Evaluation of Ornamental Eudicot Species for Phytotoxic Response to Various Pesticides in the Southeastern U.S. for Interregional Research Project #4 (IR-4)

The Interregional Research Project #4 (IR-4) is a national program which provides pest management solutions for specialty crop growers and was started at the Tifton GA location in 1977.  In the last four years, the IR-4 Project on the U.S. southeastern coastal plain has completed 30 phytotoxicity experiments on twelve ornamental eudicot genera including Buddleia, Buxus, Hedera, Hydrangea, Ilex, Lantana, Ligustrum, Portulaca, Rhaphiolepis, Rhododendron, Spiraea, and Verbena. Three herbicides were applied at label rates as either a broadcast granular or as “over-the-top” foliar sprays. Over this same period, seven fungicides were applied to eudicots using either foliar or drench applications. Field experiments were designed as randomized complete blocks with application method and pesticide treatments assigned to a specific cultivar or eudicot species. Phytotoxicity was recorded on a 0 to 10 scale (0 = no injury; 10 = dead) at intervals required by the protocol which differed for each species and chemical combination. Plant height and width were also measured at initial and final evaluations to assess any adverse chemical impact on plant growth and marketability. Data were analyzed in ARM (Agricultural Research Manager) using ANOVA, with means separated using Fisher’s Protected LSD at a level of 0.05.  Results indicated no injury among any of the fungicide treatments, but significant differences in phytotoxicity between the nontreated controls and some of the herbicide treatments. IR-4 research data have contributed to the registration of Alibi Flora, Dimension, Echelon, Insimmo, Marengo, Mural, Tourney, and Trinity on these eudicot ornamental horticulture specialty crops.