Host-tree conditions affecting the oviposition activities of the woodwasp,Sirex nitobei Matsumura (hymenoptera: Siricidae) |
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Authors: | Hideshi Fukuda Naoki Hijii |
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Institution: | (1) Laboratory of Forest Protection, School of Agricultural Sciences, Nagoya University, 464-01 Nagoya, Japan;(2) Present address: Japan Society for the Promotion of Science, Japan |
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Abstract: | Experiments were conducted to elucidate how the oviposition activities ofSirex nitobei Matsumura could be affected by different conditions of the host trees, using logs from felled healthy trees and the dead
and living trees ofPinus densiflora Sieb. et Zucc. According to days elapsed after tree-felling, the proportions of oviposition defined as the proportion of
eggs laid to the potential fecundity of a female during her lifetime, could be divided arbitrarily into three groups. The
proportions of oviposition on the logs within 0–3 days after felling,i.e fresh logs, varied greatly from log to log, and about half of female adults showed proportions of oviposition under 50% (mean
±SD: 39±32%). However, all the females that oviposited on the logs 4–24 days after felling,i.e. intermediate logs, invariably showed proportions of oviposition over 50% (88±1.5%). On the other hand, proportions of oviposition
in most of the females that oviposited on the logs over 25 days after felling,i.e. old logs, were less than 50% (26±17%). The proportions of oviposition were significantly different between intermediate logs
and old logs. The mean proportion of oviposition on living trees and that for dead trees were 45 and 58%, respectively. Thus,S. nitobei in the field would exhibit its preference for weakened trees ofP. densiflora as oviposition sites, as it did for the logs 4–24 days after felling in this study. |
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Keywords: | host-tree condition oviposition activity Pinus densiflora Sirex nitobei woodwasp |
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