2011 Annual Report
1a.Objectives (from AD-416)
The long-term objective of this project is to develop improved strains of beneficial insects and baculoviruses through traditional breeding techniques. The specific objectives are to:.
1)select and develop beneficial lines of a predator, the spined soldier bug, Podisus maculiventris, for improved bionomic traits such as increased female fecundity, sex ratio, development time, and shelf life,.
2)select and develop baculovirus lines for important biopesticide traits such as increased speed of kill, persistence, and broadened host range, and.
3)in partnership with small and urban vegetable growers, develop novel beneficial insect and baculovirus delivery systems for application, using such strategies as chemical attractants, artificial diets, and release mechanisms.
1b.Approach (from AD-416)
The goal of this research is to select biological control agents with improved traits for controlling pest insects in greenhouse, organic and small field applications. This project will generate a highly fecund line of the spined solder bug, Podisus maculiventris (and if time permits, a line tolerant to cold storage) and naturally occurring stable, efficacious strains of the celery looper baculovirus, Anagrapha falcifera nucleopolyhedrovirus. We will measure genetic variation within and between the predator populations and the virus populations to assess their potential for selection procedures. Initially we will use egg production traits to direct the selection of predator lines and virulency to direct the selection of virus lines. For the predator lines, genetic variation will be assessed and polymorphisms will be used to identify and confirm associations between genotype and the high fecund phenotype. For the virus strains, genetic variation will be assessed and variable regions will be sequenced to identify genes related to efficacy and stability. Together, this research will produce significant advancements in knowledge of the genomic basis underlying complex traits. It also will build our capability to breed lines of insects and strains of viruses with enhanced production traits and pest control efficacy. We have established collaborations to test the improved lines of predators and viruses at the greenhouse and small plot levels. Two key end products, which we will transfer to industry and producers, will be improved beneficial agents with increased value to commercial insectaries and producers and the technology required to achieve these improved agents.
This project replaced 3622-22000-032-00D and 3622-22000-033-00D and began on 8/19/10. Significant progress was made on all three objectives. For Objective 1, repeated field collections of a beneficial predatory insect were made in Missouri and Mississippi. Laboratory colonies were established from those collections. The colonies were of sufficient size and health to support genetic selection efforts. Genetic variation was confirmed within a domesticated colony and a group selection process was initiated with a field colony.
To accomplish milestone 2a, baculoviruses were propagated from Missouri field collected insects that had died from apparent virus infection. From these, six baculovirus samples were chosen and tested in two different species of caterpillars to begin identification of the most effective baculovirus isolate. Analysis of the viral DNA from these samples confirmed each contained celery looper baculovirus but also revealed a contaminant RNA virus that was removed. Because each of these collected samples was composed of a mixture of celery looper baculovirus isolates, the most efficacious individual isolates were separated. These isolates will be tested in bioassay to determine the viral host range and eventually the most promising isolates will be field tested. Laboratory collections of celery looper virus were also propagated and the genetic variation of these isolates was examined.
On Objective 3, feasibility tests using cage studies to simulate field dispensing of a beneficial predatory insect were conducted. A cloth and screen cage design worked well and will be used for further studies. Additionally, initial laboratory and field testing of a fast acting and slower acting isolate of the fall armyworm baculovirus was conducted. Several different formulations of the baculoviruses were tested. The number of viral particles produced by the two isolates was compared. Future tests will include a blend of the two baculovirus isolates.
Selection of highly reproductive beneficial insect predators. Applications of synthetic chemical insecticides have introduced severe challenges to our environmental and agricultural sustainability. The concept of biological control of insects is a potentially powerful alternative to synthetic insecticides. Augmentative biological control is based on the idea that releases of large numbers of beneficial insects can reduce pest insect populations and the economic damage due to pest insects. The problem, however, is the costs of mass rearing beneficial insects limits their potential use. One approach to reducing costs is to improve the reproductive capacity of the beneficial insect so fewer adults produce more progeny and thereby reduce the overall cost of production. ARS researchers at Columbia, MO and collaborators at the University of Nebraska developed a selection method that is easy to implement and would be favored by industry. A group selection method was applied through 10 generations and samples from each generation were preserved. The combination of egg production data and DNA analyses will be used to determine whether the group selection method will lead to colonies of predatory insects with high reproductive potential. This new research will be directly useful to scientists who are working to improve the efficacy of biological control methods. The ensuing improved biological control methods will benefit a wide range of agricultural producers and support the long-term sustainability of agriculture.
Rowley, D.L., Popham, H.J., Harrison, R.L. 2011. Classification, genetic variation, and biological activity of nucleopolyhedrovirus isolates from three heliothine pests. Journal of Invertebrate Pathology. 107:112-126.