Defense From Flea Beetles

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The adults can be from 1/16 to 1/5 of an inch long, depending on the species. Under a hand lens, the different species usually will be a dark color, but a few species will show some light-colored stripes.
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For many years we noticed the tiny holes in the leaves of different garden plants before we actually went investigating. We were continually frustrated at seeing only the holes, but not actually seeing the bugs.

For many years we noticed the tiny holes in the leaves of
different garden plants before we actually went
investigating. We were continually frustrated at seeing
only the holes, but not actually seeing the bugs. It was
after reading about these little mysteries that we realized
flea beetles are given the name “flea” because they have
great jumping back legs and actually leap off their chosen
leaves when big monsters, like gardeners, approach. We
hadn’t been observant enough to notice this escape
maneuver.

You have to look closely to see these tiny creatures,
members of about 370 species of one subfamily of the beetle
order Coleoptera. The adults can be from 1/16 to 1/5 of an
inch long, depending on the species. Under a hand lens, the
different species usually will be a dark color, but a few
species will show some light-colored stripes. At least a
dozen different species are happy munching on common garden
crops. Some species will feed on more than one plant crop,
but many are tied to single crops or closely related crops.

Flea beetles are found throughout North America. Adults
overwinter and lay eggs in early spring on or in the soil
near the base of the host plant. The egg-larval-pupal
stages take four to five weeks, after which the new adults
emerge in search of fresh greenery. The thin, white larvae
do some feeding on roots of the host plants and leave snaky
markings on potatoes, but the adults are the hungriest
competitors for our garden groceries, and most damage is
done to the foliage. Adults are attracted to young plants
and chew the typical “shot-holes” in the underside of
leaves. Some plants that attract these beetles are cole
crops, corn, eggplant, grapes, potatoes, spinach, sweet
potatoes, tobacco, tomatoes and cucumbers.

The best perennial defense against flea beetles is a
healthy, nutritious garden soil. When crops grow quickly
and with balanced nutrition, the growth can compensate for
slight damage. The easiest tactic for immediate defense is
to use row covers in the early spring. The beetles eschew
chewing on older plants, so the covers simply can be
removed as the season progresses.

Presuming you are rotating crops, you won’t trap beetles
under the covers that remain from the same crop the
previous year. Crop rotation, though obviously good for
other reasons, does not fool the very mobile adult flea
beetle. Shallow hoeing for weeds will do double duty as
flea beetle eggs are exposed to the air and predators. A
few ‘Chinese Daikon’ or ‘Snow Belle’ radishes work well as
a flea beetle catch-crop when interplanted with cole crops.
(For more pest-control tactics, see
www.attra.ncat.org/pest.html.)

A second or third generation of flea beetles can appear in
a single summer, so when putting out late plantings for
fall, cover them when young, too.

Flea beetles also feed on many non-garden plants, including
Virginia creeper, pokeweed, horse nettle, pigweed and wild
mustard family plants.