Xanthomonas Leaf Spot -- Xanthomonas campestris pv. Pelargonii (most common)
Host: Geranium, zinnia, begonia, iris, poppy, poinsettia, canna, heuchera, rudbeckia, phlox, astilbe
Symptoms: Xanthomonas most often appears as small, round, brown lesions that may turn into brown wedges. Spots may be accompanied by a yellow halo or large areas of chlorosis. Wilting of individual leaves or the entire plant are signs of systemic infection.
Conditions Favoring Disease: Symptoms appear most rapidly and spread most easily in warm temperatures. Infected stock plants often do not show symptoms until cuttings are taken in the spring.
How Pathogen Survives/Disperses: The bacteria will spread by splashing water and can be picked up by root systems through subirrigation or unsanitary practices.
Photo provided courtesy of Chase Research Gardens, write up by GPN Staff.