Incidence of Yellow Rice Stem Borer Scirpophaga incertulas Walker in Haiphong, Vietnam and Control Efficacy of Egg Mass Removal and Insecticides

The yellow rice stem borer (YRSB) Scirpophaga incertalas (Walker) is one of the most serious pests of rice in Southeast Asia. In the present study, the incidence of YRSB was surveyed in 2011 and 2012 at Anlao, a main rice growing district of Haiphong Province, Vietnam. Efficacy of removing YRSB egg masses and spraying with three insecticides was also examined. The results showed that the densities of YRSB larvae and pupae were very low in main rice-cropping times, i.e., late spring and middle summer seasons. In fact, the percentages of dead hearts and white heads were low. However, in middle summer, the density of YRSB and the percentage of damaged stems were higher than those in late spring rice. Efficacy of controlling measures was then evaluated with 11 treatments consisting of egg mass removal and insecticide applications. The results demonstrated that all measures provided better control of YRSB than the control. However, different measures resulted in different percentages of white heads. Efficacy of two newly used insecticides Virtako 40 WG and Prevathon 5 SC was highest when applied twice. The efficacy was followed by removal of egg mass twice, spraying Virtako 40 WG once or Prevathon 5 SC once with and without removal of egg mass and spraying Regent 800 WG. A combination of removing egg masses and spraying Regent 800 WG once provided a better result than spraying Regent 800 WG twice. Effective YRSB management tactics were discussed on the basis of the results obtained.