Populations of terrestrial planarians affected by crop management: implications for long-term land management

On agricultural land in New Zealand terrestrial planarians are normally fou nd under debris refuges at field margins. In a maize field which had been z ero-tilled for several years, significant numbers of terrestrial planarians , including an Artioposthia sp. known to prey on lumbricids, were found in mid-field. The presence of these planarians was associated with a marked de cline in lumbricid earthworms. The refuges provided by maize residues and t he absence of cultivation-induced planarian mortality are thought to accoun t for the situation. If this effect is general it may be necessary to inclu de occasional conventional tillage in zero-till cropping systems as a means of controlling planarian populations.