The Influence of Nitrogenous Fertilizer on the Grassland Auchenorrhyncha (Homoptera)

Abstract

1. Samples of Auchenorrhyncha were collected from fertilized plots between April 1978 and November 1979. 2. Twenty-nine species were recorded of which twenty-six probably breed regularly on the experimental area. 3. NPK fertilizer addition reduced leafhopper species diversity by disproportionately increasing the total number of individuals which effectively reduced the equitability index. 4. Delphacids were more abundant on plots receiving nitrogen fertilizer whereas cicadellids were more abundant on control (unfertilized) areas. 5. The major effect of nitrogen addition was to increase the food quality and the living area (plant architecture) available to leafhoppers. Both increased food quality and increased living area were beneficial to the leafhopper complex allowing the community to rapidly increase in numbers (i.e. the total captured in 1978 was 4122 whilst in 1979 the total captured was 17 964). 6. Leafhoppers were more abundant on plots with a 'preferred' leaf nitrogen level. Adult aggregation and female reproductive success were greater at the 'preferred' leaf nitrogen level.