Prevent Spread of Bacterial Leaf Blight:

Prevent Spread of Bacterial Leaf Blight
The rice disease called bacterial leaf blight occurs mostly during the wet season when water overflows in rice fields. The symptoms of this disease manifest at 45 to 55 days after transplanting (DAT) and it accounts for 30 to 40 percent of rice yield losses.

PhilRice experts, however, say that even if the wet season favors the occurrence of rice diseases like bacterial leaf blight, farmers may as well follow a number of practical tips to make their occurrence unfavorable.

The experts said strong wind, heavy rains, and 25°C-35°C temperature, excessive nitrogen, potassium and phosphorus deficiency, and use of highly susceptible variety aggravate the severity of bacterial leaf blight.

While farmers could not do anything on the first two factors, they can definitely control the other three factors.

Don’t wait to see a yellowish to brownish color on both sides of the leaf from the tip down to the base, which is the symptom of the disease. Consider the following to avoid the spread of BB, the experts said.

Reduce plant injury when pulling the seedlings for transplanting. The cut roots in the seedling will serve as an entry point for the bacteria.

Put organic fertilizer on the seedbed to soften it and make the pulling of the seedlings easy. PalayCheck, an integrated crop management system, recommends transplanting 20- to 22day old seedlings as they are young and easy to uproot and produce more tillers. However, some farmers prefer 26- to 30-day old seedlings. This farmer’s practice, according to the experts, is not recommended because old seedlings have long leaves and root systems that are easy to break when uprooted, thus increasing the occurrence of infection.

Prepare water canal outlets across the paddy to drain water easily during heavy rains. It is not advantageous to plant in the low-lying area of the ricefield where crops are usually submerged under water, resulting in bacterial leaf blight infestation. As bacteria thrive well in water, it is most likely that rice plants in the low-lying areas may get the bacteria which will gradually spread to the entire ricefield.

To avoid excessive nitrogen fertilization from 25 to 60 days after seeding, use the leaf color chart (LCC), a diagnostic tool that measures the nitrogen status of a rice plant based on leaf color. A well nourished rice crop during the wet season becomes susceptible to bacterial leaf blight and, hence, fertilizer application must be split.

Based on the minus-one element technique, an easy alternative technique for diagnosing nutrient limitations, and for determining LCC recommendations, apply NPK (nitrogen, phosphorus and potassium) fertilizer first at 10 to 14 DAT, second at 28 to 30 DAT, and the third at 42 to 60 DAT as needed. This way, infection will be delayed and, thus, crop losses would be reduced, experts said.

In the wet season, the most economical and practical management practice is to plant resistant variety such as NSIC Rc142 or Tubigan 7.

After harvesting, plow under rice stubbles or practice fallow period to eliminate the source of bacterial blight organisms during the dry season.