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Scale & Mealybug Insects

It began as a normal Tuesday. After checking email and drinking a cup of coffee you got up to check on all your house plants. That's when you found them. Scale and mealybug insects sucking the life out of your beautiful plants. Noooooo! Before you do anything else isolate the plant(s) with insects to minimize the risk of the creatures moving to other plants. Before you start tossing the plant in the garbage or reaching for the closest bottle of insecticide take a moment to learn what exactly is on your plant and how to remove it.

Scale Insects on a Strawberry Begonia (Saxifraga stolonifera)

Scale and mealybug insects are common pests outdoors and indoors. Both are sap-feeding insects that pierce plant tissue to feed. Scale insects have a waxy covering that conceals their bodies. The two main types of scale are armored(hard) and soft. They come in a multitude of textures, shapes, and colors. All of them are quite small, roughly 1/8" to 1/2" long. Mealybugs are similar to scale, but with soft bodies that resemble small cottony masses. Plants infested with scale or mealybugs may have yellowing or curling leaves, stunted growth, deformities on new growth, and general plant weakness and lackluster. You may notice a sweet sticky substance on the plant or near it on its pot or the floor called honeydew. Scale and mealybug insects excrete honeydew when feeding. Many times you will notice honeydew before you actually see any insects. Honeydew can lead to sooty mold a type of plant mold. Sooty mold looks like soot on plants. If you notice a black substance on your plant, check for pests and treat them accordingly.

Getting rid of your pest problem does not have to be difficult. The majority of infestations can be easily treated. Once you have isolated the plant and discovered that the pest is scale or mealybugs you have a few options to begin treating the plant. If there are only a few insects you can remove them with your hands. You can pick, squish, crush, or wipe off the bugs. If you are able to put your plant in a sink or bathtub and spray off mealybugs you won't need to touch them with your hands. Any stems or leaves that are heavily infested prune and throw away. (Don't leave the garbage bag in the house with the infested leaves.) Another removal option is to use a q-tip or cloth that has been dipped in isopropyl alcohol and dab individual insects. This method is very useful for succulents and cacti when you do not want to spray them with water. You can also use a small spray bottle (the travel size works great) filled with 70% isopropyl alcohol and spray directly on insects. Horticultural and neem oils are other options. These oils kill the insects by smothering. As a last resort you can use an insecticide. Insecticides have stronger side effects than the other methods. They must be used exactly as the directions state to ensure your personal health and safety. The best way to prevent an infestation from occurring is through prevention. Checking plants prior to bringing them into your home for pests is the first line of defense. Once you deem that new plant pest-free isolate it until you are sure that it is free of insects and disease. (One can be surprised how temperatures in a house can encourage unseen eggs to hatch.) Regularly inspect your plants for signs of pests. You can use a granualar systemic insecticide to help prevent insect pests. If you find an unwelcome insect treat it immediately.

Helpful links:

To learn more about mealybugs visit the Wisconsin Master Gardener site.

Read more about scales at the Iowa State Extension.

Sooty Mold, everyone's favorite mold.

Interesting and entertaining article, with videos, on honeydew and insects.

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