Evaluation of fungicides to control Pythium root rot of geranium, 2025

Geranium ‘Black Velvet’ seeds were planted in 72-cell flats at the research greenhouses of the University of Connecticut. Seedlings with three to four true leaves were transplanted on 31-Aug into 4.5-in pots containing Promix BX potting mixture and 1g/L Pythium infested millet. Sterilized millet was infested with P. ultimum (isolate 024P, originally from geranium) prior to use as inoculum. Each pot was fertilized with 1 g Osmocote and received weekly applications of 20-20-20 liquid fertilizer. No fungicides or insecticides were applied as maintenance sprays. There were 6 pots per treatment arranged in a completely randomized design. Immediately after transplant, the plants were drenched with 120 mL of fungicide solution, sufficient to displace 10% water in each pot. A second drench application was made 7 days after treatment A on Sep-7. The greenhouse was maintained between 15.5 to 29.5°C. The plants were rated for disease severity and phytotoxicity on 8-Sep, 16-Sep, and 21-Sep, and fresh weights of aboveground plant parts were recorded at the conclusion of the trial on 22-Sep. Data were analyzed by an analysis of variance (ANOVA) with means separation preformed by Fishers protected LSD test using JMP software (JMP, v. 18.0.0. SAS Institute).