fly was lost. In other species the young alatae contained only rudimentary embryos that required several days to develop to the stage at which they were normally born; in these species no larvae were born until the muscles had begun to degenerate and the ability to fly was lost. Other species fell between these two groups and in one species, Macrosiphum euphorbiae (Thomas), whether or not the aphids reproduced at all before losing the ability to fly depended upon their size. The ability of alatae of Aphis fabae Scop. to engage in long flights of 1 hr or more was retained for as long as the aphids retained the ability to fly.

THE INCIDENCE AND CONTROL OF CAULIFLOWER MOSAIC IN BROCCOLI IN SOUTH‐WEST ENGLAND

Cauliflower mosaic in south‐west England is most prevalent where there is a sequence of brassica crops that overlap in time. Broccoli yields can be increased by using plants raised in seed‐beds separated by half a mile from old infected plants. Surrounding seed‐beds with crops of kale or barley decreased the incidence of mosaic even when the seed‐beds were only 5 yd. from infected plants.Most plants infected at harvest contract infection after transplanting. A plant infected in the seed‐bed or early in the growing season can produce a group of infected plants immediately around it, and almost as many farther away. Spread can occur in the same pattern from these secondarily infected plants.Loss of yield is correlated with the time plants are infected. Plants infected as seedlings produce little or no curd or seed, whereas those infected when nearing maturity yield almost as well as uninfected plants.The movement of alate aphids is positively correlated with the numbers of infectedplants, and symptoms in field plants generally appear 8–9 weeks after infection.Cauliflower mosaic virus occurs in strains distinguishable by the severity of symptoms they cause.

Effect of Flight on Behaviour of Aphis fabae Scop.

AFTER a preliminary period of quiescence newly moulted alate alienicolae of Aphis fabae Scop. take flight, in suitable physical conditions, whatever the quality of the host they are on. When they alight on a host plant after a sufficient flight they do not take off again immediately1 as they do before sufficient flight2, and they may settle down and bear young. Moericke2 thought that this indicated two phases in the life of alate aphids, the Zugphase and Befallsphase, and Muller and Unger3 attributed the transition from one to the other to exhaustion. The following experiments show that the change can be brought about by flight itself, and that it is not necessarily permanent.

THE SPREAD OF VIRUS DISEASES TO SINGLE POTATO PLANTS BY WINGED APHIDS

Young potato plants in pots exposed in the open near plots of potatoes for limited periods at intervals during the summer, became infested with large numbers of winged aphids only during warm, calm and dry weather. Although visited by aphids during May and June, when much of the spread of viruses occurred in nearby potato crops, few of the potted plants became infected. Most potted plants became infected in July when alate aphids were leaving neighbouring potato crops. Widely different proportions of the exposed plants became infected in different years; in two of the three years, many more plants were infected with virus Y than with leaf roll virus.

Transmission of potato virus diseases. VI. The distribution of the aphid vectors on sampled leaves and shoots

Data on the distribution on potato plants of the two aphid vectors Macrosiphum gei Koch and Myzus persicae Sulz., were collected over the six seasons 1941-42 to 1946-47. In the early stages of infestation the counts of alate and adult apterous aphids approximated to a Poisson distribution, indicating random distribution in the crop. Moderate to high counts of nymphal aphids diverged widely from a Poisson distribution. In the later stages of infestation the total population showed an extremely non-random distribution, but examination revealed that this was due largely to the nymphal aphids, the adults both alate and apterous being distributed in a more nearly random way except when influenced by such events as heavy rainfall. A hypothetical example is given to show how part of the heterogeneous distribution of nymphs may be accounted for by multiple deposition, even if this should occur on randomly chosen leaves. Sampled leaves were assigned to ground cover, median or tip zones of the plant according to the known phyllotaxy of the potato plant. The ground cover was divided into basal leaves, close to or touching the ground, and ground canopy, shading the ground. It was shown that Myxus persicae deposits nymphs mainly on the ground canopy, Macrosiphum gei on the basal two or three leaves and the tip. Adults of both species wander over all portions of the foliage. The influences producing non-random distribution of aphid vectors are discussed. It is suggested that the procedure for sampling aphid populations on potato crops be modified to take account of the difference between basal leaves and ground canopy leaves.