Entomopathogenic viruses are those that infect and kill insects. They are superior to regular pesticides in that they are not harmful to humans or other vertebrates. Furthermore, each viral strain attacks only a limited number of insect species which helps to mitigate unpredicted damage.
There are two types of entomopathogenic viruses:
- Baculoviridae (ds DNA)
- Reoviridae (ds RNA)
However, the Baculoviridae viruses are the ones that are most commonly used. They are found only in invertebrates and despite rigorous testing have not been shown to negatively affect vertebrates and plants. They also have a narrow host insect range which is typically restricted to the original host genus.
The mode of action for Baculoviridae is as followed:
Baculovirus is sprayed onto foliage –> Caterpillar consumes the virus –> The protein encapsulating the Baculovirus DNA dissolves and the DNA enters the stomach cells –> Baculovirus DNA is replicated by the stomach cells until the stomach cells rupture –> The caterpillar stops eating –> Baculovirus is spread throughout the caterpillar causing a general systemic infection –> The caterpillar dies within days
The biggest issue related to the use of this method is the amount of time required before the pest dies. This is noted as being the number one reason why this method is not used on a more wide scale basis.
Baculoviruses are created in vivo and production is often automated which makes it predictable and inexpensive because of the use of inexpensive growing mediums and the natural process of fermentation. It is estimated that application in the USA costs $6-10/acre which is competitive with prices for industrialized chemical pest control options.
In order for the use of Baculovirus to expand the following improvements must be made:
- Genetic engineering must result in a 50% increase in the speed of the kill time
- Residual activity of the virus must be increased from 2 – 4 days to >7
- The role of Baculoviruses must be strengthened within successful IPM programs
- More cost-effective cell culture for the mass production of wild type and genetically modified Baculoviruses must be developed
A major example of success using a Baculovirus is the control of the Gypsy Moth (Lymantria dispar) using the entomopathogenic virus LdMNPV.