Spread of a Gammabaculovirus within Larval Populations of Its Natural Balsam Fir Sawfly (Neodiprion abietis) Host Following Its Aerial Application.

Roger Graves,Christopher J Lucarotti,Dan T Quiring

doi:10.3390/insects3040912

Roger Graves, Christopher J Lucarotti + Show 1 more

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https://doi.org/10.3390/insects3040912

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Abstract

Field trials and assessments of the balsam fir sawfly (Neodiprion abietis) nucleopolyhedrovirus (NeabNPV: Baculoviridae, Gammabaculovirus) against its natural host were conducted in July and August 2002 near Corner Brook, Newfoundland and Labrador, Canada, in naturally regenerated, precommercially thinned stands dominated by balsam fir (Abies balsamea). Two experimental blocks, each with its own untreated control, were established. The purpose of the Island Pond block was to examine the spread of NeabNPV from a 313-ha aerial treatment block out into adjacent populations of balsam fir sawflies. The purpose of the Old Man’s Pond block (2,093 ha) was to determine whether NeabNPV could disperse into populations of balsam fir sawflies within a 200-m zone between spray swaths. NeabNPV was applied to treatment blocks by a Cessna 188B AgTruck aircraft equipped with MicronAir AU4000 rotary atomizers at an application rate equivalent to 1 × 109 NeabNPV occlusion bodies/ha in 2.5 L of 20% aqueous molasses. At Island Pond, NeabNPV infection increased with time following the spray, especially for individuals close to the treatment block, and infection rate decreased to a measured distance of 400 m from the treatment block. At Old Man’s Pond, NeabNPV infection rose higher (80% vs. 15%) and sawfly densities declined more (84% vs. 60%) in the area between spray swaths than in the control block.

Highlights

Development of microbial pathogens as viable alternatives to chemical pesticides has been encouraged by public pressure for environmentally benign pest management strategies
The family Baculoviridae is divided into four genera: Alphabaculovirus and Betabaculovirus, both of which occur in Lepidoptera; Deltabaculovirus, which are NPVs in Diptera; and Gammabaculovirus, which are NPVs in sawflies [7]
Occlusion bodies of NeabNPV can only be produced in living larvae of its host, the balsam fir sawfly [17,30]

Summary

Introduction

Development of microbial pathogens as viable alternatives to chemical pesticides has been encouraged by public pressure for environmentally benign pest management strategies. Baculoviruses are generally considered ideal candidates for biological control agents because they are naturally occurring and host-specific infecting only a single species or a few closely related species of insects, can cause epizootics in host-insect populations, and persist in the environment for many years [1±5]. Baculoviruses are covalently closed, double-stranded DNA viruses between 85 and 180 kb in size [6]. The family Baculoviridae is divided into four genera: Alphabaculovirus (nucleopolyhedrovirus or NPV) and Betabaculovirus (granulovirus or GV), both of which occur in Lepidoptera; Deltabaculovirus, which are NPVs in Diptera; and Gammabaculovirus, which are NPVs in sawflies [7]. The balsam fir sawfly (Neodiprion abietis Harris) is an eruptive defoliator that is native to North Many studies have been conducted to assess the effects of NPVs on insect populations (e.g., [8±18]), with most reporting that NPV-induced mortality acts in a density-dependent manner [19] to reduce insect population densities.

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