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Katydids in Grapes
By Devin Carroll & Chris Million
2010
Katydids are a minor grape pest not
covered by UCIPM. They are important pests
of other crops, such as nectarines and citrus. It
is rarely worthwhile to use a special treatment
to treat katydids in grapes, but if a treatment
for another pest also controls katydids, so
much the better.
There are two species. Angularwinged katydid (AWK) has one hatch, in
April-May. Fork-tailed bush katydid (FTBK)
has two hatches per year. Overwintering eggs
hatch in March-April. Maturation takes about
2 months. Newly mature females lay eggs in
June. Some new eggs hatch in July-August,
and some stay dormant until the following
FTBK nymphs with leaf damage in
March.
year.
In grapes as in other crops,
katydids feed mainly on leaves, especially
young leaves. The holes in grape leaves
can be quite prevalent, but usually
growers are not very concerned. Extreme
populations early in the season may need
treatment.
Katydids may feed on a few
flowers during and shortly before and
after bloom. The damaged flowers will
fall off, along with many undamaged
flowers during shatter. Thus flower
damage
is of no importance.
FTBK nymph with nibbled flower bud in
It is not clear whether katydids
May.
feed on grape berries between bloom and
near harvest, but it is not much. The second generation of fork-tailed katydids
occasionally chews round holes in grape berries as they near ripening. Most often, we
have observed damaged grapes close to leaves in the canopy, where the katydids can step
from a leaf to a grape bunch. Grapes hanging free near the cordons seem to be damaged
less often.
Presumably, feeding holes on near-ripe grapes may lead to rot, but the damage is
so rare that it probably is not worth treating.
In our experience, high katydid
populations seem to occur most often in
conventional table grape vineyards. We
have not seen as many katydids in raisin,
wine, and organic table grapes. This
suggests that some pesticides are interfering
with biological control. Egg parasites in the
family Eupelmidae are a key natural enemy.
Spiders and birds are likely predators.
FTBK lays eggs in leaves, and
Probably katydid feeding, from a
AWK in leaves or canes. Eggs are the
vineyard with high FWBK numbers in
overwintering stage. Thus sanitation by
September.
discing in leaves during winter will reduce
spring populations.
Several good worm treatments also control katydids, including Delegate, Entrust,
and Altacor. The most effective control is when nymphs are small. Imidan controls
katydids at low rates, and may also be used to control beetles, worms or vine mealybugs.
Lannate and pyrethroids such as Danitol or Renounce also control katydids along with
many other pests, but they are disruptive to biological control of other pests as well.