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Studies On The Biology And Population Dynamics Of Lissorhoptrus Oryzophilus Kuschel In Guangxi

Posted on:2016-03-02Degree:MasterType:Thesis
Country:ChinaCandidate:Y X ZhangFull Text:PDF
GTID:2283330464470860Subject:Agricultural Entomology and Pest Control
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The rice water weevil, Lissorhoptrus oryzophilus Kuschel originated from the Mississippi valley in the United States, is the most important invasive pest of rice in China. The weevil was first detected in Tanghai County of Hebei Province in 1988. In Guangxi, this species was first found in Quanzhou County in May 2013, and has become a potential threat to the safety production of rice. In order to explore the Integrated Pest Management for the weevil, population dynamic and biological and ecological characteristics in Guagnxi were studied. The result showed as following:1. The rice water weevil occurred annually two generations and overwintered as adults in Quanzhou County of Guangxi Province. Overwintering sites of adults distributed mainly in soil from 0 cm to 3cm at the edge of ditch, forest land, hillside, ridge, or a pile of straw. In the mid-to-late of March, overwintering adults began to fed on Gramineae grasses around at the overwintering sites. Peak of adults come out from soil at the overwintering sites was observed in the early-to middle of April, and spread to early rice field. In the late April, overwintering adults have completed the dispersal.2. Overwintering adults laid their eggs in leaf sheaths in the late April, and the peak of oviposition was observed in the early May. Larvae were observed on the root portions in the mid-May, and the peak of incubation occurred in the late May. Pupae were primarily found on the root portions in the late May, and the peak of pupation occurred from early to middle in June. Adults of the 1st generation appeared in early June, and the peak of emergence occurred in late June. Occurrence of the beginning, peak and end periods were consistent with the transplanting time. A few adults stayed in the fields to form the source of the 2nd generation in single-cropping late rice.Occurrence of egg, larvae, pupae and adults of the 2nd generation were recorded in July and August. The occurrence peak of egg, larvae, pupae and adults in this generation was middle July, middle July, middle August, and late August. Adults moved to the overwintering sites after eclosion. The weevil needs 30-40d to comlete development from egg to adult.3. Results of the population dynamics monitored with lamp trap showed that the peak period of overwintering adults appeared in mid-April (1160 per day). The weather changes (e.g., rain) influence the trapping effect. Data indicated that the population dynamic of adults monitored with lamp trap was consistent with those that come out from soil. Only one individual was trapped by light (June 24,2014) after adults of the 1st and the 2nd generation emerged. The detailed reason needs further study.4. The weevil preferred to feed on the conventional rice (Simiao No.2) than Zhuliangyou 224 and super rice. Adults like to feed on the tender rice leaves. Feeding occurred mostly at 12:00,16:00-18:00 and 21:00-22:00. The fecundity was the highest that larvae fed on Simiao No.2 than those that larvae fed on conventional hybrid rice (Tianyou 5396) and super rice (Ganxin 203).5. The spatial distribution pattern of L. oryzophilus larvae was negative binomial distribution. Transplanting methods did not affect the spatial distribution pattern. The formulas of theoretical sampling number under the two transplanting methods of rice were N=t2(2.256/m+0.240)/D2 and N=t2(4.878/m+0.126)/D2 in the seedling throwing transplanting paddy rice, which based on the Iwao’s method. Double diagonal sampling was the optimal method to investigate the spatial distribution pattern for L. oryzophilus larvae under the two transplanting methods of rice.6. The weevil has higher mortality under the semi-natural condition in laboratory. The trend index of population (I) ranged from 2.89 to 3.95. The trend index of population of weevil fed on super rice Shenyou 9516 was the highest, while those that fed on conventional rice Simiao No.2 was the lowest. The natural mortality of 1-3 instars larvae was the highest than other stages. The effect of each stage of weevil on population trend index was 1st-3rd instar larvae> 4th instar larvae> eggs> pupae.
Keywords/Search Tags:Lissorhoptrus oryzophilus Kuschel, life history, occurrence regularity, host selection, spatial distribution pattern, life table
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