PHYSIOLOGICAL AND NUTRITIONAL EFFECTS OF A FLUORESCENT BRIGHTENER ON NUCLEAR POLYHEDROSIS VIRUS-INFECTED LYMANTRIA-DISPAR (L) LARVAE (LEPIDOPTERA, LYMANTRIIDAE)

Recent studies with gypsy moths (Lymantria dispar L.) show that the fl uorescent brightener, Tinopal LPW, acts synergistically with the L. di spar nuclear polyhedrosis virus (LdMNPV), lowering the 50% lethality c oncentration of the virus (LC(50)) by 1000-fold. As a continuation of this work, we investigated the effects of ingestion of LdMNPV/Tinopal on larval midgut pH, hemolymph pH, and nutritional indices. Larval fee ding for 48 h on diet treated with either LdMNPV or Tinopal did not af fect midgut luminal pH, which averaged 10.3. In contrast, after 48 h o f larval feeding on LdMNPV/ Tinopal diet, midgut pH averaged 8.5, and frass production, weight gain, and larval nutritional indices were sig nificantly reduced. These effects appeared to be irreversible after th e first 24 h of feeding ad libitum on LdMNPV/Tinopal diet, and the red uction in midgut pH was not due to feeding cessation per se. No signif icant effects on hemolymph pH were detected with any treatment. No tre atment effects were observed when ''SITS,'' a related fluorescent brig htener, was substituted for Tinopal. The severe biological perturbatio ns resulting from LdMNPV/Tinopal consumption are interpreted in light of current understanding of larval lepidopteran midgut physiology. (C) 1994 Academic Press, Inc.