Within-host interactions of Lymantria dispar (Lepidoptera : Lymantriidae) nucleopolyhedrosis virus and Entomophaga maimaiga (Zygomycetes : Entomophthorales)

The interaction of two gypsy moth (Lymantria dispar) pathogens, a nucleopol yhedrosis virus (LdNPV) and a fungus (Entomophaga maimaiga), were studied b y assessing mortality among dually inoculated hosts. When fourth and fifth instar gypsy moths were inoculated with a range of doses of LdNPV and a fix ed dose off. maimaiga on the same day, the majority of larvae died from E. maimaiga infections regardless of the dose of LdNPV. When the larvae were i noculated with E. maimaiga to days after LdNPV, there was an apparent incre ase in mortality of hosts induced by LdNPV. Among the fourth instars, the m ortality due to LdNPV in the presence off. maimaiga was significantly highe r when insects were reared at 25 than at 20 degrees C. At 25 degrees C, the LD50 of LdNPV for fifth instars was twofold greater than that for fourth i nstars. For those larvae that died from LdNPV, the median survival time (ST 50) of dually inoculated fourth and fifth instars was ca. I day shorter tha n those inoculated with LdNPV alone. The number of LdNPV occlusion bodies p roduced in the cadavers hom the dually inoculated larvae was lower than tho se inoculated with LdNPV alone. (C) 1999 Academic Press.