The root zone applications of a systemic insecticide, carbofuran, were evaluated for their impacts on the brown planthopper, Nilaparvata lugens (Stål), and spider populations in the greenhouse and rice paddy fields. In the green house experiments, no BPH nymphs were hatched at root zone treated on 40 to 50 day-old rice, while around 20 to 54 nymphs per pot were emerged in broadcasting and foliar spray treatments. This indicates that the root zone treatment can kill the eggs of BPH effectively. This is the first study ever demonstrated the high egg mortality of BPH due to the root-zone application. In the field experiments, the density of BPH in root zone treated plots were four to six times lower than in broadcasting and foliar spray plots at the 21 days after application. The BPH outbreaks and hopper-burns were observed at all treatments except the root zone treated plot at the 28 days after application. The root-zone application did not impact on the spider population, while foliar spray killed most of all spiders just one day after application. The densities of spider in foliar spray plots were always lower than in root-zone treated and control plots. The results indicated that the root-zone application of carbofuran can control BPH effectively without adverse effects to the spiders inhabited on the paddy field.

Root zone application of several systemic insecticides was tested for control of the brown planthopper, Nilaparvata lugens (Stål), in Vietnam and Korea. In Vietnam, the results indicated that carbofuran showed the highest nymphal mortality in all experiments, followed by imidacloprid and carbosulfan. When the insecticides were applied on 10-day old rice, carbofuran was shown almost 100% N. lugens mortality at six days after treatment and the efficacy was extended to twelve days after application. In Korea, various root-zone application methods were tested with carbofuran and carbosulfan. The results showed that carbofuran was the most active in reducing the egg hatching rates. When root-zone treated on 40-50 day-old rice in a greenhouse, no nymphs were hatched in carbofuran treated pots, while average of 20 nymphs were emerged in carbofuran broadcasting pots. Especially the number of nymphs emerged in carbosulfan foliar spray was 54 nymphs per pot even at the eight day after application, which was higher than in control pots. This is the first study ever demonstrated the high egg mortality of N. lugens on rice due to the root-zone application of insecticides.