Responses of nontarget lepidoptera to foray 48B® Bacillus thuringiensis var. kurstaki on Vancouver Island, British Columbia, Canada

Abstract

Impacts of a gypsy moth (Lymantria dispar) eradication program on native, nontarget Lepidoptera were assessed in 1999, on southeastern Vancouver Island (BC, Canada). The microbial insecticide Bacillus thuringiensis var. kurstaki (Btk) was applied aerially over two areas totalling 12,805 ha on May 8, May 19, and June 8, 1999, at a dosage of 50 billion international units in 4.0 L/ha. Lepidoptera were collected from two host plant species: Garry oak (Quercus garryana) and common snowberry (Symphoricarpos albus). Lepidopteran larvae were collected from common snowberry foliage at 24 urban parks and from Garry oak foliage at 28 oak-dominated habitats, representing 12 and 14 replicates, respectively, of two treatments: unsprayed (reference) and sprayed (treatment). Prespray data were collected from March 25 to May 6 for S. albus, and from April 26 to May 6 for Q. garryana. Postspray data were collected from May 10 through June 15 for S. albus and from May 10 to July 6 for Q. garryana. The 15 most abundant lepidopteran species were analyzed statistically. However, the majority of species were collected infrequently, and, therefore were pooled for statistical analysis. After the Btk spray applications, 11 of the individual species and groups of uncommon species were found to be significantly less abundant in the treatment sites than in the reference sites. The effects of sample date were statistically significant on almost all groups of Lepidoptera analyzed, both before and after Btk spray applications, indicating temporal variation in lepidopteran abundance. Significant variation in diversity of members of the Lepidoptera, as a result of Btk spray application, was not detected on S. albus or Q. garryana. However, results showed significant variation in lepidoptera richness and abundance on both host plant species.

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

“…In general, Lepidoptera in the treatment and reference sites were not significantly different during the prespray period in 1999 in terms of the abundance and species richness of larvae on snowberry and Garry oak [18]. This result should not be interpreted as proof of equality among the sites because the prespray ANOVA models contained fewer samples and were therefore of lower power than the postspray ANOVA models.…”

“…Monitoring of nontarget Lepidoptera on Garry oak ( Quercus garryana Douglas) and common snowberry ( Symphoricarpos albus [L.]) in 1999 confirmed that the eradication program was harmful to at least nine species of nontarget Lepidoptera as well as groups of uncommon species [18]. In addition, Lepidoptera species richness was reduced on both plant species [18].…”

“…Monitoring of nontarget Lepidoptera on Garry oak ( Quercus garryana Douglas) and common snowberry ( Symphoricarpos albus [L.]) in 1999 confirmed that the eradication program was harmful to at least nine species of nontarget Lepidoptera as well as groups of uncommon species [18]. In addition, Lepidoptera species richness was reduced on both plant species [18]. Although statistically significant ( p ≤ 0.05), the previously mentioned impacts of the Btk applications do not provide information about the ecological importance of the disturbance, which is, ultimately, the major environmental concern regarding the use of Btk .…”

Wood production, wood technology, and biotechnological impacts

“…Monitoring in forests in British Columbia treated with Btk to control the western spruce budworm, for example, revealed negative effects also on nontarget Lepidoptera (Boulton et al 2002, Boulton 2004, Boulton & Otvos 2004. To exclude unwanted effects by freely spraying on uninvolved insects, newer developments make use of the bacterial endotoxin genes.…”

Short communication. First field assessment of Bacillus thuringiensis subsp. kurstaki aerial application on the colony performance of Apis mellifera L. (Hymenoptera: Apidae)

“…There is a lack of studies developed to evaluate the impact of Btk aerial application on A. mellifera, although there are some studies developed to evaluate the impact on many groups of animals, such as non-target Lepidoptera (Boulton, 2004), non-target soil organisms (Addison & Barker, 2006) and songbirds (Sopuck et al, 2002). The effect on bees have been developed in some f ield and laboratory studies, although the majority of the experiments tested the toxicology of Btk used in genetically modif ied crops (O'Callaghan et al, 2005;Duan et al, 2008).…”