Preplant drip-applied fumigation for calla lily rhizome nursery

Two field trials were conducted from 2002 until 2004 to evaluate several chemicals as alternatives to methyl bromide for the production of calla lily (Zantcdescbia sp.) rhizomes. Various rates and chemical combinations were tested. The chemicals were applied through a drip irrigation system. The chemicals included iodomethane, chloropicrin, 1,3-dichloropropene, metham, sodium furfural, and sodium azide. None of the treatments reduced the viability of seed of mallow (Malva parviflora) previously buried in the plots. Propagules of nuts-edge (Cypcrus csculcntus) and seed of mustard (Brassica nigra) were controlled by iodomethane + chloropicrin, 1,3-dichloropropene + chloropicrin, chloropicrin alone, 1,3-dichloropropene alone, and furfural + metham sodium. Propagules of calla were controlled by all of the treatments except sodium azide and furfural + metham sodium. In the first trial, all treatments reduced the populations of soilborne plant pathogens, including Pythium spp., Pbytophthora spp., and Fusarium oxysporum, except for sodium, which did not reduce the population of Phytophthora spp. In the second trial, all treatments controlled Pytbium spp. but only a high rate of iodomethane + chloropicrin reduced the population of F oxysporum. For all treatments, the incidence of disease caused by soilborne pathogens was reduced compared to the nontreated control. The number and value of harvested rhizomes were greater among all of the treatments, except for sodium azide, compared to the control. The harvested value of the crop for the best treatments increased significantly compared to the control. A successful crop of calla rhizomes can be produced by combinations of iodomethane, chloropicrin, 1,3-dichloropropene, and metham, sodium.