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Small ovular or circular shells will begin to populate stems and on the underside of leaves. Although they can vary in colour, most varieties will sport warm colours that range from brown to yellow. Unfortunately, they'll also secrete a honeydew-like substance that makes the lower leaves sticky or shiny, as seen on the image below. Unlike other pests, they'll easily blend in with the foliage, so regularly checking for Scale is a good idea to prevent a further outbreak.
Scale will infest any surfaces that are strongly housed onto the plant; for instance the stems, petioles and both sides of the leaves. You'll also notice a shiny, sticky texture developing on the top-sides of the lower leaves.
N. B - Most Scale will hatch their eggs in June, so spraying the nymphs during this time is best to keep future populations down. There are multiple methods and remedies in which you can use; neem oil, rubbing alcohol and manual fingernail-prying. Although pesticides like neem oil or alcohol will significantly keep the numbers down, you may have some difficulty, to begin with as mature adults will be protected by their broad, armour-like shells.
Stepped Guide to Remove Scale
1. Using your fingernails to pry-off each bug is the safest and most efficient way to remove them. Due to the easy chance of puncturing the leaves with a sharp tool, avoid anything other than your hands.
2. Once the visible infestations are removed, take it outside and gently wash the entire plant using an outdoor hose. It's important to spray it in at least three different angles to ensure all sections of the plant has been administered. Empathise the cubbyholes, for instance, between the stem and its petioles and undersides the leaf. If the nighttime temperature is above 15℃ (59℉), keep it outside so that natural predators, (like ladybirds & green lacewings) can have a go at the bugs as well.
3. An optional tip is to replace the top 2cm (1 inch) of the soil. Not only will this improve the overall soil conditions, but it'll also remove any alive fallen bugs that have landed in it. This method can be taken once the plant has become fully dry after the first wash, and should only be performed once.
4. Consider whether to use an organic or chemical-based pesticide. The first option, of course, will avoid the use of harsh chemicals but will generally work slower than the latter option.
5. Keep the affected plant away from others in a quarantined room until the symptoms have subsided for at least four weeks. Always be wary of a relapse, and keep an eye out for possible outbreaks for several months after the last sighting.
N. B. - Although you should perform the wiping and hosing-down process BEFORE each pesticide application, you can wash the foliage at any given time to keep the infestation under control.
Insecticidal, or Horticultural Soap is the second most used organic pesticides on the market, and there are three versions to consider. The first way is by purchasing an RTU (ready-to-use) spray bottle, which can be immediately used on the plants. Although most garden centres will stock this, it's far more economical to purchase the second option - concentrated bottles. This method comes with pro's and con's but is far cheaper to use if you have multiple infestations. It's self-explanatory and highly beneficial for the outbreak as long as you use the correct levels of dilution - the only downside is its availability in local centres. It's best to buy this option online as there are many different companies to choose from, with some being cheaper than others. The final and most affordable way is by making it yourself;
There are three ingredients in creating your own insecticidal soap - a vegetable, tree or nut-based oil, non-fragrant dishwashing soap and tap water. Most oils are acceptable, with the most successful being vegetable, sunflower, neem and olive oil. Add two parts oil, one part dishwashing soap and eight parts water to create the dilution. Although it's best to fresh bottled water, tap water that has been allowed to sit for 24hrs is also fine. Spray the dilution wholly around the plant, empathising both the infestations and the potential-hit areas. This method must be performed weekly over a month or two, along with regular pest inspections - as soon as you see a bug, crush it.
Diatomaceous Earth (D.E. or DE) is grounded diatom mantels (skeletons) that can be highly abrasive to many arthropods, including Scale. Although the white powder may be soft to the human touch, the sharp tooth-like edges off each grain will begin to cut its way into the pests' eco-skeleton, causing significant discomfort and weakened health. After a period of several days, the infestation will decrease as the mature mothers won't be able sufficiently to lay her eggs. Usually, DE is applied as a thin layer across the foliage of outdoor plants, which will work until there is a rainstorm; however, you'll have to change the method of application to eradicate indoor pests. Instead of using powder to combat your infestation, mix the DE with water to create a more efficient solution to access the plant's cubbyholes and hard-to-reach areas. Add one tablespoon of DE to 500ml of water (0.11 imperial pints) and mix well. Finely mist both sides of the leaves and its stems so that the plant is covered in a thin film, which will begin its work within twenty-four hours once dry. Its eggs may be immune to the pesticide, so it's important to perform another fine spray seven days later to attack to the recently-hatched larvae. As you have followed the first five steps mentioned in the previous section, you shouldn't see any signs of an infestation for several weeks. We'd recommend waiting six weeks before deeming the specimen pest-free, as relapses of later-hatching larvae could occur. If pests do return, follow the five steps mentioned above, along with the misting of its foliage with this solution. If the infestation is large, you may wish instead to opt for a chemical-based pesticide to destroy the infestation more effectively. DE is considered safe to both pets and humans and has no links to the development of illness or cancers.
Neem Oil - This is by far the most effective and popular around the world. Not only will many online stores sell it, but it'll get to work after the first application. Dilute the liquid, (to the manufacturer's recommended strength) with water and/or dish soap and spray thoroughly onto the foliage and its cubbyholes. Any flowers must be removed instead of misted, due to the heightened chance of another infestation.
Natural Predators - The last non-organic method is by acquiring adult ladybirds or green lacewings. Although buying insects may be deemed as cruel or inappropriate, it's a natural, and least time-consuming way to remove the pests. Many online stores will sell the insects, all at varying prices and quantities. Once you've obtained the predators, release them in different sections of the plant, favouring the most infested areas first. They'll make their way around your plant, digesting both the eggs and the adults, leaving you with a potentially pest-free plant. Keep the insects and plant in an enclosed transparent box to increase the amount of digestions. Unfortunately, this method can take several days to work and could even be unsuccessful, which is why other methods are favoured.
Click here to purchase Neem Oil, an Insecticidal Spray or natural predators like ladybirds or green lacewings.
Most chemical pesticides are bought either as an RTU spray or in a concentrated bottle. Of course, it's far more economical to buy the latter as it'll last longer with multiple infestations, but RTU sprayers are still excellent for small issues. Both of these methods can be purchased at most garden centres, costing from £3 for RTU sprayers, to £7 for the concentrated variety.
If you're looking for something with even more strength, try an Isopropyl Rubbing Alcohol, which can be bought from many online stores. This pesticide will work immediately, killing the Scale within a few hours of contact. Follow the manufacturer's recommendations and repeat misting/crushing every two weeks until the infestation has elapsed.
At the local plant shop or garden centre, regulate and inspect any plants that you wish to buy. Check around the hard-hit areas, for instance, the foliage and stems, before considering the purchase. Most Scale infestations come from already-affected plants, so always keep this in mind when increasing your plant-collection.
Change the top layer of the soil when bringing any new plant from a shop. Replacing the top layer of the compost will remove any eggs & larvae that may have fallen in, or been deposited by another pest. ukhouseplants does this religiously, each time a new plant is purchased.
Regularly check for pests on your own plants. Although this may sound patronising, many gardeners forget to inspect their indoor specimens. As soon as you see a symptom, keep it quarantined and follow the steps above!
Need realtime advice for your Scale situation? Book a video or message consultation with expert Joe Bagley, THE HOUSEPLANT DOCTOR™ (author or ukhouseplants.com). Choose between a ten or thirty-minute session & a platform of your choice (WhatsApp, FaceTime, Facebook Messenger or Zoom). Ask unlimited questions in one session, including queries on your dying/challenging plants, pests eradication, terrariums, repotting advice & everything in between! Available worldwide.