Studies of Pests Population Dynamics on Rice
W. C. Lin
A survey on rice pests population dynamics has been conducted in 1977. Many insect pests were found in rice field. It included: Spodoptera maurita Boisduval, brown rice plant-hopper (Nilaparvata lugens), white black plant-hopper (Sogata furcifera Horvata), grass leaf roller (Cnaphalocrocis medinalis Guenee), rice leaf whorl maggot (Hydrellia philippina Ferino), green rice leafhopper (Nephotettix Cincticeps Uhler), Zigzag striped leafhopper (Inazuma dorsalis Motschulsky), small rice grasshopper (Oxya intricate Stal), yellow rice borer (Tryporyza incertulas Walker), rice stem borer (Chilo suppressalis Walker), pink borer (Sesamia inferens Walker).
The former nine pests occurred in 1st crop, while the latter ten pests occurred usually in 2nd crop. But brown rice plant-hopper, grass leaf roller, yellow rice borer, and green rice leafhopper are always the major pests.
In 1st crop, 2~3 rice brown plant-hoppers per hiller are found, percentage of leaf damage caused by grass leaf roller is about 0.03%, ears damaged by yellow rice borer is 0.68%, about 6.1 green rice leaf-hopper are found in every single sweep net. These four major pests mentioned above occurred mostly between rice head-sprouting and harvesting stage in 1st crop, but in 2nd crop, its occurred between rice tillering and harvesting stage.
Rice yield in 1st crop is 5561 kilograms per hectare, it seems that these insect pests do not cause yield loss. In 2nd crop, rice yield is 2596 kilograms per hectare and yield loss is about 34.5%.