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Friday, August 23, 2019  Spokane, Washington  Est. May 19, 1883
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Gardening: Start spring cleaning now to eradicate houseplant insects

Houseplants which have been dormant during winter will soon be waking up as the days get longer. Check the houseplants for insects on stems and under leaves and remove them, Pat Munts writes (Brian Plonka / The Spokesman-Review)
Houseplants which have been dormant during winter will soon be waking up as the days get longer. Check the houseplants for insects on stems and under leaves and remove them, Pat Munts writes (Brian Plonka / The Spokesman-Review)

It’s time to check your houseplants for unwanted visitors. The plants have been somewhat dormant for the last couple of months but with the increasing light, they will soon be waking up to spring; hitchhiking insects and all.

Start by looking closely at stems and under leaves for adults and egg masses. If a cloud of tiny white flies appear after you brush the leaves, you have a white fly infestation. Tiny, flightless teardrop insects on the underside of the leaves are probably aphids. Masses of cottony webs in leaf crotches are likely a sign of mealy bugs. Oval-shaped shields that don’t move are likely scale. Clouds of fruit fly-like insects around the plants are usually fungus gnats. I could go on but these are the most common.

Eliminating an infestation will take some patience and time. Start by removing old foliage from the plants and making sure water left standing in saucers is cleaned out. If you haven’t watered for a while give the plants a good drink. Wait another month to apply fertilizer as the plants are still dormant and can’t absorb it.

One of the easiest ways to get rid of aphids is to place the plants in a shower and wash them off the plant. Be sure to turn the leaves over to wash the bottoms. This interrupts the breeding cycle for the insect. You may have to repeat the wash. Another way is to take a vacuum cleaner to the pests. Put on the brush attachment and brush the leaves gently. Empty the hopper or bag when you are done.

Mealy bugs and scale are hard to eradicate. Dip a cotton swab in rubbing alcohol and then rub it on the insects. The alcohol breaks down the waxy coating that protects the insect and they dry out and die. This is a slow process. Keep the alcohol off the plants tissue where possible as it will damage the plant. These two insects are probably the hardest ones to get rid of from house plants.

Fungus gnats thrive on the top of the damp soil in the pot. Fungus grows on the damp soil surface in the pot and the bugs thrive on it. First, make sure you aren’t overwatering the plants. Let the surface of the pot soil dry out in between watering. If the problem persists, add a layer of sand or fine gravel to the soil surface so the gnats can’t reach the soil. Move the plants apart a bit to improve air circulation and reduce humidity levels.

Finally, its time for some tough love. If you find a badly infested plant, the best thing you can do is get rid of it. Hard as it may be to throw out Aunt Mary’s begonia, it is harder to get rid of a serious infestation. The infestation can also move to your other plants.

For more information check out the Colorado State University Extension article on managing houseplant pests at https://extension.colostate.edu/topic-areas/insects/managing-houseplant-pests-5-595/.

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