Subscribe and receive the newsletter: Purdue Landscape Report Newsletter. To view this article and other Purdue Landscape Report articles, please visit Purdue Landscape Report. Due to the diversity of copper products, be sure to test for phytotoxicity issues prior to large scale treatment of crops. Use of quaternary-ammonium disinfestants (KleenGrow) have been found to reduce bacterial populations and disease incidence and should be considered as part of any rotation with copper products. Products containing acibenzolar have provided inconsistent control in multiple trials but is labeled for use. ![]() Copper resistant populations of Pseudomonas syringae have been reported in other crops (vegetables, stone fruit). Avoid using copper under cool, humid conditions to reduce the risk of phytotoxicity and damaging plants. Avoid over-fertilization practices that drive excess succulent growth.įoliar sprays of some copper-based bactericides (e.g., Camelot, Kocide, and Nu-Cop) were found to reduce disease incidence in trials on lilac (Vey and Palmer, 2018).Minimize overhead irrigation when possible to minimize splashing and pathogen spread.When pruning to remove infected shoots, be sure to disinfect shears between plants.When pruning, do not mix pruning to shape woody ornamentals with pruning to manage disease.To prevent or minimize the risk of infection: Bacteria enter the plant through flowers or injury.Īll bacterial pathogens, including Pseudomonas, invade flowers or wounded tissue. Wind-driven rain, insect, or mechanical pruning spread Pseudomonas. Lilac blight is a bacterial disease spread by the wind and rain, affecting many species of lilac. In presence of water and warming temperatures, bacteria multiply and may ooze from infected tissue. The bacteria overwinter and persist in cankers, along with asymptomatic bud and twig tissue. The continued growth of the bacteria can result in cankering and blight. Infected flowers result in blossom blast. Image of infected flowers result in blossom blast.įigure 2. Cloudy droplets of sticky fluid (ooze) may accumulate on leaf tips, leaf surfaces, stems, and even infected fruit. Leaves attached to a cankered branch will wilt while the tip of the affected branch curls and droops like a shepherd’s crook (Fig. As the bacteria spread into woody tissue, dark, sunken sections of the stem (cankers) expand, working their way back toward the trunk from infected leaves and flowers. For most other hosts (cherry, pear, basswood, dogwood, hydrangea, high bush-cranberry, mountain-ash), infected leaves turn reddish brown or black and usually remain on the branch after they die (Fig. On lilac and viburnum, small spots expand to irregularly shaped brown lesions with yellow halos (Fig. Symptoms often begin as expanding leaf spots. The bacteria cause flower blights, cankers, shoot blights, and diebacks. ![]() syringae is an opportunistic bacterial pathogen that attacks a diversity of woody ornamental plants. Purdue Landscape Report: Pseudomonas syringae pv. Bacterial leaf spots are often angular with chlorotic halos, as seen on this high bush-cranberry.
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