Annals of Applied Biology (2005), 146:351–359 *Corresponding Author Email: pdr@ifas.ufl.edu © 2005 Association of Applied Biologists 351 Survival and recovery of Phytophthora capsici and oomycetes in tailwater and soil from vegetable fields in Florida P D ROBERTS 1 *, R R URS 1 , R D FRENCH-MONAR 1 , M S HOFFINE 2 , T E SEIJO 2 and R J MCGOVERN 3 1 Southwest Florida Research and Education Center, University of Florida, Institute of Food and Agricultural Sciences (IFAS), 2686 State Road 29 N, Immokalee, FL 34142, USA 2 Gulf Coast Research and Education, University of Florida, IFAS, 13138 Lewis Gallagher Road, Dover, FL 33527, USA 3 Plant Pathology Department and Plant Medicine Program, University of Florida. IFAS, 1453 Fifield Hall, Gainesville, FL 32611, USA Summary A current trend in Florida agriculture to conserve water is to irrigate with surface runoff water (tailwater) recovered in retention ponds and canals. Water filtration and lemon leaf baiting recovered Phytophthora capsici and other plant pathogenic Oomycetes in runoff water from ponds and canals. A total of 196 isolates of Phytophthora spp. and 471 isolates of Pythium spp. were recovered. Phytophthora spp. included P. capsici, P. cinnamomi, P. lateralis, P. nicotianae, P. citricola, P. cryptogea and P. erythroseptica. Species of Pythium were P. aphanidermatum, P. catenulatum, P. helicoides, P. irregulare, P. myriotylum, and Pythium ‘group F’. Isolates of P. aphanidermatum, P. irregulare, P. myriotylum, and Pythium ‘group F’ were pathogenic on pepper and tomato. Recovery of P. capsici propagules was related to soil moisture-holding capacity and time interval but not temperature. Recovery of P. capsici propagules at 100% soil moisture-holding capacity and 30°C was 57 days. In tailwater, recovery of propagules of P. capsici was 63 days at 24°C to 25°C. The potential exists to reintroduce and disseminate species of Phytophthora and Pythium when using tailwater for irrigation or other practices. Key words: Tailwater, Pythium, soil moisture holding capacity, survival, recycled irrigation water, recovery, baiting, filtering Introduction The recycling of surface runoff water, also called tailwater, is proposed as a water conservation method in vegetable production in Florida. Currently, few commercial vegetable growers use tailwater for irrigation of fields; however, some other common farming practices, such as the use of tailwater in spray tanks, do reintroduce this water into the crop. The use of this water in such operations may result in the reintroduction of economically important plant pathogens. Disease outbreaks have been attributed to water contaminated with plant pathogens (McIntosh, 1966; Whiteside & Oswalt, 1973). Several plant pathogenic microorganisms including bacteria (Schuster, 1959; Thompson, 1965), fungi and oomycetes (McIntosh, 1966; Easton et al., 1969; Gill, 1970; Thompson & Allen, 1974; Shokes & McCarter, 1979; Ali-Shtayeh et al., 1991; Lutz & Menge, 1991; Neher & Duniway, 1992; Sanogo & Moorman, 1993; MacDonald et al., 1994; Dukes et al., 1997; Wakeham et al., 1997; Pettitt et al., 1998; Ristaino & Johnston, 1999; Sánchez & Gallego, 2000; Bush et al., 2003) and nematodes (Schuster, 1959; Faulkner & Bolander, 1970) were isolated from surface irrigation water. Phytophthora and Pythium spp. are frequently isolated from the same water source, although Pythium spp. are typically more abundant (Thompson & Allen, 1974; Shokes & McCarter, 1979; Ali-Shtayeh et al., 1991; Pottorff & Panter, 1997; Wakeham et al., 1997; Bush et al., 2003). Frequently, more than a single species is recovered from the same water source, such as the recovery of seven and five species of Phytophthora from nursery effluents in California and Oklahoma, respectively (MacDonald et al., 1994; von Broembsen & Wilson, 1998). A water- recycling system at a perennial container nursery in Virginia contained Pythium spp. and six species of Phytophthora (Bush et al., 2003). Pythium and Phytophthora spp. were isolated from irrigation water sources irrigating citrus, pear, apple, and cranberry (McIntosh, 1966; Thompson & Allen, 1974; Lutz & Menge, 1991; Oudemans, 1999). In Florida, an outbreak of P. citrophthora in citrus was related to overhead sprinkler irrigation and the pathogen was recovered from the pond source (Whiteside & Oswalt, 1973). Less information is available on the recovery of Pythium and Phytophthora from tailwater from vegetable fields. Plant pathogenic Phytophthora, Pythium, Fusarium and Rhizoctonia spp. were isolated from surface irrigation ponds adjacent to vegetable fields in Georgia (Gill, 1970; Shokes