THE EUROPEAN HORSE-RADISH WEBWORM. 9 
In Europe the species has been recorded as feeding in confinement 
on wild plants of the genera Barbarea, Sinapis, and Cardamine. 
NATURAL ENEMIES. 
This species 1s apparently unusually free from natural enemies, 
judging by the experience gained from two years’ study in the 
vicinity of the District of Columbia. <A single parasite, Bracon 
montrealensis Morrison (Chttn. No. 6076°1), determined by A. B. 
Gahan, was reared from the larva of this species September 6, 1919, 
at Arlington, Va. 
CONTROL. 
It is evident, considering the fact that only one natural enemy of 
this species is known, that little can be expected from natural agencies 
of control. The arsenates of lead and lime and arsenite of zinc will 
all undoubtedly operate against the larva with equal value when 
apphed for other cabbage worms. Underspraying is necessary, be- 
cause of the habit of the larva of feeding mostly in concealment near 
the base of the plant. Hand-picking, if carefully carried out, is also 
of value when the species does not occur in too large numbers, as in 
the case of the infestation at Arlington, Va. 
In the occurrence of this species on horse-radish, it is more difficult 
of control than on cabbage and other annuals. On such crops fall 
and spring plowing and frequent cultivation would undoubtedly be 
of great service in destroying the insect in its pupal cases, which 
are usually at or near the surface of the ground. Plowing could not 
be practiced in beds of horse-radish, and here many of the pests would 
survive the winter unless a spray were applied, which should be done 
in case of severe infestation. 
SUMMARY. 
Horse-radish, and less often turnip and cabbage grown in the 
northern States, are subject to attack by the European horse-radish 
webworm (Hvergestis straminalis Hiibner), a greenish caterpillar 
with reddish or purplish tints, measuring, when full-grown, about 
three-fourths of an inch in length. 
It feeds on the lower surface of the leaves, which it frequently 
webs together near the ground, and also attacks the stalks. 
This insect came originally from Europe, and has recently made 
its appearance on horse-radish in Virginia. It is known to occur 
from New England westward to Wisconsin. 
It passes the winter as a larva in an earth-covered pupal case near 
the surface of the ground and the moths appear some time in May. 
In Virginia the eggs hatch in 7 or 8 days, and the larve begin by 
