Answer: I am copying an detailed article on Pearl Scale below, written by Sharon Dewey is a Certified Turfgrass Professional, a turfgrass troubleshooter and a Master Gardener with the University of Arizona Cooperative Extension, ad Dave Langston, Ph.D. is the Superintendent of the Arizon Maricopa Agricultural Center, an Extension Specialist in Entomology with the University of Arizona.
PEARL SCALE OR GROUND PEARL AND YOUR LAWN
By Sharon Dewey, Certified Turfgrass Professional, and
Dave Langston, Ph.D. University of Arizona, College of Agriculture
Pearl scale or ground pearl, refers to an insect that can be a problem
for St. Augustine, Zoysia and Bermuda grasses. Hybrid Bermuda grasses
are usually more affected than common Bermuda. As the name implies, an
infestation will resemble miniature pearls. Scale insects secrete a
whitish to brown substance that covers and protects their bodies, and
are seldom larger than one-sixteenth of an inch.
These insects suck the juices from plants, usually killing the root. The
grass gradually weakens, turns yellow, then brown, thins and dies, and
circular patches of dead grass will appear on the lawn. Damage will
appear in the fall as the grass is going in to dormancy. These damaged
areas will not recover the following spring when the grass begins to
In late May and lasting throughout the summer, the majority of females
emerge from their pearl scales and lay about 100 eggs in a waxy coat. In
a few days the eggs hatch into crawlers, which attach to grass roots.
They secrete a hard, waxy coating that becomes the next generation of
ground pearl scale.
Here are some tips on detecting pearl scale.
1. Dig at the edge of the damaged area that is next to an unaffected
2. Carefully dig down two to four inches. Try not to spread scale to
3. Look at the roots of unaffected area.
4. Pearl scale are obvious because of their contrasting color and their
5. The insects are soft and can be easily squashed.
6. Be very careful with contaminated soil and the tools used to examine
the lawn, as they can contaminate unaffected area.
Pearl scales are spread in infested turf and through the use of dirty
equipment. Always wash the soil off shovels, trowels or other lawn and
garden equipment after each use. Mowers are not likely to transfer
scales unless they are very dirty. There are no chemical control methods
that completely rid the lawn of pearl scale. However, there is some
evidence that applications of soil acidifiers (these reduce soil pH),
and/or the product Merit may help slow down the spread of pearl scale.
The optimal time for treating a lawn with Merit is in late May when the
females are emerging.
1. The best chance for control is early detection when the circular
patches are small and manageable.
2. Carefully remove damaged patches one foot beyond the affected area
and one foot deep. Then dispose of the affected roots and the
surrounding soil. Pearl scales may withstand long periods of drought in
the soil, and may still be alive after more than a year. So be very
careful to avoid spreading them when replacing damaged turf.
3. Most of the pearl scale will be in the upper two to four inches of
soil, but have been found as deep as grass roots grow, making control
4. After removing affected portions of the lawn replace the
contaminated soil. At this time you may want to treat with soil
acidifiers and/or Merit and then re-sod or seed the area.
5. To enhance the penetration of soil acidifiers, make holes in the
area to be treated before applying acid mixtures.
Proper maintenance helps prevent pearl scale infestations. Although
rare, some lawns, particularly common Bermuda have been shown to grow
out of an infestation when the lawn receives proper maintenance. Also,
seeded Bermuda appears to be able to better withstand pearl scale, or at
least the spots can be reseeded each year to cover the damaged areas.
This is NOT a control method but merely hides the damaged spots.
1. Water deeply (eight to 10 inches), but only as often as to avoid
2. Fertilize every four to six weeks using a complete fertilizer such
as a 21-7-14 blend.
3. Mow no more than the top one third of the grass, using a sharp mower
4. Remove thatch if it is more than one-half inch thick.
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