The pictures on this page illustrate an armored scale on the foliage of Helleborus orientalis, Lenten rose.
Because of the large numbers present on last year's foliage, the old leaves have been removed as part of an Integrated
Pest Management (IPM) strategy. Removal of the leaves reduces the numbers of next generation "crawlers" spreading
to the plant's new growth. The problem is probably not "cured." But the pruning likely reduces the numbers to a
tolerable level with minimal damage.
In this picture, the plant on the left is in bloom and the new foliage is glossy and light green.
The foliage to the right is the old foliage that has been removed.
This is a closer view of a leaf that is infested with scale insects.
Note the dark color.
Note the sooty mold in the center of this picture; it is the black material that is flaking off.
The bright green is the natural color of the leaf beneath. The sooty mold is a benign fungus that
thrives on the "honey dew" secreted by
scales and other insects in the same suborder. Sooty mold interferes with photosynthesis but
does not damage the plant otherwise. Sooty mold is sufficient reason to look further for
insects such as scales, aphids, or whiteflies. In this case scale insects are visible
on the leaflets to the left.
On the back of the leaf are visible the number of scales insects. Actually we can see
only the protective coating secreted by the adult. The microscopic insect is hidden beneath. Eggs will hatch
beneath the armor of female scales. The juvenile "crawlers" move to tender young foliage to set up
their own new home to continue the cycle. It is expected that removal of the infested foliage has
interrupted this cycle for most of the insects present.
Because of the protective coating and the location of the insects on the lower side of the foliage, treatment
with insecticides is seldom effective. Removal of the infested plant parts is an easy and effective way of reducing
pest numbers to acceptable levels.