By Chris Rocheleau & Steven Wilson, ForemostCo®, Inc.
With foliage and tropical plants in general, you have far fewer diseases to watch out for than with many annuals or perennials. A greenhouse propagation area simulates foliage/tropical plants’ places of origin with increased shade, high humidity, and tropical temperatures. Foliage plants need less air movement than other bedding and houseplants, as they are well adapted to these conditions and even thrive in them.
Scout for These Symptoms
The few exceptions to these circumstances include fungi that enjoy higher, tropical temperatures, such as Cercospora, and bacterias such as Erwinia, Pseudomonas, and Xanthomonas. When scouting the greenhouse, watch for the following signs of disease:
- Cercospora: Spots show up starting on the lower/older foliage as a gray spot with a purplish halo. On the underside of the leaf, small black spots (spores) can be seen with a hand lens.
- Erwinia: Unrooted cuttings (URCs) appear with a sudden, soft kink in their stems, normally within 24 to 72 hours of being stuck. The kink has a strong, foul odor (similar to rotting fish), which is a familiar symptom of this bacterial disease.
- Psuedomonas: Black angular spots develop on the foliage.
- Xanthomonas: Shows up as water-soaked, necrotic tissue.