Recapture of Ips typographus L. (Col., Scolytidae) with attractants of low release rates: localized dispersion and environmental influences

1 The dispersal of Ips typographus L. (Col., Scolytidae) was studied using a mark–release–recapture approach in a grid of traps equipped with pheromone lures of release rates of about 8.4 mg/day of 2‐methyl‐3‐buten‐2‐ol (MB) and 0.29 mg/day of (S)‐cis‐verbenol (cV) in experiment 1, and 1.2 mg/day of MB and 0.04 mg/day of cV in experiment 2. 2 We investigated whether beetle dispersal reflected the simple diffusion pattern observed in previous I. typographus experiments, for which attractant release rates generally approached 50 mg/day of MB and 1 mg/day of cV. We also examined how environmental parameters (wind) and human activities (felling) could influence the beetles' flight. 3 The recapture percentage was higher in experiment 1 than in experiment 2: respectively, 7.0% (with 64 traps) and 2.3% (with 100 traps) of the beetles that took off were caught in the traps. 4 With the higher release rate (experiment 1), trap catches decreased with increased distance, whereas with the lower release rate (experiment 2), trap catches rose between 50 and 100 m then decreased with increasing distance. 5 Flight was little orientated by prevailing wind directions, a feature probably explained by the low wind speeds (0–1.2 m/s) observed throughout the study. 6 High trap catches of unmarked beetles close to areas undergoing thinning activities suggest that the presence of freshly cut spruce and larch material could have an influence on dispersal, attracting the beetles into the felling area. Spatial analyses show that capture patterns were autocorrelated up to distances of about 250 m.     

基于线粒体COⅠ基因的齿小蠹属昆虫DNA条形码研究

齿小蠹属（鞘翅目： 小蠹科）昆虫是植物检疫中经常截获的类群, 为探讨线粒体细胞色素C氧化酶亚基Ⅰ(COⅠ)基因的特定区段作为DNA条形码快速准确鉴定齿小蠹种类的可行性, 以齿小蠹属昆虫为研究对象, 测定分析了线粒体COⅠ基因462 bp碱基序列。序列分析结果显示： 变异位点为259个, 保守位点203个, 简约信息位点181个, 自裔位点78个。所有位点中, A, G, C和T碱基平均含量分别为30.7%, 16.5%, 17.0%和35.8%。A+T含量较高, 为66.5%, 明显高于G+C含量, 表现明显的A+T碱基偏嗜, 且A与T含量相当, 符合昆虫线粒体基因碱基组成的基本特征。转换与颠换结果显示： 该段序列未达到饱和, 可以得到准确的进化分析。利用Kimura 2-parameter模型分析遗传距离得到, 同物种间的遗传距离介于0.002~0.007之间, 不同种间的遗传距离介于0.056~0.431间, 平均遗传距离为0.199, 说明该段序列能够区分不同物种。基于COⅠ基因序列构建的邻接法系统发育树（NJ树）显示, 同一物种聚为同一小支, 且分支自展值均为100%; 近缘种能聚集在一起, 且置信度很高（≥97%）。结果表明应用基于COⅠ基因片段的DNA条形码进行齿小蠹属昆虫分类鉴定具有可行性。     

落叶松八齿小蠹体内外和坑道内真菌类群

采集落叶松八齿小蠹成虫、幼虫、蛹,以及母坑道、子坑道、蛹室的韧皮组织和蓝变组织。采用马丁氏培养基和PDA综合培养基对各虫态体表、体内、坑道内真菌进行分离培养,统计真菌检出率。对获得的真菌菌株通过形态学和分子生物学相结合的方法进行鉴定。在落叶松八齿小蠹虫体内外和坑道内共分离出真菌31种,其中接合菌3种,子囊菌8种,担子菌1种,半知菌19种。自各虫态体表共分离出真菌23种,体内共分离出真菌8种,31种真菌在坑道内均有检出。其中,Ceratocystis fujiensis为中国新记录种,Ophiostoma     

Hit or miss in phylogeographic analyses: the case of the cryptic NUMTs

Phylogeographic studies call for attention as nuclear copies of mitochondrial DNA (NUMT) may generate erroneous results. Here, we report the presence of NUMTs differing only by 1-3 bp from authentic mitochondrial haplotypes, consequently named cryptic NUMTs. In contrast to traditional NUMTs, for which reliable tools for detection are established, cryptic NUMTs question the validity of phylogeographic analyses based solely on mitochondrial DNA, like the one presented here on the European bark beetle Ips typographus. Caution is called as cryptic NUMTs might be responsible for haplotype richness found in several species, and the necessity of refined methods for NUMT detection is highlighted.     

Modified pheromone traps help reduce bycatch of bark‐beetle natural enemies

• 1 Thanasimus formicarius and Temnochila caerulea, two of the main predators of Ips sexdentatus, a well‐known forest pest in Southern Europe, are captured in high numbers when trapping I. sexdentatus as a result of the kairomonal effect of the lures used.
• 2 A preliminary field trial showed that predators could survive for at least 1 week within trapping containers, although predator mutilation and high predator death rates were observed.
• 3 Different modifications of conventional multiple funnel and slot traps with the objective of reducing natural enemy entrance into trap containers were bioassayed in field experiments conducted over four seasons. Based on the larger sizes of predators, different designs using welded wire‐mesh screens improved performance to different extents. Providing escape windows just above the screen on multiple funnel traps gave the most promising results, including when effect sizes among all tested designs were compared.
• 4 Thus, a simple modification of the lowest funnel of the multiple funnel traps would reduce the bycatch of T. formicarius and T. caerulea, hence improving the efficiency of trapping programmes by lowering the likely impact on natural populations of these predators.

     

Effect of different semiochemicals blends on spruce bark beetle,Ips typographus (Coleoptera: Scolytidae)

The spruce bark beetle, Ips typographus, is a recent new introduction to the Qilian Mountains of China. An outbreak of these beetles has infested over 0.03 million hectares of spruce forests in this area. Although primary attraction to volatiles has been clearly demonstrated for I. typographus, the existence and role of attraction to insect‐produced pheromones have been widely debated. Currently, commercial lures for I. typographus include only the volatiles ipsdienol, cis‐verbenol, trans‐verbenol, 2‐methyl‐3‐buten‐2‐ol and 2‐phenylethanol in Europe. Several potential pheromone candidates have been identified for I. typographus. Our GC–MS and GC–FID analyses volatiles from hindgut extracts of I. typographus in different attack phases demonstrated that the 2‐methyl‐3‐buten‐2‐ol, ipsdienol, cis‐verbenol and trans‐verbenol as major hindgut components, and ipsenol, 2‐phenylethanol, trans‐ myrtenol and verbenone as minor components. We tested various combinations of semiochemical candidates, to determine an optimal blend. Our results suggest that addition of 2‐methyl‐3‐buten‐2‐ol to either ipsenol alone, or to blends of ipsenol and other semiochemical candidates, significantly enhanced attraction of I. typographus. Therefore, a simple lure consisting of ipsenol and 2‐methyl‐3‐buten‐2‐ol would be an optimal blend of I. typographus in the Qilian Mountains, China. We conclude that this optimal semiochemical blend may provide an effective biological pest control method for use in forest ecosystem against I. typographus.     

Acoustic communication in the pine engraver bark beetle: do signals vary between behavioural contexts?

Acoustic communication is taxonomically widespread in bark beetles and is proposed to play an important role in a variety of social and defensive behavioural contexts. Yet our understanding of how signals vary between contexts is currently limited. The present study tests the hypothesis that acoustic signals vary between behavioural contexts in the female pine engraver beetle Ips pini (Say) (Coleoptera: Curculionidae: Scolytinae). Female Ips pini produce acoustic chirps using a vertex‐pronotal stridulatory organ. Randomly sampled chirps generated under three contexts (i.e. distress, predation and premating) are compared for their duration, number of pulses, interpulse intervals, pulse rate and amplitude envelope shapes. The results obtained show that, during premating events, chirps are significantly longer in duration and tend to have a higher proportion of descending amplitude envelopes than chirps occurring during distress and predation events. Chirps produced during distress and predation conditions are indistinguishable from one another. By contrast to the results from previous bark beetle studies, no support is found for categorizing chirps as ‘interrupted’ or ‘uninterrupted’ types based on temporal patterns. The functional significance of context‐dependent variation in chirp characteristics is discussed. Previous studies on acoustic communication in bark beetles are limited as a result of a general lack of objective sampling and measurement criteria for characterizing signals. Recommendations are outlined for future studies on the functions and evolution of acoustic communication in bark beetles.     

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     

Marking bark beetle parasitoids within the host plant with rubidium for dispersal studies

A technique using rubidium chloride (RbCl), a trace element, as internal label is proposed for marking hymenopteran parasitoids attacking a concealed host, Ips typographus L. (Coleoptera: Scolytidae). RbCl was introduced directly into spruce via the vascular system using glass tubing. RbCl passed through the food chain and was detected at the parasitoid level by electrothermal atomic absorption spectroscopy (EAAS) or flame emission spectroscopy (FES). Mark persistency until day 8 after emergence was tested in labelled Rhopalicus tutela (Walker) (Hymenoptera: Pteromalidae). The mark decreased with time only in fed females, probably due to excretion and/or egg resorption. The proportion of marked males did not vary with time or treatment.