Insects are everywhere. Most are beneficial. Wasps, ladybugs, praying mantis,
spiders (actually arachnids, not insects) and others feed on harmful
insects. Other insects such as beetles help to break down waste in the
environment.
We are concerned with the insects that cause injury to our
lawns, shrubs, and trees. When their numbers increase to the point that
significant injury is occurring, control becomes necessary.
Control means
to keep the harmful insects populations down to acceptable levels, not to
eliminate them, which is impractical and virtually impossible. Also bear
in mind that when you treat to kill harmful insects, you are killing beneficial
insects as well.
A few of the
most common insects which are damaging to our landscapes are mole crickets,
chinch bugs, white grubs, sod webworms, lacebugs,
and scale insects.
Mole crickets can cause very extensive damage to turfgrasses. They feed on the
roots and stems of the grass and their burrowing can also damage the roots by
disrupting them and causing them to dry out, especially in hot weather.
Mole crickets live one year. Eggs hatch into nymphs in late spring.
The nymphs go through several growing stages and become adult size by late
Summer. Because mole crickets live underground, they are difficult to
detect until damage starts to show up in the lawn. Signs of mole cricket
activity are small burrows or trails on the surface of the soil, softness or
sponginess in the turf (not always due to mole crickets), and thinning or dying turf. You can check for their presence by adding 5 ounces of dishwashing
liquid to 5 gallons of water and flooding a small section of the lawn where you
suspect mole crickets may be. If they are present, they will quickly come
to the surface, along with any earthworms that may be there. Control of
mole crickets is very difficult, especially when they are full sized
adults. The stage most suceptible to chemical control is the nymph, so
early summer applications are by far the most effective. As a side note,
there is a carnivorous species called the Southern mole cricket, which does not
feed on plants, and actually eats other harmful mole cricket species.
Mole Cricket
Chinch bugs can be a major problem in St. Augustine grass. They do not
attack Centipede grass. They cause damage by sucking the juices from the
stems of the grass plants. The result is a withering and browning of the
grass, which looks very similar to drought symptoms. Adult Chinch bugs are very
small (1/5") and difficult to detect until their numbers are large at which
point damage has already occurred. The various stages of nymphs are even
smaller. Chinch bug damage begins to show up in the summer. They
prefer hot, dry conditions. Fortunately, chinch bugs are not difficult to
control.
Chinch
Bug
White
grubs are the larval stages of various types of beetles. The adults
beetles lay their eggs in the soil. The eggs hatch and the larva burrow
into the soil where they live for 1 to 4 years, depending on species. The
grubs are white and C shaped and complete the life cycle by becoming adult
beetles and moving above ground.
The grubs feed on grass roots and other
plant roots in the soil. Most lawn and garden soils will contain white
grubs. It is when their numbers increase to the point where damage to the
turf occurs that control becomes necessary.
Sod Webworms are caterpillar type insects that feed voraciously on
various grasses and plants. In this area sod webworms show up in late
summer. The adults (tan colored moths) look for healthy areas of grass to
lay their eggs. The eggs hatch out into tiny caterpillar type worms which
are almost transparent in color. They begin feeding immediately on grass
blades and grow rapidly to 1 inch or more in size. Their bodies become
green colored due to the grass blades they feed on. They are active at
night and spend the days hiding in the thatch of the lawn. Damaged areas
are irregular in shape and look as though they have been scalped with a lawn
mower. Closer inspection will reveal the ragged edges of the grass blades
where feeding has occurred. Feeding increases rapidly and large affected
areas can appear overnight. Fortunately, damage is temporary and a healthy
lawn will recover quickly once the insects are controlled.
Lacebugs are very small insects that feed on the undersides of the
leaves of azaleas. Because azaleas are so prevalent in Savannah, lacebug
damage on them is widespread. The tops of affected leaves will have a
yellowish speckled appearance. This can range from just a few specks on
the leaf initially to advanced stages of damage where the entire leaf will
appear yellow. Control treatments should be made to both upper and lower
sides of the
leaves.
Lacebug
Lacebug damage
Scale insects cause damage to a wide variety of plants, and there are
hundreds of different kinds of scales. Most of them are similar in
appearance and they damage plants by sucking the plant juices. They are
strange looking in that in their adult forms, they don't look like insects at
all.
Most are white or off-white colored, and appear as small flecks or bumps on the
leaves of their host plants. They can be found on the top surface of the
leaves, the undersides of the leaves, or both. One common type, tea scale
of camellias and hollies, looks like cotton growing on the undersides of the
leaves. The damage appears as a loss of the green pigment (chlorophyll) on
the top of the leaf. The scale insects spread by the crawler stage of
their life cycle. The most effective control for scales is an oil spray,
which covers and suffocates or smothers the scale, killing
it.
Some local plants commonly affected by scale
insects are:
camellia, sasanqua, holly, magnolia, aucuba, oleander, palm, banana shrub, and
fatsia.
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