A technical guide to installing beetle traps in the upper crown of trees

Abstract

The upper tree crown represents an important habitat for many insect herbivores but, being much less commonly sampled than the understory, remains poorly understood. Here, we provide detailed instructions and quantitative cost (time) estimates for setting up insect traps in the upper crown of trees using methods adapted from tree-climbing canopy ecologists. In a sample experiment, we recorded the time it took for a two-person crew (“shooter” and assistant) to install traps in the upper crown vs. the understory of a mature stand of eastern hemlock (Tsuga canadensis (L.) Carriere (Pinaceae)), with trees 18–24 m tall. A crew with 3 yrs experience with these methods took an average of 5 min 38 s (range 3 min 13 s to 17 min 39 s) to install a trap in the upper crown, whereas an inexperienced field technician took an average of 7 min 1 s per tree (range 5 min 47 s to 9 min 19 s). In comparison, it required on average only 1 min 19 s (experienced) and 1 min 48 s (inexperienced) to install a trap in the understory. We used an average of 50 m (range 31–61 m) of rope per crown trap compared with 4.5 m (range 3.5– 5.5 m) per understory traps, which translated to a difference in cost of CDN$2.50 per trap, based on 2013 prices. Our results demonstrate that it costs more in time and materials to place traps in the upper crown vs. the understory, but the additional costs are modest. Furthermore, we show that an inexperienced person can learn how to set high traps quickly by following the step-by-step instructions laid out in this paper. We hope this both encourages and enables more use of traps in the upper crown as well as the understory when surveying for species of barkand wood-boring beetles and other forest insects.