COMPARISON OF SLUG (MOLLUSCA, PULMONATA) TRAPPING IN NO-TILL ALFALFA

A comparison of defined-area traps (DATs) and refuge traps (RTs), in n o-till alfalfa (Medicago sativa L.) to census the slug species Derocer as reticulatum (Muller), Deroceras laevae (Muller), and Arion fasciatu s (Nielson) was made. The objective of the study was to determine whet her RTs could be used in a range of crop densities and climatic condit ions to assess slug density. In relation to slug density measured by D ATs, RTs were less effective in trapping slugs in spring, when D. reti culatum was very small, but trapped relatively higher numbers than DAT s when slugs were larger. Trapping methods were assessed between May a nd November in no-till alfalfa plots with plant densities ranging from 52 to 99% total plant cover in May to 78 to 91% cover in July. Alfalf a crop density had no effect upon RT catches except in dry conditions in June, when RTs collected more slugs in plots with most vegetation c over. Neither trap collected slugs during severe drought conditions in July when soil moisture content in the top 5 cm of the soil profile d ropped to about 6%.