Do visual cues associated with larger diameter trees influence host selection by Tetropium fuscum (Coleoptera: Cerambycidae)?

Abstract

Tetropium fuscum (Fabricius) (Coleoptera: Cerambycidae) is an invasive phloeophagous beetle established in Atlantic Canada that infests stressed and moribund Picea Dietrich (Pinaceae) species. Successfully colonised trees tend to be large in diameter (>10 cm diameter at breast height), but whether diameter influences host selection, larval performance, or both, is unknown. We tested the hypothesis that T. fuscum host selection is influenced by visual cues associated with tree diameter by counting the number of adults landing on 29 Picea rubens Sargent ranging in diameter at breast height from 12.2 to 37.5 cm. All trees were wrapped with sticky bands and baited with aggregation pheromone and host volatiles to make them equally attractive with regard to olfactory cues. We found significant positive relationships between the mean number of T. fuscum per sticky band and tree diameter, and also between phloem thickness and tree diameter. We conclude that the positive association between host diameter and T. fuscum infestation is at least partially due to the positive influence of diameter on landing rate, and that this may benefit the beetle because larger diameter trees have more food for developing larvae. However, there was no effect of tree diameter on the mean number of adults per m2 of sticky band and thus no evidence that T. fuscum actively selects larger diameter hosts based on visual cues. The positive relationship between landing rate and host diameter may simply be due to greater chances of airborne beetles being passively intercepted on larger versus smaller trees.

Wrong landing on a non‐host occurs under the canopy of a host: The presumed path of the ambrosia beetle Platypus quercivorus to approach its host

“…was not significant, showing that thicker trees are more likely to be hit by flying beetles (Nelson et al, 2017). However, this possibility can be ruled out in our study because we attached sticky sheets of the same size to all the trees, meaning that the number of trapped beetles was equivalent to the number per unit area.…”

Characteristics of Trees Infested by the Invasive Primary Wood-Borer Aromia bungii (Coleoptera: Cerambycidae)

“…Previous research on other Cerambycidae beetles also reported that infested host trees were larger in size [14,15,37]. In terms of host selections, in the case of Tetropium fuscum (Fabricius) (Coleoptera: Cerambycidae), tree size positively affects the landing rate; this relationship is thought to be due to the difference in the chances of adults being passively intercepted on larger versus smaller trees [15]. This passive effect related to tree size is also suggested in the mathematical model for encounter rates in the process of random searching for host trees in tree-boring bark beetles [38].…”

“…We showed that larger trees were more susceptible to infestation. Previous research on other Cerambycidae beetles also reported that infested host trees were larger in size [14,15,37]. In terms of host selections, in the case of Tetropium fuscum (Fabricius) (Coleoptera: Cerambycidae), tree size positively affects the landing rate; this relationship is thought to be due to the difference in the chances of adults being passively intercepted on larger versus smaller trees [15].…”

“…In relation to tree-boring cerambycid beetle infestations, previous studies have focused on tree characteristics, such as tree size [13][14][15], tree species [16], tree vigor [17][18][19], bark roughness [20,21], and micro-climate [22]. Recent observational reports have suggested that host trees that are larger in size [23][24][25], more mature [3], more stressed [3], and with rolled up or cracked bark [26] are more prone to being attacked by A. bungii; however, the factor and/or combinations of factors that decisively affect infestation in the field are unclear.…”

Size and location of host‐plant shape the spatial pattern of forest insect

“…Therefore, their movements are determined primarily by the size and distribution of potential host trees within their habitat (Balogh et al, 2020). Larger diameter trees have more food for developing larvae, resulting in a positive influence of diameter on landing rate (Nelson et al, 2017). Our results are consistent with these previous studies, suggesting that bigger trees harbour more insects and suffer more attacks.…”