...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
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Scale basics
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General pest control strategy
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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.
Look closer and find the scales
that
must be there if you see shiny spots of
honeydew or the black "sooty
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.
- Watching. Everything starts here. Know what
the plant should look like, how it should grow, and check into
irregularities.
- 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.
- 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.
- 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.
- 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).
- 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.)