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Thrips are small, tubular-shaped flies that'll bring great destruction to the unfortunate plant(s). They can be introduced into the home via many different methods, but most notably being through an open window, newly-bought plant or via infected soil during transplantation. Despite their damaging destruction, they can be easily eradicated using the correct methods which will be discussed below.
You'll first notice the yellow, egg-like larvae appearing on the top sides of the foliage. After a few seconds of inspection, minuscule black and white flies will be parading over the whole plant, including the soil, stem and flowers. Yellow, dark patches will quickly develop within the next few days once an infestation takes over. Thrips can be a very damaging pest as they'll scrape the cell membranes off from the leaf - action must be taken immediately for the prevention of death.
Before we go into the remedies for addressing this pest, have a quick look at the neighbouring plants to see if they've become under attack, too. Thrips are very contagious, so the likelihood of multiple specimens sharing the infestation is pretty high.
Both sides of the leaves, but mostly on the top-side. They tend to attack middle-aged growth and will quickly destroy new growth if exposed.
Plants - Most houseplants are at risk of an infestation; however, some families, like the Cactaceæ (Desert & Jungle Cacti) and succulents, are exempt from an attack. The most common plants to be engulfed with Thrips are Palms, Dracaena (Dragon Trees) and members of the Aroid family (Alocasia, Chinese Evergreens, Dieffenbachia, Monstera, Peace Lilies, ZZ Plants). Thrips generally like broad, thin leaves that can host large numbers of eggs and nutritional sap.
1. While using a damp cloth, destroy as many bugs and their larvae as possible. Any flowers must be removed along with the worst affected leaves or stems.
2. Take the plant outside and GENTLY wash the stem, leaves and each cubbyhole using an outdoor hose. It's important to spray in at least three different angles towards the specimen to ensure thorough administration.
3. While the plant is drying-off, remove the top quarter of the soil in favour of a fresh batch of the appropriate product - ‘Cactus & Succulent’ compost for arid-dwelling species, tropical plants for ‘Houseplant’ labelled potting mixes, etc. It's vital to replace the soil, as once summer arrives, any burrowed larvae may hatch and continue to wreak havoc on the hosting plant.
4. Perform a final hose-down before placing it in a warm room, away from other specimens to dry-off. If the temperature is above 15℃ (59℉), keep it outside so that natural predators, (like ladybirds and green lacewings) can have a go at the critters.
5. Once the specimen is bone-dry, it's time to administer a pesticide. Although there is a choice between two options (organic or chemical-based sprays), ukhouseplants would highly recommend using the latter option, due to the pest's ability to bypass organic varieties.
6. 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.
Neem Oil is used across the world, and for a good reason. Not only is it accessible in many stores, but it'll also 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 lurking in the background.
Diatomaceous Earth (D.E. or DE) is grounded diatom mantels (skeletons) that can be highly abrasive to many arthropods, including Thrips. 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 (instars). As you have followed the first six 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 six 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.
Insecticidal or Horticultural Soap is another popular pesticide 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 will also be fine. Spray the dilution thoroughly 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!
Natural Predators - The last non-organic method is by acquiring adult ladybirds, green lacewings or spinosads. 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 throughout this period to increase the rate of digestion. Unfortunately, this method can take several days, if not weeks, to work and could even be unsuccessful, which is why other products are favoured.
Click on the individual links to purchase Neem Oil, Cinnamite, an Insecticidal Spray or natural predators like ladybirds or green lacewings.
We'd recommend using 'Bayer Garden Provado Ultimate Fruit and Vegetable Bug Killer Concentrate', as it worked IMMEDIATELY after one application. It's a concentrated product, meaning that you'll have to dilute it with the appropriate amount of water. Spray both sides of the leaves, along with any cubbyholes that could house the infestation. Keep the plant away from other specimens once there are no signs of an outbreak for over a month.
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 bugs within a few hours of contact. Follow the manufacturer's recommendations and repeat hosing the plant down and pesticide application steps fortnightly until the infestation has elapsed. Keep it well away from others until the plant is deemed safe.
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 new growths, before considering the purchase. Most Thrip infestations come from already-affected plants, so always keep this in mind when increasing your plant-collection!
Keep the windows and doors shut throughout May and June, as this is the time that Thrips are most active.
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 larvae that may have fallen in, or been deposited by a pest. ukhouseplants does this religiously whenever a new plant enters the house!
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!
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