Effects of leaf conditions and flight activity on the behaviour of Platypus quercivorus (Murayama) (Coleoptera: Platypodidae)

Abstract

The important role of semiochemicals in the interactions between plants and insects has been extensively investigated. The volatiles produced by oak trees are thought to attract the ambrosia beetle Platypus quercivorus (Murayama), which causes wilt disease in Quercus trees, resulting in widespread damage. In the present study, we hypothesized that (a) P. quercivorus is attracted to the leaf volatiles emitted by host trees and (b) the response of P. quercivorus to leaf volatiles is affected by flight. An experiment was performed to survey the preferences of both sexes of P. quercivorus for the leaf volatiles of Quercus crispula Blume at various stages of leaf deterioration, represented by different number of days after cutting. Additionally, the effect of flight on both sexes was evaluated by testing the beetle flight on a flight mill. The results showed that P. quercivorus was attracted to the volatiles emitted from fresh leaves and was not attracted to those emitted from dry leaves. This suggests that leaf volatiles from healthy hosts are primary attractants for P. quercivorus. Further, males exhibited increased olfactory responses to leaf volatiles as their flight duration increased, whereas the opposite pattern was observed in females. These results suggest that the different ecological roles of the sexes contribute to differences in olfactory responses. K E Y W O R D S flight mill, host selection, olfactory response, Quercus crispula, volatile, Y-tube olfactometer

Platypus quercivorusambrosia beetles use leaf volatiles in host selection

“…Flight experiments were conducted at the room conditions similar to those used for the olfactory bioassays at 25 °C and 100 lux light intensity. As in our previous study (Pham et al, 2019), the objective of flight experiments was to observe the changes in behavioral responses of P. quercivorus to leaf volatiles caused by flight, and not to estimate the flight capacity of the beetle. Therefore, we did not set a rule for how long beetles were attached to the flight mill before detachment.…”

“…Newly emerged beetles were used on each day of the experiment, and different beetles were used to test the responses to each of the tree species. In our previous study, we conducted similar assays using flight mill and Y-tube olfactometer and showed that the handling of beetles, attachment to and detachment from the flight mill, did not affect the response of beetles to leaf volatiles (Pham et al, 2019). One or two individual seedlings were used for each tree species throughout the experiments.…”

“…Using olfactometer bioassays, it has been shown that the ambrosia beetle Xyleborus glabratus Eichhoff is highly attracted to the chemical volatiles emitted by the intact leaves of their host trees, but weakly attracted to those of the non‐host trees (Martini et al, 2015). We reported that P. quercivorus was significantly attracted to the volatiles emitted from leaves of Quercus crispula Blume (Fagaceae), one of the oak species most susceptible to infestation by this beetle (Pham et al, 2019). However, in that study, we used leaves detached from trees as volatile sources, and could not eliminate the possibility that beetles were attracted to volatiles emitted from the cut ends of the leaves.…”

“…A study using Q. crispula leaves showed that P. quercivorus responded to host leaf volatiles, and the response changed in the course of flight (Pham et al, 2019). Another study of P. quercivorus revealed that its positive phototaxis declined after flight (Pham et al, 2017).…”

Use of Semiochemicals for the Management of the Redbay Ambrosia Beetle

“…Most importantly, X. glabratus is attracted to leaf volatiles of redbay and swamp bay but not by leaf volatiles of non-hosts, and this attraction occurs even if the tree is undamaged. This finding is not peculiar, as other wood borers, including bark and ambrosia beetles, may also be attracted to leaf volatiles from their host [ 47 , 48 ]. The profile of redbay leaf volatiles corresponds to the monoterpene portion of the wood volatiles that also contain highly attractive sesquiterpenes [ 38 ].…”