PRESS BULLETIN No. 294
UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATION
CASTOR BEANS ATTACKED BY CORN EAR-WORM
J. R. WATSON
The corn-ear worm, a well-known pest of corn, cotton, toma-
toes, beggarweed, beans, and other crops, is attacking the pods
and seeds of castor beans. The damage thus far, altho wide-
spread, has not been severe. As the season advances and favorite
foods become scarce, it is possible that the worm's damage to
castor beans will increase considerably.
The insect is primarily a borer. Its general habit is to eat
a hole in the food plant, and if there is sufficient room, to crawl
into the cavity and feed inside. In the early part of the season this
worm attacks tomatoes and is known as the tomato fruit-worm;
later it attacks young corn and is known as the bud worm. The
next generation attacks the silk and mines the ears and is called
the corn ear-worm. It also hollows out cotton bolls and is called
the boll worm. As the corn and cotton mature and food becomes
scarce, the worm attacks a large variety of seeds, including beg-
garweed, snap beans, and cowpeas.
The work of the worm on the castor bean is very similar to
that on the first small tomatoes of the season. It eats a hole in
the pod and feeds on the seeds. The semi-tropical army worm
and the very similar sweet-potato caterpillar, which are doing so
much damage to castor beans in some parts of the State, also
attack the pods but work in a different manner. They feed on
the whole surface of the pod and sometimes eat into the seeds,
whereas the corn ear-worm makes a relatively small hole in the
pod and then feeds on the seeds. Sometimes the corn ear-worm
mines the main stem of the spike and causes it to break off.
In experiments with this worm at the Experiment Station,
where it was feeding on young tomatoes, it was found that about
half the worms could be killed by a thoro spraying with lead
August 10, 1918
arsenate. Probably a very thoro dusting with lead arsenate, as
is advised for the semi-tropical army worm, would have about
the same degree of efficiency in controlling the pest on the castor
bean. It is only while the worms are drilling holes into the pods
or young tomatoes that they can be poisoned. While feeding
inside the pods they are safe from arsenicals as their bodies com-
pletely fill the holes so that no poison can sift into the cavity.
In fields in which the semi-tropical army worm is not also pres-
ent, perhaps the best plan is to pick off the corn ear-worms by
band. This could be done at the same time the beans are being
gathered. If the pickers are instructed to pinch in two every
worm they find mining a pod, the number of worms will be much
reduced with little extra labor.
The worms are voracious feeders and one worm will destroy
many pods, probably most of a spike, before its growth is com-
If the resulting damage this year is sufficiently severe to war-
rant it, a trap crop should be planted with the beans next year.
For this purpose, advantage can be taken of the worm's prefer-
ence for corn. Cuban or Mexican June corn shoulder planted
very late so that it will not silk until August. A double row
of corn with cowpeas every hundred feet should be sufficient.
The cowpeas will provide the moths with the shade in which they
.like to hide during the day. The corn must be cut and fed to
stock before the worms complete their growth and bore their
way out of the ear into the ground to transform into the pupal
stage. If the corn is not cut at the right time it will increase in-
stead of decrease the number of worms in the beans.
The only field of castor beans in which the writer has noticed
no damage from the corn ear-worm this year is one in which corn
is interplanted. In this field a poor stand of beans was obtained
and the vacant hills were planted to corn in early June.
The adult of the corn ear-worm is a tawny-colored moth. An
account of its life history and an illustration can be found in
Bulletin 134 of the Florida Agricultural Experiment Station.
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