Controlling scale on my potted finger lime and other citrus
To enable me to grow citrus in a cold climate I have a selection in pots so I can move them into warms spots throughout the year. Now most Citrus can be attached by soft brown scale (coccus hesperidum) but it is particularly prevalent on potted specimens.
Brown scale is a sap sucking insect and will literally sap the life out of your plants, but the biggest issue is the proliferation of “sooty mould”, a fungus that lives of the honey dew (excreta) of the scale and covers the plant in an ugly black substance that prevents it from getting light and photosynthesising. If not controlled, scale can potentially kill your plants.
I have had quite an outbreak of scale on my potted citrus this summer. It is not surprising given that they thrive in hot dry conditions.
But why do trees succumb to scale attack? Generally speaking small infestation are occurring all the time and the plants own defence mechanisms and naturally occurring beneficial insects keep things under control and we never notice them.
However, if your plants become stressed and the environment is right for scale to flourish, then it is likely that you will get an infestation.
Plants become stressed when they are trying to grow in less than optimal conditions- not the right amount of water, nutrients and light levels and perhaps trying to grow them in a climate that is not ideal- too hot, too cold, too dry, too humid etc
The secret to pest control is keeping your plants strong and healthy by providing them with optimal growing conditions. This is especially important in hot weather where it is necessary to keep the water up to them.
I also like to keep my pots in as natural an environment as possible and companion plant to attract beneficial insects so that when pest occur they are kept under control.
However, despite all my efforts I did get an infestation of soft brown scale on my Finger Lime and several of my other potted citrus.
Here are a few things I did to get rid of the scale which will now give my plants a chance to recover and become healthy again.
Scale is “farmed” by ants -they give them a free ride to other parts of the plant or move them to new plants. Ants also live off the Honey Dew. So controlling ants is necessary. What I did here was simply placed some Antrid on a piece of plastic on the top on the potting mix and replaced it every week until I saw no more sign of ants.
I them assessed the plants, if there was a particularly heavy infestation on a particular branch, which was often the case, I choose to remove the branch. Making sure it was not a major branch of course.
Once I had remove the branches I needed to remove I then moved the plant into a shady spot, (if your plant is not in a container wait till dusk) and sprayed the whole plant with Yates White Oil. I left this on for several hours then hosed the plant down. Scale breathe through the waxy covering (scale) that they produce to protect themselves, the White Oil covers the breathing holes with a film and the scale suffocates.
I repeated this process every week for three weeks, this way I will have killed most of the young scale that are often very hard to see when inspecting a plant.
I then paid particular attention to my plants health, making sure I watered and fertilised it regularly and gave it a weekly dose of seasol just to boost its immune system.
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