20 Baculoviruses : Members of Integrated Pest Management Strategies (original) (raw)
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Baculoviruses: Members of Integrated Pest Management Strategies
InTech eBooks, 2012
IPM applies different tactics, like pest resistant plants, use of entomopathogens such as bacteria and viruses, and strategies that involves cultural, physical, mechanical, biological and chemical control. The use of these combined tactics reduces the chances of generating resistance and insect survival. 2.1 Pest resistant plants (transgenesis using plant genes) Plants have a vast metabolic capability and produce many secondary chemicals which are toxic, anti-nutritional, or aversive to species might otherwise be potential predators (Norris & Kogan, 1980). Examples include the pyrethrins from chrysanthemums and alkaloids like nicotine from tobacco. Other compounds implicated in protection from insect attack include the terpenoids, steroids, flavonoids, phenolic, glucosinolates, cyanogenic glycosides, rotenoids, saponins and non protein amino acids (Gatehouse et al., 1991). As secondary compounds are the products of multi-enzyme pathways which involve the interaction of many gene products, such defense system are in most cases too complex to be used in plant www.intechopen.com
Baculoviruses: A Safe Alternative in Pest Control
Broad spectrum chemical pest control agents have been widely regarded as ecologically unacceptable. Due to this opinion, there is the increased social pressure to reduce their use in the future and gradually replace them by biopesticides. Viruses of a few families are known to infect invertebrates, but only those belonging to the family Baculoviridae have been used for biocontrol of pests. They are safe to people and wildlife, their specificity is usually very narrow. Their application as bioinsecticides was limited until recently because of their slow killing action and technical difficulties for in vitro commercial production. Successful protection of over 2 million hectares of soybean in Brazil revived the hopes for using baculoviruses as effective biopesticides. Wider application of baculoviruses for pest control is very likely to be implemented in the future and two approaches for improvements of baculovirus killing properties can be foreseen. In countries where the use of genetically modified organisms (GMOs) is restricted, the improvements will be mainly at the level of in vitro production, diagnostics, and changes in biopesticide formulations. In countries that have fewer concerns towards GMOs, the killing activity of baculoviruses may be augmented by genetic modifications of the baculovirus genome. It is expected that baculoviruses improved by genetic modifications will compete successfully with other methods of pest control in many regions of our globe, especially in most densely populated countries of the world.
Use of baculoviruses as biological insecticides
Molecular Biotechnology, 1997
Naturat!y!occurring baculoviruses can ~ =used to controI a wide range of insect ~'sts. Most baculoviruses are ~ed, laS biopesticides, that is, they are sprayed onto high-density pestpopula~0ns inamanner akin to the use 0f~ynthetic clieiriical pesticides. Howeve~, Other strategies that use the biological features 0f the:v~Ses ~e at~ol possible~::and Shouid increase as we e~pand our knowledge of baculovirus e~oio~ii'J~n~ order to fi0n systems todetailed study of pest behavior and the development of appropriate aoplicafion strategies.
Baculoviruses: Emerging Frontiers for Viral Biocontrol of Insect Pests of Agricultural Importance
Accumulated evidences gathered over recent decades demonstrated that Baculoviruses (Occlusion body forming nucleopolyhedroviruses and the host specific granuloviruses) have proven Biocontrol activities on insect and pests of agricultural importance while being non-pathogenic to humans. These studies have laid the foundations for the launch of several trials phases using Baculoviruses on specific insect pests for their efficacy as viral Biocontrol agents. After a brief overview of the biology of Baculoviruses, this review focuses on the studies which unraveled the Biocontrol properties of these agents and supported their use as biopesticides of insect pests resistant to chemical pesticides. Furthermore, this review emphasizes the development of more complex Baculovirus treatment strategies aimed at enhancing formation of occlusion bodies, accelerated virus replication of infective budded forms in insect hosts and improvement of direct lethal effects in several insect developmental forms as necessary tools for increased efficacy in viral Biocontrol of insect pests of agricultural importance. However, the review also addressed the key challenges that
Evaluation of a Baculovirus Bioinsecticide for Small-Scale Maize Growers in Latin America
Biological Control, 1999
Near identical trials conducted concurrently in maize plots in Honduras and Mexico produced similar results in the pattern of larval mortality of Spodoptera frugiperda following application of a baculovirus or a conventional synthetic insecticide. The highest application rates of virus resulted in approximately 40% mortality of S. frugiperda larvae. Virus-induced mortality decreased with time. Parasitism by wasps and tachinids also contributed up to 40% mortality in field-collected larvae. The application of chlorpyrifos resulted in a resurgence of S. frugiperda. Chlorpyrifos also reduced a number of important predators in the maize crop which is likely to have been influential in the observed resurgence of this pest. The use of granulated sugar in the viral formulation caused an increase in the population density of several maize-associated insect species, and in Mexico a transient increase in parasitism was observed in sugar-treated plots. Sugar did not appear to increase the probability of infection by acting as a feeding stimulant in either trial. A preliminary analysis of the cost of viral production and application indicates that virus was considerably more costly than conventional control. To be commercially viable, economies of scale both in the cost of raw material for the insect diet and in the efficiency of manpower-related activities are needed to substantially reduce the costs of the viral product. Despite high levels of infestation by S. frugiperda, grain weight/ cob was not significantly improved by the application of the biological or synthetic insecticide. Natural mortality factors both biotic and abiotic appear to have a large impact on larval S. frugiperda populations. For improvements in yield, the impact of control measures against S. frugiperda may be dependent on plant growth stage. Trials on timing and frequency of virus application are in progress to test this idea. 1999 Academic Press
Response of Hosts of Varying Susceptibility to a Recombinant Baculovirus Insecticide in the Field
Biological Control, 1999
In an attempt to improve the effectiveness of nucleopolyhedroviruses (NPV) as bioinsecticides of lepidopteran pests, the NPV of Autographa californica (Ac-MNPV) has been genetically modified to include a gene that expresses an insect-selective scorpion toxin, Aa-HIT. In a field trial, we compared the response of a highly susceptible 'target' host (Trichoplusia ni) and a representative less susceptible species (Mamestra brassicae), following spraying with wild-type AcMNPV and the genetically modified virus. Mortality and therefore risk of infection were significantly lower in the less susceptible species but did not differ between the wild-type and the recombinant viruses. Speed of kill was consistently faster in T. ni infected with the recombinant virus for samples collected 1, 3, and 5 days following spray application. The results for M. brassicae were more variable; time to death induced by both viruses was longer in M. brassicae than in T. ni but the genetically modified virus acted faster only in larvae taken 3 and 5 days following spraying. This contrasts with laboratory assays in which the recombinant virus took longer than the wild-type virus to kill M. brassicae. The results demonstrate that there are differences in virus productivity, distribution, and timing of virus release when two hosts with different susceptibilities are treated with wild-type and recombinant baculoviruses, which will impact on further rounds of virus replication. Thus, the effects of recombinant baculoviruses on less susceptible, potentially nontarget, hosts are not likely to be easy to predict, and they highlight the need for both more information on the behavior of baculoviruses in hosts of varying susceptibility and further studies on the impact of these factors on secondary transmission. 1999 Academic Press
Neotropical Entomology, 2005
Efeitos de Isolados do Baculovirus spodoptera em Lagartas de Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) e sua Caracterização por Meio de RAPD RESUMO-Foram utilizados 22 isolados de vírus amostrados em diferentes regiões produtoras de milho do Brasil. Os vírus foram purificados e suas suspensões fornecidas a lagartas sadias do 3º e 4º ínstar de Spodoptera frugiperda (J.E. Smith). A mortalidade foi avaliada diariamente, e as lagartas infectadas foram congeladas logo após sua morte, o que em geral ocorreu do 5 o ao 7 o dia após ingestão do vírus. Os isolados foram usados em seis concentrações (10 3 a 10 8 poliedros/ml) e uma testemunha (água). Os percentuais de mortalidade, duração do período larval e período pupal, peso de pupa e a concentração letal (CL 50) foram determinados para todos os isolados. Foram observadas diferenças significativas entre todos os isolados e concentrações testadas para todos os parâmetros avaliados, e também foi constatada a presença da interação isolado x concentração, exceto para período pupal. Os padrões de amplificação de 54 marcadores RAPD, sendo 41 polimórficos, foram utilizados para avaliar a distância genética e a sua correlação com os índices de mortalidade das lagartas. A divergência genética calculada pelo coeficiente Jaccard utilizando os dados moleculares permitiu dividir os isolados em dois grupos, com um elevada confiabilidade. O agrupamento não apresentou associação com a taxa de mortalidade causada pelos isolados ou com sua distribuição geográfica. No entanto, um fragmento de RAPD OPW04.2280 apresentou-se altamente associado com a mortalidade das lagartas e com a CL 50 , explicando 23% e 65% da variação fenotípica para essas características entre os isolados virais, respectivamente. PALAVRAS-CHAVE: Patologia de insetos, lagarta do cartucho do milho, PCR ABSTRACT-The total of 22 Baculovirus isolates surveyed in different corn producing regions in Brazil were used against fall armyworm, Spodoptera frugiperda (J.E. Smith). The viruses were purified and their suspensions were used to feed fall armyworm larvae from 4 th and 5 th instar. The mortality rate was checked daily and the infected larvae were frost after death, what generally occurred between the 5 th and 7 th day after virus ingestion. The 22 Baculovirus isolates were used in six concentrations (from 10 3 to 10 8 polyhedra/ml) and one check treatment with water. Mortality rate, larval period, pupal period, pupa weight and lethal concentration (LC 50) were determined for all isolates. Significant differences were found among all isolates and different concentrations, also interaction between isolate x virus concentration for all characteristics evaluated, except for pupal period. Amplification patterns of 54 RAPD markers, being 41 polymorphic among the isolates, were used to evaluate the genetic distance and its correlation with the fall armyworm larvae mortality rate. The genetic diversity calculated by the Jaccard's coefficient using the molecular data allowed a division of the isolates into two groups, with a high level of confidence. These groups did not present any association with the mortality rate caused by the isolates or with their geographical distribution. However, a RAPD fragment OPW04.2280 was highly associated with the larvae mortality rate and with LC 50 , explaining 23 and 65% of the phenotypic variation for these traits among the isolates, respectively.
Detection of low levels of baculovirus for outbreak-terminating epizootics in defoliating insects
Recent empirical and theoretical studies have indicated that epizootics of baculoviruses in defoliating insects may result in the termination of outbreaks starting from lower initial infection rates than previously believed. This suggests that natural epizootics can preempt the need for costly and labor-intensive pest management measures because natural epizootics reduce or end outbreaks before substantial defoliation occurs. Such cases, however, require the ability to detect small amounts of infection at the beginning of the population's life cycle. At hatching, Douglas-fir tussock moth (Orgyia pseudotsugata) larvae become infected by baculoviruses on the surface of their eggs. Prior to the larval season in an outbreak area, egg masses are collected and assayed for the presence of viruses; however, a large number of eggs may need to be sampled to detect low infection rates in which biocontrol measures are not needed. Here we used simulated sampling to detect infection rates ranging from 10-3 to 10-4 and considered whether multiple potential probability distributions of the actual infection rate affected detection. We showed that the level of sampling is considerably higher than in previously published protocols, but that increased effort via either more egg masses sampled (with a fixed number of eggs per egg mass), or more eggs per egg mass sampled without collecting more egg masses, equally improved the accuracy of detecting the virus.
Biological Control, 2002
This paper describes the validation and sensitivity analysis of a process-based simulation model (BAC-SIM) for the control of beet armyworm, Spodoptera exigua, with baculoviruses. Model predictions are compared to results of independent greenhouse experiments in which second, third, or fourth instar larvae of S. exigua in chrysanthemum plots are treated with different concentrations of Autographa californica multicapsid nucleopolyhedrovirus (AcM-NPV) and S. exigua MNPV (SeMNPV), two viruses with distinct differences in infectivity and mean time to kill. BACSIM provides robust predictions for the control of S. exigua populations in greenhouse chrysanthemum with both AcMNPV and SeMNPV. Mortality levels caused by AcMNPV and SeMNPV were generally predicted within a 25% margin of error compared to the observed values. None of the deviations was higher than 40%. All values of simulated foliage consumption, caused by S. exigua populations treated with AcMNPV or SeMNPV applications, fell within 95% confidence intervals of measurements. Simulated time to kill was, in general, lower than the measurements. This discrepancy may be caused by the behavior of S. exigua larvae which feed on the underside of chrysanthemum leaves where they are protected from polyhedra. This suggests that the larval foraging behavior may play an important role in the efficacy of baculovirus applications and should be further studied experimentally. This validated model can be used for the pretrial evaluation of the efficacy of genetically modified baculoviruses as biological control agents and for the optimization of spraying regimes in chrysanthemum cultivation. © 2002 Elsevier Science