by John Grusenmeyer, Sustainable Plant Systems-Agronomy major
It provides 70% of the dietary energy in Bangladesh and 20% of the world’s dietary energy needs (FAO). A crop that provides humanity so much of the world’s dietary energy and is absolutely crucial in some Asian countries needs to be protected and cannot be allowed to fail.
This crop is rice.
Rice (Oryza sativa) is attacked by many different diseases but one of the most important is Rice Blast caused by the fungus, Magnaporthe oryzae. Rice blast occurs in every corner of the world that rice is grown and has never been eradicated from any region.
A small infection with the right conditions can quickly turn into and epidemic that can greatly reduce yields or even destroy a field. In Japan between 1953 and 1960 annual losses ranged from 1.4% to 7.3% with hundreds of thousands of tons of rice lost. Even spraying didn’t help. In 1962, 721,000 of the 909,000 hectares sprayed were infected.
In West Africa, losses in rice paddies have reached up to 50% and even 70%.
So what should rice farmers do?
The best control for rice blast is crop rotation. By excluding the rice seedlings from areas where there is high inoculum from previous years keeps the disease pressure lower and can keep epidemics to a minimum. Another cultural control is precise fertilization as over fertilizing rice with nitrogen can increase disease pressure.
There are also cultivars of rice that have genetic resistance to rice blast. Unfortunately, it is only partially effective because of the many different races of rice blast.
Rice blast will continue to plague farmers but research continues to try to find more solutions in an ever changing battle for a crop that is crucial to humanity.
For more info
American Phytopathological Society, TeBeest D., Guerber C., Ditmore M. Rice Blast
Plantwise Knowledge Bank. Rice blast disease (Magnaporthe grisea)
Food and Agriculture Organization. International Year of Rice 2004 Rice is Life
John Grusenmeyer is a junior at The Ohio State University studying agronomy. Growing up on a farm in Miami County, Ohio, sparked his interest in agriculture. After graduation, he hopes to use his education to volunteer with an organization where he can help reduce poverty and hunger through agricultural improvements.
This blog post was an assignment for Societal Issues: Pesticides, Alternatives and the Environment (PLNTPTH 4597). The views expressed are those of the author and do not necessarily reflect the views of the class, Department of Plant Pathology or the instructor.