Disease Control 77

Disease Control - 77

Project Leader and Principal UC Investigators

Robert K. Webster, Dept. of Plant Pathology, UC Davis

J. Bolstad

W. Bockus

D.M. Brandon

C.M. Wick

At the beginning of our research program in 1969, little was known about diseases in California rice. Preliminary study at UCD confirmed the interrelationship of seedling diseases to the problems of stand establishment, although it was not known whether seed rot and seedling diseases could be controlled. Growers compensated by an ever-increasing rate of seeding and, in severe cases, by reseeding. Stem rot was first observed in 1933, but researchers and farmers considered it normal and unimportant. As research progressed, other diseases of rice were noted: sheath blight, Phythium crown blight, and Heliminthosporium leaf blight. Presently, these pose no threat to our rice crop.

Research by Dr. R.K. Webster, UC plant pathologist, proved that stem rot was an important disease and that field burning is important for economical control of stem rot, particularly in badly infested fields. Other helpful management practices have been developed.

More than 50 chemicals have been tested on organisms causing seedling diseases, Shown here killing germinated rice seed. Difolatan, captan, and Kocide SD have been registered for use by California rice growers as a result of this research. They have consistently improved rice stand establishment and reduced the need for costly reseeding.

This UCD greenhouse experiment shows the devastating effects of stem rot disease. Rice in the left front basin was inoculated with stem rot sclerotia; whereas, those basins in the right and rear were not. Yield losses of 10 to 12 percent from stem rot are common in commercial fields and have run as high as 50 percent.

Dr. R. K. Webster discusses his 4 years of research to locate a chemical which can be safely added to rice paddy water to economically control stem rot. Du-Ter looks promising when used in combination with burning, but government approval and registration are needed before Du-Ter can be used commercially. Pictured (1. to r.) are the late William J. Duffy, Jr., Sutter Basin; S.L. Clement, entomology graduate student; L.O. Drew, chairman, California Cooperative Rice Research Foundation; Jack W. Baber, Rice Research Board, Colusa; Dr. D.M. Brandon, UC rice specialist; Webster (in drain ditch); and Narval F. Davis, Rice Research Board, Firebaugh.