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Bio-ecological Characteristics And Ecological Mediation Techniques Of Boring Insects In Artemisia Ordosica Bushes

Posted on:2012-07-13Degree:DoctorType:Dissertation
Country:ChinaCandidate:J W WangFull Text:PDF
GTID:1103330335966420Subject:Forest protection
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Artemisia ordosica (Asteraceae), is a plant used widely for windbreak and. sand fixation in northwestern China. Large areas of aerially seeded A. ordosica play a significant improving in soil conditon, establishing vegetation communities and protecting the environment. Holcocerus artemisiae (Lepidoptera:Cossidae), Adosomus sp.(Coleoptera:Curculionidae), Sphenoptera sp. (Coleoptera: Buprestidae) and carpenter moth (Lepidoptera:Tortricidae) are the main pests,boring into roots and stems of A. ordosica, causing weak growth and even death of the plants. Damage caused by these pests has become an increasingly serious problem in Ningxia, Neimenggu and Shannxi Provinces, threatening the health of desert shrubs and the environment. The following aspects were systematically examined and discussed in this study:the basic bio-ecology characteristics of the main boring insects, the ecological niches of these pest and the ffect of applied synthetic sex pheromones on H. artemisiae. An investigation was also made into using a natural enemy of boring insects (Pyemotes tritici) as a bio-control agent.. The main results of the study are outlined below.1. The basic bio-ecological characteristics of three pests were systematically clarified for the first time. The results showed that:the artemisia carpenter moth, H. artemisiae (Chou and Hua) (Lepidoptera: Cossidae) had a two-year generation time. Larvae of all instars were found overwintering in roots. Mature larvae began to pupate in mid-May in the sand around the roots with the average pupal stage lasting 20 days. Moths emerged from the beginning of June to the end of August with adult able to copuate after emergence. Female moths started laying eggs around mid-June and the eggs hatched in late June. Individual larvae consumed a single root in irregular tunnels before transferring to another. The artemisia weevil, Adosomus sp. (Coleoptera:Curculionidae) occurred as one generation each year and overwintered as mature larvae or adults in roots. Overwintering adults appeared from mid- or late-April to mid-June, and overwintering larvae began to pupate in mid-May. Adults emerged from late-June to early-August, and fed on leaves to supplemental nutrition. The artemisia buprestid, Sphenoptera sp. (Coleoptera:Buprestidae) had one generation per year, and all larval instars overwintered. Mature larvae began to pupate in mid to late-April at the end of the gallery. Adults emerged from early-May to early-July and ate fresh leaves for before copulating. Copulation occurred between approximately 13:00-16:30, and adult were observed to mate several times. Larvae often aggregated in one root and overwintered in stems and roots.2. Instars of these three pests were established from larvae samples collected from the field. There were seven instars in H. artemisiae, and four in both Adosomus sp and Sphenoptera sp. The relationship of different instars and head width, first established by Dyar, showed an exponential regression with these insects.3. The type and distribution of antennal sensilla in H. artemisiae and Sphenoptera sp. were examined with scanning electron microscopy (SEM). The H. artemisiae sensilla were classified into seven types, including sensilla coeloconica, Bohm bristles, two types of sensilla trichodea and three types of sensilla squamiformia. The sensilla trichodea were the most numerous and their density was higher on the dorsal side of the antenna than that on the ventral side. In contrast, there were ten types antennal sensilla on the antenne of Sphenoptera sp., including sensilla coeloconica, pore sensilla, Bohm bristles, two types of sensilla trichodea and five types of sensilla basiconica. There were differences between males and females, and dorsal and ventral antenna side in type, number and distribution.4. The temporal and spatial niches of the major boring insects were investigated. Time niche index showed that the damage period of Sphenoptera sp. was much longer than that of the others, and it showed some overlap with the damage period of H. artemisiae. A spatial niche index showed that the distribution of Adosomus sp. larvae was wider than the other species of insects studied. The distribution of Sphenoptera sp. larvae and the other insects tended towards separation and there was much difference in resource utilization between them.5. Artificial rearing of H, artemisiae and Adosomus sp.larvae was carried out. They preferred the artificial diet containing sawdust from A. ordosica roots and stems. H. artemisiae pupation rate was 27.89±4.08% and adult emergence rate was 11.25±15.91%. The Adosomus sp. pupation rate was 46.17±26.58% and the emergence rate was 42.67±29.14%. Humidity and the antiseptic concentration appeared to affect larval development.6. The composition and structure of the phototaxis insect community in desert shrubs were defined. All the insects collected belonged to 6 orders,25 families, and 94 species. Lepidopteran insects had the highest number of individuals (88.83% of total number) and the highest species number (63 species). Most of the natural enemy insects belonged to Hymenoptera and Neuroptera. Indices of pest and natural enemy number and species richness first increased then decreased during the investigation, with peaks from June to August. The phototaxis insects showed significant selectivity to different light wavelengths. The number attracted to back-light of 365nm was the lowest, and to 368nm was the highest (90% more). Back light of 335nm attracted more moths of Cossidae, Pyralidae and Arctiidae, back light of 351nm attracted more Sphingidae moths and back light of 368nm attracted more Noctuida moths. For the parasitoids and predators, the lowest Braconidae and lacewings were lured by back light of 351nm. The fewest Panorpidae (8.35%) were also lured by back light of 351nm.7. Field trials of sex pheromones for Holcocerus artemisiae were measured quantitatively. Results indicated that trapping upwind was optimal (60% of males), and trapping crosswind was better than that of downwind. Males were trapped 30-210 m upwind, with the largest trapping numbers at 60 m. This sex pheromone could last up to 25-34 days. The boat and triangle traps were effective than practical novel types. In addition to H. artemisiae, the sex attractant also attracted Loxostege sticticalis, Protexarnis squalid and Bombyliidae.8,Parasitic enemy Pyemotes tritici was first reported as an natural control factor for boring insects, and its artificial cultivation was established. P. tritici parasitized larvae and pupae of Sphenoptera sp. and Adosomus sp., with an average parasitic rate of 15.5%. Artificial rearing of P.tritici revealed that it can reproduce on several species of boring insects, including Galleria mellonella, Chorophorus sp., Asias halodendri, Saperda populnea and H. vicarius larvae or pupae, but not on H. artemisiae. Because of a short parasite time and high reproduction ratio, A. halodendri was chosen as the ideal artificial host insect. Tying the mouthpart of G. mellonella larvae with thread improved the parasitic rate. The survival ratio of mites kept at 5-15℃decreased with time, and fell below 20% after 12 days. After 16 days, the P.tritici population became too small to control the pests. Pest control experiments performed both in the laboratory and in the field showed that P. tritici could find host larvae and parasitize them, but the ratio was lower than 30%. Extremely high temperature and ant-predation could reduce the mite population, affacting parasitism upon the host species.9,Combining general principles and methods of ecological mediation for pest control with the features of large area, single-species and ecological fragile desert shrubs, several measures were put forward to establish an ecological mediation system reducing damage by boring insects. Based on the analysis of remote sensing image data and investigation into the boring pests in A. ordosica and associated environmental factors, the relationship between remote images, plant health and pest occurrence needs to be established, in order to monitor the health of A. ordosica and pests occurrences. Standardized using of sex pheromone for H. artemisiae provides an efficient method to monitor and control the adults. A. ordosica plant source attractants can be used to monitor populations of Adosomus sp. and Sphenoptera sp. adults, combined with some suitable traps. In oeder to control these two pests effectively, application of laboratory-reared P tritici is strongly recommended. In addition, the use of 335 and 368 nm black lights are recommended for attracting more H. artemisiae moths.
Keywords/Search Tags:Artemisia ordosica, boring insects, sex pheromone, light trap, Pyemotes tritici
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