Abstract
Research Highlights: We found that the initial attack location together with the aggregation pheromones played an important role in mediating the aggressive behavior of T. brevipilosus on P. kesiya. Background and Objectives: T. brevipilosus was identified as an aggressive species, which possesses the ability to kill live, healthy P. kesiya. In this scenario, we study the top-down attack pattern of T. brevipilosus on P. kesiya during the entirety of the reproductive period. Materials and Methods: We investigated the phenology of trunk attack on P. kesiya over a period of three years in Pu’er City, China. The hindguts extracts of the females and males T. brevipilosus were analyzed by coupled gas chromatography-mass spectrometry (GC-MS). The candidate aggregation pheromone compounds of T. brevipilosus were determined through electrophysiology experiments (electroantennographic detection, EAD and electroantennography, EAG), laboratory olfactometer bioassays, and field trapping. Results: we found that the pioneer beetles preferentially infested the crown of P. kesiya at the early stage of attack following spring flight with the later arriving beetles selectively attacking the lower area of the trunk to avoid intraspecific competition and better utilize limited resources, which exhibits a top-down attack pattern. During gallery initiation, the beetles release aggregation pheromones to attract conspecifics to conduct a mass attack. The chemical analyses indicated that the hindgut extracts of gallery-initiating beetles contained a larger amount of myrtenol, cis-verbenol, trans-verbenol, and verbenone. Myrtenol and trans-verbenol were identified as candidate aggregation pheromone compounds. In addition, a blend of these two components with S-(−)-α-pinene and S-(−)-β-pinene attracted more T. brevipilosus individuals in a field bioassay. Conclusions: We concluded that the preference for the initial attack location together with the aggregation pheromones played an important role in mediating the top-down attack pattern of T. brevipilosus on P. kesiya.
Highlights
Species of Tomicus are noteworthy for their damage to pine forests in Europe, North America, Asia, and North Africa [1,2,3,4]
We concluded that the preference for the initial attack location together with the aggregation pheromones played an important role in mediating the top-down attack pattern of
It is reasonable to assume that the initial location preference along with the aggregation pheromones regulate the top-down attack pattern
Summary
Species of Tomicus are noteworthy for their damage to pine forests in Europe, North America, Asia, and North Africa [1,2,3,4]. In Southwestern China, these bark beetles are the main cause of extensive tree damage [5,6,7,8,9] They attack the fresh shoots of living trees for maturation feeding, which can weaken the host and curtail growth [10]. Tomicus brevipilosus (Eggers) is native to Asia and has been reported from China, India, Japan, Korea, and the Philippines [15,16]. This bark beetle is known to infest several Pinus species, including Pinus yunnanensis Franch. T. brevipilosus, together with other two Tomics species
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