Font Size: a A A

Biological Ecology And Aggregation Pheromone Monitoring Of Main Insect Borers In Larch Of Aershan, Inner Mongolia

Posted on:2011-01-24Degree:DoctorType:Dissertation
Country:ChinaCandidate:F YuanFull Text:PDF
GTID:1103360305464533Subject:Forest protection
Abstract/Summary:PDF Full Text Request
There had been three outbreaks of Dendrolimus superans Bulter in Aershan of Inner Mongolia. After the third outbreak, many insect borers such as Ips subelongatus Motschulsky, Monochamus urussovi Fisher, Monochamus sutor Linnaeus and Acanthocinus carinulatus Gebler invaded Larix gmelinii (Rupr.)Rupr. forests quickly. In this paper, based on the research objectives of L. gmelinii forests, the rule between these two kinds of pests and invasive sequence was analyzed; the function niche in the larch of secondary pests was studied, as for definituding the different damaged extend of insect borers and finding the relative ecological measures to control the outbreak and spreading of pests; biological characteristics of A. carinulatus was studied with detail; meanwhile as for monitoring and controlling I. Subelongatus, aggregation pheromone was used and natural enemies and their suppressive effects were also discussed and analyzed. The main results are as follows:1. Methods involved included setting sample plots, collecting adults in iron traps and measuring areas of galleries to study the invasive sequence, their ecological niche and the extent of the different effects by the main insect borers to their hosts. The results showed that the damage of D. superans weakened L. gmelinii, First I. subelongatus invaded, followed by A. carinulatus, M. urussovi and M. sutor. After the outbreak of D. superans, the average density of longhorn beetles per L. gmelinii tree increased. The ecological niche of I. subelongatus stretches almost from the base to the top of the trunk. The number of insects in older stands of L. gmelinii is larger than those in middle aged stands. They do not damage healthy trees of L. gmelinii. The ecological niche of A. carinulatus is higher in dead L. gmelinii trees than in weak ones. The degree of damage is directly proportional with age and depth of bark. M. urussovi mainly damages trunks below 4 m in weak trees; in dead trees they can do damage up to 6 m in height. M. sutor mainly damages trunks below 5 m in weak L. gmelinii trees; in dead trees they cause damage up to 7 m. Again, the degree of damage is directly proportional with age. None of the three species of longhorn beetles damage healthy L. gmelinii and younger trees. Among the main insect borers, the degree of damage caused by I. subelongatus is more serious than that of other insects.2. Studies on the ecological niche of the main insect borers in larch were carried out, main attention was paid to M. urussovi, M. sutor, A. carinulatus and I. subelongatus. The results showed that the spatial niche breadth index of I. subelongatus was the highest in weak standing larch, in middle aged and old larches it reached the values of 0.5782 and 0.5498, respectively. In the middle aged and old dead standing larches the spatial niche breadth index of A. carinulatus was 0.5143 and 0.6294, respectively, which is higher than in weak larches. The spatial niche breadth index of M. urussovi were the lowest in both weak and dead larch. Both the spatial niche overlap index and spatial niche proportion index of I. subelongatus to the three longhorned beetles were high, which indicated that the demand for space resources of the four insect species had little difference. The spatial interspecific competition coefficient of the four species was high, which indicated that the competition of space and resources was strong. Because of the different damaged areas in the trunk the four species can coexist. 3. Spatial distribution pattern of I. subelongatus galleries was examined by several aggregation indexes and regression analysis methods of Iwao, Taylor. The results indicated that the number of I. subelongatus galleries has linear relationship to the different height of larch trunk, linear regression equation is y=-10.867x+92.884 (R2=0.9995); galleries of I. subelongatus in sunny sides and shaded sides are nearly the same; when the average density of I. subelongatus reached 1120/1000cm2, galleries of I. subelongatus was uniform distribution.4. Biological characteristics of a new record pest insect A. carinulatus has been reported in China for the first time. During the last few years, outbreaks of this insect in larch plantations of the Aershan, Inner Mongolia have occurred. Each year one generation is born. The insects only damage the phloem in L. gmelinii, overwinter in galleries as larvae and pupate in May of the following year. The pupation culminates in late May. The pupal phase lasts about 45 d. Adults emerge in early June and require nutrition after emergence. Mating and oviposition occur from late June to early August and the adult males and females and may copulate many times in their lifetime. The female adults lay eggs in bark crevices. Oviposition sites with one egg occupy 70.5%,of all sites, sites with three eggs 6.8% and 22.7% of all crevices are without eggs. Eggs stay in this stage for a period of 7 to 11 d. Larvae hatch in early July and hibernate in early September. The rate of successful hatching is only 37.8%.5. Emergence regularity of I. subelongatus and attractive effect at different distance outside the forest and different hanging height in the forest were studied with aggregation pheromone of I. subelongatus in Aershan area, Inner Mongolia. The results showed the adult emerged from mid May to the end of August with two peaks. Its active time was between 12:00 and 16:00 when the temperature was relative high in a day. The effective attractive distance of I. subelongatus pheromone was about 200 m and the optimum distance was within 90 m. The best hanging height of the traps was about 1.5 m on trunk.6. Two different I. subelongatus lures (Ipslurel, Ipslure2) from two different manufacturers were tested on I. subelongatus and Thanasimus substriatus Gebler by using Gas Chromatography-Mass Spectrometry (GC-MS), electroantennogram (EAG) and field trapping. The results showed that I. subelongtus and its predator T. substriatus responded in significantly different ways to pheromone blends. Ipsenol-dominant blend attracted a high number of I. subelongatus and some T. substriatus, ipsenol with few 2-methyl-3-buten-2-ol and plant volatiles was attractive to I. subelongatus and T. substriatus as well; (S)-cis-verbenol-dominant blend attracted a high number of T. substriatus but almost no I. subelongtus. (S)-cis-verbenol with few ipsenol,1-verbenone and plant volatiles was attractive to predators but no bark beetles. These present results can be applied for population monitoring and biological control of Ips subelongatus.7. The natural enemies of I. subelongatuswere investigated. The most abundant species were the predatory beetle T.substriatus and the parasitic wasps Tomicobia seitneri (Ruschka) and Coeloides bostrichorum Giraud. In addition, some yet unidentified parasitic mites and pathogenic organisms were also recorded. The natural suppressive effects of the predators and parasitoids were analysed. The maximum predation of T.substriatus was 10.7 Ips beetles per day (1 T. substriatus with 20,40,60,80,100 I. subelongatus,17-25℃indoors). The parasitic rates of T. seitneri to I. subelongatus larvae and pupae were 20.5% and 13.7%, respectively. The parasitic rate of C. bostrichorum to I. subelongatus larvae was 6.5%. The parasitic rate of pathogenic organisms to I. subelongatus was 4.3%(larvae),5.4%(pupae) and 2.1%(adults). Our results indicate that T. seitneri is probably the most potential candidate for biological control of I. subelongatus.
Keywords/Search Tags:Dendrolimus superans Bulter, Monochamus urussovi Fisher, Monochamus sutor Linnaeus, Acanthocinus carinulatus Gebler, Ips subelongatus Motschulsky, Thanasimus substriatus Gebler, Biology, Aggregation pheromone, Monitoring
PDF Full Text Request
Related items