Optimising the Whitehead and Hemming tray method to extract plant parasitic and other nematodes from two soils under pasture

Three variations of the Whitehead and Hemming tray method for extracting ve rmiform nematodes from soil samples, and the decant and sieve method, were compared using a silt loam and a clay loam soil under long-term pasture. Co mparisons showed that greatest nematode recovery was achieved when 50 g of soil was placed in a tray lined with two-ply paper tissue and extracted for 48 h with 500 ml water. Recovery of the total nematode fauna and of plant parasitic nematodes from the tray extract was significantly better (P less than or equal to 0.001) after allowing nematodes to sediment in a 11 straig ht-sided beaker than In a 15 cm diam. filter funnel. After 48 h extraction on trays, this method recovered 77% of the total numbers of all nematodes ( 72.5% of the plant parasites) extracted over 144 h with daily collection fr om the trays. The optimum extraction duration was different for Paratylench us nanus compared to Pratylenchus sp., apparently related to differences in their mode of parasitism, with root-dwelling stages of Pratylenchus being recovered at longer times. There was a significant treatment x soil interac tion for Meloidogyne Mr sp., recovery of which was improved by beaker sedim entation in silt loam but not clay loam soil, compared to funnel sedimentat ion. A significant treatment x soil interaction was also observed for H. tr ifolii, the beaker method being better at recovering this nematode in clay loam than silt loam soil, compared to the decant and sieve method.