144 INSECTS INJURIOUS TO VEGETABLES 



to the plants, forms a more or less perfect place of concealment 

 for them. 



Remedial Measures. — A spray of Paris green applied as soon 

 as the larva hatches serves in great measure to control it. Clean 

 cultural methods should be persistently practiced, and every bit 

 of refuse material, particularly cabbage stalks and weeds, should 

 be raked up into piles and set afire by adding, if necessary, dry 

 straw to aid in their ignition. Kerosene emulsion, properly 

 prepared and applied sufficiently often to insure a permanent 

 odor, should be effective in preventing egg laying and will also 

 destroy other insects with which it may come in contact. 



The Diamond-back Moth (Plutella maculipennis Curtis) . — One 

 of the minor enemies of cabbage is the larva of the imported 

 diamond-back moth or "cabbage plutella." It is smaller than 

 any of the preceding, and as a rule its injuries are much less 

 conspicuous. Occasionally, however, it becomes ' sufficiently 

 numerous as to be quite troublesome. Its minute active cater- 

 pillar may be found on cabbage everywhere, and in this stage 

 as well as in pupa, when it rests in a beautiful white, lace-like 

 cocoon attached to the surface of cabbage leaves, it is familiar 

 to observing persons. Attack is usually confined to the outer 

 leaves, the larva feeding generally on the lower surface and 

 not eating through, as with the larger looper and some other 

 worms. At times, however, leaves are riddled with holes and 

 much of their substance devoured. 



The moth (fig. 96, /) is gray and distinguished by the black- 

 marked fore-wing. The wing expanse is about three-fifths of 

 an inch. This insect is found during winter on old cabbage 

 stalks, hibernation taking place normally as pupa, although 

 adults also occur as late as December. Two or three genera- 

 tions are produced in the more northern States, and farther 

 south four or five broods occur during a season. In the extreme 

 South the insect occurs throughout the year. 



