THE EUROPEAN HORSE-RADISH WEB WORM. 9 



111 Europe the species has been recorded as feedin<; in confinement 

 on Avild plants of the j^enera Barbarea, Sinapis, and Cardamine. 



NATURAL ENEMIES. 



This species is apparently unusually free from natural enemies, 

 judging by the experience gained from two years' stud}^ in the 

 vicinity of the District of Columbia. A single parasite, Bracon 

 Diontrealensis Morrison (Chttn. Xo. 6076"^). determined bj' 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 

 applied 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 man}' 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 

 Avebworm {E vcrgpfifh .^frruninaJh Iliibner), 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 Xew 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 ^lay. 

 In Virginia the eggs hatch in 7 or 8 days, and the larvw begin by 



