Those landscape plants may be just what you wanted, but before
you take them home,
check them closely anyway. You may find some unwanted
hitchhikers.
“Aphids are hard to control in a greenhouse or nursery
environment,” said Beverly Sparks,
an entomologist with the University of Georgia Extension
Service. “By the time they get
to the garden centers, many plants can have small aphid
populations.”
You don’t want aphids on your backyard guest list. “They have
mouthparts like little soda
straws, which they use to suck juices from plant cells,” she
said. The feeding weakens
plants and causes wilting, but that’s only part of the
problem.
The tiny gluttons suck up more plant juices than they can
digest. The part the aphids’
bodies can’t use passes through them as a high-sugar
excretion.
This sticky “honeydew” drops onto leaves or anything else
beneath them. And to add the
final insult, various fungi feed on the honeydew and create a
black coating, called sooty
mold. It’s not a pretty picture.
The worrisome pests are so small you can hardly see them. “The
problem,” Sparks said,
“is that populations can build to such large numbers that they
cause serious injury to
plants.”
Aphids infest almost any annual or perennial plant and many of
the more common woody
landscape shrubs. Two species causing problems in late April
were green peach aphids and
melon aphids.
“As the weather warms,” Sparks said, “we’ll see more problems
with crape myrtle aphids.”
One way to keep aphid populations down in your yard, she said,
is to avoid buying them
on new landscape plants.
“Check closely for signs of wilting, curling of new growth and
sticky upper surfaces on
lower leaves,” Sparks said. “Look for the aphids themselves on
the stems and underside of
leaves on the newest foliage.”
To see the aphids, she said, use a hand magnifying lens. Or
shake the foliage over a piece
of white paper. The soft-bodied insects are the size of a pencil
point.
Looking at their rear ends through a hand lens, she said, you
can see what looks like two
tiny tailpipes. Aphids are the only insects with these dual-
exhaust cornicles.
If you find the little hitchhikers, look for other plants,
Sparks said. You have enough
problems at home without buying more of them.
If you already have aphids on plants in your landscape, check
closely to see if you also
have beneficial insects. “Lady beetles can clean up an aphid
population,” she said. “Don’t
treat for aphids if you have good populations of lady beetles or
lacewings.”
If you don’t have enough good bugs, you’ll have to get rid of
the aphids yourself.
The pests will be concentrated on the newest leaves and stems.
So carefully prune off the
heavily infested foliage. Put the pruned parts into a plastic
bag and get rid of them.
You can also spray plants with an insecticide labeled for aphids
or use an insecticidal soap.
Whatever you use, though, be sure you spray the right places.
“To control aphids,” Sparks said, “you have to get thorough
coverage on the underside of
the leaves.”
