RESEARCHERS of Philippine Rice Research Institute (PhilRice) are studying the impact of the emergence of the world’s worst weed in irrigated lowland rice production.
Cyperus rotundus L. or purple nutsedge also locally called as mutha, sudsud, and barsanga, which is previously known to grow only in the upland, is now quite prevalent in the lowland.
As mutha is considered the worst weed thriving in more than 90 countries and infesting more than 50 crops, researchers are conducting experiments to learn more about the lowland ecotype and discover its management options.
Before it became an agricultural menace, the weed was a source of food during the early civilizations.
At present, the weed can cause up to 42 percent yield loss in upland rice when left uncontrolled until harvest and in vegetable farms where flooding is not practiced.
Generally, weeds reduce rice yield from 44 to 96 percent as they compete with rice for nutrients, sunlight, and water.
Mutha is difficult to control owing to its extensive network of underground tubers that serves as means for propagation.
Herbicides only affect some of the tubers and do not shoot down the entire network.
Previous studies suggest that mutha does not thrive well in areas with abundant water such as in irrigated lowland.
However, when planting rice and other crops in the wet season and dry season, respectively, became a common practice, mutha gradually emerge.
The weed grows during the non-rice periods while the tubers remain dormant during the rice season due to water abundance.
It is suggested that the weed developed new adaptive mechanism from its constant exposure in submerged environments, enabling its survival under water stress. Eventually, it evolved to live together with rice.
Previous studies and data from PhilRice confirmed the weed’s presence in other parts of the country.
It showed that the weed is no longer location-specific, and becoming a farmers’ problem because they apply herbicides to manage mutha.
The lowland ecotype has a new sense of survival.
Based on initial findings, it can grow more than a meter than its upland counterpart.
It also has larger diameter of stems and air spaces inside that give way for better survival under submerged condition.
The new ecotype has larger tubers, which means it can store more energy to survive even when under stress.
Carbohydrates are sources of energy. The more it has, the chances to thrive are greater.
The effect of this new ecotype in irrigated lowland rice yield is yet to be fully explored.
Initially, a pot experiment was conducted at the PhilRice Central Experiment Station to determine the effects of a single plant mutha in the growth and development of rice under irrigated-lowland condition.
While studies are still on-going, the stale seedbed method in controlling mutha is recommended.
The technique involves repeatedly ploughing the field during the fallow period to allow seeds and other parts of the weeds to grow.
The new plants can then be killed later. It has been proven to effectively reduce the population of weeds. (jaypeeyap@ymail.com/PN)
