Effects of temperature on stem nematode (Ditylenchus dipsaci) infestation of white clover (Trifolium repens) swards

Development of stem nematode (Ditylenchus dipsaci) infestations of white cl over (Trifolium repens) in artificially established swards and transplanted turfs was monitored at field sites with different mean daily temperatures. In artificial swards the level of nematode infestation was inversely relat ed to mean daily temperature. In transplanted turfs, nematodes caused a 46% reduction in white clover density over an 18-month period; the level of da mage was not significantly affected by mean daily temperature although the proportion of clover stolons infested was higher at colder temperatures. Re ductions in infestation levels at higher temperatures are probably the resu lt of reduced survival in soil and the upper lethal temperature for nematod es being exceeded more frequently under warmer conditions.