Field Test Using the Nematode Phasmarhabditis hermaphrodita for Biocontrol of Slugs in Spain

An experiment was carried out between May and July 1999 in Galicia (North-West Spain) to test the capacity of the nematode Phasmarhabditis hermaphrodita to protect field grown lettuces from slug damage in our field conditions. The experiment compared a single dose of nematodes (3 2 109 ha -1) with mini-pellets containing 5% metaldehyde, applied at the recommended field rate (3 g pellets m -2), and untreated plots. Slug damage for each lettuce head was estimated on six dates during the first 4 weeks after planting. At harvest, each lettuce head was weighed, scored as marketable or not by weight and external aspect, and inspected for slugs. Metaldehyde significantly reduced slug damage to lettuce plants from the first day after planting to the third week. Nematodes significantly reduced slug damage from the second to the third week. At harvest, 6 weeks after planting, the mean weight of the lettuce heads and the number of marketable heads in the nematode plots were as good as in the metaldehyde plots, and both treatments were significantly better than the untreated plots. The number of slugs within the harvested plants was significantly reduced only with the metaldehyde treatment.