What is scale and how is it treated?
Well scale are insects that feed on the sap from your plants. They stick their specially adapted mouth part into the stem of the host plant and feed from the sap. They are often called sap "sucking" insects but in reality they don't suck the sap. The plant forces the sap into them like a burst pipe under pressure.
There are many types of scale and they all have a protective coating or amour like body that shields them from the outside world. Some common ones are wax scale, cottony cushion scale, armouded scale.
These are on a citrus fruit.
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Wax scale
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As you can see the colours vary and they will from plant to plant in most cases.
What kills them?
Well there are very few systemic insecticides left on the market that really are effective.
The only spray i will suggest to use for any effect is any containing "Maldison". Now this isn't friendly stuff by any means so wear long pants and shirt, cover you face and wear eye protection. Never spray when it is windy, when it is raining and always do it in the morning.
Chemsprays "anti-scale" is one commonly found product in garden centres.
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I know many other sorts of "systemic insecticides are recommended to kill these buggers but in all honesty they are almost if not totally ineffective. Even white oil and horticultural oils will have little if any real effect on them. I don't know of any nurseries that use white oil to control them and that is because they don't work well enough.
The good news is for eastern states Homeone members you can use something called "integrated pest management" Sounds complicated but in all honesty is the simplest way to treat them. It's all about using predatory insects to control pests in the garden
Here is where you get them...
http://www.goodbugs.org.au/
The natural predator is sent to you in the mail, yes in the mail Then just release them onto the plant infested with the problem and they do all the work for you. Many nurseries use this method of pest control and find it as or more effective than traditional sprays for less money
In WA there isn't yet somewhere we can get these from but very soon there will be
If you have black gunk on the plant as well, that is sooty mould.
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It is there because of the sap the scale or sap feeding insect poos out. It is rich in nitrogen and sugars. Pointless to treat until you treat the cause (which is the scale) and it will often go away on it's own. To treat the sooty mould, you would use a fungicide like Mancozeb or one of the newer organic treatments that contain "potassium bicarbonate" like ecorose. It isn't just for roses great on lawns and any other plant as well. Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅
Ants too are commonly found with scale or sap feeding insect problems and they need to go before treatment of the scale will be effective. They put the scale there in many cases. On bigger plants rub some chalk or talc powder into the base of the trunk. The ants don't often cross it. Otherwise use some ant granules based on "Bifenthrin". Very important that
If the leaves are a bit sticky and yucky you can spray some detergent (diluted) onto the leaves and give it a good wash with the hose
Lastly once the scale have died, their little bodies will normally stay stuck on the branches. The plant will improve in health very quickly. Give it plenty of seasol and power feed and it should bounce back fine