Page 23 - Free State Summer 2022

you pop that cover off it comes completely free. Many
armored scale female bodies, once the cover is removed,
are yellow, orange, or purple in color. Soft scale are It is often difficult for the
integrated between the body and cover and the cover
does not come free easily or at all without destroying the untrained eye to detect scale
insect. insects because they don’t look like
The first two instar stages of male armored scales look a typical insect. They tend to blend
just like the females. Males stop feeding after the second
instar and excrete a wax out of their back called a carnae into the plant tissue or overwinter
made out of white wax. They continue to grow through a
third, fourth, and fifth instar before emerging as an adult, in buds.
with a more typical insect appearance. At the third instar
stage, the female forms the 3rd instar cover. The shape have been used over the years to control scale. The
of the cover varies with species but can be round, oval pyrethroids such as bifenthrin and permethrin products
or, pear-shaped, or oyster-like in shape. She continues to are available, inexpensive, and effective and have been
feed through all the instar stages, with a piercing, sucking used for many years. Unfortunately, many of these
mouth-part that is inserted into the plant. At maturity, the materials are broad spectrum and kill many beneficial
female does not have a typical insect appearance to the organisms. The preferred control for scale insects is insect
untrained eye. growth regulators, or IGRs. IGRs impact the young stage
Most arborists will identify a scale by its female cover of the scale; death isn’t immediate, so it won’t act like a
and the plant species it is found on. We suggest working pyrethroid with a quick kill.
with your Extension specialist in entomology in your state IGRs enter the body of insect and disrupt the development
to help ID difficult to recognize scale species. It is critical of the exoskeleton. Hormones in their body tell the insect
to correctly identify the species to determine when the to form a new layer of skin and shed the old one. The
crawler stage is active. The crawler stage is often the best synthetic growth regulator mimics the natural hormones
stage to control scale insects. Learning to identify the and upon entering the next life stage or instar stage, the
various scale insect may take some time but realize that hormones in the insect body go a bit crazy and they can’t
by properly identifying the pest, you can develop the best form their skin correctly and they can’t shed their old skin,
control strategy. resulting in death. It takes a few days for them to die, but

Control it is effective in killing them. The benefit of using growth
regulators is that has less impact than many broad-
The most effective control of scale insects is achieved spectrum pesticides on the predator and parasite insects
during the crawler period. This is the period when the in their adult stage. It only affects immature insects.
young insects are actively moving on the plant material
and have the least protection. Crawlers are often oval A couple of growth regulators are available such as Talus
shape, have antennae and legs and look like an insect, and Distance. The two materials have a slightly different
but are very small. Depending on the specific scale, they mode of action, which is good because we need different
have different crawler periods, from May through fall classes of materials but are still insect growth regulators.
along the Mid-Atlantic United States. Some have one In the late fall, horticultural oil may be used to control the
generation of crawlers per year, while others have two soft scales. A 2-3 per cent oil applied when temperatures
and some three. are above 50 degrees Fahrenheit is an effective control.

While the scales are producing crawlers, they are very Insects obtain their supply of air (mixture of oxygen
susceptible to insecticides. This is also the time when most and nitrogen) through openings along the side of their
scale predators and parasites are active. With the number body called spiracles. Horticultural oils work by coating
of predators and parasites attracted to the crawlers the small sensory hairs, called cilia, in the spiracles,
it is important to select the materials with minimal preventing the small cilia from moving air into the insect’s
impact on beneficial insects. Several different materials body. The oils are effective and have been refined to
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