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Pests and Diseases
Pests
The listing here is not exhaustive, but it does present the pests and diseases you are most likely to encounter with house plants. Most problems with plants are the result of improper care, so check "Common Problems With House Plants" for common symptoms and causes.
| Aphids |
These small gray or green insects are visible on the undersides of leaves and on stems. They suck out plant juices and cause curled and yellow leaves. They spread very fast and require immediate control. Rinse the plant in soapy water or spray with insecticide containing pyrethrum or rotenone. |
| Mealy Bugs |
Hidden under leaves, these sucking insects look like bits of cotton. They cause pale foliage, leaf or bud drop, and stunted growth. Treat with cotton swab dipped in alcohol and wash the plant with soapy water. Heavy attacks can be treated by spraying with malathion. CAUTION Malathion is very toxic to humans, pets and some plants. |
| Mites |
These are too small to see, but you can see their effects. Curling leaves, withered buds or tips, and webs on the underside of leaves are sure signs. Cut away infected parts and spray with dicofol. In many cases, particularly in the case of the cyclamen mite, all you can do is discard plant. |
| Nematodes |
These invisible round worms eat the roots of the plants. Repot with sterilized soil treat soil with Vapam. |
| Red Spiders |
Large numbers leave webs that make the foliage look dusty. Leaves become yellowed or bronze, and fall. Badly infected plants can be dipped in a solution of 2 teaspoons malathion to each gallon of water. Some plants may have to be discarded. These pest are especially fond of ivy, but do not like high humidity. |
| Scale |
This term covers serveral parasites that look like hard-shelled lumps or the backs of leaves. They suck juices and stunt plant growth. The first sign may be light colored spots on leaves. Scrub infected parts with a brush and soapy water. Heavy infections can be treated with pyrethrum or rotenone sprays or dipped in malathion solution as with red spiders. |
| Slugs and Snails |
Both feed on leaves at night and leave a trail of silver slime. Keep plants clean and pick these pest off by hand if you see them. A saucer beer or grape juice set next to the plant will attract and kill them. |
| Sowbugs |
These grayish black crawling pest eat young stems and roots. Pick them off by hand or spray the soil with malation. |
| Thrips |
These tiny insects cause a white mottling on leaves. New growth is distorted. Spray with malathion. |
| Whiteflies |
Pale or yellowing leaves that eventually drop are signs of whitefile larvae. Mature whitefiles rise like a cloud when the plant is distrubed. Spray with rotenone or malathion several times over a period of weeks. Whiteflies are difficult to eradicate. |
Diseases
Before you decide your plant is diseased, make sure it is getting proper care. Here are some of the most common diseases.
| Bottrytis Blight |
This fungus thrives on wet foliage. Gray, brown or yellow blotches on leaves are a gray mold are sure signs. Infected parts should be discarded and the plant can be sprayed with zineb or captan. Give the plant better air circulation and avoid overcrowding, over watering or overfeeding. |
| Crown or Root Rot |
Plants that turn brown and suddenly wilt may be suffering from rot. the problem is usually related to poor drainage. Repotting can help, and the soil can be sprayed with benomyl. |
| Fungus Leaf Rot |
Blotches on leaves that wither and die may indicate this fungus. Cut off infected leaves and keep other leaves dry. Give the plant better air circulation and lower humidity. Spray with zineb or benomyl. If the infection is too bad, discard plant. |
| Mildew |
A white or gray powder on leaves, stems or flower buds indicates mildew. Leaves may also curl. The usual cause is too much water. Cut down on watering and, if necessary, spray with sulfur, zineb or benomyl. |
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