云南切梢小蠹对云南松树的蛀干危害及致死机理

蛀干危害是云南切梢小蠹致死云南松树的关键环节。通过控制云南切梢小蠹蛀干密度,对云南切梢小蠹在自然条件下蛀干行为与危害进行了首次探讨。结果表明,云南切梢小蠹蛀干密度与云南松存活率呈负相关,蛀干密度直接决定云南松死亡或存活。研究发现,蛀干密度115坑/m2是云南松树的最低致死密度阈值,云南松树在蛀干密度低于26.4坑/m2情况下存活,在26.4-115坑/m2有部分存活,超过115坑/m2以后将被害致死。云南切梢小蠹对树干攻击形成有卵和无卵两类坑道。形成无卵坑道的蛀干攻击可导致树势衰弱,形成有卵坑道的蛀干危害严重破坏了韧皮组织,是导致云南松死亡的直接原因。

On trunk attacks and the killing mechanism of Tomicus yunnanensis (Coleoptera: Scolytinae) on Pinus yunnanensis trees

Trunk attacks by the pine shoot beetle \Tomicus yunnanensis Kirkendall and Faccoli (Coleoptera: Curculionidae: Scolytinae)\] on Yunnan pine (Pinus yunnanensis Franchet) are regarded as the principal cause of tree death. The current studies were conducted under field conditions by controlling the beetle densities that were allowed to attack the trunk. The results showed a positive relationship between attack density and mortality rate of Yunnan pine trees. The field studies demonstrated that an attack density of 115 tunnels/m2 of bark surface area was the threshold for mortality of Yunnan pine trees. All Yunnan pine trees survived when attacked by beetle densities below 26.4 tunnels/m2, but only a portion survived at the attack densities between 26.4-115 tunnels/m2. All trees were killed at the attack densities higher than 115 tunnels/m2. These attack densities were calculated using both galleries where the parent laid eggs and where no eggs were laid. The maternal galleries without eggs appeared related to host tree resistance. Trunk attacks where no eggs are laid can apparently still weaken pine trees, while attacks with eggs can cause more severe damage to the phloem tissue, and thus was regarded as the critical factor in causing mortality of Yunnan pine trees.