Figure 1. Insecticidal effect of Bacillus thuringiensis (Bt). These effects are produced by a complex of crystalline toxins. Eaten by the insect larvae these damage the gut, allowing a lethal generalized infection. The infection generally does not spread to new hosts.

Figure 2. Baculovirus structure. Baculoviruses all form protective ‘occlusion bodies’ around the infectious nucleocapsids, and are divided into two genera. These are the Nucleopolyhedroviruses, in which a single occlusion body (OB) contains multiple infectious units and the Granuloviruses, in which each OB contains a single infectious unit. During infection of the host, a nonoccluded or ‘budded’ form of the virus is produced which lacks the occlusion body. The agents formerly classified as ‘nonoccluding baculoviruses’, including Oryctes rhinoceros virus, are now considered to belong to an unclassified group of baculovirus-like agents.

Figure 3. Insecticidal effect of generalized baculovirus infection. Baculoviruses within occlusion bodies are eaten by insect larvae. The occlusion body dissolves in the insect gut releasing viruses that infect the cells of the gut by growing there. The virus then spreads throughout the body of the insect, killing it and releasing large amounts of virus from the liquefied mass that results.