A sticky screen trap for surveying aerial populations of the ambrosia beetle Platypus quercivorus (Coleoptera: Platypodidae)

Abstract

We developed a sticky screen trap to investigate the aerial population of the ambrosia beetle Platypus quercivorus (Murayama). The beetle is believed to be an important vector of an unidentified ambrosia fungus belonging to the genus Raffaelea that causes oak dieback in Japan. The trap was made of a 1-m² of polyethylene screen, 2.4 mm×2.6 mm mesh size, to obtain light, wide traps that allow air movement through the intercepting surface. An adhesive substance (Kinryusupurei, Maruzen Co. Ltd.) was sprayed on both sides of the polyethylene screen once a week. In 1999, 18 traps were set in the understory of a secondary oak forest in Ishikawa, Japan. Adults of P. quercivorus were captured from 6 July to 22 November. A total of 24,225 beetles was captured by the traps. The average number per trap was 1,345.8 (range, 353–3,408), which was greater than the trap catches in any of the previous studies. Our results showed that this trap was useful for analyzing the seasonal changes in the aerial population of P. quercivorus and its directional movement. On each surface of the traps, the distribution of the trapped adults was aggregative, that is, some parts of the trap had many beetles and others had few or none. Although in a given trap the distribution of beetles on the uphill-facing surface was spatially correlated with that on the downhill-facing surface, the parts of the trap in which the beetles tended to be caught varied widely among traps and among collecting dates. Significantly more P. quercivorus were captured on the downhill-facing surface than on the uphill-facing surface. On the downhill-facing surface of the traps, more adults were caught in the bottom half of the traps than in the top half of the traps, but on the uphill-facing surface, the catches in the bottom half of the traps were not significantly different from the catches in the top half of the traps.