Spruce budworm, Choristoneura fumiferana Clem. (Lepidoptera: Tortricidae), is the most severe defoliator of Pinaceae in Nearctic boreal forests. Three tools widely used to guide large-scale management decisions (year-to-year defoliation maps; density of overwintering second instars [L2]; number of males at pheromone traps) were integrated to derive pheromone-based thresholds corresponding to specific intergenerational transitions in larval densities (L2i → L2i+1), taking into account the novel finding that threshold estimates decline with distance to defoliated forest stands (DIST). Estimates of thresholds were highly variable between years, both numerically and in terms of interactive effects of L2i and DIST, which limit their heuristic value. In the context of early intervention strategy (L2i+1 > 6.5 individuals per branch), however, thresholds fluctuated within relatively narrow intervals across wide ranges of L2i and DIST, and values of 40–200 males per trap may thus be used as general guideline.

中文翻译：

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云杉芽虫基于信息素的幼虫阈值推导计算到落叶林分的距离

云杉芽虫，Choristoneura fumiferana Clem。（鳞翅目：Tortricidae），是近北寒带森林松科最严重的落叶者。广泛用于指导大规模管理决策的三种工具（逐年落叶图；越冬二龄龄 [L2]；信息素陷阱中的雄性数量）被整合，以得出与特定代际过渡相对应的基于信息素的阈值。幼虫密度（L2i → L2i+1），考虑到阈值估计随着与落叶林分（DIST）的距离而下降的新发现。阈值的估计值在年份之间存在很大差异，无论是在数值上还是在 L2i 和 DIST 的交互影响方面，这都限制了它们的启发式价值。然而，在早期干预策略的背景下（L2i+1 > 6.5 个人/分支），