THE INACTIVATION OF FOLIAR DEPOSITS OF VIRUSES OF TRICHOPLUSIA NI (LEPIDOPTERA: NOCTUIDAE) AND PIERIS RAPAE (LEPIDOPTERA: PIERIDAE) AND TESTS ON PROTECTANT ADDITIVES

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Abstract
Deposits of the nuclear-polyhedrosis virus of Trichoplusia ni (Hübner) and of the granulosis virus of Pieris rapae (Linnaeus) were largely inactivated within 10 days after sprays were applied to field plots. Deposits on plants retained in a growth room or in a greenhouse were inactivated but more slowly than those exposed to direct sunlight. Deposits on plants kept in the dark lost little activity indicating that exposure to light was responsible for inactivation. Activity of deposits of the viruses was extended substantially by addition of protectant materials to the sprays. The addition of charcoal mixed with skim milk powder, egg albumen, or brewer’s yeast resulted in a 3-fold increase in the period over which an LD50 of virus was maintained on the plants.