Abstract
Choristoneura fumiferana (Clemens) (Lepidoptera: Tortricidae) is a defoliating pest in Canada and the northeastern United States. Given its important ecological and economic effects in affected regions, several direct management techniques have been developed, including the application of the insect growth regulator tebufenozide (Mimic™, RH-5992) to feeding larval stages. While the effectiveness of tebufenozide, in this capacity, is understood, management programs of other lepidopteran pests have demonstrated the effectiveness of tebufenozide application when utilized against other life stages. Here, we investigated the toxicity of topically-applied tebufenozide to C. fumiferana pupae to determine if such a strategy could be feasible. We observed significant dose-dependent decreases in the likelihood of adult emergence, increases in the likelihood of pupal death or adult deformity at eclosion, and significant decreases in mean adult longevity. Estimated LD 50 (lethal dose) values for adult male and female C. fumiferana treated as pupae ≤ 4 days after pupation were approximately 1–3 and 2–3.5% ACI (active commercial ingredient) respectively. Estimated L-SD (lethal-sublethal) 50 doses for adult male and female C. fumiferana treated as pupae ≤4 days after pupation were <1, and <2% ACI, respectively. Mating success was also significantly lower in mating pairs containing adults treated as pupae. Although, the amounts required to cause appreciable pupal mortality were much higher than those currently applied operationally in the C. fumiferana system, our study illustrates the potential of tebufenozide to utilized against additional developmental stages in other lepidopteran pests.
Highlights
Choristoneura fumiferana (Clemens) (Lepidoptera: Tortricidae) is a significant eruptive defoliator of balsam fir [Abies balsamea (L.) Mill.] and white spruce [Picea glauca (Moench) Voss] in Canada and the United States
Eggs are laid on foliage beginning in mid- to late-summer with first-instar larvae hatching from eggs ~10 days afterwards
The likelihood of adult eclosion was significantly affected by the topical application of tebufenozide to pupae in both male and female individuals (Figure 1, Table 2)
Summary
Choristoneura fumiferana (Clemens) (Lepidoptera: Tortricidae) is a significant eruptive defoliator of balsam fir [Abies balsamea (L.) Mill.] and white spruce [Picea glauca (Moench) Voss] in Canada and the United States. The life cycle of this species is typically one-year in length [1,2]. Eggs are laid on foliage beginning in mid- to late-summer with first-instar larvae hatching from eggs ~10 days afterwards. First-instar larvae are primarily non-feeding, and form hibernacula within which they overwinter and moult. Second-instar larvae emerge in the spring and establish themselves on 1-year-old foliage. After moulting into a third-instar, they begin feeding on current-year foliage where available. Most of the feeding damage that is associated with the larval stage is caused by late-instar larvae (L4 –L6 )
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