There are two types of cicadas. The first is the
"dog-day" cicada, which occurs in the heat of summer each year.
The second is the periodical type that hatches in late May,
based on soil temperatures, every 13 or 17 years.
brood of Brood XIX is up this year, and numbers may be
impressive in some areas. They have already created stirrings to
the south and east. Prime areas would be heavily wooded for a
period of many years. Numbers can average over 130,000 per acre.
The adult cicada is about an inch and a half long, dark in
color, and has red or orange eyes. The female uses an ovipositor
like a saw to make slits in small twigs of trees. She then lays
eggs in the slits. When the eggs hatch, the nymphs fall to the
ground. They then tunnel into the ground, where they find a tree
root to suck sap from for 13 or 17 years.
The root-feeding activities are not the most damaging, but
the egg-laying slits can cause severe damage to young trees.
Young transplants up to 2 1/2 inches in diameter can have their
main trunk damaged to the point it will snap. On mature trees,
there is little danger of the tree dying from the damage, but
many branch ends will break off in windstorms. The favored twig
or trunk sizes are three-sixteenths of an inch to an inch and a
To protect young trees, or valuable small trees, a mechanical
barrier is the most effective. Something like screen wire
wrapped around the trunk will prevent damage. Insecticides will
also kill many of the cicadas, but it takes only one female to
do the damage. Sevin, permethrin or bifenthrin should show some
The other phenomenon that will occur is that traditional
predator numbers, such as cicada killer wasp numbers, will also
greatly increase. These are extremely large wasps that paralyze
the cicada, bury it in the ground and lay eggs in it. The
insecticides mentioned previously will also be effective against
the wasps. Remember, though, the wasps are actually beneficial.
Control should be done only in very high-traffic areas and
children's play areas when the wasps become a hazard.
As anticipated, many of the leaf diseases, such as
anthracnose and apple scab, are causing problems. These problems
include many leaves dropping from trees. Currently apples, crab
apples, sycamores, maples and many other good-quality shade
trees are affected. The maple group will accelerate even more in
the near future, as they are just entering the worst of the
What starts as spots eventually leads to more dead material
in the leaf and leaf stem. At times, especially on apples and
crab apples, the leaves then turn yellow. The dead areas cause
the leaves to be weak and weakly attached. With some wind, the
leaves then fall to the ground.
While it may look like fall, most shade trees will then put
out another set of leaves in four to six weeks. The apples and
crab apples tend not to initiate new leaves as easily and may
remain without leaves for a portion of the summer. The major
problem is the loss of the food that these leaves would make for
Since treatment is not effective once you see the problem, a
fertilizer program would be in order. Fertilize at the lawn rate
of 8 pounds of 12-12-12 or 13-13-13 per 1,000 square feet. This
would be in the drip area in the case of trees. Then, just
scatter the fertilizer on top of the ground. You may water if it
doesn't rain for a day or two after the application.
University of Illinois Extension]