Download Beneficial Insects and Control of Harmful Ones in Your Garden

Beneficial insects and control of harmful
ones in your garden
By Joe Wolf
Polk County Master Gardener
There are over 13,000 species of insects here in
Florida. Of those less than 1% are harmful to our
plants or us. The other 99% are either helpful or just
ignore us. We depend on insects. We all know that
bees pollinate most of our fruits and nuts and without
them these foods would be eliminated from our diets.
Polk’s important citrus industry depends on bees for
pollination. There are other pollinators as well:
butterflies, wasps, moths, flies, beetles, midges, thrips
and even ants. These insects pollinate many of our
Lady Bug Larvae eating aphids
vegetables, trees, shrubs and flowers. Insects do many other things in our landscapes as
well. Some beetles and ants recycle nutrients and aerate the soil. Still other insects are
predatory on harmful insects.
Because so many insects are helpful to us we need to be careful how we spray
pesticides on our plants when they are infested with a harmful insect. First we need to
identify the kind of insect which is causing our problem. Look closely at the damaged
portion of the plant and if possible find the insect causing the damage. Many insects are
small so we may just see some small bumps on the stem or the underside of the leaves.
Other times we will just see the damage but not the cause. Just because an insect is on
the plant, does not mean it is causing the problem as for example, the insect you see
may be eating the insect causing the problem: think of a ladybug eating aphids.
To control these harmful insects we should use the method least harmful to the plant or
other insects. If the harmful insect is large, like a caterpillar or grasshopper, you can just
remove it and then destroy it. But before you remove a caterpillar; be sure it is not the
larvae of a butterfly. I generally use my
gloved hands or my clippers. Sometimes if
you just throw a caterpillar far enough
from the plant it will never find its way
back. Small mites can be washed off with
the hose. They are too small to climb back
onto the plant. If only one or a few
branches are infested, you can clip off
those branches; throw them into the trash
to eliminate the problem.
A parasitic wasp
If mechanical means will not work, then use
the least offensive insecticide possible.
A parasitic wasp
Piercing/sucking insects, such as aphids,
scales or whiteflies, pierce the plant and
suck the sap from it causing some of our
worst problems. These insects don’t move
much so a simple spraying of a horticultural
soap or insecticidal oil will smother them.
After they are dead they may still be
physically on the plant but they will cause
Predatory ground beetle
no more harm. Most beneficial insects will move away and not be harmed. The soap
and oil can be used together or separately. You can purchase insecticidal soap and
horticultural oil. Follow the directions on the label for use, but generally you will use 2
to 3 tablespoons per gallon of water.
There are other times when a few leaves are eaten or a little aesthetic damage is done
to the plant that it is best to ignore the problem. You need to watch the plant closely to
insure that no serious damage is done, but you need to do nothing further.
When stronger insecticides are called for only use those labeled for the insect causing
the problem. You need to identify the insect or you may use the wrong insecticide and
cause more harm than good. Not all insecticides kill all insects and they certainly do not
kill fungus or cure nutritional problems. Use the mildest insecticide possible for the
problem insect and then spray it only on the
infested plant. Do not spray when it is windy or
just before a rain. Many insecticides need to
be kept away from lakes and streams. Read
and follow the label on the insecticide before
using it. It will tell you everything you need to
know.
The goal is to control insect pests and do as
little harm as possible. Often, if allowed, those
other 99% of helpful insects will control the 1%
harmful ones.
Green Lacewing