Infection Phase

Infection by the baculovirus takes place at the larval or caterpillar stage of the insect lifecycle. When the insect ingests infected food, the polyhedra dissolve in the alkaline environment of the mid-gut, releasing the baculovirus virions. These penetrate the peritrophic membrane lining the gut and release nucleocapsids into the cytoplasm.The virus DNA is then transported to the nucleus by the nucleocapsids.

Replication Phase

Once in the nucleus, replication occurs: producing two distinct structural forms. The primary round of replication produces nucleocapsids at 8 hours post infection (hpi). At 12 hpi they bud through the nuclear membrane, acquiring a lipid envelope: ECV.

The second generation of infected cells also produce extracellular virus, but in addition they produce virions (PDV) occluded within polyhedra (P) in the nucleus. These particles, virions genetically identical to the others, acquire their lipid envelope in the nucleus and so do not have an attached gp67 protein.

Terminal Phase

The insect liquifies to an 'amorphous puddle'; thus releasing the virus polyhedra. The polyhedra are either ingested by uninfected insect larvae, propagating the spread of virus horizontally, or can remain dormant on plant or soil surfaces for over a year.