Evaluating mustard extracts for earthworm sampling

The efficiency of using mustard extract as a repellent for earthworm sampling was investigated for two contrasting earthworm species. For the anecic Anisochaetae sp., a deep burrowing species which created vertical bur-rows, mustard extract produced a 67 % higher abundance than the formalin (74 versus 44 m(2)). Handsorting underestimated abundance by 21 % and biomass by 67 % because of its failure to include the adults /subadults which escaped quickly to below 10 cm depth but were effectively sampled by using mustard. Excessively concentrated mustard extract reduced sampling efficiency by reducing the number of juveniles. The most optimal concentration was achieved by shaking 106 g dry mustard powder in 1 L of 5 % acetic acid overnight which was then diluted with water in the ratio of 15 mt to 1 L. For Aporrectodea trapezoides, an endogeic species which tends to create horizontal burrows not all directly connected to the surface, using mustard extract was a completely ineffective method of sampling compared to handsorting because most of the earthworms were adversely affected and remained in the 0-10 cm layer. From these results, mustard extract at optimal concentration is a more efficient and environmental friendly repellent for only certain earthworm species, particularly the anecic earthworms.