A Complete Guide to Removing Pests From Your Plants

Skip to a pest, or read on about plant pest removal best practices:

Why do plant pests exist?

Plants come from complex ecosystems and are intertwined with all the denizens of those environments for better or worse. Some organisms have evolved to be herbivorous, and others carnivorous, and generally the carnivorous ones keep the herbivorous ones in check. However, when we are growing plants in our homes and greenhouses, we are growing the plant outside of its normal habitat. Because of that, sometimes when one of those herbivores come along with the orchid into our growing spaces, there’s no other organism that can keep them in check, so they multiply out of control, and the plant starts to take damage from them.

General Pest Information

So, you’ve gotten your first plant, or maybe you’ve amassed a small collection, and you begin to think – what happens if bugs get into my plants? Well, fear-not! We will tell you all you need to know to have a happy, healthy plant collection.

Orchids become infested with pests most commonly in some combination of three methods: purchase of an infested plant, movement from infested areas to un-infested plants that are in contact with each other, and windblown colonization. The best way to keep your orchids pest-free is to start off with good stock, and treat all plants in a quarantine area before assimilating with the rest of your collection. By not bringing pests in, in the first place, you will be saving yourself a lot of work later on. Indeed, the best way to prevent pests getting into your collection is to start off with clean, pest-free plants.

Insects (and Arachnids), or “bugs” are rather predictable, modular creatures. They do not do anything beyond what nature has programmed them to do. For example, while aphids are annoying pests that seem to come out of nowhere, they do not jump on you and hitch a ride, and they don’t hang around areas with no fresh green foliage around to suck on. Additionally, they won’t be found that much in the bark of a tree, but they will definitely be found where the leaves are. Because insects are mostly predictable, we can use that information to control them for either Integrated Pest Management outdoors and in greenhouse, as well as eradicate them indoors.

IPM, or Integrated Pest Management is a method of insect/pest control that is commonly implemented in outdoor gardens/greenhouses. The alternative to IPM is Eradication. Indoors, it is very possible to completely eradicate pests, given that your home is (for all intents and purposes) a closed system[1]. Outdoors, that’s not the case, and so we use IPM to manage or live with pests in populations that lead to acceptable plant damage. Again, the idea of IPM is to live with the pests in tolerable, low populations. This can be achieved by regular pesticide sprays or by cultivating beneficial insects to live with your plants. It’s difficult to do both, as pesticides will kill both the good with the bad insects. It’s best to spray pesticides initially, to cull high pest populations, then to introduce beneficial insects later, or to only spray badly infested plants.

The best way to control a pest is to make it as inhospitable for that pest to live and breed, as well as using good cultural practices when caring for your plants.

This varies according to the pest, but the same general rules listed below apply to everything:

Never bring in a new plant from a vendor or a plant from outside without treating it at LEAST twice for insects in a quarantine area.
Bugs are everywhere, and all plant shops have SOME baseline of pests that you WILL bring home with you.
Quarantine all plants brought in, in an area away from your collection, even if the light is not ideal – this situation is temporary. Plant pests don’t travel too far from their hosts, so if you place new plants in a completely different room from your collection, the pests will predictably cling to the plants they are on, making them easier to eradicate.
If you just got a new plant, and it looks like there are no pests, just spray twice as a precautionary.
When spraying, drench the leaves and all aboveground parts of the plant with insecticide from every angle (more on insecticides below). Think like a bug – bugs hide in every nook and cranny, so GO OVERZEALOUS with spraying the top, bottom, sideways, well, you get the point. Leave no part of the plant unsprayed, including the top of the media and around the pot. Any tiny crevice that is unsprayed is an opportunity for one to survive, multiply, and wreak havoc.
MOST IMPORTANTLY… REPEAT, REPEAT, REPEAT the treatment at least three times or until you no longer see signs of pests. Then you may wash and then assimilate the plant into your collection.
Use the right pesticide for the right pest!
Don’t be fooled! Sticky traps only monitor pest populations – they will not control pests!
People who think systemic pesticides are a cure-all will be doomed to be plagued with mites and thrips for 1,000 years!!! Systemics don’t work on all pests, especially mites and thrips.
Broad-action insecticides like insecticidal soaps or horticultural oil (petroleum-based) are fabulous and do not risk resistance
BE diligent about when your windows are open, when your plants come inside, and when you assimilate new plants into your collection.
If you want beneficial insects to stick around, do some research, and plant their “alternate hosts[2] [3]” and “insectary plants[4]” – plants that beneficial insects use to breed and survive times when pest populations are low. In the absence of these alternate hosts/insectary plants, the beneficial insects leave.
The label of whatever you choose to use is your gospel. Do not deviate from those instructions unless a professional (see “has a horticulture or chemistry degree” and is not a YouTube channel) instructs you to. Again, this is a matter of safety, which we take very seriously. Always consult the safety information (SDS, or MSDS) of whichever product you are using as gospel.
Again, read the label, and take the recommended precautions and spray the recommended doses that are on the label of the pesticide that you choose.
Cultural care is the frontline of defense. Making it uncomfortable for pests by cleaning debris, removing dead leaves where they can overwinter, keeping good space and airflow, etc. are the frontline of defense around keeping pests at bay. The below are good reads:
- Rutgers, The State University of New Jersey – Creating a Master Plan for the Greenhouse
- University of Missouri Extension – IPM in Greenhouses
- Oklahoma State University Extension – IPM in Greenhouses and Cultural Practices

Pesticides

Different pesticides have different “modes of action”, which are ways in which they kill insects. Broad-spectrum insecticides, such as insecticidal soaps have low risk of pest-resistance, but only work on contact. That means that the pest has to be directly sprayed for this type of insecticide to work. For soaps, the idea is, is that the soap dries out the exoskeleton and joints of the pest, causing cracking in the shell and death of the insect.

Other pesticides are highly targeted and can kill pests that come into contact with the residue, but are more toxic to humans and risk the insects evolving resistance. These are typically the industrial pesticides, intended for one or a few specific pests that they need to get to a low enough population to ensure a good crop.

Systemic pesticides are taken up by the plant, and don’t bother the plant, but only affect insects that suck the phloem sap of the plant. They are best used as a preventative.

Insect Growth Regulators (IGRs) are the newest pesticide on the scene, and some are even food-grade-safe for humans! The catch is, is that these pesticides don’t kill insects, but rather, prevent them from reaching maturity and preventing molting. It’s best to combine IGRs with another pesticide for maximum efficacy.

I get questions all the time about “organic pesticides” or “safe to use pesticides”. If a pesticide is safe for you to use, then it’s probably safe for the insects too, and won’t kill them. “There’s no such thing as an “organic pesticide”. Organic is a methodology of growing, and pesticides… well, they kill pests. Please do not conflate the two unless you want to see me writhe in agony.

The best methodology is to start with the weakest pesticides first, and if they don’t work, ease up to more hardcore ones. The idea being that we don’t want to jump to the hardcore pesticides from the start, because that risks the chance of the insects becoming immune to the pesticide. Additionally, the label of whatever you choose to use is your gospel. Do not deviate from those instructions unless a professional (see “has a horticulture or chemistry degree” or “works for the Department of Agriculture” and not a YouTube channel or some other blog) instructs you to. Again, this is a matter of safety, which I take very seriously. Of course, consult the safety information (SDS, or if you’re old like me, MSDS) of whichever product you are using as gospel.

This is for the folks who never read the safety instructions

Problems that are not insect problems can be mitigated through cultural care; more on this in another article. But while we are on the topic, it’s best to thin-out bushy plants if there is an infestation. For really bad infestations, it may be best to prune off the most infested parts.