脐腹小蠹聚集信息素的提取鉴定和引诱效果

Extraction and identification of aggregation pheromone components of Scolytus schevyrewi Semenov(Coleoptera: Scolytidae) and trapping test

为了确定脐腹小蠹Scolytus schevyrewi Semenov的聚集信息素成分,对脐腹小蠹成虫后肠和虫粪的挥发物进行了提取鉴定和引诱试验。经气相色谱-质谱联用仪(GC-MS)鉴定,结果表明:雌成虫后肠挥发物成分有十四烷、十五烷、十六烷、十八烷、十九烷、十二酸和十四酸,其中十四酸含量最高,达到了42.2%;雄成虫后肠挥发物成分有十一烷、十四烷、十五烷、十六烷、十八烷和十九烷,十六烷(23.3%)和十九烷(21.5%)含量最多;雌成虫虫粪挥发物成分有十一烷、十二烷、十四烷、十六烷、十八烷和十九烷,十九烷含量最高,为29.9%;雄成虫虫粪挥发物成分有庚烷、十一烷、十二烷、十四烷、十六烷、十八烷、二十二烷和二十三烷,庚烷(20.5%)相对含量最多。此外,借助触角电位仪测定了脐腹小蠹雌雄虫触角对这些单一物质刺激的反应,结果显示,触角电位相对值较大的为十二酸、十四酸和十八烷。雌雄间比较发现十二酸、十四酸和十九烷刺激后雌雄间触角电位相对值差异达到了显著水平(P<0.05)。田间诱捕结果显示,十二酸、十四酸、十九烷对脐腹小蠹的引诱数量雌雄间差异性达到了显著水平(P<0.05),成虫诱捕总量最多的是十八烷,诱捕量达32.1头,其后诱捕量较多的为十二酸(24.1头)和十四酸(22.7头)。可以推断,十八烷、十九烷、十二酸和十四酸是脐腹小蠹聚集信息素的主要成分。

The banded elm bark beetle （BEBB）, Scolytus schevyrewi Semenov （Coleoptera： Scolytidae）, is a pest of Ulmus pumila L. This pest, which was first reported in Asia, carries spores of tmhe fungal pathogen that causes Dutch elm disease. In recent years, an extensive elm forest in Yanchi County, Ningxia Province, was severely damaged by the BEBB, resulting in large-scale destruction and death of trees. At least 98% of the mortalities occurred in forestry stations, with the extent of damage similar to that produced by a raging fire. The staff of local bureaus of environmental protection and forestry bureaus implemented various measures to revive these forests; however, their efforts yielded little success. Foreign countries have installed traps to preserve their forests from further destruction due to BEBB infestation. For example, these pests were collected in Colorado, USA, using traps containing attractants for woodborers （i.e., α-pinene and ethanol） as bait, whereas those in Utah were gathered in traps baited with ethanol or the 3 components of the aggregation pheromone of the Eurasian spruce engraver, Ips typographus L. （Coleoptera： Scolytidae）. Chemical communication in bark beetles using aggregation pheromones plays a key role in mate location and in harming host plants. However, the components of the aggregation pheromone of the BEBB remain unidentified. To screen the chemicals of the BEBB aggregation pheromone, the volatiles in male and female adult hindguts and feces were analyzed by gas chromatography-mass spectrometry in the laboratory and in the elm forest fields in Yanchi County. The volatiles of male adult hindguts mainly contained seven components-tetradecane, pentadecane, hexadecane, octadecane, nonadecane, dodecanoic acid, and myristic acid of which myristic acid was predominant （42.2%）. The volatiles of the female adult hindgut consisted of six ingredients-undecane, tetradecane, pentadecane, hexadecane, octadecane, and nonadecane of which hexadecane （23.3%） and nonadecane （21.5%） were the predominant types. Volatiles in male feces consisted of six components-undecane, dodecane, tetradecane, hexadecane, octadecane, and nonadecane-of which nonadecane was predominant （29.9%）, whereas those in female feces contained eight chemicals-heptanes, undecane, dodecane, tetradecane, hexadecane, octadecane, docosane, and tricosane of which the alkanes accounted for 20.5%. In addition, the responses of adult antennae to 10 μL of individual volatiles at a concentration of 10 μg/μL were measured using an electroantennogram （EAG） detector. Among the various substances examined, dodecanoic acid, myristic acid, and octadecane showed the strongest response. By comparing the EAG values of the substances in the antennae in females with those in males, dodecanoic acid, myristic acid, and nonadecane reached significant levels （P 〈 0.05） in terms of responses. Both adult males and female BEBB were collected in the field using cross-shaped traps containing chemoattractants from June 25th to July 4th in 2010. There was a significant difference （P 〈 0.05） between the number of male and female BEBBs captured using dodecanoic acid, myristic acid, and nonadecane. In terms of the trapping effect, octadecane was most effective, resulting in 32.1 adults trapped, followed by dodecanoic acid （24.1 adults）, and myristic acid （22.7 adults）. Therefore, octadecane, nonadecane, dodecanoic acid, and myristic acid are the most probable main components of the BEBB aggregation pheromone.