Abstract
The extraction efficiencies of the double-layer centrifugal-flotation method (DCF)and the modified Baermann funnel technique (BF) were estimated, based on the number of nematodes detected by direct examination (DE) of soil samples obtained from a sweet-porato field. Although the dead nematodes were extracted by DCF, no successful extraction of dorylamid nematodes and nematode eggs was attained. The maximum likelihood values of mean extracction efficiencies of DCF with Meloidogyne incognita larvae, Helicotylenchus spp., tylenchid-, aphelenchoid-, monhysterid-, dorylaimid nematodes, "others"(mainly rhabditid nematodes) and a total summation of all nematodes were 68.1-86.6%, 51.5-62.3%, 73.7-81.0%, 56.5-85.7%, 18.0-46.9%, 1.9-5.4%, 71.1-84.5%, and 66.5-72.9%, respectively. Those of BF with above nematode groups recovered within 24 hr from the bottoms of funnel stems were 0.1-3.1%, 0.2-4.9%, 6.1-20.8%, 21.5-42.2%, 0-74.3%, 02.-1.8%, 15.6-22.5%, and 6.1-7.8%, respectively. The efficiencies of BF were strikingly affected by several factors; nematode species and their stages, extraction time and temperature, and sampling seasons.
