Warm temperatures favor Xanthomonas . Symptoms can develop in as little as 7 days at 81 o F, but may develop in three weeks at 60 o F. Ivy geraniums are very susceptible to bacterial blight but infected plants do not develop distinctive symptoms. Infected plants may be off-color resembling a nutrient deficiency symptom or mite feeding damage. An important defense strategy is to avoid placing ivy geranium crops over bench-grown zonal geraniums to eliminate potential disease spread as water drips unto susceptible zonal geraniums below. However, water stress, root rot disease, or a fungal pathogen such as Verticillium wilt can also cause wilting.
Prompt diagnosis is critical to reducing crop losses.
When geraniums are infected with Southern bacterial wilt, lower leaves may also wilt, turn yellow and drop off the plant. However, no leaf spots occur. Burkholderia wilt has a wide host range including impatiens, marigolds, zinnia, salvia, tomatoes, peppers, and petunia to name a few. Prompt rouging can help to reduce crop losses. Continue to closely monitor your crop and rogue as needed.