How to Manage Pests

UC Pest Management Guidelines

SYMPTOMS AND SIGNS

Symptoms of bakanae first appear about a month after planting. Infected seedlings appear to be taller, more slender, and slightly chlorotic when compared to healthy seedlings. The rapid elongation of infected plants is caused by the pathogen's production of the plant hormone, gibberellin. Plants with bakanae are often visible arching above healthy rice plants; infected plants senesce early and eventually die before reaching maturity. If they do survive to heading, they produce mostly empty panicles.

COMMENTS ON THE DISEASE

Bakanae is one of the oldest known diseases of rice in Asia but has only been observed in California rice since 1999 and now occurs in all California rice-growing regions. While very damaging in Asia, the extent to which bakanae may effect California rice production is unknown.

As diseased plants senesce and die, mycelium of the fungus may emerge from the nodes and may be visible above the water level. After the water is drained, the fungus sporulates profusely on the stems of diseased plants. The sporulation appears as a cottony mass and contaminates healthy seed during harvest. The bakanae pathogen overwinters as spores on the coat of infested seeds. It can also overwinter in the soil and plant residue. However, infested seed is the most important source of inoculum.

MANAGEMENT

The most effective means of control for this disease is the use of noninfested seed. Also, when possible, burning plant residues with known infection in fall may help limit the disease. Research is under way to identify effective seed treatments. Field trials indicate that a seed treatment with sodium hypochlorite (Ultra Clorox Germicidal Bleach) is effective at reducing the incidence of this disease. Using a thoroughly premixed solution of 5 gallons of bleach to 100 gallons of water, seed is soaked for 2 hours, then drained and soaked in fresh water.

PUBLICATION

UC IPM Pest Management Guidelines: Rice
UC ANR Publication 3465
Diseases
R. K. Webster, Plant Pathology, UC Davis
C. A. Greer, UC Cooperative Extension, Colusa Co.
Acknowledgments for contributions to the disease section:
C. Wick, UC Cooperative Extension, Butte Co.
S. C. Scardaci, UC Cooperative Extension, Colusa Co.

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