Leaf spots caused by bacteria are often light green initially and then look water soaked. Eventually, the leaf spots turn brown or black and may have definite margins.

Bacterial leaf spots may be mistaken for fungal leaf spots, but when you hold infected leaves up to the light, bacterial spots are typically translucent. Pseudomonas and Xanthomonas attack a number of greenhouse plants from English ivy and geranium to poinsettia and zinnia.

Criminal history

Bacteria are often splashed from the soil onto wet foliage where they enter through stomates or wounds. Bacteria spread from leaf to leaf when plants are watered or during rainy periods. Overhead irrigation often aids in the spread of bacteria. Bacteria can live on benches and tools.