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Pest of the week – scale

November 18, 2014 by Jonas Dupuich

Fall, in moderate climates, is a key time to look out for pests on bonsai. In colder climates, many insects are killed by cold weather.  Not where I live. Within the past week I’ve found all varieties of unwanted guests in the garden. This week I’ll focus on scale.

Scale on olive branch

Healthy looking olive foliage

Scale on olive branch

What’s this – a small black dot. Could it be?

Scale on olive branch

Yes, it’s scale

Scale come in thousands of shapes and sizes, and just about all varieties of bonsai are susceptible to some scale or other. Closely inspecting your trees on a regular basis is the best way to stave off bad infestations.

Scale on olive branch

Scale on olive foliage

The crafty creatures on this olive grew between the wire and the branch making them very hard to spot. It was when I de-wired this olive that I realized I had scale. It was the first time I’d seen scale on the tree.

Scale on olive branch

Scale

How do scale get around? Once you see them on your trees, they likely don’t. Newly hatched “crawlers” find a good spot to latch on and rarely move after that, relying instead on their typically hard shells for protection. Scale can also move from plant to plant via the wind and can be carried around by other insects like ants.

What did I do when I found them? I picked them off with tweezers. The next step is to spray prophylactic oil. This works well for minor infestations – nastier infestations and tricky-to-treat scale like the pine needle scale require a stronger plan of attack – more on that Friday.

Scale

Tiny scale (photo courtesy Trung Ho)

Scale

Tiny scale (photo courtesy Trung Ho)

Scale are commonly found on junipers too so be on the look out.

Scale

Scale on procumbens juniper

ScaleScale on shimpaku

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Filed Under: Bonsai Care Tagged With: Pests, scale

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Reader Interactions

Comments

  1. endsurg says

    November 18, 2014 at 1:24 pm

    Since scales survive off of the nutrients of a leaf or branch and they sink their suckers into the veins, they are very susceptible to systemic insecticides. I find that using Bayer’s tree and shrub once or twice a year completely prevents scale growth and/or kills them.

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