The roots of "tubli," scientifically named Derris elliptica, contains rotenone which causes the suffocation of fishes when applied in ponds but does not affect shrimps, according to the Los Baños-based Philippine Council for Aquatic and Marine Research and Development (PCAMRD).
In shrimp farming, PCAMRD noted, imported teaseed cake is commonly used in eradicating unwanted fishes in ponds without affecting the main crop. For freshwater ponds, hazardous chemicals such as sodium cyanide and insecticides are used for fish control.
"Tubli," on the other hand, is equally effective as teaseed cake, does not cost much, and is safer to use than chemicals for pond management, PCARMD pointed out.
Researchers of Aquatic Biosystems, a Laguna-based private firm, found that the application of coarse tubli root powder at 10 kilos per hectare was effective in controlling fish predators such as mudfish and catfish in freshwater ponds.
The root powder is mixed with water at a proportion of one kilo in 50 liters prior to application at a pond water depth of one-tenth meter.
"Pond treatment is best done at noon. After 24 hours, the pond can be refilled to its normal depth of one meter and the culture fish safely stocked," PCARMD stated. – Rudy Fernandez