Plusia Gamma Research Articles

Factitious prey and artificial diets: do they all have the potential to facilitate rearing of Typhlodromus bagdasarjani (Acari: Phytoseiidae)?

ABSTRACTThe rearing possibility of Typhlodromus bagdasarjani (Phytoseiidae) on three factitious prey (Ephestia kuehniella eggs, cysts of Artemia franciscana and Tyrophagus putrescentiae), and nine artificial diets including a basic artificial diet (AD1) and the others (AD2–AD9) consisted of 80% AD1 enriched with different nutrients including maize pollen, haemolymph of Plusia gamma L., Ephestia eggs, Artemis cysts, Ephestia larvae, multivitamin syrup, bovine serum albumin and bull sperm, as well as a natural pollen diet (almond+ maize pollen) were investigated. None of the three factitious prey supported development of T. bagdasarjani beyond protonymphal stage. The highest GRR (gross reproductive rate), R0 (net reproductive rate), r (intrinsic rate of increase) and λ (finite rate of increase) were obtained when the adults were reared on cysts of Artemia, immediately after their emergence. On pollen diet, all population growth parameters except T (mean generation time) were higher than artificial diets. The mites reared on AD6 and AD8 could not develop beyond deutonymphal stage. Although r was negative on both AD3 and AD5, its value on AD3 was higher. In conclusion, except pollen diet, none of diets tested is recommendable for mass rearing of this predator and utilizing on crop as alternative food.

Attempt to Develop Cost-Effective Rearing of Amblyseius swirskii (Acari: Phytoseiidae): Assessment of Different Artificial Diets.

Commercial production of Amblyseius swirskii Athias-Henriot based on storage mites needs both space and labor to maintain large cultures of these prey, and also may lead to health problems for workers. Therefore, the accessibility of a suitable artificial diet could eliminate the mentioned problems; however, the artificial diets must support the persistent production of high quality progeny. This study endeavored to find a more easily available and cheaper nutrient that may further reduce the cost of diet production for A. swirskii. The predator's performance was determined when it was fed on a basic artificial diet (AD1) composed of honey, sucrose, tryptone, yeast extract, and hen egg yolk, and on eight other artificial diets consisting of 80% AD1 enriched with different nutrients including maize pollen (AD2), hemolymph of Plusia gamma L. (AD3), Ephestia eggs (AD4), Artemis cysts (AD5), Ephestia last-instar larvae (AD6), multivitamin syrup (AD7), bovine serum albumin (AD8), and bull sperm (AD9). The lowest development time was on AD2. The highest value of fecundity and oviposition period were observed on AD5, followed by AD2 and AD4. The intrinsic rate of increase (r) and the finite rate of increase (λ) reached the maximal value on AD5. Feeding on AD2 and AD5 resulted in highest value of R0 (net reproductive rate). Our results indicated that Artemia cysts and maize pollen had better potential to be used as nutrient in artificial diet for mass production of A. swirskii. Overall, it seems that AD2 is the most cost effective than others.

Relationship between wingbeat frequency and resonant frequency of the wing in insects

In this study, we experimentally studied the relationship between wingbeat frequency and resonant frequency of 30 individuals of eight insect species from five orders: Odonata (Sympetrum flaveolum), Lepidoptera (Pieris rapae, Plusia gamma and Ochlodes), Hymenoptera (Xylocopa pubescens and Bombus rupestric), Hemiptera (Tibicen linnei) and Coleoptera (Allomyrina dichotoma). The wingbeat frequency of free-flying insects was measured using a high-speed camera while the natural frequency was determined using a laser displacement sensor along with a Bruel and Kjaer fast Fourier transform analyzer based on the base excitation method. The results showed that the wingbeat frequency was related to body mass (m) and forewing area (Af), following the proportionality f ∼ m1/2/Af, while the natural frequency was significantly correlated with area density (f0 ∼ mw/Af, mw is the wing mass). In addition, from the comparison of wingbeat frequency to natural frequency, the ratio between wingbeat frequency and natural frequency was found to be, in general, between 0.13 and 0.67 for the insects flapping at a lower wingbeat frequency (less than 100 Hz) and higher than 1.22 for the insects flapping at a higher wingbeat frequency (higher than 100 Hz). These results suggest that wingbeat frequency does not have a strong relation with resonance frequency: in other words, insects have not been evolved sufficiently to flap at their wings' structural resonant frequency. This contradicts the general conclusion of other reports-–that insects flap at their wings' resonant frequency to take advantage of passive deformation to save energy.

Epizootics caused by a nuclear polyhedrosis virus in populations ofspodoptera exiguain southern Spain

A nuclear polyhedrosis virus (NPV) has been identified as the etiological agent causing epizootics in natural populations of Spodoptera exigua in the south of Spain. The incidence of this NPV has been determined from samples of larvae collected from sunflower fields and vegetable greenhouses at two sites located 500 km apart. The NPV was the only disease agent identified at both sites. Through the period surveyed the percentage of NPV‐infected larvae increased from 4.3% to 23% and from 22.5% to 100% in S. exigua larvae collected from sunflower fields and vegetable greenhouses respectively. No mortality attributed to the NPV was found in Spodoptera littoralis, Heliothis armigera, Peridroma saucia and Plusia gamma larvae collected in the same survey from the same sites. This is the first report of epizootics caused by NPV in S. exigua populations in field and greenhouse crops in Europe.

Deterrent and insecticidal chromenes and benzofurans from Encelia (asteraceae)

Four analogous chromenes and benzofurans that are among the major natural products of the genus Encelia were bioassayed for deterrency and toxicity against pest insects. The chromene encecalin has both antifeedant and insecticidal properties towards larvae of the noctuid pests Peridroma saucia and Plusia gamma. In addition to reducing larval growth and decreasing survivorship of neonate larvae fed artificial diets containing encecalin, this chromene was directly insecticidal to neonate larvae after 4 hr using a residue contact bioassay. Topical application of encecalin to third instar larvae of Peridroma led to a reduction in dietary utilization, indicative of a metabolic cost of handling the compound. The demethyl analogue of encecalin is considerably less active, and the benzofurans euparin and methyleuparin, all common constituents of Encelia, were essentially inactive or only weakly active in all bioassays against the insects.

Host range and virulence of five baculoviruses from lepidopterous hosts

SUMMARYThe host range and virulence of five insect baculoviruses (two multiply‐enveloped nuclear polyhedrosis viruses (MNPVs) from Agrotis segetum and Mamestra brassicae; one singly‐enveloped NPV from Plusia gamma and two granulosis viruses (GVs) from A. segetum and Pieris brassicae) were studied for seven lepidopterous pests of temperate agriculture (A. segetum, Agrotis exclamationis, Lacanobia oleracea, M. brassicae, Noctua pronuba, P. gamma and Pieris rapae). None of the viruses killed all species but M. brassicae MNPV failed to infect only P. rapae. The other viruses were restricted to the homologous host, or members of its genus or subfamily. In all examples except A. segetum GV, the median lethal dose for the most susceptible host, was less than 22 virus inclusion bodies and median lethal times for all infections ranged from 5·5 to 16·6 days. The low susceptibility of A. segetum and other noctuids to GV infections is discussed in relation to the structure of inclusion bodies and the nature of the infectious unit in baculoviruses.

Virus particle packaging in baculovirus and cytoplasmic polyhedrosis virus inclusion bodies

The structure of the inclusion bodies (IBs) of three multiply enveloped nuclear polyhedrosis viruses (MNPVs), one singly enveloped NPV (SNPV), two granulosis viruses (GVs) and one cytoplasmic polyhedrosis virus (CPV) were compared. A method was devised to calculate the numbers of virus particles and nucleocapsids in IBs using data from light microscopy and thin sections. The three MNPVs, from Agrotis segetum (English and Polish virus isolates) and Mamestra brassicae had similar concentrations of virus particles ranging from 17.3 to 19.6 per μm 3 of IB. Plusia gamma SNPV had a higher density of 59.6 virus particles per μm 3 of IB, which partly compensated for its having smaller IBs (mean volume 0.65 μm 3) than the MNPVs (2.60–9.71 μm 3). The English A. segetum MNPV isolate had the most nucleocapsids in each virus particle (mean, 4.04) and the largest IBs (mean volume, 9.71 μm 3), giving 674 nucleocapsids per IB on average. The GVs, from A. segetum and Pieris brassicae, mainly contained one nucleocapsid per IB. P. gamma CPV IBs had a much higher density of virus particles than the baculoviruses (260 per μm 3 compared with 17–60 per μm 3). These data are discussed in relation to the biological properties of these viruses, and possible adaptational advantages of alternative IB designs are considered.

Diet Periodicity of Entomophthora gammae in the Soybean Looper 12

The soybean looper, Pseudoplusia includens (Walker), is a common pest of soybeans in South Carolina. Loopers contribute to a group of general defoliators which may reach population levels sufficient to cause economic damage. Working with P. includens in Alabama, Harper and Carner (1973) reported that larval populations often are infected with the fungus, Entomophthora sp., which under certain conditions may reduce or eliminate looper populations. Current opinion (MacLeod, personal communication) regards this pathogen as the same species ( Entomophthora ( Tarichium ) gammae ) described by Weiser (1965) infecting Plusia gamma (L.).

FLIGHT ACTIVITY OF PLUSIA GAMMA IN THE LABORATORY

Aktograph experiments showed lowered light thresholds for flight during the first three days after emergence of adult moths. Maximum flight duration was also reached at the third day. These three days probably represent the time when migration would occur in wild insects.Migration of insects usually begins post tenerally so it should be possible to direct migratory behaviour (i.e. the tendency for continued flight) in young adults of each generation of a species that migrates. The flight behaviour of Plusia gamma L. was studied in the laboratory to test this possibility.RésuméACTIVITÉ DE VOL DE PLUSIA GAMMA AU LABORATOIREDes expériences utilisant un actographe ont montré une inhibition moins forte de la lumière sur le vol pendant les trois premiers jours suivant leur émergence. La durée maximum de vol est atteinte au 3ème jour. Il est suggéré que ces premiers trois jours de la vie imaginale pendant lesquels le papillon a tendance à voler de facon continue, correspondent à la période d'activiTÉ migratoire.

Relationship between Larval and Pupal Periods of some Lepidopterous Insects

EXPERIMENTS have been carried out in the United Kingdom and the United Arab Republic (Egypt) to show the effect of population density on the silver Y moth, Plusia gamma L. and the cotton leaf worm, Prodenia litura (Fab.) respectively. In these experiments two parallel cultures of solitary and crowded conditions were maintained for each species.

The pigments in colour phases of the larvae of Plusia gamma L. (the silver-Y moth).

The pigments in colour phases of the larvae of Plusia gamma L. (the silver-Y moth).

The Selection and Rearing of Leaf-eating Insects for Use as Test Subjects in the Study of Insecticides

A number of leaf-eating insects have been studied with the object of selecting species suitable for rearing in the laboratory.Four species have proved satisfactory for large-scale rearing throughout the year. These arePlutella maculipennis, Plusia gamma, Diataraxia oleraceaandPhaedon cochleariae. A number of species possess certain disadvantages : (1) apparently obligate diapause (Mamestra brassicae, Sphinx ligustri). (2) The same as (1) with the additional disadvantage of lack of food-plant in winter (Lymantria dispar). (3) Uncertain copulation and oviposition (Pieris brassicae). When available, these species may be reared satisfactorily in large numbers.Mesographe forficalis, Xanthorhoë fluctuata, Lema melanopaandCrioceris asparagihave been reared in relatively small numbers. They possess certain disadvantages but should be satisfactory for large scale rearing at any rate during some part of the year.At present laboratory rearing ofPhlogophora meticulosa, Agrotis segetum, Triphaena pronuba, Aclypea opacaandAthalia colibriis considered impracticable. A number of leaf-eating species, particularly Hymenoptera, which appear to possess suitable qualities for laboratory rearing, have not yet been obtained and studied in the laboratory.Particular attention has been paid to factors influencing development of leaffeeding insects with the object of determining the conditions under which healthy stocks of uniform resistance can be maintained. The results of experiments on the effect of food-plant, temperature, humidity and illumination are described. Studies on the factors influencing diapause in the various species are mentioned. Descriptions, are given of the rearing techniques that have been developed.

Observations on the Moth Plusia gamma in Denmark in 1946

THIS year the noctuid Plusia gamma has been more abundant in Denmark than at any time since 1905. It is likely that the swarms arrived here in June; the first report of damage caused by the larvae came from the southern part of Denmark, and was followed by similar reports from more northern parts, thus closely corresponding to the seasonal progression recorded in England1. The adults appeared about August 1.

Migrations of the Silver-Y Moth (Plusia gamma) in Great Britain

Migrations of the Silver-Y Moth (Plusia gamma) in Great Britain