Root rot of hydroponically grown spinach caused by pythium aphanidermatum and pythium dissotocum
Bates, M.L.; Stanghellini, M.E.
Plant Disease 68(11): 989-991
ISSN/ISBN: 0191-2917 Accession: 006356569
Root rot was the limiting factor to commercial production of spinach (Spinacia oleracea) in a greenhouse recirculating hydroponic system in Arizona [USA]. Infected plants either died or were severely stunted. P. aphanidermatum and P. dissotocum were associated with root rot. P. aphanidermatum predominated as the primary causal agent of root rot during the warm summer production months, when nutrient solution temperatures were higher than 23.degree. C; P. dissotocum was the primary or sole causal agent during the winter production months, when nutrient solution temperatures were between 17.degree. and 22.degree. C. Disease symptoms, identical to those observed in the commercial greenhouse, occurred within 6 days after spinach plants were inoculated with either P. aphanidermatum or P. dissotocum. Metalaxyl, at concentrations from 1 to 10 .mu.g a.i.[active ingredient]/ml in the nutrient solution, was effective in controlling root rot of spinach.