Avian Dispersal of Nuclear Polyhedrosis Viruses after Induced Epizootics in the Pine Beauty Moth, Panolis flammea (Lepidoptera: Noctuidae)

Abstract

Birds were trapped in three forest sites in Scotland after nuclear polyhedrosis virus (NPV) from the pine beauty moth, Panolis flammea, or cabbage moth, Mamestra brassicae, had been applied to control P. flammea populations. Collections were made late in the larval period when NPV infection was apparent in the field. In one site birds were also sampled when the P. flammea larvae were in the early instars and after the larvae had pupated. Bioassay of droppings collected from the captured birds showed that 9 of the 15 species trapped at NPV-treated sites had fed on virus-contaminated material. The proportion of NPV-positive birds collected late in the larval period ranged from 11.3%, in a trapping site near where small areas of forest had been treated, to 77.1% and 63.5% in sites where much larger areas had been sprayed. Samples collected early in the larval period yielded no virus, whereas 27.5% of the birds caught after the larvae had pupated were NPV positive. Estimates of the quantity of virus excreted by the birds ranged from 6 × 103 to 2.5 × 106 NPV polyhedra/mg of dropping and from 5 × 104 to 5.3 × 107 polyhedra/dropping. Restriction endonuclease analysis of NPV DNA from the samples confirmed their identity and demonstrated that most birds had ingested both P.flammea and M. brassicae NPV.