Baculovirus and Pest Management

Introduction
Since their discovery in 1527 baculoviruses have become a central focus for the development of bio-pesticides.

Baculovirus are virus pathogens that attack insects and other arthropods however not plants and humans.

These viruses affects primarily the larval stages of insects in the major groups including Lepidoptera, Hymenoptera and Coleoptera.

Baculovirses may fall in one of the two major groups depending on the number of virions contained in the occlusion bodies. The first group contains only one virion in the occlusion body and is called granuloviruses, while the second group consists of numerous virions in the occlusion bodies and is called nucleopolyhedroviruses

The larvae acquire the virus though feeding on foliage of plants where they ingest occlusion bodies, which are solubilized in the midgut to release the virion particles.

Diamondback moth (Plutella xylostella), beet army worm (Spodoptera exigua) and cabbage loppers (Trichoplusia ni) are all major Lepidopteron pests that have over the years caused tremendous loss to farmers. These pest have also shown increased resistant to new and old pesticides.

Due to its narrow host range the discovery and use of viruses would reduce the level of risk to both humans and the environment, and also due to the long persistent of polyhedra produce by the viruses farmers would spend less on buying and applying such pesticide.

Insect larvae affected with virus pathogen.
Virus particle
Occlusion bodies with viruses

Phase-contrast micrograph of varied cell size containing occlusion bodies extracted from Plutella xylostella.

Research Topic
Initial:
Isolation, identification, characterization and determination of LC50 of baculovirus of Plutella xylostella and its efficacy as a potential pesticide against Plutella xylostella

Current:
Isolation, identification, characterization and determination of LC50 of baculovirus of Plutella xylostella, Spodoptera exigua, and Trichoplusia ni and their efficacy as a potential pesticides against these insect pest.

Objectives
The major goal of the project is to identify baculovirus/es affecting Jamaica’s major Lepidopteron pest and determine its efficacy as a potential biopesticide to facilitate safe and efficient management of these pest population. Specific objectives include:
Isolation and identification of baculovirus from larval tissues
Molecular characterization of baculoviruses
Determination of LC50 using bioassays to determine the efficacy of the virus as a potential biopesticide.

Research Questions/Hypothesis

It is hypothesized that there are naturally occurring baculovirus(es) affecting Jamaica’s Lepidopteron pest population. If found these viruses can be use as an effective control mechanism to reduce the alarming pest population. Based on this the following research questions are formulated:

Is there baculoviruses affecting local population of Lepidopteron pest?
 
If found, can these isolated viruses be use as a potential biopesticide to manage these pest?

Methodology
The following methods will be used to answer the research questions asked:

Survey and Insect Larvae Collection
Farms with the specific pest population will be surveyed
Larvae with disease like symptoms (puffy pale yellow appearance) will be collected as well as healthy larvae.
Larvae will be photographed digitally to illustrate disease symptoms as well as healthy larvae.
As many larvae will be collected as possible and will be stored and transported to laboratory on ice.

Verifying any Fungal Pathogen Presence
Since these insects are susceptible to a wide array of pathogens, fungal verification is important.
Collected larvae will be surface sterilized.

The surface sterilized larvae will be plated on potato dextrose agar (PDA).

In the case of any fungal pathogens characterization of the fungus will be carried out to determine the name and the possible effects on the insect larvae.

Extraction of Viral Pathogens
A modified extraction method proposed by Kumar (2011) will be employed.
The larvae will be vortex in sterile distilled water and centrifuge.
The supernatant will be discarded and the pellets re-suspended and stored at 4oC for short term.

Identification of Virus using Electron Microscope
The virus(es) extracted will be identified using the Transmission Electron Microscope.

Virus Characterization
Characterization of the virus will be done using restriction endonuclease analysis (REN analysis)

Bioassays
Based on the different isolates of the virus determined from characterization bioassay will be carried out using different concentration of the virus with different instars of the different pest.

Statistical Analysis
A probit analysis will be carried out using the data gather from the bioassay to determine the LD50 (lethal dosage at which 50% of the pest is killed). Other statistical analysis will conducted where appropriate.

How will the findings help?
These findings may be the first case in which baculoviruses are isolated and documented in Jamaican Lepidopteron pest.

The identification of baculoviruses can lead to the development of a suitable biopesticide against these pest (Mishra, 1997).

For example: diamondback moth

These findings will set the pace for the effective development of a safe bio-pesticide.

Thank You!






(References available upon request)