When you can beat one scale...

...you can probably beat 'em all!

In the battle to control pests our biggest advantage is that we can think.
So we should use our heads.
Here's how, with


Scale basics

Scales, like other insects, have predictable life cycles. Each type of insect is locked in to both a place and a time -- to a plant/plant group and a season. Learn the insect's cycle and you can step in at the point when it can be most easily broken. (For a book that helps you use plants' development to predict pest emergence, see Coincide from our library list.)

Most scales on outdoor plants emerge as crawlers in spring. They're elegantly timed to capitalize on fresh food.

So watch for bud break on the host plant -- that's when the scales that covered the plant's shoots all winter, are pushed open by swelling tissues within. Look then for scales.



Take action if you see them or signs they're there (right). That might be rinsing the plant forcefully, frequently, releasing predators or applying an oil to smother the crawlers.




Right: Sucking insects, including scales, excrete a sticky, clear liquid called honeydew (arrow). It splatters in tiny drips on leaves and stems below the scale's location -- and furniture and pavement, too.



On this bay (below) the scale crawlers emerged as new growth developed (the lighter green shoot in the center of the picture). In this photo the left arrow points to a soft brown scale becoming noticeable as it develops a covering. Right arrow points to the honeydew beginning to appear on a leaf that was below the indicated scale.











sootymold.jpg   Look closer and find the scales that
   must be there if you see shiny spots of
   honeydew or the black "soo
ty mold"
   that follows
(left) as fungi develop
    to consume the honeydew.

   Hold off if you see Ma Nature has
   tipped the scales, so to speak. That is,
   if you see that predators of scales
   such as lady beetles are at work,
   non-interference is a wise course.






Controlling scale is much like controlling any garden problem.

General pest control strategy


Every plant, every problem, every year is different yet overall patterns remain the same. The most important pattern? These six steps.

  1. Watching. Everything starts here. Know what the plant should look like, how it should grow, and check into irregularities.
  2. When something strikes you as not right, identify the problem. How?
    • Take a photo and show it to others (our Forum is a good place to do this), or
    • Leaf through a pest I.D. book, or
    • Search the Internet using an image filter and the term "scale insect (plant name)" (here's help to make such a Search more successful), or
    • Take a sample to an Extension office or garden center that has a diagnostic service.
  3. Once you have the insect's (or disease) name you have all the ammunition you need to look into its life cycle and control options. If it's an insect, each has its own host plant(s), timing, resting locations, and vulnerable times.
  4. Determine whether it is a serious threat. Credible references and experts say it straight out: It's life-threatening, or it's cosmetic/not serious. Evaluate how much damage it's done or might do.
  5. Decide what you will do, if anything. Choose an action that will have the narrowest effect, before you break out any big, environment-altering bombs.
    Start with something that affects the pest but little else. Escalate only if necessary (step 6).
    Don't limit yourself. There are many categories of control action, such as:
          • Doing nothing (because the pest is not a serious threat)
          • Changing the way you grow a plant
          • Physical control (picking off the offenders by hand)
          • Exclusion (covering a plant with a screen or row cover, for instance)
          • Releasing or encouraging natural predators
          • Applying chemicals (organic mixes, soap and ready-made sprays all fall into this last category).
  6. Watch what happens so you can learn and adapt. This last step is critical, yet it is really not the last step. These six steps are not a line but a loop, with step 6 leading back to step one: Resume watching!


Don't panic in July

If you notice the scale in July -- that is, you see the immobile adults -- they almost certainly were there as controllable crawlers 6 to 8 weeks before. Almost as certainly, they are nearly immune to control as adults, and all the damage is done for the year anyway. The smart thing is then to focus on how you can stop them next year as they first begin their feeding.

Right: Magnolia scale is probably the largest scale species a gardener willl ever deal with. They are also about the only one with a markedly different timing. Rather than producing crawlers in spring, they do so in late summer. So the gardener must take action in mid-August to early September if the scale population is getting out of hand.



Boom and bust can work in our favor

Insect species' populations often follow boom and bust cycles. When the pests are most numerous, their predators feed heavily and grow in number, too. So after a bad year, a pest insect's numbers may crash. A devastating year can be followed by an almost eerie lack of trouble.

We have seen many such booms and busts. One that remains most memorabe occurred when Asian spotted lady beetles moved into our area from the South (more about these beetles in What's Coming Up #50).

Two scale infested magnolia trees alerted us to the bust. They were trees we had been watching for over 10 years, two we passed regularly but had no say in their care. They had been plagued with scale for so many years in a row that we were beginning to wager on when one or both would show major dieback. That very year the beetles moved in. The next spring those trees were so clean it was as if they had been touched by a magic wand and a bark scrubber to boot. (That was many years ago. They're still growing and doing well.)