Abstract
It is well-known that the severe damages to Japanese red and black pine in pine stands throughout western Japan have been attributed to the attack of nematode (Bursaphelenchus lignicolus) and sawyer (Monochamus alternatus).
A Loblolly pine (P. taeda) at Shirahama Experiment Station in Wakayama prefecture and a Lace-bark pine (P. bungeana) at Kamigamo Experiment Station in Kyoto prefecture were withering respectively in autumn, 1974 and 1975, and these stems were infested with Japanese pine sawyer.
DBH and tree height of Loblolly pine were 13.2cm and 13.0m in 1974, and the adults of Monochamus alternatus emerged from its stem in 1975. In the case of Lace-bark pine, its DBH and height were 12.6cm and 7.4m in 1975, and the adults emerged in 1976.
Size of Monochamus alternatus adults emerged from these stems was measured with length of body and elytron, and the entrance of gallery, pupal cell and emerged hole was observed in 1975 and 1976, respectively.
The results obtained from the investigations were as follows:
1. The fed wound by longicorn had been marked on 1～5 years old branches in Loblolly pine, and 1～7 years old branches in Japanese black pine. The total numbers of the fed wound on twigs or branches were 243 in a Loblolly pine and 231 in a Japanese black pine, especially there were many fed wound on 1～3 years old branches (Fig. 2).
Its width was 2～10mm in Loblolly pine and 3～10mm in Japanese black pine, and fed wound of 4～6mm width was about 78% in the former and about 70% in the latter. The longest adult feeding mark was 143mm length in the Loblolly pine, and 135mm length in the Japanese black pine. But there were many less than 30mm in length (Fig. 3).
2. The area of fed wound on twigs or branches was in proportion to the product of length and width. Namely, the area was 0.886 times of the product of length and width (Fig. 4), it was estimated that the total wound area was 235cm² in a Loblolly pine, and 305cm² in a Japanese black pine. In the case of the mean area of adult feeding marks on branches of same age, the younger the branch age was, the larger the mean area of fed wound was.
3. After the larvae of Monochamus alternatus bored a hole into xylem, the sawyers died about 45% before the adults emerged from xylem (Fig. 8). The emerged hole was in average of whole stem 0.21 in Loblolly pine, 0.15 and 0.24 in Japanese black pine and 0.12 in Japanese red pine per 100cm² of stem surface.
4. Monochamus alternatus adults emerged from May 25 to July 22 from Loblolly pine stem in 1975 and emerged from May 25 to July 2 from Japanese black pine in 1976 at Shirahama, and the emergence of longicorn was observed from June 22 to July 14 in 1976 at Kamigamo (Fig. 9).
5. Size of adult (length of body and elytron) emerged at Kamigamo was larger than that emerged at Shirahama (Fig. 10 and 11, Table 1).
6. In the case of Loblolly pine and Lace-bark pine infested with Monochamus alternatus, height growth in withering year was similar to annual growth on height, and also diameter growth amounted to half of annual growth on DBH.
7. The nematode (Bursaphelenchus lignicolus) was recovered from Monochamus alternatus adult emerged from Loblolly pine and Lace-bark pine.
8. It seemed that Loblolly pine and Lace-bark pine were withering by the influences of the nematode and were attacked by longicorns.
