The transmission of a granulosis virus following the contamination of Pieris brassicae adults

The granulosis virus of Pieris brassicae, when applied as a paste to the tip of the abdomen of females, was readily transmitted to their progeny. Mortality of the progeny decreased with increasing time after treatment from 75.6% immediately after contamination to 2.0% on day 16. The overall mortality of progeny was 31.6%. Transmission following contamination of the tip of the male abdomen with a virus paste was less, with a peak of 11% mortality of progeny on day 2. The maximum mortality of progeny following contamination of the female abdomen with a virus dust was 19.3% with an overall mortality of 9.5%. There was no transmission following the contamination of the male abdomen with a virus dust.     

Transcriptional analysis of Pieris rapae in response to P. rapae granulovirus

Pieris rapae granulovirus (PrGV) is an important pathogen that has been exploited as a microbial insecticide to control agriculture pests. They can specifically infect cabbage butterfly (Pieris rapae), causing a series of pathological symptoms. In this infected P. rapae at 6?h and 72?h. As a result, a series of host genes were significantly modulated following PrGV infection, including those correlated with exoskeleton, ribosome, heat shock protein (HSP), proteasome, oxidation-reduction and apoptosis. Taken together, our study unveiled the P. rapae response to PrGV at different time point and provided a potential strategy for pest management.     

Transmission of a granulosis virus in the eggs of a virus-free stock of Pieris brassicae

Tests with a virus-free stock of Pieris bassicae and a particular strain of granulosis virus failed to demonstrate transmission of the virus transovarially. There was no evidence that the virus could enter the micropyle of the egg as an external passenger on the spermatazoa.     

Quantitative characterization of a viremia produced by the granulosis virus infection of the cabbage looperTrichoplusia ni [Lep.: Noctuidae]

Mortality responses ofTrichoplusia ni neonate larvae fed with the homologous granulosis virus are reported. The onset, duration and intensity of the associated viremia are described. The prolonged eclipse phase of granulosis virus replication is compared with other baculoviruses.      

Serological study on the transmission of a granulosis virus of the armyworm,Pseudaletia unipuncta (Lepidoptera: Noctuidae), to other lepidopterous species

The synergistic (Hawaiian) strain of a granulosis virus (GV) from the armyworm, Pseudaletia unipuncta, was transmitted to Spodoptera exigua, Autographa californica, and Trichoplusia ni. The viruses isolated from these hosts were tested by radial double-immunodiffusion (RDD) and immunoelectrophoresis (IE) for their relationship to the original virus. Untreated and heat-treated virus inclusion bodies (capsules) were compared for their antigenic properties but no differences were detected. The antiserum elicited against the whole capsule was more sharply specific for the antigenic determinants than the one elicited against the dissolved capsule proteins. The viruses obtained from S. exigua and T. ni elicited precipitin lines that differed from those of the P. unipuncta GV in their electrophoretic mobility with the one-trough IE method; however, with the two-trough method, the lines fused indicating that the antigens were identical. The major precipitin line indicating identity of the viruses wasthat produced by the synergistic factor (SF) purified from the capsule proteins of the synergistic GV strain. The presence of SF in the GV produced in alternate hosts indicated that its production was virus directed. The SF was not detected in the GVs of Laspeyresia pomonella and Pieris rapae and in the nonsynergistic Oregonian GV of P. unipuncta. A field-collected GV from S. exigua exhibited a different precipitin pattern from that of the synergistic GV, but one of the precipitin lines shared partial relationship to the SF.     

A simple action treshold for timing applications of a granulosis virus to controlPieris rapae [Lep.: Pieridae]

Pieris rapae (L.) an important pest of cole crops in the northeastern United States, is susceptible to a granulosis virus,Pieris rapae GV (PrGV), that has been shown to be an effective control measure by researchers in several countries. As an alternative to weekly applications of virus to protect cabbage, we tested the use of an action threshold of one small (first-third instar) larva per plant. Results were compared with those obtained using the same threshold with permethrin, and with weekly applications of virus. Plots treated weekly with virus received 5 applications but the action threshold was exceeded only once. In all virus-treated plots, numbers of large (fourth-fifth instar) larvae remained below 0.35 per plant, and were lower at the end of the season (0.07 in plots treated weekly and 0.1 in plots treated once) than in either the untreated or permethrin-treated plots (0.5). In late August, numbers of large larvae in the check plots reached almost 3 per plant. At harvest the number of feeding holes over 0.3 cm in diameter in the 4 innermost frame and the 4 wrapper leaves were counted. Check plots differed from treated plots by an average of 124.2±6.5 holes per plant in the frame and wrapper leave; virus-treated plots had 51.1±6.9 holes more than the permethrin plots. The difference in overall damage between plots treated 5 times with virus during the season and those treated once was not significant. Plots treated once with virus had significantly more damage (7.6±2.7) to wrapper leaves than those treated five times and marketability ratings were somewhat lower, based on fresh market standards. There were no significant differences in head weight among the treatments. At harvest, a high proportion of larvae collected from the check plots were diseased (77% versus an average of 46% in the treated plots). Because of the high numbers of large larvae in the check plots in late August and the extensive damage to plants, we assumed that virus did not affect a significant number of larvae in these plots until late in the growing season. These results indicate the usefulness of PrGV in a cabbage IPM program and that the use of action thresholds can be highly effective, particularly when insect numbers only occasionally reach damaging levels. While cabbage treated with permethrin had the least amount of injury, that treated weekly with virus was not significantly different by fresh market standards, and all cabbages treated with virus met processing standards. For the fresh market, in which cosmetic standards are more important, PrGV may have to be used weekly or with an action threshold lower than one small larva per plant.      

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.     

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 fumigant action of formaldehyde incorporated in a semisynthetic diet on the granulosis virus of Pieris brassicae and its evaporation from the diet

If Pieris brassicae eggs contaminated with granulosis virus ¹ in the form of intact inclusion bodies are exposed to formaldehyde gas under suitable conditions, the virus can be inactivated without preventing the eggs from hatching. The formaldehyde may be derived from formalin solutions, but it is more convenient to enclose the 1-day-old eggs with the diet containing formaldehyde on which the young larvae are intended to feed and to open the jar the day before they hatch. This involves less handling than washing the eggs. As would be expected, transovarially transmitted infection is not reduced.     

The comparative potencies of the crystalline endotoxin of eight varieties of Bacillus thuringiensis to larvae of Pieris brassicae

A microdisc technique is described for the administration of a predetermined dose of the crystalline endotoxin of Bacillus thuringiensis to host insects allowed to feed freely. It combines a high degree of precision with ease of execution and allows the elimination of insects that fail to ingest the full dose.The technique was used to compare the potencies of eight varieties of B. thuringiensis in fifth-instar larvae of Pieris brassicae. The varieties thuringiensis, morrisoni, entomocidus, and galleriae all showed similar toxicities, variety tolworthi was one-third and aizawai one-twentieth as toxic, while the varieties alesti and sotto were too weakly toxic to allow their potencies to be accurately determined.Preliminary tests with the same varieties on larvae of Bombyx mori indicated an entirely different order of potencies, in which entomocidus, sotto, alesti, galleriae, and aizawai were the most toxic and tolworthi and thuringiensis the least.     

Site of action of a synergistic factor of a granulosis virus of the armyworm, Pseudaletia unipuncta

A synergistic factor (SF), which is present in the capsule matrix protein of a granulosis virus of the armyworm, Pseudaletia unipuncta, enhances baculovirus infection in armyworm larvae. The site of action of the SF was investigated. The oral inoculation of SF did not enhance the infectious hemolymph virions which had been inoculated into the hemocoel. The SF also did not enhance the infection of purified enveloped virions when both virus and SF were inoculated into the hemocoel, but enhancement occurred when they were inoculated orally. Thus, the activity of the SF was confined to the midgut lumen. Observations with ferritin-conjugated antibody indicated that the site of action of SF was the cell membrane of the microvillus. There were more ferritin particles attached to midgut cell membranes of larvae inoculated orally with SF than to those of control larvae inoculated with buffer.     

Selection of a strain of the granulosis virus of the codling moth with improved resistance against artificial ultraviolet radiation and sunlight

A six-step sequence of selection of the granulosis virus of Laspeyresia pomonella led to a strain with increased resistance to sunlight. Each step consisted of irradiation of dry deposits of the virus on apples with near range ultraviolet light, infection of freshly eclosed codling moth larvae with the irradiated virus, and propagation of the virus thus produced in large fifth-instar larvae. Compared with the original virus, the new strain was 5.6 times more resistant to artificial ultraviolet irradiation in the laboratory and remained twice as long infective in the field.     

Parasitism capacity and searching efficiency of Diaeretiella rapae parasitizing Brevicoryne brassicae on susceptible and resistant canola cultivars

Different cultivars of aplant species can affect the foraging and efficiency of natural enemies, both directly through physical and biochemical properties or indirectly through the herbivore's diet. In this study, the parasitism capacity and functional response of Diaeretiella rapae McIntosh were determined on the cabbage aphid, Brevicoryne brassicae (L.) reared on susceptible (Opera) and resistant (Okapi) canola cultivars under laboratory conditions at 25?±?1?°C, 60?±?5% RH and a16:8?h L:D photoperiod. The parasitoid exhibited Type II and Type III functional responses on the resistant and susceptible cultivars, respectively. The estimated value of searching efficiency (a) was 0.1637?±?0.1095?h^?1 on the resistant cultivar whereas its value was dependent on host density on the susceptible cultivar. The handling times (T_h) on the susceptible and resistant canola cultivars were 0.108?±?0.040 and 0.320?±?0.048?h, respectively. The net parasitism rate (C₀) of the parasitoid wasp varied from 128.09 hosts per parasitoid lifetime on the susceptible to 71.01hosts on the resistant canola cultivar. The transformation rate from host population to parasitoid offspring (Qp) was equal to 1 on both cultivars (C₀?=?R₀). The finite parasitism rate (ω) on the susceptible cultivar (0.819 hosts per parasitoid per day) was significantly higher than that on the resistant one (0.578 hosts per parasitoid per day). In conclusion, canola cultivars affected the performance of D. rapae in controlled small-scale laboratory experiments and compared with the susceptible cultivar, the resistant one had anadverseeffect on the efficiency of the parasitoid.     

小菜粉蝶颗粒体病毒颗粒体蛋白基因的序列测定及在大肠杆菌中的表达

根据颗粒体病毒颗粒体蛋白(Granulin)基因在其起始密码子上游的12个碱基高度保守序列(TATAAGGAATTT)以及大菜粉蝶颗粒体病毒(PbGV)的颗粒体蛋白基因的序列[1]设计引物,PCR扩增得到850bp左右大小的片段,核苷酸序列测定结果表明该病毒的granulin基因全长为855bp,起始密码位于第38~40位碱基,终止密码位于779~781位碱基,编码框序列全长为744;推测该基因编码一段由247个氨基酸组成的多肽,分子质量约为2.9178×104道尔顿。与其它颗粒体病毒颗粒体蛋白基因进行同源性比较,核苷酸同源性都在70%以上,氨基酸同源性都在75%以上,最高的为大菜粉蝶颗粒体病毒(PbGV),核苷酸同源性为97%,氨基酸同源性为98%。构建了重组表达载体pet-28a-Gran,IPTG诱导后经SDS-PAGE检测,表明获得了颗粒体蛋白基因在大肠杆菌BL21中的特异表达。     

小菜粉蝶颗粒体病毒颗粒体蛋白基因的序列测定及在大肠杆菌中的表达

根据颗粒体病毒颗粒体蛋白(Granulin)基因在其起始密码子上游的12个碱基高度保守序列(TATAAGGAATTT)以及大菜粉蝶颗粒体病毒(PbGV)的颗粒体蛋白基因的序列[1]设计引物,PCR扩增得到850bp左右大小的片段,核苷酸序列测定结果表明该病毒的granulin基因全长为855bp,起始密码位于第38～40位碱基,终止密码位于779～781位碱基,编码框序列全长为744;推测该基因编码一段由247个氨基酸组成的多肽,分子质量约为2.9178×104道尔顿.与其它颗粒体病毒颗粒体蛋白基因进行同源性比较,核苷酸同源性都在70%以上,氨基酸同源性都在75%以上,最高的为大菜粉蝶颗粒体病毒(PbGV),核苷酸同源性为97%,氨基酸同源性为98%.构建了重组表达载体pet-28a-Gran,IPTG诱导后经SDS-PAGE检测,表明获得了颗粒体蛋白基因在大肠杆菌BL21中的特异表达.     

The effect of juvenile hormone on pupal pigmentation of Pieris brassicae L.

The role of juvenile hormone (JH) in the morphological colour adaptation of pupae of Pieris brassicae controlled by environmental factor was analyzed. First the effects of JH I and its analogue, Farnesyl-Methyl-Ether (FME) were tested. Secondly the JH-titres of the last instar larvae were measured under various light conditions which influence the future pigmentation of the pupae.During the sensitive period, which occurs before pupation, blue light (410 nm) produces the strongest, darkness medium, and yellow light (570 nm) the lightest pigmentation of the pupae.JH I as well as FME has an inhibiting effect on the formation of the black spots in the cuticle. However, this effect only becomes apparent (a) if the insects are kept under blue light during the sensitive period (which normally leads to a strong black pigmentation) and (b) only when these animals were treated with JH I or FME either at the beginning, or 10 hr after the beginning of the sensitive period. In the last larvae instar, JH could be found only during the sensitive period. Fourteen hours after the beginning of the sensitive period the JH concentration reaches a maximum of 30–100 pg JH per insect. The JH-titre resulting from blue light conditions is significantly different from those of the larvae kept under white or yellow light. An additional maximum of 60 pg JH per animal was found 8 hr/after the beginning of the sensitive period. Obviously, JH affects the process of pigmentation of the pupae, but the described results are not sufficient to explain thoroughly the regulation of pigmentation modified by environmental factors. The effects of further factors are discussed.