Phytotoxicity of Herbicides, Fungicides, and Insecticides/Acaricides on Ornamental Horticultural Crops in Southeastern U.S. for Interregional Research Program (IR-4)

The Interregional Research Project (IR-4) is a joint USDA-ARS and Land Grant Institution program that has been the primary resource in the United States for facilitating registration of sustainable pest management technology for specialty crops including fruits, vegetables, nuts, herbs, spices, and non-food ornamental horticulture crops. The IR-4 Ornamental Horticulture Program on the U.S. southeastern Coastal Plain focuses its research on phytotoxicity experiments with herbaceous annual/perennial and woody ornamentals. Experiments are designed to measure phytotoxicity of specific pesticide/commodity combinations that address insects, weeds, and plant diseases of ornamental horticulture crops in the southeastern U.S. In the last five years, we have completed 59 ornamental horticulture phytotoxicity trials on 20 genera including Begonia, Buddleia, Buxus, Hedera, Hemerocallis, Hosta, Hydrangea, Ilex, Juniperus, Lantana, Ligustrum, Liriope, Pinus, Portulaca, Raphiolepis, Rhododendron, Spiraea, Verbena, Viburnum, and Zinnia. These included 15 herbicide trials using 6 herbicides to treat 10 ornamental crops and applied as either a broadcast granular or “over the top” liquid. It also included 38 fungicide and 6 insecticide combinations using 8 fungicides and 3 insecticides to treat 26 ornamental crops using foliar applications. Results indicated no injury among any of the fungicide and insecticide treatments, but significant differences in phytotoxicity between the nontreated controls and several of the herbicide treatments. Regional data from around the U.S. are compiled into summaries and ultimately submitted to manufacturers, who review and incorporate the information into technical literature and product labels. Over 35,000 crop uses have been registered since 1977, when the Ornamental Horticulture Program was established.