Fumigant Alternatives to Methyl Bromide for Managing Nematodes and Weeds in Snapdragon

Effect of several soil fumigants on plant-parasitic nematodes, weeds, and snapdragon ( Antirrhinum majus L.) production were evaluated in a commercial site in southeast Florida in 2002-03. Treatments consisted of methyl bromide (98%) + chloropicrin (2%), metam sodium, metam sodium + chloropicrin, and a nontreated control. All fumigant treatments reduced (P < 0.05) weed populations compared to the nontreated control. Stubby-root nematode ( Paratrichodorus spp.) numbers were reduced initially by the soil fumigants, but recovered after 5 months. Root-knot nematode ( Meloidogyne spp.) levels were low, variable, and not affected (P > 0.10) by treatment. Heights of plants in nontreated plots were stunted compared to plants in fumigated plots, and more plants were lost (8.7%) from nontreated plots than from fumigated plots (2.1%). The number of cut flowers harvested from nontreated plots was 7.0% lower than the harvest from plots treated with methyl bromide + chloropicrin. In most instances, the performance of the alternative fumigants, metam + chloropicrin or metam alone, was similar to that of methyl bromide + chloropicrin. Florida ranks second among U.S. states in ornamental crops, including foliage plants, bedding plants, and cut flowers, with a total production value of $743 million in 2001 (Florida Agricultural Statistics Service, 2002). Many ornamental crops are produced in containers, but some, such as caladium ( Caladium × hortulanum Birdsey) and certain cut flowers, are produced directly in the field (Gilreath et al., 1999; McSorley and Wang, 2002). While field production is economical, crops may be exposed to nematodes, weeds, and other soilborne problems. Currently, soilborne pest problems are managed by fumigation with methyl bromide, a chemical that is facing increasing restrictions and impending phase-out (McMillan and Bryan, 2001; Obenauf, 2002). Much work on chemical alternatives to methyl bromide has been conducted on vegetable crops (Obenauf, 2002), but the need for alternatives is critical on floral and other ornamental crops as well (Gilreath et al., 1999; McSorley and Wang, 2002). Many flower crops are susceptible to problems with rootknot nematodes ( Meloidogyne spp.) (Goff, 1936). These include a number of species that are commonly grown for cut flower production, such as snapdragon ( Antirrhinum majus This research was supported in part by the Florida Agricultural Experiment Station and approved for publication as Journal Series No. N-02264. 1 Corresponding author; e-mail: [email protected].