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Quick Guide to Diagnosing Your Plant's Pest Issue & How to Eliminate the Problem 🩺

Updated: Jan 14

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PESTS are a daunting & common dilemma when it comes to keeping houseplants.

If one of your plants looks less than healthy, don't you fret, it is more than likely the cause of improper care. Most plant complications are due to factors such as overwatering or under-watering, excessive heat or dropping temperatures, failure to meet recommended light requirements, or too little or too much fertilizer.

However, in some cases the problem results from pest infestation.

There are several types of insects that will happily risk their lives to thrive off of your beloved houseplants, so it is crucial to always keep your eyes peeled. Those little buggers will stop at nothing to feast on your healthy plants!


While there are a number of ways the initial infestation can occur, pests are most likely to appear after a new plant is introduced into your collection from a foreign environment. Another popular way for pests to invade your houseplants is when you send your plants outside for the summer to get some of that fresh, warm, & humid air. After all, that's what all the plant websites say houseplants need, right? Humidity! And where better to find some thick, moisture filled air? During the summer in Atlanta, GA -- that's where. But, I digress.

Whether you leave your plants outdoors for a small duration of time or keep them outside for the entire summer, once they leave the safety of your home they are susceptible to pests.

Don't let this discourage you from letting your houseplants experience the outdoors. Plants are like children, you have to let them live their life sometime. Besides, you deserve a break plant mama! Let them drink some rain water every now & then!


COMMON HOUSEPLANT PESTS

APHIDS

Aphids are small insects commonly found on new growth on the underside of leaves.


These little stinkers suck the plant juices & excrete a shiny, sticky sap, called "honeydew." This sap attracts other insects, such as ants, & encourages the growth of sooty mold.


What To Look For?

Aphid infestations are often evident by the white cast skins that are left behind when the aphids molt. They attack many different houseplant species & will sometimes cause the leaves to curl or become disorted.


How to Control Aphids

Wash the aphids off plants use a water misting bottle.

Remove parts of the plants that are completely infested. Sanitize properly by removing the infected plant pieces & placing them in a sealed bag to prevent bugs from moving to other plants.

Apply insecticidal soap or horticultural oil. When using an insecticide from the store, make sure to check if the plant will tolerate it's ingredients.



If there are only a small amount of aphids* & you are able to remove them manually, use a bowl off water & dish soap. Stir the soap, so a small layer of suds stay on top. To dispose of the aphids, drop them into the bowl of soapy water. Repeat until all of the bugs you can see have been removed from the plant.

*While you may only see a few at first, make sure to examine the plant closely, because when there's one, there's usually a bunch more.

If the infestation is out of control a systematic soil-applied insecticide or a foliar-applied insecticide that is labeled for use on the plant species.


MEALYBUGS

Mealybugs are white, small, oval shaped insects that suck the sap from the plant it is hosting on.


What to Look For?

Mealybugs will cover houseplants with a cottony, waxy, & powdery material, that are

often found on the undersides of leaves, or where leafstalks join stems. Plants succumbed to a mealy bug infestation include stunted plant growth, yellowing, & leaf wilting. Similar to aphids, Mealybugs excrete "honeydew" & attract ants.

Check carefully in tight crevices on the plant (in-between leaves & stalks), behind or inside the leaf base, within leaflet folds, or in flowers or flower-clusters.


How to Control Mealybugs

Due to their similarity with aphids, removal techniques are similar as well.

Scraping or washing them off plants is the most popular way to remove mealybugs from plants. Spray them with water, remove them manually, dispose of infected plant pieces, & consider the use of horticultural oil or insecticidal soap labeled for the particular species.


Unfortunately, controlling Mealybugs can be difficult. If the infestation doesn't respond to removal techniques, or the outbreak is uncontrollable, the best solution may be to dispose of the plant before more of your plants are infected.


For house plant infestations, one of the most popular solutions is using 70% (or less concentrated) isopropyl rubbing alcohol. Apply the alcohol to a cotton swab & apply the swab directly to the bug.

To ensure the alcohol doesn't hurt the plant, try a test on a small part of the plant before attacking every area.


FUNGUS GNATS

Fungus gnats can become one of the worst types of infestations on houseplants because of the way they fly around indoors. When they emerge from the soil, some equivocate the nuisance of a fungus gnat to a mosquito. They are relatively weak fliers, but the adults can be considerable nuisance pests indoors when flying near people, food, or light sources.

There are several varieties of fungus gnats that live outdoors, as well, so they can easily enter the home from outside through doors & windows.

Fungus gnats are harmless to humans, but an infestation will damage plants due to feeding on roots by the gnat's larvae.

Adult insects are dark, delicate-looking insects, with a liking to mosquitoes, but smaller. They are relatively weak fliers, but the adults can be considerable nuisance pests indoors when flying near people, food, or light sources.


What To Look For?

The files generally live near potted plants & can be found running or resting on growing parts of plants, soil, or plant debris. You may also see tiny black dots on leaves from their fecal matter.

Adults are attracted to light, so looking for them near light sources is beneficial for your search.


How to Control Fungus Gnats

Sometimes defense is your best offense. The best way to control fungus gnats is to work on prevention tactics. Begin by throughly inspecting any plant coming in the house that has been brought or kept outside during cold weather.

To keep the adult bugs from outside from infecting your houseplants you can put up screens on your windows & patio doors.

Always use sterilized potting soil when repotting, rather than dirt from the ground.

Overwatering & under-watering, soil with poor drainage, or lack of drainage holes are are easy ways to attract fungus gnats, as they keep the soil moist, so it begins to grow fungus. Eliminate standing water & let soil dry out before watering again.

Practice good sanitation by throwing away the debris fallen from plants or old material in & around other pots.


Use of yellow sticky traps in & around the pot are a popular way to control the population by reducing the number adults.


WHITEFLIES

Both adult & juveniles whiteflies attack houseplants. The younger insects will attach t

hemselves to the underside of the leaves, such the plant's juices, & excrete honeydew. The adults are small, white to yellowish winged insects that can be seen flying around infected plants.


What to Look For?

Whiteflies commonly infect plants causing their leaves to turn yellow & drop. They will usually be flying around the plant, but if you don't see them merely waving your hand around the plant will cause the insects to take flight.


How to Control Whiteflies

Isolate your plant from any others.

Use of sticky tape traps when insects are found in containers can work to reduce populations by trapping adults.

To further control infestations, wash eggs & crawling juveniles with water, dispose of infested pieces, & if the bugs seem uncontrollable apply horticultural oil or insecticidal soap repeatedly.

Unfortunately, if a whitefly infestation becomes too large, it may be best to discard the plant.



Ultimately, the best way to protect your plant from destructive insects is by utilizing preventative measures. After all, it is easier to prevent a pest infestation than it is to eliminate one.


PEST PREVENTION TECHNIQUES

  • Considering stressed plants tend to be more susceptible to pests than healthy ones, provide your plant with its individual optimal growing conditions, so it is more likely to grow vigorously, therefore more likely to fend off pests most easily.

  • The first step to purchasing a new plant is to choose the variety you wish to purchase. When making this decision, select plants with growing requirements (especially light & temperature needs) that fit the environment found in which they will be grown. Again, healthy plants are less vulnerable to attack by pests & diseases, & they will recover from these attacks more successfully & quickly if they are brought into a similar environment as they were originally grown in.

    • This step is not imperative, but it is helpful, especially if you are new to the gardening game.

  • Once you have found the plant you want to purchase, remember how important it is to examine the plant & it's container for signs of pests before adding this new plant to your collection. Check areas of the plant that bugs popularly reside. For example, mealy bugs are usually found on the undersides of leaves & in small crevices in the stems, where as aphids are commonly seen where new foliage develops. A diligent inspection would include leaf surfaces, leaf bases, flower & fruit stalks, as well as the roots.

  • Examine the soil in the pot before bringing home. Don't be hesitant to ask the plant distributor if it is ok for you to remove the plant to check the soil. A plant that has been outside for the summer, especially one that has been grown sitting on the ground, may have pests that have crawled into the pot via the drainage hole & made a home in its soil.

    • Mealy bugs, along with other pests, are attracted to the nitrogen in fertilizer, as well as the nutrients found in the roots. While checking the soil, make sure to search diligently, digging deep enough into the soil to reach the roots.

    • Reject plants that show evidence of insect or mite infestations, as well as possible disease symptoms, such as discolored stems & roots or leaf spots. These blemishes are not likely to disappear. As long as you are respectful, any plant distributor will understand your hesitation.

  • If your new plant has passed its inspection, it is time to bring it home. Once you have, isolate it from your own collection of plants for at least 6 weeks. This will ensure that any pest that could have been missed in your initial inspection will be less likely to spread.

    • While your new plant is isolated, carefully examine them for signs of pests or damage on a regular basis for around a week's time. Again, pay special attention to the undersides of leaves where pests are most often found. For a more diligent inspection, use a 10x magnifying lens to make it easier to see the tiny pests. Magnifying the leaves will also help you find pests that are still in their immature stages. Finding immature pests is crucial in controlling an infestation. If you pass over the baby insects, they can mature at an incredibly fast rate & you will have a plant full of bugs before you know it.

    • In many cases, early detection & removal of a pest or disease, when it is still restricted to a single leaf or part of a different piece of the plant that can be removed, might be all that is necessary for eradication & successful management. If no problems are found after several weeks of monitoring, the inspection interval can be extended to once a month.

  • After the 6 weeks have passed & you have cleared your new plant of any suspicion of infestation, it is finally time to repot it from it's original nursery pot into one of your choosing. Remember, just because you haven't spotted any issues up until now does not mean there are not pest eggs waiting to hatch in your soil or on the plant. Continuous inspection is necessary, but can be extended to once a month.

    • When repotting, make sure to use a commercially prepared soil, rather than a soil retrieved from the outdoors. Soil taken from the ground will more than likely have pests living in it. Whether or not you can see any pests, using a foreign soil may prove all of the diligent & time consuming preventative tactics useless.

  • Once you have examined your plant & its original soil, kept the new plant in quarantine for at least 6 weeks, & repotted it in a fresh, commercially prepared soil, it is finally time to introduce it to the other plants in your collection.

  • Even though you have deemed your plant worthy of joining your other specimens, that does not mean your preventative techniques are finished.

    • Washing smooth-leaved plants every 2 to 3 weeks discourages pest infestations, while simultaneously improving the appearance of the foliage. While this is beneficial to most plants, it is essential to research your specific plant's preference regarding moisture levels on its foliage.

      • Some plants will favor quick drying to keep foliage from being wet for an extended period of time -- prolonged wetness of foliage may favor disease development in some plants.

      • Other plants may not mind water on its foliage. In these cases you may even "wash" the plant.

        • Small plants can be inverted & swished in a bucked of tepid (lukewarm) water. To prevent loss of soil, cover it with aluminum foil or plastic wrap.

        • Large plants can be hosed down gently, or upper & lower surfaces of leaves can be wiped down with a soft, wet cloth. Large plants could also be rinsed in a tepid shower.

  • Since cut flowers from the garden can be a source of pests, keep them separate (or far away from) the houseplants.

  • Pests of houseplants can enter homes from outdoors, so make sure the plants are in rooms where screens cover windows & doors fit well.


Ideally, these preventative measures will keep you from having to deal with pests all together.

Unfortunately, especially during the warmer weather months, insects can be relentless.

For this reason knowing how to identify popular pests, the damage they leave behind, & knowing how to control an infestation are all integral parts of being a responsible plant parent.


If prevention techniques fail, identifying which pests are tormenting your plants by evaluating the damage your plant have received & then following up with the proper elimination procedures will rid your plants of those pests, while keeping your plant babies safe.











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