J. Catindig, S. Villareal, International Rice Research Institute, Los Baños, Philippines and R. Saltin, Department of Agriculture, Iloilo City
In Iloilo, planthopper outbreaks have damaged about 6700 ha and 2700 ha have suffered significant yield losses. Damages in Iloilo were much higher than outbreaks in Capiz and other areas reported earlier (Read: Outbreaks in Philippines). We conducted a survey of 33 farmers in 3 barangays in Iloilo and found that 18 farmers’ fields (54%) had hopperburn symptoms. The farms where hopperburn had occurred were mostly planted with PSB Rc 120. The degree of damages varied from low (1-10%) in 8 fields, medium (30-50%) in 2 fields, and high (70-90%) in 2 fields. Six more farmers had hopperburn but could not estimate the extent of loss.
The two fields with 70-90% infestations were sprayed 5 times with cypermethrin insecticides starting from 15 days after transplanting with subsequent spray applied at weekly intervals. Other fields were yellowing due to high hopper densities were also sprayed with cypermethrin between 2 to 5 times. The risk value for cypermethrin is moderate but when applied 5 times, the fields could be 5 times more vulnerable (Read: Assessing BPH outbreak risks).
The yields of farmers with 1 to 6 insecticide sprays were not significantly different although there was a general negative relationship. (Read: Do insecticides increase yields?). Yields varied from 1 to 8 t/ha and the farm that used only 1 spray yielded 8 tons, while the farm that used 5 sprays had only 1 ton because of hopperburn.