Submitted to: Journal of Entomological Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 22, 1998
Publication Date: N/A
Interpretive Summary: The gypsy moth nuclear polyhedrosis virus (NPV) has been registered as a general use pesticide against the gypsy moth, a serious defoliater of forest and shade trees. This is the eighth in a series of reports on efforts to adapt strains and formulations of this virus with or without enhancing agents, for use by arborists and nurserymen using ground equipment. One goal of our program is to develop usage patterns for the virus that take advantage of the virus's ability to persist and to spread. A knowledge of the timing and pattern of mortality resulting from the application of the virus is essential to this goal. In this study, we used a bugs-in-bags approach to elucidate additional aspects of the relationship between the virus and the optical brightener (known to enhance the activity of the virus) Blankophor BBH under the field conditions similar to that encountered by arborists. The results should assist our efforts to develop new cost effective usage patterns for the virus with or without enhancer, which would potentially help all managers of gypsy moth-infested properties (homeowners, arborists, and local, state, and federal programs).
We examined aspects of the gypsy moth/nuclear polyhedrosis virus (NPV) relationship, and the effects of Blankophor BBH on that relationship, that might impact the periodicity of virus expression. We studied this relationship both for virus and enhancer applied together and applied separately. We found that a portion of larvae ingesting NPV will 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 PIBs per 378 liters). Furthermore, the pattern of mortality resulting from NPV ingestion was elucidated, and this pattern was affected by Blankophor BBH, but again, only when the virus dose is above a certain higher level (in this study, 1011 PIBs per 378 liters). We also found that Blankophor BBH alone had no obvious effect on the course of the disease in larvae that had previously ingested NPV; it did not cause 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 NPV 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 NPV at 1011 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.