Study On The Semiochemicals Of Three Tomicus Species In Pinus Yunnanensis Franch.

Tomicus yunnanensis Kirkendall & Faccoli, T. minor Hartig, and T. brevipilosus Eggers bark beetles are important insect pests of pines, Pinus spp. As the important afforestation and timber tree species in southwest China, P. yunnanensis Franch has been seriously damaged by the pine shoot beetles since 1980 s,and a large number of trees were killed every year. In order to develop the better monitoring and control techniques, semiochemicals of this three species were studied., We first studied the antenna and sensilla which is the main olfaction organ used for the perception of the semiochemicals. Secondly, we compared the attraction effect the Yunnan pine bolt bundles with the attraction effect of semiochemicals. Then we test, analyze and verify the semiochemicals of the three species. In addition, we supplemented the knowledge of their biological behavior and find a quick and easy method for distinguish the females and the males. The main results are as follows.(1) In the insect collection, four points should be noted: ① a small amount of two males with one female, two females with one male and two females with two males were found in a single mother gallery; ② the beetles in the front of maternal gallery were not always the females and the beetles in the back were also not always the males; ③ in generally, the early and late truck-attacked T. yunnanensis were evenly distributed on the trunk at different heights, and the early truck-attacked T. minor would attack the middle trunk while the late truck-attacked T. minor would attack the lower part. We also found the last tergum of the abdomen in females is wider, bigger and more semicircular than that in male and the letter is smaller and approximately parallel at the bio-side.(2) The antennal morphology and sensilla ultrastructure of T. yunnanensis, T. minor and T. brevipilosus were studied by scanning(SEM) and transmission electron microscopy(TEM). Eight common sensilla types were recorded: 1) sensilla trichodea types 1 and 2 were located on the club,with apical and cuticle pore, were innervated by five and eight dendrites respectively; 2) sensilla chaetica types 1 and 2 had no pore in surface and no dendrites in the sensilla lymph lumen; 3) sensilla basiconica, top-protuberated sensilla basiconica and fluted cones occurred on the club; and B?hm bristles occurred on the funicle. Multiporos sensilla basiconica were the most abundant and were innervated by 10-14 dendritic branches. Top-protuberated sensilla basiconica, as a new sensilla type with apcial pore, were innervated by one dendrite. Multiporous fluted cones were innervated by five dendrites. Only three SEM images of sensilla furcatea were visible on the antennae of female T. yunnanensis. The potential functions of these sensilla are discussed in relation to their morphology and ultrastructure. No statistical differences between sexes were found in the size and numbers of each sensilla type. Although the three species had similar antennal morphology and sensilla type, sensilla on sub-segments 3 and 4 of the antennal club of T. minor were much sparser than those of T. yunnanensis or T. brevipilosus. Concerning the antennae of T. yunnanensis, there were more sensilla trichodea type 2, sensilla chaetica type 2 and sensilla basiconica, the size of sensilla trichodea type 1 and sensilla basiconica were significantly greater than those of T. minor.(3) More T. minor were attracted by the serious infested Yunnan pine bolt bundles than the un-infested control. The peak of traped beetles were emerged near 15 th day. There were signifficantly higher relative content of s-(-)-α-pinene, 1R-(+)-a-pinene,(+)-camphene,(1s)-(-)-β-pinene in the serious infested Yunnan pine bolt bundles than that of uninfested control.(4) More T. minor were captured in the bolts introduced with T. minor locating in maternal galleries <2 cm in length, than the control and also more T. yunnanensis were collected in the bolts introduced with T. yunnanensis locating in maternal galleries <2 cm in length than the control. There were more T. minor captured on the bolts introduced a pair of female and male than control. In the response of the two species to the bolts introduced T. yunnanensis locating in the shoots, more beetles were captured on the beetle-introduced bolts than the control. The volatiles of the infested and un-infested bolts were analyzed. The content of s-(-)-α-pinene, 1R-(+)-a-pinene, myrcene and(-)-limonene differ obviously in different T. minor introduced bolts and the control, and also the content of 1R-(+)-a-pinene,(+)–camphene,(+)-3-carene and(1s)-(-)-β-pinene differ obviously in different T. yunnanensis introduced bolts and the control. These compounds may be related to the semiochemicals to these species.(5) Content of s-(-)-α-pinene, 1R-(+)-a-pinene, myrcene,(s)-cis-verbenol,(-)-trans-verbenol, L-(-)-verbeone and myrtenol in the hindguts of T. yunnanensis and T. minor in different development phases were significantly different,, which may be the active semiochemicals.(6) The three species showed intensive response to(s)-cis-verbenol,(-)-trans-verbenol, L-(-)-verbeone, myrtenol and s-(-)-α-pinene in EAG test.(7) In Dec. 2010, signeficently more T. minor and T. yunnanensis were attracted to lure D than to the foreign commercial lure for T. minor in Yuxi and Qujing. In Dce. 2011, more T. minor were captured by the trap baited with a new lure in Beishan Forest Farm of Yuxi compared the best lure in Dec. 2010. Simarly in field trial in Qujing in Dec. 2011, more beetles of the three species were attracted to new lure compared with the best lure in Dec. 2010. From above analyses, compound 1, 11, 12 and 13 were the common active semiochemicals for the three species while compound 8 showed more attractive to male T. brevipilosus. As far as the color was concerned, the black funnel trap could collect more beetles.