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If you're getting into container gardening, at some point you'll have to deal with a pest infestation. If you've landed on this article, then the odds are good you are already experiencing an issue.
Pests in your garden, particularly in citrus trees grown in containers, can be incredibly tricky to deal with. When the trees are outside, you have numerous options such as waiting for a good soaking from the rain, strong winds, a hot day to dry the soil out, or even the ability to apply large-scale insecticide applications.
Indoors, not so much.
Over the years, we've had numerous infestations of our plants once we brought them indoors including gnats, spider mites, mealy bugs, and other soil-based insects. So in this one, we thought we'd share some of the things we have tried to manage each of the populations, and identify which ones we think have (so far at least) worked the best!
Gnats / Fruit Flies
After bringing our citrus trees indoors for winter, the first pest we often notice is small gnats flying around the soil in our trees- particularly noticeable after we water as the gnats fly up and away when the soil is damp.
These gnats seem to be harmless in their adult state, but many outlets report that the larva that burrows into the soil can wreak havoc on your plant's roots- so getting rid of them quickly is quite important. We have found a two-pronged approach helps us get rid of gnats in our citrus trees once they are indoors.
First, we add several sticky strips across the top of our pots, facing downward, to catch as many gnats/fruit flies as we can when they fly up from the soil. By capturing the adult population, we can hopefully minimize the number of eggs they subsequently lay. This method, however, is not 100% effective, so we add one more element here. This is not recommended when outdoors as sticky strips can catch other beneficial insects like bees.
Second, these pests love a damp environment and thrive when your soil is moist. As such, we then let the soil in our citrus trees dry out as long as possible to help create a hostile environment for the gnats and larvae before watering again, as dry conditions are thought to eliminate the population. Of course, you have to be careful to not let your plants dry out too much as it could damage them as well.
This combination generally works wonders at knocking down the gnat population in our trees, with the sticky strips getting the bulk of the population and drying the soil eliminating what remains. Once we've managed the population with our indoor plants, we tend to be pretty clear for the rest of the winter until the trees go outdoors again.
Alternatives: If the above doesn't get you all the way, you could always consider adding a layer of diatomaceous earth to your soil when it is dry to help kill any stragglers. The fine particles will kill most small bugs, but note that any moisture present will cause it to clump and lose effectiveness. Be sure to read all safety recommendations with diatomaceous earth, wear recommended PPE, and be careful with the extremely fine powder.
Mealy Bugs
Mealy bugs are a pretty big pain for our potted citrus plants because it doesn't take much before you have a population explosion on your leaves. These tiny insects can be quite small, almost looking like tiny dots without taking an extremely close look, and leave a mess on your plants with sap that attracts other pests like ants over time.
If you ever see a few leaves with a sticky residue on the top of them that won't dry after a short period of time, or a gathering of small shavings of organic matter (like fine wood shavings almost), start to look on the underside of leaves, on new growth, flowers, and at plant node spots nearby as these pests are likely not too far away.
Many conventional sources suggest a good spray with insecticidal soap will get rid of mealy bugs, but in our experience, we did not see a significant improvement even with many successive passes. Part of this is because insecticidal soap is typically most effective when the pest is covered in the soap, which is quite difficult to do effectively on the underside of leaves. After several passes, we thought we ran the risk of spraying our leaves with too much moisture and creating fungus/mold issues, so we looked for an alternative.
- We also tried filling a squirt bottle with diluted Neem for local applications indoors; however, we found that the mixture often clogs our (cheap) bottles. There is a reason why you use an industrial sprayer outside for this one, sadly. Your mileage may vary if trying this route.
- When using any chemical application, make sure it is safe to use on trees with edible fruit. Some insecticides are not suitable for application on trees that produce edible fruits!
The next most common recommendation you see is to dab the infected area with a tissue or cotton swab soaked in 70% isopropyl alcohol. The alcohol is thought to kill the bugs on contact, and the light pressure often causes the bugs to be forcibly removed from the tree itself- so even if they somehow didn't die from the alcohol, they are still removed from the tree. (Always test a small area of your tree when applying a new chemical as some can be sensitive.)
We found this one to be much more effective in cleaning out individual leaves as a spot removal upon identification; however, we would have to repeat the process several times over the course of a few weeks as we inevitably would miss some, they'd lay eggs, and the cycle repeats. As such, this one is really only great for spot removal and not plant-wide treatment.
Another option to try is to take your plants into the shower (or outside, if warm) and spray them down with a showerhead/hose, respectively- trying to get direct contact with all the growth of the trees. The water pressure will help flush many bugs away, hopefully off your trees entirely, and minimize their population for a period of time. Any that remain can be quickly disposed of with an alcohol-soaked tissue.
Finally, if you found a large concentration on just a few leaves, you could always prune them, too. But in our experience, if you find a cluster on a few leaves, odds are good they are elsewhere, and you just don't know it yet.
Spider Mites
Spider mites are another pest that can lead to a rapid infestation in your trees. You'll notice this likely first from webbing that appears, which, if untreated, can likely envelop entire branches of your tree in a nasty, pest-filled web.
If your tree is already in the latter stages, you may find that simply pruning a branch off is a possible remedy; however, from there, spider mites can often be removed by spraying your plant with water from the shower or insecticidal soap applied directly to the mites. As previously mentioned, soap is typically a kill-on-contact method, and if you miss some of the mites, odds are good they will not be impacted too much.
We have, thankfully, never had a huge spider mite infestation to date, but only because we caught some of the early warning signs and treated our plant either with soap or pruning methods. But as with all things, do not be surprised if you'll need multiple passes.
Other Soil Based Bugs
Over time, we have noticed other bugs crawling around our soil that typically appear on the surface after watering (we had symphylans in one of our pots once, for example).
We urge a bit of caution here because it is quite easy to misidentify soil-based pests without being careful. Some of these are harmless to your plants, soil, and roots. Others may be quite damaging. Some sources may even say a pest is harmless whereas another says it should be eliminated!
We do not want to go down the rabbit hole of identifying more soil-based pests here due to this concern, but if you have found an infestation of a pest you believe to be a problem, you have a few standard options for dealing with them.
The first is attempting to dry your soil like you would for gnats. A similar thought process happens here that most pests need moisture to survive, and a period of harsh, dry conditions may eliminate the problem. Next up, try spraying them directly with insecticidal soap when they are on the surface. Much like other pests, direct contact with soap is thought to help kill pests on contact. You could also just remove them with a tissue when you see them as well. But the latter two points here only deal with the ones you identify- not all of them.
In extreme cases, you can go further with dry soil by adding a layer of diatomaceous earth (just as you would with gnats); however, be sure to keep in mind all safety issues and the fact that it is only effective in dry conditions- any moisture, as stated, will cause the diatomaceous earth to become a clumped mess that is not effective. Others may even introduce beneficial nematodes as natural predators (note, we have not tried this yet).
We are keeping this section here general simply because we don't want to incorrectly identify a possible pest in your soil. These are just options to consider if you notice a problem and want to pursue corrective action.
Prevention Starts Outside
The above are just a few of the infestations we've had to do deal with in our potted citrus trees after bringing them indoors each winter. We do our best to keep them healthy when indoors, but the truth is most all of our infestations came along for the ride from outside.
As such, an ounce of prevention can go a long way for winter health.
There are many things you may want to consider trying before bringing your plants indoors for winter, including the following:
- Hose the leaves and trunk of the tree down really well before bringing the trees inside to wash off any pests.
- Treat each plant with a spray of Neem to help kill off any pests before taking it indoors. Both the pressure and the chemical will help reduce pest numbers.
- Spread some sticky strips across the top of your pot a few inches off the top of the soil, facing down when you bring them inside- great at catching soil-based pests that fly.
- Let the soil in your plants dry out sufficiently to help neutralize any soil-based pests.
- Consider a layer of diatomaceous earth on the soil when dry if you had any summer infestation concerns, and remove before bringing inside (wear safety gear as always).
Finally, when your plants are inside, you may want to give them a fair bit of space between any neighboring plants if you are able. One of the reasons I believe we have some pest problems is simply that our trees are clustered together in our south-facing windows, which makes it easy for an infestation to spread from tree-to-tree. So if you have space, it can't hurt to give your trees a little room, too.
Have you figured out a way to manage pests on your tropical citrus trees when in doors? Comment to share!