Battle of the Scales

September 22, 2010

Several weeks ago, I noticed that the leaves on two “Stairway to Heaven Jacob’s Ladder” (Polemonium reptans) were sticky. Thinking aphids had infected them, I hosed both plants (above photo ) off after each watering. I did this for two or three weeks. It was only when the lower, underneath leaves turned yellow that a serious problem became clear.

Spreading the plants apart for a slower look, I saw hundreds of insects feasting on the stems and leaves. I took a sample to the Amador Master Gardener’s office and learned that the insect was scales. Scales are so small they are difficult to spot in the beginning. Still, if I had paid attention, looked deeper, taken more interest maybe the scales could have been controllable. Now, there’s a chance scales will infect neighboring potted plants.

Here’s what I found in my Pests of Landscape Trees and Shrubs book on scales:

The newly hatched scale nymphs, called crawlers, emerge and walk along branches or are spread by the wind or inadvertently by people or animals. Scale crawlers are usually pale yellow to orange and about the size of the period. Within 1 to a few days, crawlers settle and insert their strawlike mouthparts to feed on plant juices. After settling, armored scales secrete a waxy covering and remain on the same plant part for the rest of their lives; nymphs of soft scale species can move a little, usually from foliage to bark before leaves drop in the fall.”

Considering how infested the plants were and that scales live on the plant(s) for a lifetime, and can easily spread, I pulled them out and placed them in a tightly sealed bag for the incinerator. Before doing this, I saved a sample to submit to the State of California Pest Prevention Services in Sacramento. Identifying what type of scale may help eliminate or control any future spread of this insect.

For information on how you can submit samples troubled with disease or insects to the California Pest Prevention Services, call 1-919-262-1100. Forms and submission information is not available online. However, their website http://www.cdfa.ca.gov/phpps is worth viewing.

If you have an insect from the United States or Canada, and want it identified, you can upload images at http://bugguide.net. (If you misplace the web address, you can find it here, under Helpful Resources.) This is an amazing sight, from which the family can benefit.

Your local master gardeners can also help identify insects and disease, and offer possible solutions.



  1. Very helpful info. I normally just grab a bottle of spray when infestation of insects become really bad. Sometime I don’t know what type/kind of insect I have and then wonder why it didn’t help.
    One size doesn’t fit all.


  2. I have a Meyer lemon bush and not too long back noticed on the underside of some of the leaves located primarily on the vein running down the middle of the leaves a line of white, which I think were scales. I cut off most of the offending leaves that I could find as the “scales” seemed to be concentrated in one area. I don’t think they would have been considered mealy bugs as they weren’t concentrated in the joints. Can scales look white? My husband treated the front area of the bush with something for scales. I don’t see any evidence of them still being there at this time.


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