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Houseplant Pests

Mealybugs on philodendron stem by Jeff Hahn

University of Minnesota Extension, Stearns County News
January 20, 2016        
Source:  Beth Berlin, Extension Educator-Horticulture
University of Minnesota Extension
Stearns & Benton Counties


Houseplant Pests
By Beth Berlin, University of Minnesota Extension

ST. CLOUD, Minn. (01/13/16) — Winter has finally thrown cold temperatures at us so it is the perfect time to take a few moments and thoroughly inspect your houseplants.  There are numerous pests that can infest your favorite houseplants, from aphids to spider mites; these tiny pests can cause major issues.

Many of these pests thrive in dry, warm conditions, which is why they become so prevalent in the winter months when our homes are being heated and moisture levels drop. Inspect your houseplants closely for signs of pests; inspect both the top and bottom side of the leaves. Symptoms of some pests include the leaves becoming speckled or mottled.  Aphids and scale insects will actually secrete a shiny, sticky honeydew. Spider mites will create a fine web material often concentrated in areas.  Finally some pests fly such as whiteflies and thrips which will be noticeable when the plant is shaken or brushed over.

One non-chemical treatment is to wash your plants. Wash your smooth-leaved plants regularly to help remove dirt and grime; which blocks light from penetrating the leaf surface and prevents photosynthesis. In addition a dirty surface attracts and harbors pests. Simply use a moist, soft cloth to wipe the leaves of the plant. Tiny leaves can be sprayed with lukewarm water. Another option is to wrap the soil and pot and then quickly tip the top of the plant in a tub. A few drops of mild liquid dish soap, that doesn’t contain degreaser, can be added to the bucket or tub of water. It is not recommended to use a feather duster to clean your houseplants, because you may actually be transferring unwanted pests from one plant to the next.

Sticky traps are available on the market that can assist with any pest infestation on your houseplants, but will not work stand-alone.  The sticky traps are very useful to catch some of the pests in order to identify and then determine what method of control to use. Common pests that will be caught on sticky traps include: fungus gnats, whiteflies, winged aphids, and thrips.

Chemical insecticides are also available at nurseries, garden centers, or even fleet or hardware stores.  Select the correct product for the pest and the plant, treating a plant that is not listed on the label may cause significant damage to the plant. Insecticidal soaps can be effective on soft bodied pests such as aphids, mealybugs, immature scales, thrips, whiteflies, and spider mites.  Insecticidal soaps are a contact insecticide, and are only effective when insects come in direct contact with the product while still wet. Several applications may need to be done to eliminate the pest population.

CAUTION: Always read pesticide labels carefully before buying and again before using these products. This is especially important as the availability and recommended use of specific pesticides may change from year to year.  The label is the final authority on how you may legally use any pesticide.

Remember the first line of defense is prevention; inspect and isolate any new plants or those with potential issues before pests spread. For more information on houseplant pests and ways to treat them visit


PHOTO: Mealybugs on philodendron stem, by Jeff Hahn


Beth Berlin
Extension Educator, Horticulture
(320) 255-6169
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