This item is only available as the following downloads:
a, a, a, Butterflies (or adults) with wings in natural positions;
b, b, larvae (caterpillars, or "worms"); c, c, pupae (chrysalids-
the resting stage); d, cabbage plant showing typical feeding injuries.
(Upper illustration: a, b, and c about one-half natural size; d
slightly less than two-thirds natural size. Lower illustrations: a,
b, and c about natural size.)
(See other side for life history and control)
Bureau 4 Entrtr .ilv A-,.' PAn .'. Ij.4r- iin--
United S'?,Ae D. rtrmcnt A.r;:. I- ,,r Picture Sheet Nn,,. 0
IMPORTED CABBAGE WORM
(Picris rapae (L.))
General Life History
The imported cabbage worm is tlhe larva of a white butterfly,
which passes tlhe winter in the chrysalis or pupal stage in tlhe Northern
States. In tlhe more soultheirly States the larvae, or "worms," may be
found from Miarch uintil Decemlber, and in some areas throughout the
win ter. The butterflies emnergte from tlie chrysalid(s earlyy in the spring.
The female butterfly deposits ea(cl, egg sej)aiately, in contrast to the
lhabit of many otlier insects which deposit their es. in masses. The
e,,szs are usually liai(1 on tle u jlder side of the leaves of cabbage, collards,
cal'iflo\\er, broccoli, ald other food plants. Tlhe time required for
the v-arious stares of the insect to develop varies with the season.
However, tle, eggs usually hatch within a week, and the larval and
Ipupal stages eachli develop in from 1 to 2 weeks; so there are several
broods each year, ranging from 3 to 6 in different parts of the country.
The velvetv-green larvae, or caterpillars, are especially fond of the
tender, immature heads of cabbage, to which they often cause severe
The imported cabbage worm is readily controlled by the use of
one of several insecticideles.
The safest and one of the most effective methods is the use of a
(lderris or cube dust mixture containing from 0.75 to 1.0 percent of
rotenone. Applications should be made at intervals of about 10 days
from the time the caterpillars are first dliscerned on the plants until
such time as the pest is brought under control or the harvesting of the
crop is completed. The dust may be obtained already prepared, in
which case the amount of rotenone present is shown on the package; or
it may be made by mixing tlhe derris or cube root powder with talc,
pulverized clay, sulfur, or tobacco dust. For example, to prepare a.
4-percent rotenone dust from a derris powder which contains 4 percent
of rotenone, use 1 pound of derris to 5 poun(ls of the talc or other
material; for larger quantities, use 16 pounds of the derris to 84 pounds
of other material. For best results the dust applications should be
made late in the afternoon or early in the evening when the air is
practically calm and the plants are slightly moist witlih dew. Special
care should be givenn to see that the insects and the "buds," or heads
of the plants, are reached by the insecticide. Thle dosage will vary
according to the size of the plants, but should range from about 10 to
25 pounds per acre per application.
Fresh lpyrethrum flowers powder (containing approximately 0.9
percent of total pyrethrins) diluted with 2 parts of talc or one of the
other materials listed will also give satisfactory control.
Although (Itdusts have, in g (eral, given better results than sprays
in controlling the imported 'a ge worm, the( materials previously
mentioned may be applied as spray vs. A spray consisting, of from 2 to
21. pounds of a lerrisi powder (contailiihig 4 percent of rotenone) to 50
g"illous of wante.r, to which may be added a nonalkalime sprea(lder or
sticker, is- recIlimen)l(ed. SprayNs made from extracts of (lerris or
pyrethrum, or a combination of them, wle, prepared according to the
imanliffactirner's directions, may also be used.
April 1911 U. S. Gov'erniiiint Printing Office
For S.Cle1the siritlllelt or Docuents, UNIVERSITY OF FLORIDAilil
3 1262 09082 4672
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