Pathology of a nuclear polyhedrosis virus of the alfalfa looper in alternate hosts

The symptomatology and histopathology of a nuclear polyhedrosis virus isolated from a larva of the alfalfa looper, Autographa californica, was studied by examining 13 tissues in the original and following alternate hosts: cabbage looper, Trichoplusia ni; beet armyworm, Spodoptera exigua; saltmarsh caterpillar, Estigmene acrea; corn carworm, Heliothis zea; cotton leafperforator, Bucculatrix thurberiella; and diamondback moth, Plutella xylostella. In all hosts, the hypodermal, tracheal matrix, and fat body cells were infected. Other tissues infected in some hosts included the Malpighian tubules, muscle, hemocytes, ganglia, midgut, hindgut, juvenile tissue (imaginal buds), and testes. No major changes in tissue tropisms were observed. The external symptoms were typical of nuclear polyhedrosis in all species except the corn earworm; in this host, development of the disease and death were delayed.