152 



INSECTS INJURIOUS TO VEGETABLES 



attack it, and in many regions hold it down to moderate num- 

 bers save in exceptional seasons. In dry, warm weather the 

 insect enemies are most active, while in cooler dry weather 

 they are less efficient and then the plant-lice frequently gain 

 the ascendency, to the detriment of the cabbage crop. 



Its first appearance is usually noticed in June, and it remains 



Fig 102.— Cabbage aphis, a, So-called " male " ; b, wingless viviparous female. Greatly 

 enlarged; natural size indicated by small outlines. (After Curtis) 



until quite cold weather. In the District of Columbia the writer 

 has observed this species active as late as the middle of Decem- 

 ber, mostly, however, at this time, in the hearts of cabbage, 

 where the aphides had crawled for protection. 



Practically the same or related insect enemies of the pea 

 aphis which have been mentioned in preceding pages attack 

 the cabbage aphis. 



Remedies. — The cabbage aphis can be controlled by much the 

 same remedies as advised for the melon aphis (page 165), the 

 free use of pyrethrum applied by a bellows at any stage of the 

 growth of the cabbage or other plant ; or by kerosene emulsion, 

 which is of value when the plants are young and until the 

 heads begin to complete their growth. Soap solutions may be 

 used if preferred, those known as whale-oil soap, made of fish 

 oil, and potash soaps, made from caustic potash, being the best. 

 A strong stream of water directed upon the plants from a 



