Rice tungro disease management - IRRI books - International Rice ...

Cotabato, and Laguna) during 1995-97 showed that most farmers had experiencedthe RTD problem and could recognize symptoms of RTD (Warburton et al 1996,1997, Truong et al, this volume). Only a few farmers (8%), however, were aware thatGLH is the vector of RTD. Most of them did not know the relationship between thedisease infection and the vector spreading the disease from an infected crop to a healthyone. Consequently, they were not aware of the risks posed by a nearby infected crop,which serves as a source of disease inoculum. They usually associated the spread ofthe disease to factors such as kind of insect on the crop, water, soil, rain, and others.Some confused RTD with nutrient deficiency symptoms because the causal organismsare not observable. Their assessment of crop losses was based on past cropfailures. Control practices focused more on preventive measures for all kinds of insectpests because farmers know more about insects than RTD. Most farmers. whethertrained or untrained on tungro management technologies in “hot spots,” intensivelyused insecticides as a tool against RTD and other pests. Cypermethrin, a pyrethroidcompound, was effective against GLH in experimental fields (Batay-an and Mancao’this volume). Its effectiveness, however, was not always observed by farmers becauseRTD infection had spread. This control strategy aimed more at producing aclean crop than making farming sustainable although some realized that insecticideuse was not always effective in controlling RTD.Meanwhile, most farmers were reluctant to remove the infected crop becausethey had already incurred costs in purchasing production inputs. In Negros Occidental,farmers preferred to broadcast salt in RTD-infected fields although this practicehas no scientific basis, while others practiced roguing infected plants. Tiongco et al(1998), however, pointed out that roguing as a tactical means of control was not effectivebecause it is usually done late, when infected plants are observed. Infectedplants without symptoms remain in the field and serve as virus sources. It is thus achallenge for research and extension workers to look for an alternative control techniqueand to help strengthen farmers’ skills and efficiency in making decisions onRTD management.On the other hand, farmers in RTD-endemic areas in North Cotabato are verykeen on selecting varieties and establishing the crop for RTD management (Truong etal, Community-based rice pest management. this volume). They have more experiencewith direct seeding (DS), and they claim that a crop established by this methodhas a reduced risk of pest infestation compared with transplanting. Trained farmersfrom the Farmers’ Field School (FFS) had adopted GLH-resistant varieties such asIR56, IR62, PSB-Rc 10, PSB-Rc 18, and PSB-Rc 34 to control RTD. Untrained farmers preferred their selections.Current trends in RTD research and extensionThe use of resistant varieties is a cost-effective component of RTD management. ThePhilRice Varietal Improvement Program and the Department of Agriculture have focusedon developing varieties with high yield and good quality and, at the same time,resistance to insect pests and diseases. Baria (1997) summarized the protocols onvarietal selection of the National Cooperative Test network and approval of recom-Rice tungro disease 3