Effects of Organic Farming of Rice Plants on Population Density of Leafhoppers and Planthoppers. I. Population Density and Reproductive Rate.

Abstract

We studied the effects of organic farming of rice plants in a paddy and in a chemically-fertilized plot, a poultry-manured plot and a non-fertilized plot on the population densities of the green leaf-hopper, Nephotettix cincticeps UHLER, the white-backed planthopper, Sogatella furcifera HORVATH, and the brown planthopper, Nilaparvata lugens STAL. The density of the green leafhopper in the organically-farmed paddy was the lowest probably due to the low population density during the fallow period. The density of the white-backed planthopper in the organically-farmed paddy was the lowest because the reproductive rate was extremly low. The density of the brown planthopper in the organically-farmed paddy was also the lowest. The density of natural enemies in the organically-farmed paddy was lower or similar to that in the other plots. Therefore, natural enemies did not contribute to the lower density of leafhoppers and planthoppers in the organically-farmed paddy.