Recovery of nontarget Lepidoptera on Vancouver Island, Canada: One and four years after a gypsy moth eradication program

Abstract

The gypsy moth (Lymantria dispar) is a destructive defoliator that is not established in British Columbia, Canada, because of successful eradication programs involving the microbial insecticide Bacillus thuringiensis var. kurstaki (Btk). In 1999, three aerial applications of Btk were made over two areas, totaling 12,805 ha, on southern Vancouver Island, Canada. The impacts of these Btk applications on nontarget Lepidoptera were studied from 1999 to 2004 on Garry oak (Quercus garryana) and common snowberry (Symphoricarpos albus). In 1999, lepidopteran larvae were collected from S. albus foliage at 24 urban parks and from Q. garryana foliage at 28 oak-dominated habitats. The initial impacts (i.e., 1999 data) were published previously, and the present paper is a continuation of the same study. We tested two hypotheses: Reductions of nontarget Lepidoptera would be more severe at 12 to 13 months postspray than at one to two months postspray, and recovery would be significant, though not necessarily complete, at four years postspray. The total number of nontarget Lepidoptera on S. albus and Q. garryana was significantly reduced in the treatment sites in each year of the study: the reduction was greatest in 2000. Relative to the reference sites, each of 11 species that were initially reduced by the Btk applications showed an increase in the treatment sites between 2000 and 2003, by which time only four species remained significantly reduced in the treatment sites. The uncommon species were significantly reduced in 1999 and 2000 but not in 2003, indicating that some recovery had occurred. Limitations and economic implications of the present study are discussed.

Lepidoptera-specific insecticide used to suppress gypsy moth outbreaks may benefit non-target forest Lepidoptera

“…Boulton et al . () sampled larval Lepidoptera up to 4 years after Btk application and found the system's diversity mostly recovered, although rare species were the slowest to recover. In a 7‐year study of non‐target Btk effects on native arthropods in Virginian and West Virginian forests, Lepidoptera whose phenology was determined to be most sensitive to the Btk application experienced significantly decreased abundance during treatment years but returned to pre‐treatment and comparable control levels 2 years after treatment (Strazanac & Butler, ).…”

“…Surveying was conducted 3 years after defoliation and Btk applications occurred, allowing us to assess the long‐term effects of these disturbances on forest moths. Based on previous work (Sample et al, ; Work & McCullough, ; Rastall et al , ; Boulton et al, ; Timms & Smith, ), we predicted that undisturbed sites (no defoliation or spraying with Btk) would have a higher abundance and local ( α ) diversity of moths than sites that were defoliated but not sprayed with Btk and sites where defoliation was mitigated by Btk application. We also expected that moths sharing host plants with gypsy moths would be most affected by defoliation (Redman & Scriber, ; Work & McCullough, ).…”

“…In addition, existing studies investigating how the diversity of non‐target insects is affected by defoliator outbreaks and suppression have not addressed whether the impacts vary from local to regional scales (Sample et al , ; Work & McCullough, ; Rastall et al , ; Boulton et al , ; Timms & Smith, ). Previous studies have focused on diversity within individual localities (sites) but, as is recognized within community ecology (Whittaker, ), regional (γ) diversity results from a combination of both local ( α ) diversity and variation in diversity across space ( β ‐diversity).…”

Eradication of Invading Insect Populations: From Concepts to Applications

“…There is little evidence of adverse effects of aerial Btk treatments on human health (86, 88). Concerns exist about the effects of Btk treatments on nontarget Lepidoptera (14,78); however, most eradication treatments are applied over relatively small areas such that immigration might be expected to facilitate rapid recovery of affected species. Indeed, the effects of Btk treatments on nontarget populations are generally temporary (39).…”

Bats from different foraging guilds prey upon the pine processionary moth

“…In addition to its effect on tree growth (Jactel et al, 2006; Kanat, Alma & Sivrikaya, 2005), the urticant setae of the larvae also are a health hazard for humans and animals (Moneo et al, 2015). Current control methods (2009/128/EC) largely involve direct application of a preparation containing spores and toxins from the bacterium Bacillus thuringiensis kurstaki , which disrupts midgut epithelial cells of arthropod larvae, with limited consequences on non-target lepidopterans (Rastall et al, 2003; Boulton et al, 2007). While this treatment has short term negative effects on the pest populations, the control treatment does not seem to suppress cyclical outbreaks, promoting a debate over the suitability of spraying as an efficient management action (Cayuela, Hódar & Zamora, 2011).…”