Plant pathologists based at the Midsayap station of the Philippine Rice Research Institute (PhilRice) advised farmers to plant different rice varieties for succeeding seasons as this maintains resistance against major crop diseases.
The recommendation was released following findings that planting NSIC Rc158 for two consecutive cropping seasons caused the occurrence of rice blast in Kabacan, North Cotabato. Blast caused by the fungus Magnaporthe grisea injured rice plants in this area during the vegetative stage.
According to Frezzel Praise Tadle, PhilRice Midsayap monitoring team leader, the successive planting of the same varieties weakens resistance especially when the seed is disease-infected. Blast, commonly known as mata-mata (Filipino); agupaw (Waray), and taya-taya (Cebuano) could reduce yield by 50 to 85 percent.
“Always use healthy seeds. Infected seeds from harvested plants should not be used for planting,” she said.
In their monitoring, the team found that a minimal blast infestation occurred in the area during the dry season in 2010. However, rice farmers ignored the incidence and planted the seeds from the infected plants as the disease did not previously cause significant yield loss.
They also found that traders’ additional incentive of P0.50 for a kilo of NSIC Rc158 motivated farmers to plant the same variety for this year’s dry season.
Tadle further stressed that frequent rains experienced in the province since early this year intensified disease infections as rice blast survives in cool areas. High relative humidity and long-hour exposure to dew also favor disease development.
“Fungus produces thousands of spores, which can be easily carried by the wind and infect other healthy plants,” she explained.
Tadle warned farmers that blast-infected panicles from booting to heading stages could result to higher losses as these are the stages critical for the rice plant.
To minimize further damage to plants, PhilRice recommends the following:
1.Farm activities such as weeding and fertilizer application should be avoided when rice leaves are wet because spores scatter easily. Germination immediately occurs once spores land on wet leaves;
2.Dense planting should also be avoided as this could easily transfer spores from one plant to another;
3.Nitrogen fertilizer should be done in split application;
4.Continuous flooding at all crop stages after transplanting should be practiced; and
5.Fungicides such as benomyl, edifenphos, pyroquilon, tricyclazone, and isoprothiolane can be applied but this should be the last resort to manage rice blast. Two applications are recommended to avoid plants in infecting the panicles. This may be done at early heading and when the heads have already emerged.