Viral Insecticides Research Articles

Antiviral function of peptidoglycan recognition protein in Spodoptera exigua (Lepidoptera: Noctuidae).

Peptidoglycan recognition proteins (PGRPs) are a class of molecules that play a critical role in insect immunity. Understanding the function of PGRPs is important to improve the efficiency of microbial insecticides. In this study, we investigated the role of PGRP-LB (a long type PGRP) in insect immunity against viruses using Spodoptera exigua and Spodoptera exigua multiple nucleopolyhedrovirus (SeMNPV) as an insect-virus model. We cloned and identified a PGRP-LB gene from S.exigua; the gene consisted of 7 exons that encoded a polypeptide of 234 amino acids with a signal peptide and a typical amidase domain. Expression analysis revealed that the abundance of SePGRP-LB transcripts in the fat body was greater than in other tissues. Overexpression of SePGRP-LB resulted in a significant decrease of 49% in the rate of SeMNPV-infected cells. In addition, the multiplication of SeMNPV was significantly decreased: a decrease of 79% in the production of occlusion-derived virion (ODV), and a maximum decrease of 50% in the production of budded virion (BV). In contrast, silencing of SePGRP-LB expression by RNA interference resulted in a significant 1.65-fold increase in the rate of SeMNPV-infected cells, a significant 0.54-fold increase in ODV production, a maximum 1.57-fold increase in BV production, and the larval survival dropped to 21%. Our findings show that SePGRP-LB has an antiviral function against SeMNPV, and therefore this gene may provide a target for lepidopteran pest control using virus insecticides.

Establishment of an immortalized cell line derived from the pupal ovary of Mythimna separata (Lepidoptera: Noctuidae) and identification of the cell source.

Determining the source of primary cells is conductive to enriching sufficient cells with immortal potential thereby improving the success rate of establishing cell lines. However, most of the existing insect cell lines are established by mixing and fragmentation of explants. At present, the origin of cell lines can only be determined according to the cultured tissues, so it is impossible to determine which cell types they come from. In this study, a new cell line designated IOZCAS-Myse-1 was generated from pupal ovaries of the migratory pest Mythimna separata by explant tissues to derive adherent cultures. This paper mainly shows the further descriptive information on the origin of primary cells in the process of ovarian tissue isolation and culture. Phospho-histone H3 antibody-labeled cells with mitotic activity showed that the rapidly developing somatic cells in vivo gradually stopped proliferation when cultured ex vivo. The primary cells dissociated outside the tissue originated from the lumen cells, rather than the germ cells or the follicular epithelium cells. The results suggest that the newly established cell line IOZCAS-Myse-1 had two possible sources. One is the mutation of lumen cells in the vitellarium, and the other is the stem cells with differentiation potential in the germarium of the ovarioles. Moreover, the newly established cell line is sensitive to the infection of Autographa californica multiple nucleopolyhedrovirus, responds to 20-hydroxyecdysone and has weak encapsulation ability. Therefore, the new cell line can be a useful platform for replication of viral insecticides, screening of hormone-based insecticides and immunology research.

Susceptibility and tissue specificity of Spodoptera frugiperda to Junonia coenia densovirus

The fall armyworm, Spodoptera frugiperda, which destroys many economic crops such as rice and maize, has recently invaded China. Insect viruses as biological control agents play important roles in killing pests. One potential viral insecticide is the environmentally highly infective and virulent densovirus. We successfully rescued Junonia coenia densovirus (JcDV) using its infectious clone in different insect cell lines and larvae of three insect species. Results showed that the lysate of cultured insect cells transfected by the JcDV infectious clone killed the 2nd instar S. frugiperda. The LD50 of homogenate from JcDV-infected Spodoptera litura to the 2nd instar S. frugiperda (1.76×108 viral genome copies per larva during 10 d post infection) was higher than that of the 2nd instar S. litura (7.39×107 JcDV genome copies) or Helicoverpa armigera larvae (9.71×107 JcDV genome copies). The LT50 of the S. litura homogenate (2.60×109 viral genome copies each larva) to the 2nd instar S. frugiperda was 6.96 d, longer than that of the S. litura (6.18 d) or the 2nd instar H. armigera (5.94 d). JcDV could infect the fat body of H. armigera, but not S. frugiperda or S. litura. Although JcDV can infect all three lepidopteran species, their susceptibility to the virus differs. JcDV has great potential as a biological control agent against pests such as S. frugiperda.

The system for regulation of cotton bollworm population on tobacco in crop rotation of organic agriculture

The results of development of the control system over the population of cotton bollworm Helicoverpa armigera Hbn are presented to protect seed plantings of tobacco with the use of plant isolation. The studies were conducted in the Krasnodar Territory on a tobacco variety Yubileiny novy 142. The regulation of the cotton bollworm population on tobacco seed plantings was carried out by the method of mass capture of male pests with pheromone traps in order to change the gender balance. This was done together with the application of a biopreparation and sowing of a trap crop (corn) to attract and catch butterfl ies at an earlier stage. At a high degree of bollworm population (4–10 specimens / tobacco infl orescence) on non-isolated plants, insecticides based on baculovirus of nuclear polyhedrosis of cotton bollworm FermoVirin XC (in the doze 1.0– 4.0 g/ha) and Helicovex (0.05–0.2 l/ha) were used three times with an interval of 7 days in combination with “male vacuum”. Biological effi ciency was 38– 77 and 62–84% in reducing the number of bollworm larvae, 41–75 and 60–79% in decreasing the damage, respectively. The decrease in the number of bollworm larvae on isolated plants reached 36– 70 and 58–79%, the decrease in damage – 39–69 and 60–72%, respectively. Treatment of seed plots with virus insecticides allowed to save from 22 to 43 kg of the biological yield of tobacco seeds per 1 ha on non-isolated plants and from 21 to 51 kg on isolated plants. With a low number of hatching larvae (14 specimens / 100 plants), a single use of the preparations Bitoxibacillin (Bacillus thuringiensis var. Thuringiensis) and Lepidocide (Bacillus thuringiensis var. Kurstaki) reduced the amount of phytophage by 47–75 and 48–64%, respectively. The system is recommended for use on other crops damaged by cotton bollworm, including in organic farming technologies.

Post-mortem incubation influences occlusion body production in nucleopolyhedrovirus-infected larvae of Spodoptera frugiperda

The inefficient production of nucleopolyhedrovirus occlusion bodies (OBs) can limit the commercialization of virus-based insecticides. The production of OBs in SfMNPV-infected Spodoptera frugiperda fourth instars was compared among groups of larvae that were frozen (−20 °C) immediately following death, or subjected to a 9-day period of post-mortem incubation at 5 °C or 15 °C. Incubation at 15 °C resulted in a ∼40% increase in total OB production and OBs per mg larval weight, compared to the −20 °C and 5 °C treatments. OBs from the 5 °C treatment were ∼10% smaller in cross sectional area and small OBs (<1 µm2) were more abundant than in other treatments, possibly due to reduced post-mortem OB maturation in this treatment. SfMNPV genomic DNA in OB samples was 3.6-fold higher in the −20 °C treatment than the 5 °C treatment and 1.7-fold higher than the 15 °C treatment, possibly due to differences in the exposure of viral genomes to degradative enzymes. However, these differences did not affect the concentration-mortality relationship or speed of kill of OBs from the different treatments. The abundance of aerobic microbes increased from ∼3 × 107 CFU/ml in the −20 °C treatment, to approximately 2 × 108 and 3 × 108 CFU/ml in the 5 °C and 15 °C incubation treatments, respectively, similar to levels seen in other nucleopolyhedroviruses produced in insects. We conclude that post-mortem incubation at 15 °C likely involves continuing processes of virion occlusion and OB maturation that increase overall OB production without loss of insecticidal activity, although the value of this step in commercial virus insecticide production will depend on the cost of the incubation step and the value of the additional OBs produced.

Acquisition of lethal infection, hypermobility and modified climbing behavior in nucleopolyhedrovirus infected larvae of Anticarsia gemmatalis

The Anticarsia gemmatalis multiple nucleopolyhedrovirus (AgMNPV) is the basis for viral insecticides in several countries in Latin America. The rate of acquisition of infection and the transmission of the pathogen from infected to healthy conspecifics both influence the efficacy of virus insecticides. By comparing the leaf area consumed by larvae with their stage-specific susceptibility to infection, we estimated that fourth instars were approximately twice as likely to acquire infection as second or third instars. Greenhouse trials indicated that 63% of third instars became infected within 1 h of exposure to soya plants treated with 1.5 × 107 occlusion bodies (OB)/m2 obtained from mixtures of local AgMNPV isolates, as did 90% of larvae sampled at 24 h. Acquisition of lethal infection was slower in field trials performed in the soya-growing Huastecas region of Mexico. Virus-induced mortality varied from 43 to 79% in natural infestations of larvae sampled at 72 h post-application depending on the dose of unformulated OBs applied with wetting agent, although the majority of larvae had already acquired a lethal infection at 24 h post-application. Spray application volume (200 or 400 l/ha) did not significantly affect the prevalence of infection at 1 h post-application. Infected fifth instars moved twice as far and died significantly higher on plants than control larvae. Overall, 22% of third instars that subsequently foraged on these plants acquired a lethal infection. We conclude that most insects acquire infection within 24 h of virus application and that OBs in feces and regurgitate of infected larvae contribute significantly to pathogen transmission.

Virus and calcium: an unexpected tandem to optimize insecticide efficacy.

The effective control of insect pests is based on the rational use of the most efficient and safe insecticide treatments. To increase the effects of classical insecticides and to avoid the ability of certain pest insects to develop resistance, it is essential to propose novel strategies. Previous studies have shown that calcium-dependent phosphorylation/dephosphorylation is now considered as a new cellular mechanism for increasing the target sensitivity to insecticides. Because it is known that virus entry is correlated with intracellular calcium concentration rise, this report attempts to present the most important data relevant to the feasibility of combining an insect virus such as baculovirus or densovirus with an insecticide. In this case, the insect virus is not used as a bioinsecticide but acts as a synergistic agent able to trigger calcium rise and to activate calcium-dependent intracellular signalling pathways involved in the increase of the membrane receptors and/or ion channels sensitivity to insecticides. This virus-insecticide mixture represents a promising alternative to optimize the efficacy of insecticides against insect pests while reducing the doses.

Two year field study to evaluate the efficacy of Mamestra brassicae nucleopolyhedrovirus combined with proteins derived from Xestia c-nigrum granulovirus.

Japan has only three registered baculovirus biopesticides despite its long history of studies on insect viruses. High production cost is one of the main hindrances for practical use of baculoviruses. Enhancement of insecticidal effect is one possible way to overcome this problem, so there have been many attempts to develop additives for baculoviruses. We found that alkaline soluble proteins of capsules (GVPs) of Xestia c-nigrum granulovirus can increase infectivity of some viruses including Mamestra brassicae nucleopolyhedrovirus (MabrNPV), and previously reported that MabrNPV mixed with GVPs was highly infectious to three important noctuid pests of vegetables in the following order, Helicoverpa armigera, M. brassicae, and Autographa nigrisigna. In this study, small-plot experiments were performed to assess concentrations of MabrNPV and GVPs at three cabbage fields and a broccoli field for the control of M. brassicae. In the first experiment, addition of GVPs (10 µg/mL) to MabrNPV at 106 OBs/mL resulted in a significant increase in NPV infection (from 53% to 66%). In the second experiment, the enhancing effect of GVP on NPV infection was confirmed at 10-times lower concentrations of MabrNPV. In the third and fourth experiments, a 50% reduction in GVPs (from 10 µg/mL to 5 µg/mL) did not result in a lowering of infectivity of the formulations containing MabrNPV at 105 OBs/mL. These results indicate that GVPs are promising additives for virus insecticides.

History and current status of development and use of viral insecticides in China.

The use of insect viruses as biological control agents started in the early 1960s in China. To date, more than 32 viruses have been used to control insect pests in agriculture, forestry, pastures, and domestic gardens in China. In 2014, 57 products from 11 viruses were authorized as commercial viral insecticides by the Ministry of Agriculture of China. Approximately 1600 tons of viral insecticidal formulations have been produced annually in recent years, accounting for about 0.2% of the total insecticide output of China. The development and use of Helicoverpa armigera nucleopolyhedrovirus, Mamestra brassicae nucleopolyhedrovirus, Spodoptera litura nucleopolyhedrovirus, and Periplaneta fuliginosa densovirus are discussed as case studies. Additionally, some baculoviruses have been genetically modified to improve their killing rate, infectivity, and ultraviolet resistance. In this context, the biosafety assessment of a genetically modified Helicoverpa armigera nucleopolyhedrovirus is discussed.

Tea: Biological control of insect and mite pests in China

Tea is one of the most economically important crops in China. To secure its production and quality, biological control measures within the context of integrated pest management (IPM) has been widely popularized in China. IMP programs also provide better control of arthropod pests on tea with less chemical insecticide usage and minimal impact on the environment. More than 1100 species of natural enemies including about 80 species of viruses, 40 species of fungi, 240 species of parasitoids and 600 species of predators, as well as several species of bacteria have been recorded in tea ecosystems in China. Biological and ecological characteristics of some dominant natural enemies have been well documented. Several viral, bacterial, and fungal insecticides have been commercially utilized at large scale in China. Progress in biological control methods in conjunction with other pest control approaches for tea insect pest management is reviewed in this article. Knowledge gaps and future directions for tea pest management are also discussed.

Immunological effects of Anticarsia gemmatalis multiple nucleopolyhedrovirus (AgMNPV) by stimulation of mice in vivo and in vitro

Baculoviruses are highly specific and only capable of replication in arthropod hosts. The Autographa californica multiple nucleopolyhedrovirus (AcMNPV) is the most studied baculovirus at the molecular level and the Anticarsia gemnatalis multiple nucleopolyhedrovirus (AgMNPV) is the most used viral insecticide worldwide. AcMNPV have also been shown to stimulate the mammalian immune response acting as an adjuvant. In order to evaluate the effects of AgMNPV in modulating macrophage and lymphocyte activation, we have stimulated these cells in vitro and inoculated BALB/c mice intranasally with the two viral phenotypes (PIBs and BVs) and compared with the response induced by the same phenotypes of AcMNPV. Our results showed that baculoviruses are able to modulate mammalian immune response; in vitro they increase phagocytosis, NO2 production and Th1 cells response. In vivo, AgMNPV BVs or PIBs do not induce an inflammatory reaction in normal lung but during a fungal lung infection they can change the type of adaptive response developed. Considering our data, AgMNPV can be considered more useful as a vaccine vector or immune adjuvant than AcMNPV.

파밤나방의 미생물적 방제를 위한 병원성 곰팡이 Nomuraea rileyi의 특성 및 병원성 검정

파밤나방(Spodoptera exigua)은 유기합성 농약을 이용한 화학 살충제 외에 뚜렷한 방제방법이 알려져 있지 않으나, 그에 대한 저항성과 더불어 식물을 가해하는 방법에 있어 그들만의 독특한 숙주 가해습성으로 인해 난방제 해충으로 알려져 있다. 화학살충제에 대한 저항성의 해결을 위하여 곤충병원성 바이러스 및 세균을 이용한 살충제가 개발되어 있으나, 이들 역시 파밤나방 유충이 줄기 속으로 들어가는 가해습성으로 인하여 효과적이지 못한 실정이다. 그러므로 본 연구에서는 그들의 가해습성과 저항성을 극복할 수 있는 새로운 방제원으로써, 체벽과의 일시적인 접촉을 통해 살충성을 발휘할 수 있는 파밤나방에 대한 병원성 곰팡이를 분리하고 그 특성 및 살충성을 조사하였다. 파밤나방 병원성 곰팡이는 파밤나방 누대사육 중 곰팡이병 증상을 보이며 이병된 사충으로부터 분리하였으며, 분리 곰팡이는 배지에서의 증식상 및 현미경적 관찰을 통한 형태학적 동정과 더불어 ITS, <TEX>${\beta}$</TEX>-tublin 및 EF1-<TEX>${\alpha}$</TEX> 부분의 염기서열 분석을 통해 Nomuraea rileyi로 최종 동정하고 N. rileyi SDSe로 명명하였다. 분리 균주의 파밤나방에 대한 살충력 검정은 <TEX>$1{\times}10^4-10^8conidia/ml$</TEX>까지의 다양한 포자현탁액에 파밤나방 3령 유충을 침지하는 조건으로 수행한 결과, 20-54%의 살충률을 나타냈으며 포자현탁액의 농도가 증가할수록 살충력도 증가하는 양상을 나타냈다. 본 연구결과 분리된 N. rileyi 균주가 비록 높은 살충력을 보이지 않았으나, 파밤나방이 난방제 해충임을 감안할 때 다른 방제방법과 함께 종합적 해충 방제 방법에 있어 효과적인 방제수단의 일환이 될 수 있을 것으로 기대된다. To date, chemical control remains the most common way to reduce beet armyworm (Spodoptera exigua) populations. However, this insect has become more tolerant or resistant to many chemical insecticides and the insect larvae usually hide inside hollow, tube-like leaves of host plant so they were difficult to kill by spraying insecticides. The use of viral and bacterial insecticide to solve these problems has not been successful because of their novel feeding habit. To overcome these problems, in this study, the biological characteristics and virulence of an entomopathogenic fungus isolated from the cadaver of larvae beet armyworm were investigated. Isolated entomopathogenic fungus was identified as Nomeraea rileyi (Farlow) Samson by morphological examinations and genetic identification using sequences of the ITS, <TEX>${\beta}$</TEX>-tubulin gene and EF1-<TEX>${\alpha}$</TEX> regions. This fungus was named as N. rileyi SDSe. Virulence tests against 3rd larvae of beet armyworm were conducted with various conidial suspensions from <TEX>$1{\times}10^4$</TEX> to <TEX>$10^8$</TEX> conidia/ml of N. rileyi SDSe in laboratory conditions. Mortality rate of beet armyworm showed from 20 to 54% and the virulence increased with increasing conidial concentrations. Although N. rileyi SDSe showed low mortality rate against beet armyworm, it is expected that N. rileyi SDSe will be used effectively in the integrated pest management programs against the beet armyworm.

In vivo Enhancement of Nucleopolyhedrovirus Infection in Helicoverpa armigera (Hübner) by the Granulovirus of Spodoptera litura Fabricius

Biopesticides based on baculoviruses offer great scope as promising viral insecticides against Helicoverpa armigera (Hubner). However, an important limitation in the use of baculoviruses is their reduced efficacy against grown up larvae. The infectivity of NPV against grown up larvae were reported to be enhanced by the presence of a viral enhancing factor (VEF) in granuloviruses (GV). Hence, we investigated the possible interaction of GVs of Spodoptera litura (SlGV), Agrotis segetum (AsGV), Plutella xylostella (PxGV), Achaea janata (AjGV) and Chilo infuscatellus (CiGV) separately with the NPV of H. armigera (HearNPV) against second, third, fourth and fifth instar H. armigera . Of the GVs tested with HearNPV, SlGV alone synergized HearNPV action with reduced LC 50 values. The integration of SlGV with HearNPV resulted in 9.38, 10.93, 10.70 and 13.32 fold reduction in LC 50 values against the second, third, fourth and fifth instars respectively. Tests conducted with heat inactivated (at 75, 80, 85 and 121°C for 10 min) and heat shielded SlGV could give similar effects with HearNPV indicating that the cause for the virulence enhancement rests with the capsular protein and not the virions of the SlGV, since the virions could be inactivated at temperatures more than 70°C. Integration of SlGV and HearNPV was found to shorten the LT 50 values.

Baculoviruses and insect pests control in China

China is rich in insect viruses. Helicoverpa armigera nucleopolyhedrovirus (HaSNPV), was the first commercial insecticide registered in 1993. Subsequently, 13 viral insecticides were registered and released into the market as pesticides, including nine nucleopolyhedrovirus (NPV), three granulovirus (GV), one densonucleosis virus (DNV), and one cytoplasmic polyhedrosis virus (CPV). Industrial exploitation of viruses in China started more than three decades ago. To date, at least 24 baculovirus insecticides have been or are currently used in field trials in China, 12 of which are unregistered. Examples of successful applications and benefits of entomopathogenic viruses as microbial insecticides are presented in the current paper. However, chemical prevention is still the main measure for the management of insect pests in China. Effective public extension services, government policies, and farmer education are important to expand the use of viral insecticides as well as for the further development in the production and use of these insecticides. Key words: Microbial control, baculoviruses, viral insecticide, sustainable agriculture.

Effects of coadministration of chemical insecticides with nucleopolyhedrovirus SpltNPV on the dietary intake of the common cutworm Spodoptera litura (Lepidoptera: Noctuidae)

Chemical insecticides were administered to larvae of the common cutworm Spodoptera litura (Fabricius) concomitantly with a viral insecticide containing nucleopolyhedrovirus SpltNPV, in order to decrease the level of dietary intake of the virus-infected larvae. Aqueous solutions of imidacloprid (Admire), flubendiamide (Phenix), or cartap (Padan) at non-lethal doses, together with a lethal dose of SpltNPV occlusion bodies (Hasumon-Tenteki), were prepared. The surfaces of small blocks of food were treated with the mixtures and presented to S. litura larvae for 24 h. On the following day, a new diet block was provided which had been treated with one-third or one-fourth of the initial dose of the chemical insecticide. The larvae were reared for 5 days and the level of dietary intake was recorded. The administration of flubendiamide and cartap decreased the dietary intake more strongly in virus-infected larvae than in non-infected larvae.

Evaluation of seven viral isolates as potential biocontrol agents against Pseudoplusia includens (Lepidoptera: Noctuidae) caterpillars

The caterpillar Pseudoplusia includens (Walker, 1857) (Lepidoptera, Noctuidae), known as soybean looper, is a pest that has recently assumed greater importance in soybean in Brazil. Isolates of nucleopolyhedroviruses (NPVs) of this pest have been identified from cotton in Guatemala and soybean farms in Brazil, providing an interesting perspective of potential use of viral insecticide against the insect in lieu to chemical insecticides. With the objective to contribute to the characterization studies of this virus, morphological and molecular analyses and biological activity were carried out with seven P. includens viral isolates (I-A to I-G). Electron microscopy of viral samples, purified from macerated infected larvae, showed particles with typical morphology of the Baculoviridae family, genus Alphabaculovirus ( Nucleopolyhedrovirus – NPV) presenting virions with only a single nucleocapsid per envelope (SNPV) occluded in a protein matrix, forming occlusion bodies (OB). This virus was then classified as P. includens single nucleopolyhedrovirus (PsinSNPV). OB particles analyzed in SDS–polyacrylamide gel showed an intense band corresponding in size to NPV polyhedrin protein. DNA restriction profiles of the PsinSNPV isolates showed differences in the fragment size and number suggesting the existence of genotypic variants, except between I-E and I-F profiles that were similar. Among the isolates tested for infectivity against P. includens, I-A, I-E and I-F were the most virulent. Survival times (ST 50) varied according to viral concentration, with significant differences among isolates for the three higher concentrations.

Stability of the viral-enhancing ability of entomopoxvirus spindles exposed to various abiotic factors

The proteinaceous paracrystaline structures called spindles that are produced by some entomopoxviruses (EPVs) are known to strongly enhance the infectivity of various nucleopolyhedroviruses (NPVs). These proteinaceous bodies thus may be potential synergists of bio-control agents (such as NPVs) for insect pests. Although the infectivity-enhancing ability of spindles needs to be highly stable when they are used as synergists in the field, little is known regarding the effects of various abiotic factors, e.g. high temperature and ultraviolet (UV) irradiation, on this stability. In the present study, we exposed Anomala cuprea EPV (AcEPV) spindles to various abiotic factors and examined their subsequent ability to enhance the infectivity of Bombyx mori NPV in B. mori larvae. The enhancing activity of AcEPV spindles was stable against high temperature, UV-B irradiation, ethyl alcohol, or the bactericide benzalkonium chloride and persisted after long exposure to formaldehyde. These results suggest that spindles are stable materials, even though they are composed of proteins, and thus are promising potential synergists of various viral insecticides.

Effects of Long-Term Storage on Potency of TM Biocontrol-1, the Registered Viral Insecticide of &lt;I&gt;Orgyia pseudotsugata&lt;/I&gt; (Lepidoptera: Lymantriidae)

The article presents the results of bioassaying 39 samples of TM Biocontrol-1, a viral insecticide, from 10 different lots and various sizes of vacuum-sealed packages that were stored at -10 degrees C for 5-15 yr. This is the first study to present potency data for a registered virus product stored for this length of time. Laboratory bioassays in insects from the same colony from which the TM Biocontrol-1 was produced showed that the stored viral insecticide is still effective, although it lost approximately 30% of its effectiveness during storage. A direct correlation of this loss with the length of time in storage is not apparent. Bioassays also showed that there are significant differences in the susceptibility of Douglas-fir tussock moth, Orgyia pseudotsugata (McDunnough), larvae from different geographic regions to OpMNPV (family Baculoviridae, genus Nucleopolyhedrovirus) infection. Package size did not affect the potency of stored TM Biocontrol-1. There were no clear, significant differences in the effectiveness among lots of TM Biocontrol-1 processed by different organizations.

Effects of Long-Term Storage on Potency of TM Biocontrol-1, the Registered Viral Insecticide of Orgyia pseudotsugata (Lepidoptera: Lymantriidae)

Effects of Long-Term Storage on Potency of TM Biocontrol-1, the Registered Viral Insecticide of Orgyia pseudotsugata (Lepidoptera: Lymantriidae)

Investigating the horizontal transmission of the Cydia pomonella granulovirus (CpGV) in a model system

Repeated applications of Cydia pomonella granulovirus (CpGV) can effectively control the codling moth (CM) in apple orchards. However, it is still unknown whether horizontal transmission of the virus from infected to uninfected larvae contributes to the efficacy of the virus insecticide. Horizontal transmission of CpGV was assayed using detached apples. In experiments using artificially applied virus dots on the apple’s surface or infected CM larvae as virus inoculum, it was found that the likelihood of infection of healthy CM larvae relied mainly on the larval behavior. The amount of virus inoculum, either applied artificially or produced by the infected larvae, impacted the infection rate only to a small degree. In the experiments, CM larvae exhibited a strong preference in entry sites, increasing the chance for horizontal transmission. Depending on the experimental design, horizontal transmission rates of about 40% were observed in laboratory assays.