Effect of Fertilization of Pasture on Larval Survival and Development of the Armyworm Pseudaletia separata WALKER and on Its Predation by the Wolfspider, Pardosa laura KARSH

Abstract

To analyse the effect of fertilization of grass on the survival and growth of the armyworm, Pseudaletia separata walker, and the interaction between armyworms and a wolfspider, Pardosa laura karsh, field and pot experiments were carried out. Fertilization of orchardgrass, Dactylis glomerata L., increased the nitrogen contents, height and density of the grass. Survival and growth rate of the armyworms increased with increasing grass nitrogen contents due to fertilization. Although the armyworms occurring on non-fertilized grass walked about more actively than those on fertilized grass, the larval mobility had little effect on the degree of wolfspider’s predation. The wolfspiders on non-fertilized grass preyed on a larger number of larvae of the armyworm than those on fertilized grass. For the same level of fertilization, the wolfspiders occurring on short or sparse grass preyed on a larger number of larvae than those on tall or dense grass. These results suggest that fertilization of grass increases the survival rate of the armyworm due to the increase of the grass nitrogen contents as nutrient for the larvae, as well as the increase of grass height and density which interfere with the wolfspider’s predation. © 1987, JAPANESE SOCIETY OF APPLIED ENTOMOLOGY AND ZOOLOGY. All rights reserved.