Top 8 Common Houseplant Problems Solved, Continued

7. Odema
A Condition caused by over watering. Brown spots appear on the leaves.

8. Bacterial & Fungal Problems
Although these two classes of diseases are caused by two very different types of microscopic (or very small) organisms, they both are usually the result of stressful or poor growing conditions. It is normal for some bacteria or fungi to be present on plant material, however problems arise when poor growing conditions cause them to multiply and grow. Since bacteria and fungi are often spread by water, it goes without saying that water is also the method in which these diseases are often spread. Poor air circulation, over watering or under watering, poor drainage, too little light, and crowding can also be factors in these types of infections. The high humidity of the summer months and the low lighting conditions of the winter months are the prime times for these diseases to occur.

Bacterial diseases are usually expressed as leaf spots that look water soaked and can have yellow halos. If conditions are really wet, these spots will usually be the same size and can run together. Under really dry conditions, these spots will not increase in size, but will turn reddish brown and will dry out. There is no cure, but you can carefully prune and discard the infected leaves. You will need to disinfect your cutting tools with a solution of nine parts water to one part bleach between each cut. If the plant is really infected, the best solution is to discard the plant before other plants are infected.

Fungal diseases can be expressed as leaf spots, wilting stems and/or root rot. The most common fungal disease is root rot, usually caused by letting the plant set in a pot with no drainage, or simply by over watering. The leaves and stems of the plant may show wilting symptoms and the roots can be brown and soft. If symptoms are not too severe to warrant discarding, the plant can be repotted (remove bad roots) with sterilized potting soil and a fungicide drench may be applied (following manufacturers directions). Fungal leaf spots are small brown spots with yellow margins, that can have a target pattern. They can run together and make the entire leaf die. If you take a hard lens, you can often see the small reproductive spores. If these are not too far along, you can use a fungicide spray at the recommended rates and intervals. Powdery mildew, which is a whitish-colored fungal infection, can be one of the hardest types of fungal diseases to control.

The best control for both bacterial and fungal diseases is simply prevention. Since water is most often the mode of spreading these types of infections, practicing proper watering procedures helps to reduce the risk of infection. Do not water houseplants from above (on their foliage); instead, water at the base of the plant (or the lip of the pot). Check the soil to make sure it is dry and the pot to make sure there is adequate drainage. Properly space your houseplants to make sure there is plenty of space and air movement between plants. Make sure there is adequate light for the type of plant you are growing. If you purchase healthy plants and follow these conditions, you should be able to keep your plants healthy and disease-free.

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