Quote:
Originally Posted by greenhouser
Hello
My previously healthy hydrangea bush has developed some sort of problem, see attached pic. The scabs are about 3-5mm long but don't seem like the mealy bug or scales disease I've found info on - can anyone advise what it is & an effective treatment? I've tried spraying it with a non-systemic greenfly & mite spray but it doesn't seem to have helped. It's still flowering ok but a fair few leaves have died.
Thanks in advance.
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Hi there,
These are indeed one of the many species of the sap-sucking Cushion Scale Insects. They are highly resistant to most insecticides, but once they've attached they are immobile, so it's actually relatively easy (if time consuming) to remove them using a sponge and soapy water. Try to get as many of the fluffy white masses as possible as these can contain eggs. Collect everything in a bowl as you go so you can flush the whole lot away.
Alternatively, if the infestation is really severe or has spread to other plants, you can use one of the "Insecticidal Soaps" based on Potassium Salts of Fatty Acids. These dissolve the insects exoskeletons and are highly effective, whilst still considered organic. Also, once dry the spray is harmless to Ladybirds & Lacewings which are the natural predators of Scale Insects.