284 VEGETABLE GARDENING 



as the cabbage louse, has been known in America for 

 over a century, and has become disseminated throughout 

 the country. Its destructiveness varies greatly from 

 year to year, depending upon seasonal conditions and the 

 prevalence of natural enemies. In many states it was 

 especially troublesome and caused heavy losses in 1908 

 and 1909. Both seasons were drier than usual, and it 

 seemed that neither insect nor fungous foes had much 

 effect in checking the ravages of the aphis. Protracted 

 drouth unquestionably favors the multiplication of this 

 pest, while low temperatures with heavy rainfalls are 

 the most unfavorable conditions. 



This insect usually appears in the North the latter 

 part of May or early in June, and feeds upon both upper 

 and under sides of the leaves, which they cause to curl. 

 The pest multiplies with marvelous rapidity, producing 

 from a dozen to a score of broods in a season. (Bulle- 

 tin 2, Virginia Truck Experiment Station, Norfolk, Va.) 

 The bodies of the mature forms are green, but are cov- 

 ered with a grayish, powdery coating, which at a dis- 

 tance gives the appearance of mildew. The young are 

 ready to reproduce in five or six days. 



The eggs, which pass the winter attached to the stems 

 and the refuse leaves, give rise to the first broods next 

 spring. This suggests the most effective means of pre- 

 vention : all refuse in infested fields should be destroyed 

 in the fall. It is also important to destroy remnants of infested 

 plants from which the summer crop has been harvested. 



Spraying with kerosene emulsion, diluted to 15 parts, 

 is a satisfactory means of controlling the insect on grow- 

 ing plants. The first application should be made before 

 the infestation becomes general. A knapsack sprayer, 

 with the proper nozzle and extension attachments may be 

 used to advantage in spraying isolated rjlants and 

 small plantations. It is important that the material be 

 applied to the underside of the leaves as well as to the 



