Persistence ofHeterodera trifolii(Nematoda) cysts in the absence of host plants

Abstract

Emergence of H. tri/olii juveniles from cysts stored in moist (35% water), dry (5% water), cool (2-4°c), or warm (12-23°c) soil was followed over 180 weeks. Each of these factors significantly reduced emergence of juveniles, and all interactions were significant. In all treatments emergence declined with time, but after 180 weeks, juveniles were found in each treatment. This persistence, the host range of H. fri/olii, and the effect of stock movement in dispersing cysts all indicate that control of H. fri/olii in New Zealand pastures by management is unlikely.