Submitted to: Crop Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 11, 2008
Publication Date: January 1, 2009
Citation: Copes, W.E. 2009. Concentration and Intervals of Hydrogen Dioxide Applications to Control Puccinia hermerocallidis on Daylily. Crop Protection. 28:24-29. Interpretive Summary: Hydrogen dioxide (H2O2) is a disinfestant used to kill fungal spores on plant surfaces. Many trials have shown label rates at weekly applications are not effective. In a laboratory study, fewer rust spores would germinate and grow as the H2O2 rate was increased until 100% of the spores were killed at 11.9% H2O2. In a outdoor study, one label rate (0.27% H2O2) and two high rates (5.4 and 10.8% H2O2) were applied 1 and 2 times per week on healthy daylily plants. Only the highest H2O2 rate, which damaged plants, provided rust control equal to the fungicide treatment (azoxystrobin and chlorothalonil rotation). In a greenhouse study, rates labeled for plants (0.20, 0.27% H2O2) and production surfaces (0.34% H2O2) were applied 2, 3, and 5 times per week on healthy daylily plants. Five applications per week at 0.27% H2O2 did not damage plants and provided rust control equal to the fungicides when non-treated plants had moderate levels of disease. When non-treated plants had high levels of disease, control obtained with H2O2 was not equal to the fungicides. This information will help extension scientists and commercial producers use H2O2 products more effectively.
Technical Abstract: Hydrogen dioxide (H2O2) is a disinfestant used to kill fungal spores, such as urediniospores of Puccinia hemerocallidis, on plant and production surfaces. Excised sections of daylily leaves with sporulating rust pustules were sprayed with rates from 2.4 to 11.9% H2O2. Treated spores were rubbed onto the surface of PDA, and germination of >100 spores per replication per treatment was determined 24 hr later. Germination decreased with increasing H2O2 concentration until 100% mortality (zero germination) was achieved at 11.9% H2O2. In an outdoor study, one label rate (0.27% H2O2) and two high rates (5.4 and 10.8% H2O2 selected based on results from the germination trial) were sprayed 1 and 2 times per week on healthy daylily plants, exposed to naturally-dispersed inoculum. The level of rust incidence and severity decreased with increasing rate and number of applications of H2O2 per week. H2O2 at 10.8%, provided control equal to a fungicide treatment (azoxystrobin and chlorothalonil plus thiophanate-methyl rotation), but also damaged 15.4% of the plant’s surface area. In a greenhouse study, two rates (0.20 and 0.27% H2O2) labeled for application on plants and one rate (0.34% H2O2) labeled for application on production surfaces were sprayed 2, 3, and 5 times per week on healthy daylily plants, exposed to naturally-dispersed inoculum. With 58.8% of the leaves of plants treated with water having at least one rust pustule (experiment one), 0.27 and 0.34% H2O2 applied 2 to 5 times per week provided control equal to a fungicide treatment. With 89.4% of the leaves of plants treated with water having rust signs (experiment two), 5 applications of H2O2 of 0.20 to 0.34% H2O2 provided control that was better than the water treatment but not as good as a fungicide treatment. Higher label rates (0.27% H2O2) and multiple applications per week ('5) improve disease control with H2O2, but at high of disease pressure the level of control obtained with H2O2 was not as effective as with the fungicide treatment.