Details on the situation of Lissorhoptrus oryzophilus in China
The rice water weevil, Lissorhoptrus oryzophilus (Coleoptera: Curculionidae – EPPO Alert List) originates from the Southern USA where it reproduces sexually and feeds on gramineous and cyperaceous weeds as its native hosts. Damage to introduced rice was reported in Georgia as early as the 1880s, and L. oryzophilus is now considered as the most destructive pest of rice in North America. Invasions of parthenogenic populations were then reported in Asia. L. oryzophilus was first reported in Japan in 1976 (Aichi Prefecture) and within 10 years it spread to the whole of the Japanese Archipelago. It was found in China and the Korean Peninsula in 1988, and in Taiwan in 1990.
In China, L. oryzophilus was first detected in Tanghai county in Hebei Province (1988). Since then, it has become one of the major rice pests in the region with yield losses ranging from 10 to 80%. It poses a challenge for rice production, particularly in areas where integrated pest management programmes had been put in place before its arrival. As of 2003, L. oryzophilus was found in the following 12 provinces (Anhui, Fujian, Guangdong, Guangxi, Hebei, Hunan, Jiangsu, Jilin, Liaoning, Shandong, Shanxi, Zhejiang) and municipalities (Beijing, Tianjin), infesting over 400,000 ha of rice. A dispersal rate of 10-30 km/year was observed in China. CLIMEX studies have shown that L. oryzophilus has the potential to continue its spread towards the North and West, but that its progression would probably be stopped by winter stress in Helongjiang and Jilin Provinces, by high elevations in Sichuan and Yunnan Provinces, and by dry summers and cold winters in Inner Mongolia and Gansu Provinces. Field and laboratory studies have shown that adults of L. oryzophilus could feed on a wide range of plants (64 species in 10 families).
Significant efforts had been made in China to try to prevent the spread of the pest. As soon as it was detected, surveys were initiated to delimit the extent of the outbreak. As L. oryzophilus can survive in stored rice grain, straw or plant for more than a month, the transport of rice seeds, seedlings and plants was forbidden from infested areas. Fumigation of potential host material was required, as well as disinfection of vehicles leaving quarantined areas. Despite all these efforts, the pest could not be contained in China, probably because of the following factors: adults can fly (dispersal by natural flight is estimated at 10-20 km/year), irrigation systems and rivers spread the pest, and occasional hitchhiking on human transportation can most probably take place.
Sources
Chen H, Chen Z, Zhou Y (2005) Rice water weevil (Coleoptera: Curculionidae) in mainland China: invasion, spread and control. Crop Protection 24(8), 695-702.