The Aster Leafhopper (Homoptera: Cicadellidae) in California Rice: Herbicide Treatment Affects Population Density and Induced Infestations Reduce Grain Yield

Abstract

Macrosteles fascifrons Stal is associated with broadleaf weeds and sedges in California rice fields. Factors that result in a sparse rice plant density or fewer rice tillers allow greater aquatic weed growth. In factorial field experiments, rice plant and rice water weevil densities were manipulated to test the effect of timing of herbicides for controlling broadleaf weeds and sedges on aster leafhopper density. 2-Methyl-4-chlorophenoxy acetic acid, a phenoxy herbicide, is used extensively on California rice to control broadleaf weeds and sedges. The recommended time of application is 35 to 65 days after seeding. Data suggested that late applications (52 and 58 days after seeding) resulted in movement of M. fascifrons from weeds to rice in plots with a sparse rice plant density. No such movement occurred following an early application 38 days after seeding. Induced infestations of M. fascifrons in small experimental plots significantly reduced rice grain yield—ll.6% in 1980 and 12.2% in 1981—primarily by reducing the number of panicles per plant. Negative evidence is given that carbaryl, which was used to eliminate leafhoppers on control plants, did not directly affect rice grain yield. Nymphs and adults preferred senescent to green rice foliage.