How to kill scale

Discussion in 'HortForum' started by Maiolicagirl, Feb 3, 2019.

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  1. Maiolicagirl

    Maiolicagirl Member

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    Inhave been battling scale on my potted plants for 2 years now. I have been able to control it on my potted citrus and bay plants by hand picking and spraying with neem oil and Safers soap. I now have a huge infestation on my potted corokias. It will be almost impossible to pick the scale off of the tiny stems and leaves. I am going to give the plants a good pruning and hope that a continued spray program will help.
    Is there anything more effective to control scale? I don’t want to to use a systemic solution but I am getting desperate. The corokias are quite large and they are overwintering under lights.
     
  2. Junglekeeper

    Junglekeeper Contributor 10 Years

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    I've had scale on my citrus in the past. Care must be taken to physically remove all the adult scale before spraying with insecticidal soap. The sprays must then be repeated a number of times with 7-10 days in between. Periodically inspect the plant for surviving adults and remove them if necessary as some adults, those with nearly transparent shells, may have escaped initial detection. Persistence is key.

    Infected plants should be quarantined and hands should be washed after handling to prevent passing the infection to other plants.

    By the way, I believe systemics are no longer available at retail.
     
  3. Maiolicagirl

    Maiolicagirl Member

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    Thanks, I will have to be more persistent. As I mentioned in my post it is extremely difficult to hand pick the scale from the teeny tiny corokia leaves and stems. I have them quarantined for now and in the summer Inmay just out them in an isolated area in my garden.
     
  4. Junglekeeper

    Junglekeeper Contributor 10 Years

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    You may want to look into using horticultural oil for the corokias and other outdoor plants. I've not used it before but it's apparently more effective for plants with a lot of foliage in which pests can hide.
     
  5. Eric La Fountaine

    Eric La Fountaine Contributor UBC Botanical Garden Forums Administrator Forums Moderator 10 Years

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    I was able to finally rid my Citrus hystrix of scale by washing it with strong water flow from a garden hose. It is a large shrub so picking them off was very difficult. It takes a very strong spray though--I used a small tight spray--not a lot of water, but a strong jet. Citrus leaves are fairly tough, it might just blow the leaves off a corokia.
     
  6. Anna Kadlec

    Anna Kadlec Active Member

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    Any suggestions for a scale-infested Clematis armandii? I can't reach most of it : (
     
  7. Maiolicagirl

    Maiolicagirl Member

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    Great idea, and Cedar Rim Nursery just sent an email flyer with hort oil on sale. I will prune today and spray again with neem and soap then do oil next week.
     
  8. Maiolicagirl

    Maiolicagirl Member

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    I will try that once it warms up. Such a tenacious pest.
     
  9. Junglekeeper

    Junglekeeper Contributor 10 Years

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  10. Margot

    Margot Well-Known Member

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    As a last resort, you might consider cutting it back to a few feet from the ground where you can control the scale and then let it regrow, hopefully scale-free. Clematis armandii grows so quickly, it would probably not take too long for an established plant to re-cover the same space as it did before.
     
  11. Tom Hulse

    Tom Hulse Active Member

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    I will second what Daniel said. I have also completely cured potted plants of hard scale with a strong blast of water. Around here all the home centers sell those cheap hose nozzles with a 7-way dial head. One of those settings is "flat" that shoots out a very sharp, flat stream of water at just the right pressure to blast the scale as forcefully as possible without ripping off the leaves.

    Take the plant outdoors every to blast it every time it is due for a watering. You can do it safely if it's above freezing with nearly any tropical plant for the quick 15 minutes it takes. Get out your spectacles or a magnifying glass to make sure you are getting most of them. Also consider refreshing the top 1/2" or so of soil. Forget the chemicals as they're bad for you and don't work well enough. The sharp water spray method is a 100% cure for even severely infested plants. Works for soft scale/ mealy bugs and spider mites also.

    I'm not sure in Surrey if you keep those outdoors this time of year, but if you do, and it already has all the water it needs, you can cover the soil with a couple overlapping pieces of plastic to avoid adding excess water.
     
  12. Maiolicagirl

    Maiolicagirl Member

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    Is it safe to use Hort oil on the corokias and citrus? The instructions say to apply before foliage develops in the spring. I also found scale on a bay tree. Ugh. I will certainly try the hard water spray once spring arrives and I put the plants outside.
     
  13. Junglekeeper

    Junglekeeper Contributor 10 Years

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  14. Michigander

    Michigander Active Member

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    This party really needs a skunk. The first stage of scale's life is a teeny tiny little winged beast that can fly to a new host. So small, for all intents and purposes, invisible. They are hermaphrodites, too. If you miss a single one, she can fertilize herself and have another ton of babies. As much as y'all would like to believe that the world is a really touchy-feely place where crabby ogres love to poison everything in sight because they're ignorant and evil, the truth is that everything is in competition with everything else for their piece of the pie, -winner take all. Your only two choices are: deal with it and choose which year you lose the output of your plant, or give it up.

    Scale especially like close quarters like the axils. Washing scale off of something is pretty borderline _ _ _ _ _ _ , and ignorant of the basic mechanics of the critter. The only solution is to use hort oils and the dreaded systemic which means giving up one whole year of production, at least, and also doing the same on any other hosts in the vicinity. That means your neighbors hosts, too. If you're not willing to kill all the scale in your environment, it will continue on your plants, and other hosts, too, and only get worse. And, I'll be here to say, "I told you so..."
     
  15. Tom Hulse

    Tom Hulse Active Member

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    Michigander, out of all of us in this thread, there seems to be only one of us who has both worked extensively around scale and has had substantial success actually curing infestations. I know for a fact you are flat-out guessing that water sprays won't work . In 3-4 months time from right now these plants could have zero detectable live scale pests. They would also have a minuscule risk of re-infestation if simple watering techniques are followed. This year's crop can easily be saved.

    Couple of things you are missing:
    1. It's true scale may be pervasive in a local environment (like mine), but for potted plants grown indoors in the winter, we do have plenty of control over that environment. More than enough to easily control this pest. How we water is the biggest control that affects scale. Plant placement is another, smaller, factor.
    2. You misunderstand the basic mechanics of the critter! You don't just catch these bugs, then aw shucks you're infested, get out the nasty poison. You do have control. Both hard & soft scale on potted plants is an indicator of poor plant care. While any plant summering outdoors can have a stray occasional pest, an infestation will not occur if the plant is healthy and it's leaves and stems are washed regularly. Fix the poor plant care and the scale cannot survive. The sharp watering method speeds up that fix to just a few months or so.
    3. These plants are indoors right now and will be again. Systemic poison is bad advice for indoor plants with hard scale. It's either terrible for your health, or the milder systemics approved for indoor use (still bad for your health) are just not effective enough against hard scale to bother using. Horticultural oils work, but not as fast or as well for potted plants as the method I described.

    Michigander it sounds like your advice comes from experience as a commercial grower? It's true that it would never be viable commercially to spend an hour per plant carefully getting these bugs off. And then very careful hand-watering up under the leaves and stems of every plant would also never work commercially, but it absolutely does make sense for someone's precious collection at home. A typical schedule for a massively infested plant with hard scale might be: day 1 drag the plant outdoors & spend .5 to 1 hour sharp spray blasting off all visible domes; 90% reduction in pests. Next watering in a week or two drag the plant out again, repeat for 15 min, 97% gone. Keep doing it at every watering for 3-4 months to guarantee complete cure. The time it takes will diminish down to just a few minutes at the end. Indoors vacuum well & frequent in the area the plant is kept, wash windowsills, keep other plants well away. Outdoors in summer avoid placement in the shadow of bigger trees that may be infested; every plant watering then must also water the leaves and stems where they hide, preferably with strong pressure, especially in the month leading up to bringing them back indoors. Start now, don't wait for spring!
     
  16. Michigander

    Michigander Active Member

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    To say the very least, that's a hellavalot of work for one indoor plant. And for those in the landscape?
     
  17. Tom Hulse

    Tom Hulse Active Member

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    With horticultural oil, you still have to drag the plant outdoors and back in for these type of plants. You still have to take the time to water it, and you should still be taking the time to wash the leaves of overwintered indoor plants at least a couple times during the winter. The actual blasting time is mostly just on the first pass, much quicker after that. Not really that much difference but worth it for a one time effort to rescue a valued plant.

    Regarding your question about landscape plants, in this area outdoor hard scale is a common fact of life. It's not a problem unless it's a massive infestation that becomes a visual eyesore or threatens the health/life of the plant. Almost all of those problem cases can be traced back to poor plant selection or placement. For instance growing a tree rated for colder hardiness zones, one zone too warm. Homecenters sell them, people plant them, they'll seem to grow fine; but someday they could much more easily fall prey to a massive infestation. That's where I sometimes use the horticultural oils especially for fruit trees. I have a beautiful tri-color beech that was a bad decision 20 years ago from both the hardiness zone and the plant placement. Aphids will overtake the leaves by late summer, but if I hose off the undersides of the leaves a couple times starting in early summer it will control the problem all year. It's similar with scale. Start with the right plant in the right spot and you won't have a problem.
     

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