Showing papers on "Aphid 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-

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.

An ecological study of insect populations on cabbage in southern California

Abstract: An ecological study of insect populations on cabbage plantings was conducted over a two-year period in a coastal environment of southern California. Eleven orders of insects were represented in the collections. The Hymenoptera ranked first in the number of species represented, and the Collembola ranked first in number of individuals. Approximately 375 species of insects were collected, including about 125 each in the Hymenoptera and Diptera, and 50 in the Coleoptera. The cabbage aphid and the western flower thrips were the most numerous phytophagous species. Diaeretiella rapae (M’Intosh), a primary parasite of the cabbage aphid, was the most abundant parasitic species; the coccinellid, Hippodamia quinquesignata punctata Lec., and the syrphid, Allograpta obliqua (Say), were the two most common predators. The imported cabbageworm, cabbage looper, and diamondback moth were the most numerous lepidopterous larvae. Each year, the imported cabbageworm larval population peaked in August, the cabbage looper in September, and the diamondback moth in February and October. Their combined population averaged 15 larvae per plant in August. Twelve species of parasites were reared from the cabbage looper, nine from the imported cabbageworm, and five from the diamondback moth. Voria ruralis (Fallen), Pteromalus puparum (L.), and Diadegma insularis (Cresson) were the most common parasites on these three pests, respectively. Trichogramma pretiosum Riley was the only parasite reared from the lepidopterous eggs. Cabbage plants were severely injured by the cabbage aphid during the winter and spring months and by the imported cabbageworm and cabbage looper during the summer and early fall. Injury by the diamondback moth was minor in comparison. This study shows that although natural enemies of cruciferous crop pests should be conserved and augmented, current biological control methods alone are not adequate to control these insect pests under certain conditions without the supplemental use of pesticides.

Performance of Aphis fabae and Brevicoryne brassicae on plants treated with growth regulators

Abstract: It was shown that the fecundity of aphids may be altered on plants treated with plant growth stimulators and retardants. There was evidence that the reduced fecundity and smaller size of Aphis fabae on broad beans treated with ethylene bisnitrourethane was related to the reduced nutritional value of the plants to the aphids, levels of soluble nitrogen being reduced. The reduced fecundity of A. fabae on broad beans treated with gibberellic acid may be related to the apparent toxicity of the compound when fed directly to the aphid. CCC (chlormequat chloride) seemed toxic to both A. fabae and Brevicoryne brassicae, and the number of embryos per adult A. fabae reared on CCC-treated beans was reduced, although this did not reduce fecundity. Apart from any direct action of CCC on the aphids, there is evidence that the substance may reduce the availability of nutrients from the phloem of treated plants to the insects by reducing translocation, and there is further evidence that amino acid content of the sap may be reduced.

Biotic Factors Involved in Crucifer Aphid Outbreaks Following Insecticide Application

Abstract: Applications of carbaryl and cryolite (sodium hexafluoroaluminate) altered the basic structure of the arthropod community associated with collards at Ithaca, N, Y. Population outbreaks of aphids occurred when carbaryl was applied at weekly intervals throughout the season. Aphid populations declined early on plots in which carbaryl applications were stopped in mid-season. Extensive leaf injury caused by flea beetles was associated with low and declining aphid densities. The density of aphid predators increased after carbaryl was withdrawn. However, predators were relatively rare in all treatments. The percent of the aphids parasitized did not differ significantly 011 treated and untreated plots in the late season when the aphid outbreaks occurred. It is suggested that reduced inter specific competition may have been an important factor in the complex chain of events that led to the aphid outbreaks.

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.

Probing Behavior of the Pea Aphid, Acyrthosiphon pisum. IV. EfEects of Starvation on Certain Probing Activities

Abstract: Individuals from 1 group of A. pisum (Harris) were starved for 1, 4, or 24 hr prior to their access to leaves of Vicia faba L. Other individuals from the same group were not starved prior to access. Following the starvation treatments, the aphids were permitted to probe until they had made 5 probes or until they ingested fluid from the plants. The time of ingestion was restricted to 10 min. Six parameters of probing activities were statistically analyzed. There were statistically significant differences between unstarved aphids and starved aphids in all but 1 parameter. More starved aphids ingested fluid from the sieve elements than did aphids that were not starved. The plant tissues from which ingestion took place were determined by using histological procedures. Individuals from another group of pea aphids were starved for 24 hr. Other individuals from the same group were not starved. Following starvation or nonstarvation, the aphids were permitted a 24-hr access to leaves of V. faba . Nine parameters of aphid-probing activities were analyzed statistically. Significant differences were evident in the following parameters: mean number of probes, mean base time, mean total X waveform time, mean total ingestion time, and mean total probe time. The results of 7 of the 9 above-mentioned probing activities were plotted as a function of time. A lag effect appeared between the activities of starved and unstarved aphids. At least 4 hr passed before the probing behavior of starved aphids was similar to the behavior of unstarved aphids. Preacquisition starvation is discussed in relation to its effect on the length of the latent period of a circulatiye or propagative plant virus within the aphid vector. It is suggested that the length of the latent period may be directly correlated with the magnitude of a virus charge and the rapidity with which the virus is accumulated by the aphid vector.

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.

Temperature and the Preference of the Spotted Alfalfa Aphid for Resistant and Susceptible Alfalfa Plants

Abstract: When excised leaves and whole plants of resistant and susceptible alfalfa clones were held at 27°C Therioaphis maculata (Buckton) given a free choice generally preferred the more susceptible plants. When the alfalfa was held at 10°C the aphids reacted to some resistant plants as if they were susceptible. Also, the preference of the aphids for 1 clone changed depending on whether excised leaves or whole plants were offered.

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.

Grain aphids in New Brunswick. IV. Effects of malathion and 2,4-D amine on aphid populations and on yields of oats and barley

Abstract: Aphid populations on oats (Fundy and Stormont) and barley (Charlottetown 80) were studied in the field and yields of these grains examined under the different levels of aphid infestation resulting from applications of malathion and 2,4-D amine to the crop.Two species of aphid, Rhopalosiphum padi (L.) and Macrosiphum avenae (Fab.), occurred on the grains, and the greatest populations developed on barley. In all cases highest numbers were associated with applications of 2,4-D amine. Applications of this herbicide to similar aphids under laboratory conditions showed that the species differed in their responses as measured by reproduction and longevity.One malathion treatment, applied when aphids were dispersing into the field, reduced ensuing aphid numbers on oats by 29% and on barley by 64%. Yields of oats were increased by 47% and of barley 32% when malathion alone was used. When malathion and 2,4-D amine were applied together, aphid results and yield results were confusing.In all treatments, aphid populat...

Toxicity of Malathion and Parathion to Predators of the English Grain Aphid

Abstract: The LD50 and/or LC50 values of malathion and parathion for the English grain aphid, Macrosiphum avenae (F.), and the dominant insect predators in South Dakota (adults and larvae of the convergent lady beetle, Hippodamia covergens Cuerin-Meneville; adults and nymphs of Nabis americoferus Carayon, larvae of Chrysopa Cornea Stephens) indicated that all predators, in general, were less vulnerable to the insecticides than the aphid. The potential for an integrated program to control cereal aphids with selected doses of malathion or parathion thus appears promising.

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.

Population increase of the cabbage aphid, brevicoryne brassicae, on different host plants

Abstract: Longevity and fecundity data are presented for cohorts of cabbage aphid, Brevicoryne brassicae (L.), reared on different hosts (Barbarea vulgaris, Brassica pekinensis, and two varieties of Brassica oleracea) and under constant and fluctuating environmental conditions. Changes in fecundity and development were the chief causes for the different rates of population increase (r) observed on each host. Alate forms developed only in the cohort reared on B. vulgaris, the most resistant host studied. Host factors, acting during the late prenatal period or during postnatal development, appear to be capable of influencing form determination in this aphid.

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.

Behavior of the Spotted Alfalfa Aphid on Resistant and Susceptible Alfalfas

Abstract: As the number of adult Therioaphis maculata (Buckton) decreased on resistant alfalfa clones, the total production of nymphs also decreased, but the rate of production probably did not decrease. Although adult survival on resistant clones was similar to that of starved aphids and of aphids on broadbean, total production of nymphs was about 4 times greater on resistant clones than on the nonhost (broad bean). Thus, both resistant and susceptible alfalfa apparently contain something that increases the production of nymphs. Leaves of resistant alfalfa seedlings were more resistant than petioles or stems. The aerial parts of all mature alfalfa plants, except the flower petals, were highly resistant; the flower petals were not resistant. Although differences in the stage of growth of the plant did not affect aphid survival on resistant alfalfa, survival on susceptible alfalfa was reduced on mature shoots compared with that on rapidly elongating shoots. It is indicated by the results obtained when aphids were offered a choice between resistant and susceptible plants or were transferred to susceptible plants after either starvation or feeding on resistant plants that aphids are driven from resistant plants by a repellent in the phloem, or by the possibility that such plants do not satisfy dietary needs.

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.

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.

Effects of Temperature and Light on Dispersal of the Pea Aphid, Acyrthosiphon pisum, and a Braconid Parasite, Aphidius pisivorus, in the Field

Abstract: Alate pea aphids, Acyrthosiphon pisum (Harris) (Homoptera: Aphididae), and braconid parasites, Aphidius pisivorus C. F. Smith (Hymenoptera: Braconidae), were collected at 30-min intervals from 28 April to 17 May 1967 with Johnson-Taylor segregating suction traps placed level with the tops of alfalfa. Simultaneous records of air temperature and light intensity were taken at crop level. Data indicate the parasites were in flight 1 hr earlier in the morning and 21 min later in the evening than alate aphids. Temperatures below 0°C did not noticeably reduce populations of the pea aphid or parasite, but flight of both species was inhibited below about 6°C. The median temperature thresholds for parasite and aphid flight were 19.8 and 21.8°C, respectively. Parasites were in flight at lower light intensities in the morning and evening than alate aphids. The median light intensity thresholds for parasite and aphid flight were 2800 and 4300 foot-candles, respectively.