Plant Protection Bulletin (Taipei) (2005) 47, 305-318

C.T. Liao and C.C. Chen (2005)
Spreading, seasonal migration and population fluctuations of the rice water weevil (Lissorhoptrus oryzophilus) (Coleoptera: Curculionidae) in central Taiwan
Plant Protection Bulletin (Taipei) 47 (4), 305-318
Abstract: The rice water weevil (RWW), Lissorhoptrus oryzophilus Kuschel, was first observed in Taichung County in the second-crop rice of 2000, and soon spread to the coastal towns of Taichung County in central Taiwan in the first-crop rice of 2001. Subsequently, RWW further invaded the northwestern part of Changhua County in the first-crop rice of 2002, and the infested area reached to 8,100 ha, although the southern spreading of RWW has been retarded in subsequent years. This study investigated the inhabiting sites of adult RWWs during rice fallow periods in the winter and summer seasons to better understand their migration characteristics. In the period when rice is not planted in the winter season, adults were detected in 16.7%~33.3% of samples from rice stubble. The results indicated that adult RWWs hibernate at the base of rice stubble during fallow winter periods. Otherwise, adult RWWs also hibernate in the surface soil and leaf litter of bamboo groves, woodland groves, and at the base of grasses clumps and ground trash on levees. After harvesting the first cropping rice, adult RWWs were detected in 50%~75% of samples from rice stubble and 25%~58.3% from levees. Furthermore, during the fallow periods of the summer season, adult RWWs were not detected in the soil or leaf litter of bamboo groves or woodland groves; but fed on Gramineae grasses on levees and newly germinated rice seedlings from dropped grain in paddy fields. This indicates that newly emerged adults do not have an obvious dormant behavior at this time. The RWW has 2 generations annually in central Taiwan. The density of adult RWWs reached its peak in mid-March and larvae were observed on the root portions in late March. The maximal larval density occurred in late April. Pupae were found primarily on the root portions in early May. The first-generation adults began to pupate in late May. During the second cropping rice season, larvae were observed mostly in mid-August, with maximal densities from late August to early September. Second-generation adults began to pupate in mid-September.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)

Research topic(s) for pests/diseases/weeds:
population dynamics/ epidemiology
general biology - morphology - evolution

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Lissorhoptrus oryzophilus	Rice (Oryza)	Taiwan