TREATMENT FOR SCALE … BY GEORGE EDGAR
Now is the time
to treat for scale insects. Two weeks ago I sprayed my Dogwood tree,
Redbud tree, and Red Twig Dogwood shrub for scale. If you have a Lilac
shrub or a whole row of Lilacs like I do, they also will need to be
treated for scale now.
(and organic) treatment this time of year is horticultural oil. You may
find it labeled as“dormant oil” or as an “All Seasons Oil”. The
dormant oil is heavier than the All Seasons Oil. I like the All Seasons
Oil as I can use it whenever the air temperature is warm enough.
Make sure what you use is “horticultural oil” and be sure and
read the label to make sure that the plant you are treating is listed.
If the tree or shrub has not started to leaf out, you can apply the oil
at the dormant spray rate. If the tree or shrub has started to leaf out then apply at
the summer rate. Spray
using a small pump up sprayer and thoroughly coat all of the branches,
and also the leaves if any. According to Don Janssen, Extension Educator
at University of Nebraska Cooperative Extension in Lancaster County,
“Oils are not poisons. Instead, the thin film of oil covers the target
insect or mite and plugs the spiracles or pores through which it
breathes. The cause of
death is primarily suffocation.”
oils are a good preventative. Spray
must be applied when the air temperature is warmer than 40 degrees F.
but no hotter than 90 degrees F. Oil should not be used on glaucous
(blue) evergreens such as Colorado Blue Spruce, and Koster Spruce as it
will remove the blue color. The tree will not recover the color. As with
all pesticides, be sure and read the label before application.
As a dormant
application, (before the leaves start to appear on the plant) the
horticultural oil in addition to scale will also help to control aphids
eggs, certain caterpillars, mite eggs, sawfly eggs and larvae, and
whitefly during immature stages. For some plants, such as fruit trees
and roses, lime sulfur should be mixed with the oil. Lime sulfur is an
organic fungicide and helps to prevent some disease problems. As a
caution, do not apply lime sulfur and horticultural oils separately,
unless it is 30 days before or 30 days after application of the other.
However, you can mix them together and apply at the same time. Two weeks
ago I sprayed all my fruit trees with “Oil & Lime Sulfur Spray”
that was already mixed. A second application 6 to 10 weeks later may be
applied and is quite often recommended.
If the scale
has hatched and is in the “crawler” stage, use a contact insecticide
such as acephate (Isotox, or Orthene), permethrin (Eight, or Super
Eight), carbaryl (Sevin), or Malathion. Make sure the label says it
works on scale and is appropriate for the plant you are spraying. Always
follow label directions. The crawler stage is usually from mid May to
early July depending upon the kind of scale and the plant.
For more information
go to http://ianrhome.unl.edu/search.
In the top box scroll down to “Lancaster County”. In the bottom box
type in “scale”. Entry #6 is Don Janssen’s article
“Horticultural Oils for Pest Control”, published March 10, 2006
Or go to http://www.ipm.iastate.edu/ipm/hortnews.
In the search box type in “Scale”. A list of publications will
appear and you can click on the one you want.