Management of Pratylenchus penetrans on Oriental Lilies with Drip and Foliar-applied Nematicides.

Pratylenchus penetrans is a pest for producers of oriental lilies in northern California. Concern over groundwater contamination from 1,2-dichloropropane following shank injections of 1,3-dichloropropene-l,2-dichloropropane mixture and granular applications of aldicarb prompted testing for alternative methods of controlling P. penetrans. In field trials, nematicides applied by drip irrigation (ethoprop, fenamiphos, oxamyl, sodium tetrathiocarbonate, water extracts of marigold and vetch, and 1,3-D plus emulsifier) were tested with and without foliar applications of oxamyl. Nematode populations were reduced (P = 0.05) relative to controls in soil or roots on one or more sampling dates by all drip-applied nematicides except the plant extracts. On some sampling dates, additional reductions (P = 0.05) occurred as a result of three foliar applications of oxamyl. Foliar-applied oxamyl alone also reduced (P = 0.05) nematodes in soil or roots. Lily bulb weight was not affected (P = 0.05) by chemical treatments.