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INVESTIGATOR: Groth, D. E.

PERFORMING INSTITUTION:
RICE RESEARCH STATION
LOUISIANA STATE UNIVERSITY
BATON ROUGE, LOUISIANA 70893

MANAGEMENT STRATEGIES FOR RICE DISEASES IN LOUISIANA

OBJECTIVES: To survey for yearly fluctuations in rice diseases in Louisiana and to monitor the rice crop for new diseases or changes in status of the minor diseases to predict future research needs. To improve disease management strategies for control of rice blast, sheath blight, bacterial panicle blight, brown spot, narrow brown leaf spot, leaf smut, and other foliar, stem, grain, and seedling diseases of rice by integrating host resistance, cultural management, pesticides, and other disease control methods. To develop and conduct screening programs in the field and greenhouse evaluating disease resistance in rice to multiple diseases. To conduct field, greenhouse, and laboratory screening programs for determining pesticide efficacy against rice pathogens using the best application timing and rate under various management systems. To develop scouting and disease prediction techniques and economic thresholds for pesticide applications.

APPROACH: Changes in the levels of major diseases or in the status of minor diseases will be determined by disease surveys as needed and by observing disease development in plots at the Rice Research Station at Crowley, LA. Recommendations will integrate the use of pesticides with cultural practices, disease resistance, and biological control practices. These recommendations include the control of blast, sheath blight, stem rot, brown spot, narrow brown spot, watermolds, leaf smut, and other diseases on rice. The effect of varying cultural practices, such as crop rotation, fertilization, water management, seeding method and rate, planting date, and tillage practices, on the efficacy of pesticides will be investigated in small plot tests. Rice varieties and breeding lines will be screened for disease resistance. Field testing will be conducted in small plots and single row tests at the Rice Research Station and at off-station trials whenever diseases express themselves differentially. Fungicides will be screened for disease control in rice. Field testing will be conducted on plots large enough to be harvested by a small-plot combine. When possible, milling samples will be collected and processed. Application numbers and timings will be adjusted for environmental conditions and diseases progress. Timings will be by growth stages whenever possible. Methods for determining disease development at early stages or for predicting disease incidence and severity will be developed for use in making spray recommendations. Lesion numbers and development at early growth stages of the rice plants will be correlated with disease severity at maturity and regression models will be used. The effects of rain, humidity, temperature, and length of dew period on disease development will be evaluated and correlated with disease development in the field.

NON-TECHNICAL SUMMARY: Sheath blight, blast, and bacterial panicle blight are the three most important diseases of rice in Louisiana. How a farmer manages these diseases often means the difference between a profit or a loss. A constant effort is needed to keep rice diseases under tolerable levels. A solution to these problems is to integrate pesticide usage, inherent disease resistance, cultural practices, regulation, and biological control into a continuously changing disease management program, which responds to changes affecting each control practice and minimizes the development of epidemic conditions.

PROGRESS: 2002/01 TO 2002/12
Germplasm lines were introduced into the United States. These lines were used in the rice breeding, genetics, and tissue culture programs. Over 3000 breeding lines were evaluated for resistance to multiple diseases, including sheath blight, brown spot, leaf smut, blast, and narrow brown leaf spot. Crosses were made to promising lines by the breeding program. Effect of sheath blight epidemic start and fungicide timing were tested in the field. Yield reductions of 25% and 5 percentage points decrease in head rice were detected. Sheath blight losses were equal for all inoculation times. Fungicides were tested on multiple rice varieties and at multiple locations for ability to control diseases and increase yield and milling. Several new fungicides showed excellent activity against sheath blight and blast on all varieties. Copper fungicides and antibiotics were tested for control of bacterial panicle blight at multiple locations. Kocide and TopCop fungicides showed some activity in reducing grain sterility but tended to be phytotoxic on rice. Antibiotics had better activity.

IMPACT: 2002/01 TO 2002/12
Control of diseases using host resistance, cultural management, and chemical control greatly improved productivity and profitability of rice production. New environmentally safe and more effective fungicides improved disease control. New germplasm with resistance to multiple diseases improved breeding efforts. Efforts to delineate which disease is causing certain damage allowed better scouting methods, timing of control agents, and research efforts.

PUBLICATIONS: 2002/01 TO 2002/12
1. Bollich, P.K. et al. 2002. Louisiana Rice Variety Trials 2001. La. Agri. Exp. Stn. Research Summary #135. 88 pp.
2. Groth, D.E. 2002. Disease control in a conservation tillage system: To spray or not to spray? Proc. National Conservation Tillage Conf., 5:36-37.
3. Groth, D.E. 2002. Timing and rate effects on rice fungicides. Louisiana Agriculture 45:18-19.
4. Groth, D.E. 2002. Timing is the key to rice fungicide performance. Proc. Rice Tech. Wk. Grp. 29:83.
5. Groth, D.E. 2002. Timing, rate important to using fungicides. La. Rice Res. 2:4.
6. Groth, D.E. and F.N. Lee. 2002. Rice Diseases. Pp. 413-436 In: Rice: Origin, Production, and Technology. Edited by C. Wayne Smith. John Wiley & Sons Inc., NY.
7. Groth, D.E and S.D. Linscombe. 2002. LMT1: A new source of resistance to sheath blight and bacterial panicle blight. Proc. Rice Tech. Wk. Grp. 29:87.
8. Groth, D.E. et al. 2002. Rice disease control studies, 2001. Ann. Res. Rpt., Rice Res. Stn., La. Agri. Exp. Stn., LSU AgCenter, 93:313-369.
9. Shao, Q.M., D.E Groth, S.D. Linscombe, and M.C. Rush. 2002. Potential for rice sheath blight control using Liberty herbicide. Proc. Rice Tech. Wk. Grp. 29:92.
10. Jang, J. et al. 2002. Development and preliminary field evaluation of transgenic U.S. rice tolerant to sheath blight disease. Proc. Rice Tech. Wk. Grp. 29:95.

PROJECT CONTACT:

Name: Groth, D. E.
Phone: 337-788-7531
Fax: 337-788-7553
Email: dgroth@agcenter.lsu.edu
URL: http://www.lsuagcenter.com