我国新上升的四种吉丁甲科蛀干害虫记述

【目的】为准确识别和鉴定目前国内新上升的4种吉丁甲科蛀干害虫,便于生产上对其开展有效的监测和防治。【方法】将收集到的标本通过比对文献以及与国内外同行讨论、标本检视、生物学危害特征观察等方法进行比较和分析。【结果】对中国新记录的沙蒿尖翅吉丁Sphenoptera sp.和柠条窄吉丁Agrilus sp.鉴定到种,对栎窄吉丁Agrilus cyaneoniger Saunders体色多型现象进行了描述,对弗氏窄吉丁Agrilus fleischeri Obenberger的形态特征进行了再描述,并根据4种吉丁甲科害虫生物学特性和危害特征提出了相应的防治建议。【结论】沙蒿尖翅吉丁学名为Sphenoptera canescens Motschulsky,柠条窄吉丁学名为Agrilus unguiculosus Obenberger;栎窄吉丁体二色型主要分布于中国东北,南方分布的主要为全体黑色型;弗氏窄吉丁的分布范围在不断扩大。对这些具有潜在高风险的蛀干类吉丁甲害虫,加强检疫和营林措施防止其扩散传播是非常必要的,保护天敌有助于抑制其种群数量快速上升,局部暴发时采取化学防治也是必要的应急手段。     

我国五种重要吉丁虫学名订正及再描述(鞘翅目:吉丁甲科)

【目的】吉丁甲类昆虫是我国重要的农林害虫,但多年来国内文献资料包括一些高校教科书中存在诸多学名问题,如国际上已修订的学名国内长期未更新、错误鉴定、同物异名、种名误记等。本文对我国5种重要吉丁虫进行学名修订。【方法】本研究基于多年来积累的吉丁虫标本,通过比对文献以及与国内外同行讨论、标本检视、解剖生殖器、生物学危害特征观察等方法,对我国5种重要吉丁虫的形态和生物学特征进行比较和分析。【结果】重新描述了5种重要吉丁虫的主要形态特征,并记述了其分布范围、寄主植物、危害习性等,明确了金缘吉丁、杨十斑吉丁、杨五星吉丁、核桃缘吉丁和柳窄吉丁的正确学名分别为Lamprodila limbata(Gebler),Trachypteris picta picta(Pallas),Capnodis miliaris metallica Ballion,Meliboeus ohbayashii primoriensis(Alexeev)和Agrilus pekinensis pekinensis Obenberger。【结论】本研究厘订了我国吉丁甲文献中长期存在的一些学名错误,对解决我国部分吉丁甲类昆虫在研究和防治应用中的学名混乱问题具有重要意义。     

沙蒿尖翅吉丁生物学特性的研究

沙蒿尖翅吉丁Sphenoptera sp.是黑沙蒿上主要的钻蛀性害虫,引起沙蒿长势下降甚至死亡。对其形态特征及生物学特征的观察和研究结果表明:该虫在宁夏1年发生1代,以各龄幼虫在被害沙蒿根部越冬。老熟幼虫于4月中下旬开始化蛹,成虫始见于5月上旬,羽化期有两个高峰,分别是5、6月下旬。成虫羽化后并不马上离开蛹室,2～3d后咬出羽化孔,钻出蛹室。成虫需取食沙蒿叶片补充营养,2～7d后开始交尾,集中在13:00-16:30,雌雄成虫均可多次交尾。幼虫常多头聚集危害同一株沙蒿。大多数老熟幼虫在距坑道端部5mm处的根部化蛹,少数在直径为5～8mm的较粗的枝条内化蛹。沙蒿尖翅吉丁幼虫期有2种寄生性天敌,蛹期和成虫期各有1种寄生性天敌。     

松阴吉丁对不同树种的选择

【目的】松阴吉丁Phaenops yin KubánBily是危害油松的重要蛀干害虫,研究其成虫对不同树种的行为趋向反应,可为配制人工植物源引诱剂,利用化学生态手段开展有效防控奠定基础。【方法】室内利用养虫笼观察松阴吉丁对不同树种的选择行为,采用Y-型嗅觉仪和单盒单头饲养方式进一步测试松阴吉丁对于具引诱活性的植物气味源的趋性反应及取食量。【结果】松阴吉丁成虫在阔叶树毛白杨、国槐、垂柳的枝条上既无着落现象,也无取食现象;在雪松枝条上偶有着落现象,但无取食痕迹;在油松及白皮松枝条上均有着落和取食现象。松阴吉丁雌性成虫对白皮松针叶、油松针叶以及油松韧皮部的趋性反应与空白对照相比均达到显著水平,其对白皮松针叶的趋性反应及取食量均大于油松针叶,但差异不显著。雄性成虫对白皮松针叶、油松针叶的趋性反应与空白对照相比均达到显著水平,对油松韧皮部的趋性反应大于空白对照,但差异不显著。与白皮松针叶相比,雄虫更趋向于油松针叶气味源,但差异不显著,其对油松针叶的取食量也明显高于白皮松针叶,差异达到显著水平。【结论】松阴吉丁不喜阔叶树。白皮松针叶和油松针叶均能引诱松阴吉丁雌雄成虫,且伴有取食现象。野外尚未发现松阴吉丁危害白皮松,因此白皮松可能是松阴吉丁的潜在危害寄主。另外,在防控松阴吉丁时,除利用油松和白皮松的挥发性成分配制植物源引诱剂外,可考虑采用阔叶树中对试虫具有拒避作用的挥发性物质配制拒避剂,以期更好的利用"推-拉"理论,有效防控松阴吉丁。     

松梢隐翅虫林间种群动态

【目的】研究松梢隐翅虫Placusa pinearum林间种群分布及年消长动态,为进一步研究其作为载体昆虫携带天敌开展微红梢斑螟Dioryctria rubella生物防治提供依据。【方法】2013—2014年,对江苏、安徽地区4个林分进行调查,比较林分、树种、虫害梢直径、蛀道长度、微红梢斑螟虫态对松梢隐翅虫分布的影响,分析其年消长动态。【结果】松梢隐翅虫在不同林分中的分布率:安徽明光老嘉山林场>江苏句容下蜀林场>安徽明光管店松林>安徽明光张八岭松林;在不同树种虫害梢内分布率:马尾松Pinus massoniana>火炬松P.taeda>黑松P.thunbergii。松梢隐翅虫在虫害梢蛀道内的分布与虫害梢直径与蛀道长度显著相关(P<0.01),与微红梢斑螟虫态相关不显著(P>0.05)。松梢隐翅虫主要分布于虫害梢直径4.22~15.36 mm、蛀道长度23.2~354.6 mm的蛀道内,随着虫害梢直径和蛀道长度的增加,虫口密度、分布率呈上升趋势;松梢隐翅虫在各龄微红梢斑螟幼虫及蛹的蛀道内均有分布,3龄幼虫蛀道内的虫口密度及分布率较低。成虫几乎全年可见,盛期为5—7月和9—11月,幼虫盛期为5—8月。【结论】松梢隐翅虫林间种群分布以及年消长主要受微红梢斑螟幼虫数量及其特定生境(微红梢斑螟蛀道)的影响,成虫采集宜在5—7月和9—11月进行。     

松梢隐翅虫林间种群动态

【目的】研究松梢隐翅虫Placusa pinearum林间种群分布及年消长动态,为进一步研究其作为载体昆虫携带天敌开展微红梢斑螟Dioryctria rubella生物防治提供依据。【方法】2013—2014年,对江苏、安徽地区4个林分进行调查,比较林分、树种、虫害梢直径、蛀道长度、微红梢斑螟虫态对松梢隐翅虫分布的影响,分析其年消长动态。【结果】松梢隐翅虫在不同林分中的分布率:安徽明光老嘉山林场江苏句容下蜀林场安徽明光管店松林安徽明光张八岭松林;在不同树种虫害梢内分布率:马尾松Pinus massoniana火炬松P.taeda黑松P.thunbergii。松梢隐翅虫在虫害梢蛀道内的分布与虫害梢直径与蛀道长度显著相关(P0.01),与微红梢斑螟虫态相关不显著(P0.05)。松梢隐翅虫主要分布于虫害梢直径4.22~15.36 mm、蛀道长度23.2~354.6 mm的蛀道内,随着虫害梢直径和蛀道长度的增加,虫口密度、分布率呈上升趋势;松梢隐翅虫在各龄微红梢斑螟幼虫及蛹的蛀道内均有分布,3龄幼虫蛀道内的虫口密度及分布率较低。成虫几乎全年可见,盛期为5—7月和9—11月,幼虫盛期为5—8月。【结论】松梢隐翅虫林间种群分布以及年消长主要受微红梢斑螟幼虫数量及其特定生境(微红梢斑螟蛀道)的影响,成虫采集宜在5—7月和9—11月进行。     

取食和交配对苹小吉丁飞行能力的影响

【目的】苹小吉丁Agrilus mali是一种严重危害苹果树的钻蛀性害虫。本研究旨在明确苹小吉丁的飞行扩散能力及对其飞行能力产生影响的关键因子。【方法】以SUN-FL型智能飞行磨系统对苹小吉丁不同日龄雌雄成虫的飞行能力进行了测定,同时评价了取食和交配情况对其飞行能力的影响。【结果】苹小吉丁飞行能力均随日龄的增加先增强后逐渐降低,初羽化的成虫飞行能力最低,11日龄成虫的飞行能力最强。雌成虫飞行能力强于雄成虫。在24 h内雌雄成虫的最长飞行距离分别为0.4165和0.3559 km;最长飞行时间分别为0.4582和0.4873 h;最大飞行速度分别为2.4639和1.8561 km/h。取食的3日龄雌成虫的平均飞行距离和平均飞行时间分别为0.047 km和0.048 h,雄成虫的分别为0.044 km和0.042 h;而未取食的雌成虫平均飞行距离和平均飞行时间仅分别为0.016 km和0.013 h,雄成虫的仅分别为0.013 km和0.012 h。交配对飞行能力的影响存在性别差异,已交配雌成虫的飞行能力要强于未交配雌成虫的,而已交配雄成虫的飞行能力却低于未交配雄成虫的。【结论】日龄对苹小吉丁成虫的飞行能力影响作用显著。取食显著提高苹小吉丁雌雄成虫的飞行能力,交配显著提高雌成虫飞行能力。     

松树蜂形态及危害特点的研究

在发生松树蜂的林场利用"五点取样法"进行调查,调查样方内树木种类、胸径大小、生长情况、蛀干害虫种类和在树干上的分布情况;同时,选取虫害木,解剖并统计不同蛀干害虫的羽化孔数量和特点,幼虫钻蛀特征和危害特点;研究松树蜂自然种群的寄主选择规律和垂直分布特点。结果表明,松树蜂在我国仅危害衰弱的樟子松,30-40年生的中龄林受害最严重,平均有虫株率为10.94%±8.67%。松树蜂产卵后的树皮表面有流树脂现象,呈点状或流泪状。同松幽天牛和吉丁危害状不同,松树蜂羽化孔呈正圆形,直径大小约为7 mm,分布在树干0-4.20 m的高度,其中90%的集中分布在0-3 m范围内。松树蜂幼虫坑道横截面为正圆形,无排粪孔,虫粪和蛀屑都呈粉末状,紧实堆满蛀道,颜色和蛀道周围颜色无明显差异。     

弗氏窄吉丁对山杨和钻天杨危害特性的差异

[目的]弗氏窄吉丁Agrilus fleischeri Obenberger是我国东北地区新发现的一种杨树蛀干害虫。为探讨该害虫的有效防治策略,指导生产上科学营林,我们调查研究了弗氏窄吉丁对本地杨树山杨Populus davidiana及外来引种杨树钻天杨Populus nigra var.italica的危害情况。[方法]试验设置了钻天杨与山杨两块纯林样地,采用完全随机取样法于两样地内各选取20株样木进行环割以诱集弗氏窄吉丁。调查两树种的自然受害和人工胁迫后的受害情况,通过解剖感虫株分析虫口密度、死亡率及天敌种类。[结果]钻天杨的自然受害株率(11.76%)显著高于山杨(0),人工环割后钻天杨和山杨的受害株率分别为90%和65%,感虫的钻天杨和山杨平均虫口密度分别为61.95头/株和34.89头/株。钻天杨树上的卵孵化率(91.78%)显著高于山杨(77.61%)。弗氏窄吉丁幼虫在钻天杨树上的蛀道长度(48.68 cm)与山杨(29.59 cm)相比差异显著。对比两树种上的蛹室,发现其长度、宽度和深度差异不明显。分析比较弗氏窄吉丁成虫羽化孔在两树种上的分布,发现在钻天杨上主要分布在1~6m的主干,山杨为1~3m。此外,两样地中弗氏窄吉丁幼虫的生态位宽度也存在不同,钻天杨林中为0.53,山杨林中仅为0.32。[结论]研究结果显示,相对于本地树种山杨而言,非本地的引种树种钻天杨更易感虫。研究结果可为生产上防治该害虫和受害林分的合理改造提供基础信息和科学依据。     

楔形潜吉丁的重描述及近似种的形态学比较(鞘翅目:吉丁科:潜吉丁族)

由于楔形潜吉丁Trachys cuneiferus Kurosawa, 1959的原始描述过于简单,且缺少鉴别特征图,本文根据2018年在广西猫儿山国家级自然保护区采集的楔形潜吉丁标本。对其进行了形态重描述,并给出了详细的鉴别特征图和标本整体图。此外,对楔形潜吉丁及近似种(莎氏潜吉丁T.saundersi Lewis, 1893、杂灌潜吉丁T.auricollis Saunders, 1873和托里诺潜吉丁T.toringoi Kurosawa, 1951)进行形态比较。结果表明,尽管纹饰高度相似,仍可根据头部和前胸背板的光泽、上唇长宽比、前胸腹板的形状、鞘翅侧缘、阳茎等特征将楔形潜吉丁与近似种区分。     

Laboratory study of conspecific avoidance by host-colonizingDendroctonus frontalis Zimm. (Coleoptera: Scolytidae)

Bark/phloem disk sandwiches (100 cm²) were colonized with one to six mating pairs of the southern pine beetle, Dendroctonus frontalis Zimm., to observe gallery construction and evaluate if avoidance behavior occurs between beetles. Frequencies of turn aways, touches, and crosses (three characteristics used to describe conspecific interaction) all increased significantly with beetle density. A threshold of three mating pairs within the 100- cm² phloem area was the density at which avoidance behavior became evident. At a threshold of five mating pairs the number of gallery crossings was significantly greater than at lower densities. Single and paired female beetles introduced into artificial galleries crossed empty neighboring galleries significantly more often than when neighboring galleries were occupied with other D. frontalis. The data suggest that D. frontalis females can regulate gallery spacing within the host through their ability to detect nearby beetles and their galleries. Possible spacing mechanisms are discussed.     

Death of vigorous trees benefits bark beetles

Bark beetles (Coleoptera: Scolytidae) are commonly associated with live host trees that are stressed, a relationship that has been attributed to lower host defenses or greater nutritional quality of these trees. However, most bark beetle species commonly inhabit freshly dead trees where induced host defenses are absent. In this study, we investigate the role of tree vigor at the time of death for pine engraver bark beetles, Ips pini (Say), breeding in freshly dead jack pine, Pinus banksiana Lamb. As indices of tree vigor, we considered tree size, phloem thickness, and several measures of recent growth rate (last year's growth increment, mean annual increment and basal area increment in the past 5 and 10 years, and periodic growth ratio). We examined the relationship between these indices in three stands, aged 60, 77, and 126 years, and found that phloem thickness, previously shown to have a strong positive effect on bark beetle reproduction, was only weakly associated with tree growth rate and inconsistently related to tree size among the three stands. To examine the effects of tree vigor on pine engraver reproduction, we felled 20 trees of various sizes from the 77-year-old stand, and experimentally established breeding males and females in 25-cm-long sections. Offspring were collected and characteristics of breeding galleries were measured. Using stepwise regression, we consistently found that indices associated with tree growth rate best explained beetle reproductive performance, as they were positively related to parental male and female establishment on logs, female reproductive success, length of egg galleries, proportion of eggs resulting in emerged offspring, and negatively related to the length of the post-egg gallery. Surprisingly, phloem thickness had no unique effect on pine engraver reproduction, except for a weak negative effect on the establishment success of parental females. The strong effect of tree vigor observed in this study suggests that substantial mortality of vigorous trees, such as caused by windthrow, can contribute to significant increases in bark beetle populations that could trigger outbreaks in living trees. Received: 3 February 1999 / Accepted: 27 April 1999     

Density-mediated responses of bark beetles to host allelochemicals: a link between individual behaviour and population dynamics

Abstract  1. Bark beetles (Coleoptera: Scolytidae) accept or reject host conifers based partly on concentrations of phloem monoterpenes. They colonise trees in aggregations, in response to pheromones that attract flying beetles to trees undergoing colonisation. A series of entry and gallery construction assays was conducted to determine whether responses by individual beetles to monoterpenes are altered by pheromones and/or the presence of other beetles.
2. Entry into the amended media by Ips pini and the length of time until entry were not influenced by the presence of aggregation pheromones.
3. Entry into amended media was influenced by the presence of other beetles on the surface of, or constructing galleries in, the substrate. The effects of alpha-pinene and limonene on host entry behaviour were mediated by the density of beetles on the surface of the assay arena, and by the density of beetles constructing galleries within the medium.
4. The percentage of beetles entering medium amended with higher concentrations of monoterpenes increased with increased density of beetles on the surface of the assay arena, until a threshold density of three or four beetles per assay arena, after which entrance rate declined.
5. The presence of other beetles constructing galleries elicited more rapid entry by the test beetles.
6. Gallery lengths were generally higher in the presence of aggregation pheromones.
7. Gallery lengths increased with increased density of beetles within the assay arena.
8. These results suggest a link between the density of bark beetles and responses of individuals. This linkage may partially explain behavioural changes observed during population eruptions.     

Behavior of male and female spruce bark beetles,Ips typographus,on the bark of host trees during mass attack

The behavior of 118 spruce bark beetles, Ips typographus,was observed on trees under colonization. Most individuals were followed from when they landed until they entered or left the tree. Both males and females spent most time inspecting crevices and searching for a place to start boring or for a hole to enter. These behaviors accounted for 87 and 70% of all behavioral acts recorded for males and females, respectively. Females entered galleries with males only after a period of pushing at the gallery entrance. Males spent on average 3 min and females 4 min on the bark before entering or leaving the tree. Thirty-three percent of the beetles eventually entered the tree, 31% flew away, 35% dropped from the host, and one beetle was eaten by a predator. The results are discussed in relation to the question of mate choice in bark beetles and to studies on attack dynamics of spruce bark beetle populations.     

Fitness consequences of pheromone production and host selection strategies in a tree-killing bark beetle (Coleoptera: Curculionidae: Scolytinae)

Timing of arrival at a resource often determines an individual’s reproductive success. Tree-killing bark beetles can reproduce in healthy trees by attacking in adequate numbers to overcome host defences that could otherwise be lethal. This process is mediated by aggregation and antiaggregation pheromones. Beetles that arrive early in such a “mass attack” must contend with undiminished tree defences, and produce enough pheromones to attract more beetles, but have a head start on gallery construction and egg-laying. Beetles that arrive late may be impeded by competition and diminishing availability of phloem, but should experience fewer costs associated with pheromone production and battling tree defences. We investigated relationships between timing of arrival, body size, pheromone production and fitness in the southern pine beetle, Dendroctonus frontalis. In field experiments, we captured beetles that arrived early (pioneers) and late on slash pine trees, Pinus elliottii, and measured pheromone amounts in their hindguts. We marked gallery entrances of beetles as they landed on a tree and measured their reproductive success after the attack terminated. We found no difference in body size or pheromone amounts between early and late arrivers. Most beetles arrived at the middle of the attack sequence, and excavated longer galleries per day than early arrivers. The number of offspring produced per day by beetles that established galleries midway through mass attack was higher than those that arrived early or very late in the sequence. Our results suggest that beetles do not exhibit adaptive phenotypic plasticity in pre-landing pheromone production, depending on the extent of previous colonisation of a host. Rather, it appears that stabilising selection favours beetles that attack in the middle of the sequence, and contributes to attack synchrony. Synchronous attack on trees is essential before population booms characteristic of tree-killing bark beetles can occur in nature.     

Oviposition behavior and reproductive success of the cerambycid Acanthocinus aedilis in the presence and absence of the bark beetle Tomicus piniperda

The influence of Tomicus piniperda (L.)(Col.:Scolytidae) attacks on Acanthocinus aedilis (L.)(Col.:Cerambycidae) (1) oviposition behavior, (2) breeding material preference and (3) reproductive success was investigated in caged pine bolts with and without egg galleries of T. piniperda. In addition, A. aedilis oviposition behavior was studied in the field. In the presence of T. piniperda attacks most A. aedilis eggs were laid through the entrance holes of the bark beetle egg galleries. In the absence of bark beetle attacks most A. aedilis eggs were laid at places where the outer bark had been damaged and the phloem was exposed. In cages, A. aedilis preferred to oviposit in bolts with bark beetle attacks. Thus, A. aedilis oviposited in all 17 of bark beetle attacked bolts but in only four of nine bolts without T. piniperda attacks. Neither the number of A. aedilis offspring nor the body size of emerging adults differed significantly between bolts attacked by bark beetles and unattacked bolts. Nor was there any significant relationship between the density of bark beetle egg galleries and the production of A. aedilis offspring.     

Suitability of native and ornamental oak species in California for Agrilus auroguttatus

Goldspotted oak borer, Agrilus auroguttatus Schaeffer (Coleoptera: Buprestidae), is a new invasive species in southern California, USA. The extent of the host range of this insect is not known, but this knowledge will have a major impact on assessment of the risks that this pest poses to oaks [Quercus spp. (Fagaceae)]. We conducted laboratory tests to determine the potential suitability of native and ornamental oak species for larvae and adults of A. auroguttatus. We infested 179 cut logs (from 163 different trees) with eggs or larvae, measured neonate survival and, after 5 months, counted feeding galleries, and noted the proportion of galleries with late instars. Initial larval survival was generally high when larvae penetrated the phloem (range: 62–98% among oak species), and low by the time larvae began to feed at the phloem/xylem interface (range: 0–25% among oak species). The majority of larvae that established a visible feeding gallery survived to the fourth instar (total of 73% for all oak species). Larval galleries were established with greater frequency in red oaks (Section Lobatae) compared with other oaks (19 vs. 7 or 4%). All red oaks tested (Q. agrifolia Née, Q. kelloggii Newberry, and Q. wislizeni A. DC.) were likely suitable hosts for larvae. Larvae were apparently able to feed on some of the other oaks (Q. chrysolepis Leibmann, Q. suber L., Q. lobata Née, and Q. douglasii Hook & Arn), although it remains unclear whether these species would be preferred hosts under natural conditions. Adult longevity and fecundity varied little by species of oak foliage fed to adults. The host range of A. auroguttatus is likely limited by suitability of oak species for the larval rather than the adult life stage. Results support published field observations that red oaks are more suitable hosts than white oaks.     

Fungus Symbionts Colonizing the Galleries of the Ambrosia Beetle <Emphasis Type="Italic">Platypus quercivorus</Emphasis>

Isolations were made to determine the fungal symbionts colonizing Platypus quercivorus beetle galleries of dead or dying Quercus laurifolia, Castanopsis cuspidata, Quercus serrata, Quercus crispula, and Quercus robur. For these studies, logs from oak wilt-killed trees were collected from Kyoto Prefecture, Japan. Fungi were isolated from the: (1) entrances of beetle galleries, (2) vertical galleries, (3) lateral galleries, and (4) the larval cradle of P. quercivorus in each host tree. Among the fungus colonies which appeared on YM agar plates, 1,219 were isolated as the representative isolates for fungus species inhabiting in the galleries based on their cultural characteristics. The validity of the visual classification of the fungus colonies was checked and if necessary properly corrected using microsatellite-primed PCR fingerprints. The nucleotide sequence of the D1/D2 region of the large subunit nuclear rRNA gene detected 38 fungus species (104 strains) of which three species, i.e., Candida sp. 3, Candida kashinagacola (both yeasts), and the filamentous fungus Raffaelea quercivora were isolated from all the tree species. The two yeasts were most prevalent in the interior of galleries, regardless of host tree species, suggesting their close association with the beetle. A culture-independent method, terminal restriction fragment length polymorphism (T-RFLP) analysis was also used to characterize the fungus flora of beetle galleries. T-RFLP patterns showed that yeast species belonging to the genus Ambrosiozyma frequently occurred on the gallery walls along with the two Candida species. Ours is the first report showing the specific fungi inhabiting the galleries of a platypodid ambrosia beetle.     

Hybrid aspen is not preferred by the large poplar borer (Saperda carcharias)

An industrially valuable tree, aspen, suffers from several fungal diseases and insect pests such as the large poplar borer (Saperda carcharias). The role of the beetle as a pest of aspen and hybrid aspen was investigated in five aspen and three hybrid aspen stands in Finland. Approximately 50% of the trees in the study had signs of the large poplar borer. Of these trees, 5% had insect exit holes. Approximately 70% of the trees with larval galleries had only one or two larval galleries. The trees with larval galleries were on average 2 m shorter than those without larval galleries. No significant difference could be detected in the diameter growth between these two groups. The proportion of decay was greater in hybrid aspen (27%) than in aspen (14%). These results show that the large poplar borer is an important pest of both aspen and hybrid aspen in Finland. No significant difference was observed between the aspen and hybrid aspen stands in the number of trees with larval galleries. Hybrid aspen therefore does not appear to be more sensitive to damage caused by the large poplar borer. Thus, a change from hybrid aspen to regular aspen in aspen cultivation is unnecessary, presuming that healthy saplings and an optimal rotation time are used.     

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。