An examination of methods used to extract virus vector nematodes (Nematoda: Longidoridae and Trichodoridae) from soil samples

D. J.F. Brown, B. Boag

Abstract


The efficiency of the different methods used to collect and extract virus-vector nematodes (Longidorus, Paratrichodorus, Trichodorus and Xiphinema) were examined as part of a collaborative assessment by staff at the principal Nematology laboratories in Scotland, of methods for field sampling, handling and excracting these nematodes. Vehicular transportation of soil samples from field to laboratory did not reduce the numbers of nematodes recovered but several short drops did, by up to 39%, largely by soil compaction. The two-flask method was found to be much slower and was less effective than the decanting and sieving method for recovering longidorid nematodes: When using the decanting and sieving method a 200 g soil sample stirred into suspension in a 5 I pail, given a 15 s settling time and the supernatant poured through a sieve with a 150 /-1m aperture mesh held over an empty 5 I pail was found to be satisfactory. This collects the large longidorid nematodes. The residue on the sieve is washed onto a 95 /-1m aperture mesh plastic sieve which is then placed in a water-filled Baermann funnel. Smaller trichodorid nematodes and juvenile longidorids were collected by passing the supernatant collected in the second pail through individual 75 /-1m and 53 /-1m aperture mesh sieves. The residue on both sieves is washed onto a 2-ply tissue supported in a plastic sieve which is placed in a second water filled Baermann funnel. Most longidorids had fallen to the bottom of the funnel after 24 h, but if required for biological studies were collected after 4 to 6 h. Trichodorids took longer and were recovered after 48 h or, 24 h if required for biological studies. Water temperature in the funnels should be maintained at 15 to 20°C.

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