Houseplant Pests: Why Prevention Is The “BEST REMEDY”

mealybugs upclose on axil of leaves

Here’s the deal on houseplant pests and plant care. Many houseplant owners would save lots of plants from an early doom by only keeping plants healthy and trouble-free. This makes plant health largely a matter of prevention and not cure.

Rarely Infested With Pests & Disease

Houseplants rarely become naturally infested with plant pests or diseases as their outdoor brethren do. The home acts as a protective environment shutting out bugs and blights.

When insects or diseases do show up, you may be the one to blame. Many insect pests enter homes only by hitching rides on plants or in the potting soil.

The cause of a majority of houseplant ailments comes from overzealous doctoring or disregard for environmental and nutritional requirements.

Learn The Plant Pests Danger Signs

Learn to recognize the danger signs and inspect plants carefully before OK’ing to bring them into your home.  Plants that look clean and healthy at the garden center may actually carry the “seeds” of an infestation.

  • Could the few specks on the underside of a leaf harbor the forerunners of thousands of swarming spider mites?
  • Will the tiny insignificant scales in a stem crevice later multiply into a big ugly mess covering the entire stem?
  • Can one small brown spot lead to many more spots that destroy the beauty of the plant and perhaps kill it?

Diagnosing Ailments By Looking For Obvious Culprits

When diagnosing plant ailments, look for the more obvious culprits first:

  • Insects
  • Mites
  • Root-knot nematodes

If they are not the cause, look for more elusive factors:

  • Disease
  • Improper environmental and nutritional conditions

Practically all the common destructive houseplant pests feed by sucking the sap from foliage or stems.

Scale Insects

The most obvious are scale insects. The uninitiated seldom recognize them as house plant pests but think of them as some scaly growth or disease.

But you’ll find these tiny, pear-shaped, oval insects on fern, cactus, ivy, palm, rubber plants (Ficus), citrus, camellia, begonia, orchid and croton.

To avoid scale insects, give all new plants a good cleaning and remove any suspicious-looking objects. Spray new plants before moving inside with Neem tree oil or a safer insecticidal soap as an effective preventative measure.  Frequent additional baths should prevent scale that sneaked by from gaining a foothold.

The chemical Malathon generally controls and kills all feeding stages of scale.

Mealy Bugs in The Leaf Axils

Look for mealybugs in leaf axils, bud clusters and any crevice they can squeeze into on:

The young look very similar to the crawlers of scale insects, but as they grow older, they cover themselves with a protective, powdery white waxy substance. They excrete a sticky honeydew, which harbors a sooty mold, blackening badly infested plants. Use the same prevention and control of mealybugs as recommended for scale insects.

Whiteflies Most Persistent Houseplant Pest

Whiteflies are perhaps the hardiest and most persistent house plant pest once established.

The young, pale, inactive spiny creatures excrete plentiful amounts of honeydew. 

For the young tough babies, nothing seems to work on them. For this reason, concentrate control on the adults. I always start with a weekly spraying of Neem oil, if Neem does not work or control, try malathon.

Tiny Spider Mites

With tiny spider mites, you normally see their damage, a grayish stippling of foliage, before you find the red or yellow 8-legged midgets and their round glistening eggs.

Their shed skins, amidst the fine webbing on leaf undersides, look like white chaff. A long list of plants may harbor spider mites. Most commonly you will find them on asparagus fern, begonia, cactus, fuchsia, ivy, African violet, dracaena and ficus.

A cold-water washing will usually control spider mites. However, in some cases, try spraying with malathon, neem oil insecticide or these essential oils as needed.

The cyclamen mite produces stunted, cupped or distorted leaves and flowers on African violet, begonia, ivy, crassula, fuchsia, geranium and cyclamen. In African violets, the center growth stays pale and stunted.

Destroy badly infested plants, for this pest is very difficult to control. Only bring healthy plants into the house and propagate only from clean stock.

Fungus Gnats and Springtails

The last insects to consider are springtails and fungus gnats control. People notice these slim white jumping insects not because of them being pest but because so many people see them and think they injure their plants.

They live on decaying matter in the soil and usually appear when driven out by watering. Malathon and Neem oil should take care of them.

House Plants and Diseases

Now, on to houseplant diseases. The secret of disease-free plants comes down to prevention. For most diseases are incurable, and even if a particular disease can be cured, it frequently leaves the plant scrawny and unattractive.

To keep plants healthy and prevent the appearance of disease, the average house plant owner needs only practice the following rules:

  • Sterilize all soils used for potting and propagating. Buy sterilized bagged potting mixes.
  • For propagating, use only clean, healthy-looking plant parts from healthy plants.
  • When buying plants, bulbs and corms, inspect them closely and select only those with no blemishes or abnormalities.
  • When spotting disease on one of your plants, remove the affected plant parts or destroy the whole plant together including the soil. Do not leave such a plant around to contaminate other plants.
  • Wash your hands with soap before handling plants and after handling diseased plants.
  • Do not overwater soil.
  • Syringe plants with water no more than once a week, and provide adequate ventilation so the leaves will dry off quickly.
  • If a fungus disease is present and uninfected foliage needs protection, apply a protective fungicide such as Captan (1 teaspoonful per quart of water) at weekly intervals.

Houseplant Root Rot

Discoloration, decay of roots or stems and finally wilting, characterize the houseplant diseases known as root rots, stem rots and wilts.

Almost all house plants find themselves susceptible to some form of rot or wilt, but these diseases most frequently occur in coleus, geranium. cactus, African violet, gloxinia and begonia. Overwatering encourages the bacteria or fungi responsible for soil born diseases. No cure – only prevention.

Occasionally, house plants may be infected with virus diseases. Spotted wilt (a brown streaking of stems and leaves) often attacks amaryllis, begonia, geranium and gloxinia; mosaic (yellow and green mottling of leaves), coleus and geranium; and ring spot (rings of yellow tissue on leaves), camellia and peperonia.

However, in many instances, leaf spots, leaf blights (browning and drying up of leaves), leaf discoloration and failure of plants to grow or bloom may be caused not by viruses, bacteria, fungi (or pests) but rather by nutritional or environmental conditions. In fact, the symptoms just named are the most common protest signs of plants growing under unfavorable conditions.

Flower and bud blights caused by fungi occur only under damp conditions and are not common in house plants. But bud blast (dropping of buds) and lack of flowering may be due to improper environment or nutrition.

Knowing and meeting your plants’ requirements and following the preventive measures outlined will normally insure against many of these houseplant troubles.