Lisa Eldred Steinkopf studied horticulture at Ferris State University and has worked in the nursery industry for 13 years. She is a Michigan Certified Nurseryman, a Certified Green Industry Professional and a houseplant expert.

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5 Houseplant Enemies and What to Do
by Lisa Eldred Steinkopf       #Containers   #Insects   #Pests

Healthy houseplants cozy up a seating area without worry about insects or diseases.


You may notice yellowing or dropping leaves, or a sticky substance on the leaves or floor before you ever see a pest. Those are some of the symptoms that may clue you in that your plants have a problem.


Hitching rides
If you recently purchased a plant, it may have been harboring pests that were undetectable at the time you bought it. This is the reason to always quarantine your houseplants for a month or so when you bring them home from the store or garden center. That way, if the plant has pests, you will see them before they spread to your other plants. If, after a few weeks, you see no obvious pests, it should be safe to move the plant to its permanent home.

Another scenario: Pests can hitch a ride on plants you bring in from their outdoor summer vacation. You may not see any pests, but their eggs may be there. They hatch and now are observable with the naked eye.
 

Mealy bugs are easy to spot against the succulent green foliage of a jade plant (Crassula ovata). • Mealybugs are extremely slow moving insects, which like to hide in plant crevices and under leaves. • This Schefflera arbicola is losing leaves and looking sad because of an infestation of scale. The honeydew is literally dripping off the plant.


Pests 101
Regardless of how they arrived, the pests are now in your home and you need to identify them and decide on a treatment plan. We are going to talk about the top five most common houseplant pests, how to detect them and how to get rid of them.


Mealybug
These are extremely slow moving insects, which like to hide in plant crevices and under leaves. When the infestation is bad, mealybugs are very hard to eradicate. Mealybugs love cactus and succulents, so be vigilant. On cactus, mealybugs resemble the fuzzy areoles that surround the spines.

Mealybugs suck the life out of plants. The symptoms are yellowing leaves and overall loss of plant vigor. The most obvious sign that you have mealybugs, though, is the sticky honeydew (insect feces) that covers the leaves. If it is an extreme infestation, the honeydew can drip on the floor.


The scale is obvious on this bird’s nest fern (Asplenium spp.).


Scale
Scale looks like brown bumps attached to your plant. Scale is 1/16 to ¼-inch long, depending on the type. Scale only moves in juvenile, crawler stage, which is when they are easiest to kill, but harder to detect. Scale usually isn’t obvious until it is in the adult form and not moving. Scale also sucks the life out of plants, causing yellow leaves and an overall lack of vigor.

On many plants, especially Ficus and Hibiscus, it is very hard to tell you have scale on their brown bark. Scale also secretes honeydew and quickly can become a very big problem. It is difficult to eradicate.


Spider mites reveal themselves on this palm frond with tiny dots in the leaves and webbing. The palm also has a few scale insects gnawing away.


Mites
The third pest isn’t an insect at all but a mite, an arachnid, such as spiders and ticks. Their feeding makes for a speckled leaf, because the mites suck juices out of the plants. If numbers are large, webbing will appear. The speckling and webbing are probably all you will see. Mites are so small, less than 0.04 inch, they are not easy to see with the unaided eye.

Dry conditions contribute greatly to the proliferation of the mites. Keep your soil evenly moist and the humidity high to reduce their population. Insecticides do not work on mites, so a miticide must be used. An insecticide kills mites’ natural enemies, which makes the problem worse. Miticide does not kill the eggs, so it has to be reapplied at 10 to 14 day intervals.  Always read and follow the label directions.

Thrips may only be 1/10 inch long and can be very hard to detect.


Thrips
Thrips also may appear on our indoor plants. Like mites, thrips are very hard to see. They may or may not have wings and are very small, from less than 1/10 of an inch to about ½ inch. They are quite often found on African violets (Saintpaulia hybrids).

Spilled pollen on the petals of the plants is a telltale sign of thrips. The worst thing about thrips is their ability to spread virus and disease.


Fungus gnats
The last pest is the most obvious because it flies around. Although easily detected, fungus gnats are frequently incorrectly identified. People think they have fruit flies in their plants. I tell people if you don’t have any rotting fruit, you don’t have fruit flies. Fungus gnats, which are black and about one-eighth inch long, and resemble fruit flies, but live in too-moist soil.

Let soil dry out between watering. If the infestation is extremely bad, the soil, or at least the top couple of inches, will need to be replaced. Fungus gnats live and reproduce in the top 1 inch of soil. I really believe commercial potting mix is too heavy for most houseplants and is the instigator of the problem. Add one-third perlite to two-thirds of the bagged potting mix to make it faster draining.


Fungus gnats resemble fruit flies and live in houseplants’ potting mix that is too wet.


Get control
How do you eradicate these juice sucking insects? One way is to get some cotton swabs, dip them in rubbing alcohol, and touch each one of the insects. The alcohol dries them out and removes their protective coating. Obviously, this would be a procedure to use if you catch the problem early.

Another solution and it can be used in combination with the alcohol, is neem oil. I use a product called Bonide Rose Rx, which contains neem oil and seems to help keep insects under control by smothering them.

If these remedies do not work, a systemic insecticide may be your next step. Bonide Houseplant Insecticide has a very low percentage of the insecticide imidicloprid. The product, placed in the soil, moves through the plant when watered. The insects chew on the plant and die. I wouldn’t recommend using this on plants your cats or dogs would chew on, or where children are present. Always read and follow the label directions.

 

A version of this article appeared in a November/December 2015 print edition of State-by-State Gardening.
Photography courtesy of Lisa Eldred Steinkopf, lightkeeper/iStockphoto.com, Keith S. Eldred, P.M.J. Ramakers/bugwood.org, and Jim Baker/bugwood.com

 

Posted: 10/31/18   RSS | Print

 

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