Keeping houseplants is a hobby that
has recently seen a huge resurgence. Now, nurseries that were all
but shuttered for the winter are hosting houseplant parties and
other events to help people keep their hands dirty all year.
Tending to houseplants is a way to maintain our connection with the
natural world when conditions aren’t conducive to outdoor gardening,
such as in the winter, for apartment dwellers, or just for those who
don’t have time to maintain larger landscaping beds. Houseplants
offer a wide variety of colors, textures, and requirements to fit
anyone’s tastes and situation. But what do you do when things go
wrong?
Healthy Plants are Better Able to Resist Pests
The first thing to remember is that, like humans, healthy plants can
better resist disease. Keeping plants properly watered and
fertilized and repotting them, when necessary, will help to ward off
unwanted guests. Frequently monitor plants to catch infestations
early when they are more treatable. Closely inspect the soil, top,
and undersides of leaves, and stems for anything unusual, such as
discoloration, damage, or other evidence of pests. Using yellow
sticky traps can also help to monitor for bugs. A hand lens can be
useful in identifying pests. However, modern cell phone cameras are
also great for enlarging images of bugs. Below are some pests to
watch out for.
Fungus gnats cause little damage to plants but can be a big
nuisance. They prefer damp areas, so this may be a sign plants are
being watered too frequently or that standing water is being left in
condensation trays. Many indoor gardeners become frustrated with
fungus gnats due to the difficulty in treating them. Many
insecticides are ineffective against them because the larvae spend
much of their time in the soil, and adults are highly mobile. Yellow
sticky traps can help prevent egg laying, but the best control is
letting the top 2 to 3” of the soil dry out between watering. If
they persist, the potting medium can be changed out entirely,
rinsing the roots before repotting to remove any stragglers.
Scale insects are sometimes mistaken for leaf spots, as they often
form a covering to protect the soft-bodied insect inside. They may
align along leaf veins. There are many types of scales, including
soft scales and armored scales. Soft scales suck plant juices and
secrete honeydew, a sticky substance that will often lead to sooty
mold. This will cause the leaf to appear to have a powdery black
coating. Armored scales do not produce honeydew. Feeding from any
scale insect can cause yellowing of leaves, stunted growth, dieback,
and death of the plant. For a small infestation, scale insects can
be scraped off with a fingernail or toothbrush. Depending on the
type of scale, horticultural oils or systemic insecticides may be
effective.
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Mealybugs are a type of slow-moving
scale that feeds on plant juices. The first sign of mealybugs is a
white, cottony substance often seen on leaves. Because they can hide
in tiny crevasses, mealybugs can be difficult to eradicate, but it
can be done with some dedication. Dip a cotton swab in rubbing
alcohol and wipe down any cottony spots. This will desiccate the
bugs. Follow this with a horticultural oil to smother any that were
missed. Check the plant every few days for new signs of bugs. Severe
infestations may require the use of a systemic insecticide.
Thrips are tiny and can be difficult to spot. If the leaves have
irregular silver patches and/or small black fecal specks or
distorted flowers, the plant may have thrips. Thrips spend part of
their lifecycle in the soil, so repeated treatments, including the
soil, may be required.
If the use of insecticides is
warranted, first, isolate infested plants to protect other plants
from also becoming infected. Once a positive identification of the
pest is made, look for insecticides labeled to treat the culprit and
follow all label directions. Frequent monitoring of the plant
afterward is required, and repeat treatments may be needed to fully
eliminate the infestation. Do not bring the plant out of isolation
until the pest has been completely eradicated.
For more on houseplant pests, connect with the local University of
Illinois Extension office.
[Jamie Viebach, University of
Illinois Extension Horticulture Educator] |
