Effects of Blankophor BBH, a Virus-Enhancing Adjuvant, on Mortality of Gypsy Moth (Lepidoptera: Lymantriidae)

Abstract

We examined aspects of the gypsy moth, Lymantria dispar (L.)/nuclear polyhedrosis virus relationship, and the effects of Blankophor BBH on that relationship, that might impact the timing of virus kill in a cohort of treated larvae. We studied this relationship both for virus and enhancer applied together and separately. We found that a portion of larvae ingesting virus polyhedral inclusion bodies die later (more than 4 wk after infection) in the season, and that this can be affected by the presence of Blankophor BBH if the virus dose is above a certain level (in this study, 107 polyhedral inclusion bodies per 378 liters). Furthermore, the pattern of mortality resulting from virus ingestion was elucidated. This pattern was affected by Blankophor BBH, but only when the virus dose was above a certain higher level (in this study, 1011 inclusion bodies per 378 liters). We also found that Blankophor BBH alone had no obvious effect on the course of the disease in gypsy moth larvae that had previously ingested virus; it caused neither an increase in mortality, a decrease in time to kill, nor any obvious effect on the pattern of kill. Most larvae died between 18 and 29 d. Few larvae ingesting virus died earlier (13 to 17 d); however, about 5% of the larvae died later than 30 d after infection, which may be late enough to contribute to the second wave of mortality. A combination of Blankophor BBH at 0.5% and virus at 1011 inclusion bodies resulted in an increase in mortality and a decrease in time of kill compared with that seen for that level of virus without the enhancer, while eliminating the “tail” of mortality occurring 30 d after infection. However, a combination of Blankophor BBH at 0.5% and virus at 109 inclusion bodies still give higher mortality than expected with the virus alone, but did not decrease the time of kill or eliminate the “tail.”