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Severe white scale insect on rhododendrons

mwynd58mwynd58 Posts: 2
in Problem solving
After acquiring a garden with 51 spectacular rhododendrons last year I was devastated to find white scale insect and sooty mould. Blooms are not affected but leaves are. I sprayed with insecticides from July through to November at 2 to 3 weekly intervals. I thought I had won but they came back with a vengeance a few weeks ago.  I have started to spray again but should I just keep going or is there a particular brand which anyone has had success with. About 10 are really bad and the others are infected in the middle or lower branches.

Posts

  • Fran IOMFran IOM Posts: 2,872
    @mwynd58. Welcome to the forum.  :)
    Your post seems to have slipped through without an answer to your query. I feel sure there must be a member of the forum who can give you an answer. Not something I would be able to advise you on. Hope you have some luck this time. 
  • FairygirlFairygirl Posts: 55,117
    Constantly spraying really won't work. If you have scale insect, you need to treat that. They're weakening the plants and making them susceptible to infections.

    It's also possible that the shrubs are congested, with poor air flow,  and that can make them more vulnerable to any insect attacks. Without seeing them, it's impossible to judge.

    Wipe off the sooty mould with a wet cloth or similar, and treat the scale insect  :)
    It's a place where beautiful isn't enough of a word....



    I live in west central Scotland - not where that photo is...
  • mwynd58mwynd58 Posts: 2
    Thank you for your advice. What specifically should I treat the scale insect with if you don't think a general pesticide spray will work?
  • Pete.8Pete.8 Posts: 11,340
    It's usually a plant in poor health that gets scale insects which can be caused by something like a lack of water.
    The sooty mould will wash off with rain eventually, but will take a while.
    A really good tonic for all plants is seaweed extract and that will help your plants resist future attacks.

    As to how to treat the existing problem, there's a lot of helpful info from the RHS here-
    https://www.rhs.org.uk/biodiversity/scale-insects

    Billericay - Essex

    Knowledge is knowing that a tomato is a fruit.
    Wisdom is not putting it in a fruit salad.
  • FairygirlFairygirl Posts: 55,117
    You can often scrub them off with a brush and some soapy water, or just water. If that doesn't work, a popular method is a cotton bud dipped in meths and dabbed onto them.
    In the right conditions and site, rhodos need no help, so they may well be stressed by other factors. Frequent mulching of the surrounding soil is about all they need. Leaf mould and/or bark are the best materials, as long as they aren't dry when applying it.

    Without seeing them - we can only guess as to their conditions though :)
    It's a place where beautiful isn't enough of a word....



    I live in west central Scotland - not where that photo is...
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