Bakanae Disease: The Silent Threat to Rice Crops

The world’s biggest source of food: Agriculture, being the mainstay of many economies. Among these, plant disease emerges as a major threat to crop yields. One of the camouflaged enemies is the Bakanae disease which attacks rice plants. 

What is Bakanae Disease?

Bakanae is a seedborne fungal disease which is translated from the Japanese word for foolish seedling and affects rice (Oryza sativa) plants. This is a disease whose causal agent is the fungus Gibberela fujikuroi. Notably, the metabolic pathways of this fungus provide a high yield of gibberellic acid, which is responsible for the specific signs of the disease. 

How does Bakanae Spread?

1. Seed Transmission: The transmission of Bakanae mainly occurs through seeds, which are contaminated by the fungus. When farmers have seeds, which are contaminated with fungal spores, they, in one way or another, bring the pathogen into the fields.

2. Plant Material and Soil: The pathogen can also be transmitted through plant organs, plant products, or through the soil. For this reason, Bakanae can hit even without seed transmission. 

3. Wind and Water: For example, wind and water are the agents that spreads the spores of fungi from one plant to another. It can spread from one field to another or different rice plants within the same field. 

Identifying Bakanae-Infected Plants: 

1. Abnormal Growth: The plants become stunted due to the infection and the grains they produce are often malformed. They are giant plants with sheer white and scrawny leaves.

2. Fewer Tillers: Plants infected with Bakanae produces fewer tillers, which is a minus point as far as production is concerned.

3. Empty Grains: Grains are either partially full or contain nothing at all.

4. Root Lesions: Seedlings may develop root lesions, which in turn cause early death.

5. White Powdery Growth: Simple signs include a white powdery substance at the base or lower part of the plant.

6. Root from Above-Ground Nodes: Some of the plants grow roots from some nodes on the stems and these roots are called aerial roots.

Impact on Crop Yield: 

The consequences of Bakanae disease can be severe: 

1. Crop Losses: In outbreak cases, crop losses can reach upto 20%. In Japan, losses of 20-50% have been observed.

2. Global Impact: India and Thailand have reported yield loss of 15% and 3.7% respectively. 

Managing Bakanae Disease: 

Effective management strategies are crucial to mitigate Bakanae's impact:

1. Use Clean Seeds: Reducing disease incidence through using clean, disease-free seeds.

2. Salt-Water Sepration: In seed soaking, it is recommended to use salt water to separate light weight infected seeds.

3. Fungicides as Seed Treatments: 

- Treat with fungicide containing benomyl or benomyl-t (1-2% of seed weight) to coat the seeds when they are dry.

- Soak seed in a fungicide solution (1:1000 for one hour or 1:2000 for five hours).

4. Avoid Resistance: Pay particular attention to the applications of benomyl due to the possibility of the development of the resistance of the fungus. Possible substitute for that compound are triflumizole, propiconazole and prochloraz, or thiram and benomyl. 

Bakanae disease may be hidden but it has serious effects on the economy. Periodically and on a case basis, we are able to manage the factors that cause disease and that threatens our rice crops and hence food security for millions of people.