The comparative susceptibilities of Pieris brassicae and P. rapae to a granulosis virus from P. brassicae

A comparison was made of the dosage-mortality responses of larvae of Pieris brassicae and P. rapae to infection by P. brassicae granulosis virus (GV). Bioassays with first, second, third, and fourth-instar larvae of both species revealed a marked difference in susceptibility between instars and between species. Median lethal dosages (LD₅₀s) for P. rapae larvae ranged from five capsules for the first instar to 662 capsules for the fourth instar. With P. brassicae, this range extended from 66 capsules to 2.3 × 10⁷ capsules. The time-mortality responses of the two species were similar when fed virus dosages equivalent to an LD₉₀. Median lethal times (LT₅₀s) ranged from 5 days for first-instar larvae to 7–8 days for fourth-instar larvae. A comparison between a long-established laboratory stock of P. brassicae and a stock recently acquired from the field showed no significant difference in their susceptibility to GV. The implications of the pronounced species differences in susceptibility to GV infection are discussed in relation to the potential field control of P. rapae and P. brassicae.     

Histopathology and bioassay of Plathypena scabra granulosis virus

A granulosis virus was found infecting Plathypena scabra larvae in Iowa. The capsules averaged 377 ± 25 × 222 ± 19 nm. On the basis of light microscopical observations, the virus appeared to infect the epidermis, fat body, and tracheal matrix cells. The LC₅₀ and LC₉₅ were 6.7 × 10⁷ and 1.5 × 10⁹ capsules/acre, respectively. The LT₅₀ values varied from 3 to 9 days for 1 × 10¹² and 1 × 10⁸ capsules/acre, respectively.     

Experimental studies on parasitization byApanteles Glomeratus V. Relationships between growth rate of parasitoid and host age at the time of oviposition

The growth and development ofApanteles glomeratus L. eggs and larvae in the host larva (Pieris rapae crucivora Boisduval) was investigated by calculating their volume. WhenA. glomeratus eggs increase 90 fold in volume after being laid, larvae hatch from them. The larvae grow exponentially and the growth rate of the parasitoid is dependent on the host stage. Being laid in the 1st instar host, the parasitoids grow more slowly than those laid in 2nd–4th instar host. A pupal host stage prevents the parasitoids’ development. When larvae exceed the threshold size of 5.0×10⁸ μ³, they enter the 2nd instar. A few days after they attain the maximum size of 3.3×10⁹ μ³, they moult and egress from the host body.     

The effects of a granulosis virus infection and temperature on the food consumption ofPierus rapae [Lep.: Pieridae]

The effects of temperature and granulosis virus infection both on the development ofPieris rapae L. and the area of cabbage leaf consumed by larvae were investigated. The duration of the larval period increased from 12.9 days at 24°C to 45.3 days at 13°C. The thermal constant for larval development was 196.1 day °C above the threshold temperature of 9.4°C. The area of cabbage leaf consumed per day increased with larval age so that 5th instar larvae ate 70.9% of the total food consumption. Virus infection extended the larval instar in which death occurred and reduced the potential food consumption by as much as 99.6%. Larger virus doses reduced food consumption within the same instar more than smaller doses. The results are discussed in relation to the feasibility of using granulosis virus for the control ofP. rapae.

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Résumé L'étude a porté sur les effets de la température et de l'infection provoquée par le virus de la granulose sur le développement dePieris rapae L. et la quantité de feuillage de chou consommée par les larves. La durée du stade larvaire a augmenté de 12,9 j à 24°C à 45,3 j à 13°C. La constante thermique pour le développement larvaire a été de 196,1°C au-delà du seuil de température de 9,4°C. La superficie de feuillage consommée par jour s'est accrue en fonction de l'age des larves de sorte que les larves au 5^e stade ont mangé 70,9% de la superficie totale consommée. L'infection provoquée par le virus a augmenté la durée du stade de mortalité et a diminué la consommation potentielle de feuillage de 99,6%. Des doses plus élevées de virus ont réduit la consommation dans le même stade davantage que les doses plus faibles. Les résultats sont discutés par rapport à la possibilité d'utiliser le virus de la granulose dans la lutte biologique contreP. rapae.

     

The susceptibility of the pea moth, Cydia nigricana, to infection by the granulosis virus of the codling moth, Cydia pomonella

Laboratory studies demonstrated that neonate larvae of the pea moth, Cydia nigricana, are susceptible to infection with a granulosis virus (CpGV) isolated from the codling moth, Cydia pomonella. Comparative LC₅₀ values for C. nigricana and C. pomonella are 1.90 × 10⁵ and 1.54 × 10⁴ capsules/ml of diet, respectively. The virus extracted from CpGV-infected pea moth larvae is serologically related, and probably identical, to CpGV.     

The susceptibility ofTribolium castaneum [Col.: Tenchrionidae] toFarinocystis tribolii [Protozoa: Schizogregarinida]

The LT₅₀ ofFarinocystis tribolii Weiser to larvae ofTribolium castaneum (Herbst) increased with the age of the insect indicating that older larvae were relatively more tolerant to the infection though there was 100 % mortality ultimately. The adults were less susceptible than larvae and between sexes, females were more susceptible than males. The number of spores produced increased with the stage of the larvae, but there was no variation in the size of spores in the different instars. The LC₅₀ on 20th and 40th day of inoculation were 1.4×10⁷ and 2.1×10⁶ respectively. Mortality-time due toF. tribolii was shorter at 35 °C than at 25 °C. Sporulation occurred earlier at 35 °C than at 25 °C.     

Microbial control of the fruit tree leafroller,Archips argyrospila [Lep.: Tortricidae] in California

Field populations of larvae of the fruit tree leafrollerArchips argyrospila (Wlk). were practically eliminated following spray application ofBacillus thuringiensis Berliner serotype III at 192 and 80×10⁶ I.U. per litre on the host trees,Cercis occidentalis. Spray applications of lower rates ofB. thurienginsis serotype III at 18.9 and 32.1×10⁶ I.U. per litre and mist application ofB. thuringiensis serotype 1 at 8.0 and 16.0×10⁶ I.U. per litre gave partial control of populations ofA. argyrospila larvae. A granulosis typeBaculovirus, applied by hand sprayer at 1.4×10⁹ granules/ml produced approximately 50% reduction of 5th instarA. argyrospila larvae onC. occidentalis trees. It was concluded thatB. thuringiensis and the granulosis typeBaculovirus are promising control agents forA. argyrospila larvae.     

Production and field evaluation of codling moth granulosis virus for control of Cydia pomonella in the United Kingdom

Codling moth granulosis virus (Cp GV) was produced in larvae of Cydia pomonella reared on artificial diet. The average yield of virus (9 × 10⁹capsules/larva) was increased by raising the larvae on diet containing methoprene, a juvenile hormone analogue. In field trials in 1978 and 1979, one or two high-volume applications of Cp GV at 7 × 10¹⁰ capsules/litre achieved reductions in numbers of mature larvae and damaged fruit that were little different from those obtained by two applications of azinphos-methyl. A field trial in 1980 showed that at concentrations of Cp GV ≥ 6 × 10⁸ capsules/litre, damaged diminished slowly with increasing virus concentration. Following virus application in 1980, Cp GV infectivity was reduced by half in 3 days, but some activity persisted at least 4–8 wk after spraying. The results indicate that codling moth GV is an effective control agent particularly in reducing numbers of larvae and the more severe forms of fruit damage.     

Susceptibility of Hyphantria cunea to a granulosis virus isolated from Diacrisia virginica

The dosage-mortality response of Hyphantria cunea larvae to a granulosis virus isolated from Diacrisia virginica was studied. Serial decimal dilutions of the D. virginica granulosis virus were fed to early second-instar H. cunea larvae. the LD₅₀ for this virus (7.9 × 10⁵ capsules/larva) was significantly greater than the LD₅₀ calculated for the H. cunea granulosis virus (7.06 × 10⁴ capsules/larva) against the same instar of H. cunea. Time mortality studies demonstrated that the LT₅₀ values for the D. virginica granulosis were four to six times greater than for comparable dosages of H. cunea granulosis virus. Based on the mortality response of assayed H. cunea, it is possible to distinguish between the D. virginica granulosis virus and the H. cunea granulosis virus.     

Effects of a granulosis virus on aphids

When capsules, capsule protein, and free virions of a Pieris rapae granulosis virus were fed to or injected into the aphids Myzus persicae and Rhopalosiphum padi, considerable mortality resulted without apparent infection. Free virus was most effective, boiled capsules the least. Macerates and honeydew of aphids fed on capsules were infectious when bioassayed, but recovery of infectious virus depended upon the concentration of capsules fed to aphids. Electron microscopy of the midguts of aphids revealed that most, if not all, capsules remained intact. It is concluded that granulosis capsules and/or capsule components exert a nonspecific toxic effect on aphids when applied internally. Externally applied capsules, capsules on the leaf surface, or an internally applied plant virus (tobacco mosaic virus) which was used for comparison did not cause lethality.     

Occurrence and accumulation of the granulosis virus of Pieris rapae in treated field plots

The granulosis virus of Pieris rapae, the imported cabbageworm (P. rapae GV), persisted in soil after application. Virus produced by epizootics of the disease in populations of the host accumulated in soil in nontreated plots with concentrations of the virus in soil and on foliage, being similar at harvest to concentrations in virus-treated plots. Also P. rapae GV produced in epizootics of the disease increased concentrations in soil of virus-treated plots and maintained substantial residues of the virus on the foliage. Little virus accumulated in plots treated with some chemical insecticides and Bacillus thuringiensis because few host larvae survived to support late-season epizootics. Small quantities of P. rapae GV were found in heads of cabbage harvested from plots in October, but these residues were not related to plot treatment.A study in which nontreated and virus-treated plots were replanted for 2 years after treatment indicated an increase in concentrations of P. rapae GV in surface soil in years following treatment. Concentrations of P. rapae GV in soil in virus-treated and nontreated plots were similar in the autumn of the year of treatment and in subsequent years of the study. Concentrations were nearly unchanged during the winter, were reduced by cultivation preparatory to planting in the spring, and increased with epizootics of the disease in host populations in summer and autumn.P. rapae GV disease was prevalent during September and October in populations of P. rapae larvae in plots in which substantial concentrations of the virus were found and contributed to late-season control of the pest insect.     

The use of a microinjection procedure for large-scale production of the microsporidian Nosema eurytremae in Pieris brassicae

Nosema eurytremae, a microsporidian parasite of Malaysian trematodes, was injected at the rate of 1 × 10⁴ spores/larva into Pieris brassicae. The larvae, which subsequently pupated, were incubated at 25 to 26°C and on harvesting 19 days later yielded an average of 6 × 10⁸ spores/pupa. This was equivalent to 60,000 times the initial dose. Purity of filtered, washed spore suspensions ranged from 80 to 99% with up to 20% host debris.     

Some pathogenic effects of a species ofPleistophora [Protozoa,Microsporida] forAgrotis exclamationis and other noctuids

Larvae of noctuids were inoculatedper os with spores of a species ofPleistophora isolated fromAgrotis exclamationis (L.). The mean median lethal dose for mainly 3rd instar larvae ofA. exclamationis was 1.38×10⁵ spores per larva accumulating 34 or 35 days after inoculation and the mean slope for the regression of mortality on dose was 0.82. Third instar larvae ofA. exclamationis andSpodoptera frugiperda (J.E. Smith) inoculated with 2.5×10⁴ spores gained weight quicker than uninfected ones until between 8 days (A. exclamationis) and 13 days (S. frugiperda) post-inoculation. Thereafter they grew slower than uninfected individuals. Correspondingly, the feeding rate of inoculated larvae ofA. exclamationis was greater than that of untreated ones until 14 days post-inoculation but thereafter was less. Larvae ofNoctua pronuba (L.)Phlogophora meticulosa L. andSpodoptera littoralis (Boisduval) but notAgrotis segetum (Denis & Schiffermüller) were also susceptible to infection. The species ofPleistophora considered here corresponds toP. schubergi noctuidae (Veremtchuk & Issi) in spore morphology, tissue specificity and host range, except that is was non-infective for the typehostA. segetum. It is probably insufficiently pathogenic for use in the biological control of noctuids.     

Some properties of a new virus of Pieris rapae

A new insect virus of Pieris rapae was purified using a chloroform-butanol treatment followed by two differential and sucrose gradient centrifugations. The sedimentation coefficient of the purified virion was approximately 132 S, and it banded at a density of 1.39 g/cm³ in cesium chloride. The virion has a nonenveloped capsid with icosahedral symmetry. Several virions were shown to have a regular hexagonal contour about 25 nm in diameter and to be composed of many capsomeres. Full and empty viral particles, with 12 capsomeres around the periphery of the capsid, were noted. In some particles a small core has been observed which is spherical, about 15 nm in diameter. Both purified virus and partially purified virus preparations from dead, infected larvae gave only one precipitin band with a reaction of identity when tested against the antiserum to partially purified virus. When crude extracts of uninfected larvae and purified virus were tested against antiserum to partially purified virus, the pure virus produced a precipitin band. The band was formed independently and did not join to the band of the uninfected insect producing a typical reaction of nonidentity.     

Response of the wasp (<Emphasis Type="Italic">Cotesia glomerata</Emphasis>) to larvae of the large white butterfly (<Emphasis Type="Italic">Pieris brassicae</Emphasis>)

The large white butterfly (Pieris brassicae L) first invaded northernmost Japan from Siberia around 1994, and after a few years, began to expand its range. The wasp, Cotesia glomerata (L) parasitizes larvae of the small white butterfly (Pieris rapae crucivora Boisduval), a usual host in the same geographic area. Some Pieris brassicae larvae in Hokkaido have been parasitized by Cotesia glomerata, but the parasitism rate of Pieris brassicae larvae tends to be lower than that of Pieris rapae. To examine the process of parasitizing Pieris brassicae larvae, we observed how the parasitoid wasp responded to the host larvae on damaged leaves. Cotesia glomerata females tended to avoid Pieris brassicae larvae, and even when female wasps inserted their ovipositors into Pieris brassicae larvae, none laid eggs. The parasitoids obtained from Pieris rapae larvae failed to parasitize Pieris brassicae during the host-acceptance step.     

Essai en culture de choux-fleurs du virus de la polyédrose nucléaire deMamestra brassicae [Lep.: Noctuidae]

Résumé Une préparation expérimentale de virus de la polyédrose nucléaire (VNP) deMamestra brassicae L. a été appliquée dans les conditions de la pratique dans un champ de choux-fleurs pour lutter contre cette noctuelle. La préparation, appelée virusine M.B., est fabriquée à partir de chenilles mortes, après infection en élevage de larves du 5^e stade. La période de traitement a été déterminée selon le vol des papillons, suivi par piégeage sexuel. Six traitements par virus ont été effectués tous les 5 à 8 jours. Les 3 doses expérimentées (resp. 0,6 10¹²/3.10¹² et 1,5 10¹³ polyèdres par ha) ont proportionnellement diminué aussi bien l'effectif de la population larvaire que les dégats à la culture de choux-fleurs.

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Summary An experimental preparation of nuclear polyhedrosis virus (NPV) ofMamestra brassicae L. (named “virusine M.B.”, was applied under routine conditions to a field of cauliflower for control of this noctuid. The preparation was made from a filtrate of dead larvae, after infection of stock culture of 5 th instar larvae. This filtrate, with the addition of inert materials, was made into a powder in an industrial spray-drier. The resulting powder had the following composition: 50% vegetable charcoal, 35% skim milk powder, and 15% dried larval filtrate. It contained 6×10⁹ polyhedra/g. The biological activity of the preparation was evaluated by bioassay against the crude material prepared by acetone precipitation of a sample of the same filtrate. The objective of the field experiment was to determine the dosage of the preparation necessary to use under field conditions on cauliflower in the Rhone valley. The infection of newly hatched larvae was attempted, to take advantage of their susceptibility compared with later instars. The application period was determined by the flight of males into traps baited with virgin females reared in the laboratory. Six applications of virus were made, August 11, 18, and 24 and September 1, 6, and 13, 1977 (every 5 to 8 days). Between August 23 and September 2 a complementary release of 65 pairs ofMamestra was made to ensure a high population density of larvae in the crop. This action was unnecessary because it was demonstrated that the natural infestation was dense enough. Each dosage was applied to 4 plots of 180 m² with an average of 400 plants each. In addition, 2 spraying with Bactospeine (aBacillus thuringiensis preparation) was applied againstPieris brassicae L. on all 4 plots. The results of the treatment with virusine M.B. againstM. brassicae were quite satisfactory with regard to insect mortality and crop protection.

     

A synchronous peroral technique for the bioassay of insect viruses

A relatively fast and simple peroral technique for the bioassay of insect viruses is described in which newly hatched larvae ingest a uniform volume of virus suspension. Three isolates of the Autographa californica nuclear polyhedrosis virus (NPV) and one isolate of the Heliothis zea NPV were used to test the procedure with Trichoplusia ni and H. zea larvae, respectively. Within-assay and between-assay variation was very low with coefficients of variation averaging 0.012 ± 0.006 and 0.20 ± 0.04 for time-mortality and dose-mortality tests, respectively. The synchronous uptake of virus removed the acquisition-time component of the LT₅₀ values while the constant volume improved the accuracy of LD₅₀ values. The procedure was shown to be suitable for a wide variety of lepidopterous species, including Spodoptera frugiperda, S. eridania, Estigmene acrea, Plutella xylostella, Choristoneura fumiferana, Ostrinia nubilalis, Plodia interpunctella, and Pieris rapae.     

Pathogenicity of a nuclear polyhedrosis virus of the almond moth, Cadra cautella

Tests were conducted with neonate Cadra cautella larvae to determine the pathogenicity of a nuclear polyhedrosis virus. A bioassay on an agar base diet showed that concentrations of 0.25, 0.50, 2.00, and 4.00 polyhedra/mm² killed 27, 55, 87, and 92% of the test larvae, respectively. A study of the time of death showed that most larvae died on the 9th or 10th day after exposure to 4 polyhedra/mm² at 27°C. When larvae were exposed to 8, 16, 32, and 64 × 10³ polyhedra/g of bran diet, recorded mortalities were 18, 22, 48, and 80%, respectively. All the samples of virus in bran diet which were incubated at various temperatures for 7, 14, and 28 days remained stable at all test conditions except the sample incubated at 42°C for 14 days, and those held at 37° and 42° for 28 days. Larvae of C. cautella, Plodia interpunctella, Ephestia elutella, and Paramyelois transitella placed on a diet with 40 × 10³ polyhedra/g had mortalities of 75, 59, 16, and 4%, respectively. Light and electron microscopical examination of P. interpunctella cadavers showed that they were infected with a multiply occluded nuclear polyhedrosis virus.     

Demonstration of Cytotoxicity against Wasps by Pierisin-1: A Possible Defense Factor in the Cabbage White Butterfly

The cabbage white butterfly, Pieris rapae, produces pierisin-1, a protein inducing apoptosis of mammalian cells. In the present study, the biological activity of pierisin-1 as a protective agent against parasitic wasps for P. rapae was examined. Pierisin-1 caused detrimental effects on eggs and larvae of non-habitual parasitoids for P. rapae, Glyptapanteles pallipes, Cotesia kariyai and Cotesia plutellae at 1–100 µg/ml, levels essentially equivalent to those found in P. rapae larvae. In contrast, eggs and larvae of the natural parasitoid of P. rapae, Cotesia glomerata proved resistant to the toxicity of pierisin-1 through inhibition of pierisin-1 penetration of the surface layer. The expression level of pierisin-1 mRNA in the larvae of P. rapae was increased by parasitization by C. plutellae, whereas it was decreased by C. glomerata. In addition, C. plutellae was associated with elevation of activated pierisin-1 in the hemolymph. From these observations, it is suggested that pierisin-1 could contribute as a defense factor against parasitization by some type of wasps in P. rapae.     

Influence ofNosema bordati (Microsporida: Nosematidae) on the biological cycle ofChilo partellus (Lep: Pyralidae), a stem borer of cultivated graminae

The biological cycle ofChilo partellus (Swinhoe) was described on artificial diet. From egg to adult, it lasted 32 to 49 days with an average of 36.6 days. About 2,000 larvae from the 2^nd to the 5^th instars were artificially infected by ingestion with doses ofNosema bordati Goudegnon, varying from 2×10² to 2×10⁷ spores per ml. Only 72 survived (7.66 %) of these infected larvae.N. bordati, when present in the larvae, continued to multiply in the resulting pupae. The parasite affected the adults of this Pyralid reducing in a proportion of 5 the productivity of infected females and increasing the production of sterile eggs in the proportion of 8.