Morris Arboretum Nursery Trial: A Study of Rose Care Treatment

The Arboretum’s IPM program has been striving to reduce pesticide use in the Rose Garden. In 2010, Justin Jackson, the Rose Garden Section Leader, proposed a sustainable landscape management plan that would incorporate compost tea into the Rose Garden’s IPM program. The study of improving the quality of the compost has been on-going. The intent of this project was to determine the efficacy of three organic fungicides. The project was divided into two phases, the pre-trial phase and trial phase. A treatment plan was applied from the end of spring until the end of fall, 2012. The four treatments for the trial were control (just water), compost tea, CEASE, and Green Cure. CEASE and Green Cure were sprayed onto the leaves once a week as recommended and compost tea was sprayed and drenched once a month. Black spot and downy mildew were found on almost all of the rose leaves or canes in the entire Rose Garden. As a fungal disease, the intensity of damage caused by black spot and downy mildew tends to be influenced mostly by weather conditions and the disease resistance of the rose varieties. Many hybrid tea, grandiflora, and floribunda roses are susceptible, whereas many of the shrub roses show more resistance. This observation also shows that the resistance level might be variable in different places and conditions. Nine weeks after planting, which includes four weeks of treatment that took place in early June, the rose plots did not have comparable treatment results in growth, vigor, and performance. The black spot or fungal diseases on the leaves had not significantly changed the growth and performance of the plants. In order to have better study results, continuing treatment and observation is encouraged until the end of October to determine the percentage of fungal disease present or the percentage of defoliation among the treatments and varieties