The rice water weevil, Lissorhoptrus oryzophilus, is the most harmful insect pest of rice in the United States, causing yield losses of up to 25 percent.
The rice water weevil, Lissorhoptrus oryzophilus, is the most harmful insect pest of rice in the United States, causing yield losses of up to 25 percent.

The rice water weevil, Lissorhoptrus oryzophilus, is the most harmful insect pest of rice in the United States, causing yield losses of up to 25%. Adults inflict damage by consuming leaf tissue, and the larvae feed on the roots of rice plants. A native of the southeastern U.S., the rice water weevil invaded Japan in 1976, Korea in 1980, China in 1988, and Italy in 2004.

Luckily, rice growers now have a new resource for controlling it. An open-access article appearing in the Journal of Integrated Pest Management discusses the rice water weevil's life history and invasion biology, as well as management strategies and future directions of research.

Authors Mohammad-Amir Aghaee and Larry D. Godfrey, both from the University of California, Davis, tell the story of the weevil since it was first identified as a pest in 1881 by C. V. Riley and L. O. Howard. They then discuss reasons why it has been able to spread so rapidly -- up to 36 kilometers per year in some cases -- which is partly because of its ability to reproduce asexually.

"This invasive ability is aided by a particular and peculiar aspect of this weevil's biology, the fact that a small percentage of the population in its native range reproduces by parthenogenesis," they wrote.

The authors also discuss methods of monitoring and sampling -- including the use of aquatic barrier traps -- as well as management options, including cultural control methods such as draining fields, delayed planting, winter flooding, and nutrient augmentation. They also suggest that insect-resistant transgenic varieties, such as a newly-developed Bt rice plant transformed with the Cry3A gene, might be another management option if approved for cultivation.

Microbial control options using the entomopathogenic fungus Beauveria bassiana and the soil bacterium Bacillus thuringiensis are also discussed, as are other management options which may be available in the future.

The full article, "A Century of Rice Water Weevil (Coleoptera: Curculionidae): A History of Research and Management With an Emphasis on the United States," is available at http://dx.doi.org/10.1603/IPM14011.

The Journal of Integrated Pest Management is an open-access, peer-reviewed, extension journal covering the field of integrated pest management. The journal is multi-disciplinary in scope, publishing articles in all pest management disciplines, including entomology, nematology, plant pathology, weed science, and other subject areas. The intended readership for the journal is any professional who is engaged in any aspect of integrated pest management, including, but not limited to, crop producers, individuals working in crop protection, retailers, manufacturers and suppliers of pest management products, educators, and pest control operators.

JIPM is published by the Entomological Society of America, the largest organization in the world serving the professional and scientific needs of entomologists and people in related disciplines. Founded in 1889, ESA today has nearly 7,000 members affiliated with educational institutions, health agencies, private industry, and government. Members are researchers, teachers, Extension service personnel, administrators, marketing representatives, research technicians, consultants, students, and hobbyists. For more information, visit http://www.entsoc.org.