INJURIOUS TO CABBAGE AND RELATED CROPS 27 

 The Turnip Aphis 



Aphis pseudobrassicoe Davis 



Although the turnip aphis has undoubtedly been causing 

 serious injury to cruciferous crops for many years, particularly 

 in the South, it has been confused with other forms and its 

 injuries attributed to other species. This aphid was not recog- 

 nized as a distinct species until 1914 when it was described 

 from specimens collected in New York and Indiana. It has 

 received careful study in Texas where it is a serious pest of 

 turnip, radish, cabbage and mustard, but is also found on kale, 

 collard, rutabaga, rape and lettuce. It has been reported as 

 feeding on bean but this attack was probably exceptional. The 

 turnip aphis is most destructive in the fall, winter and early 

 spring. Reproduction is rapid and the plants soon become 

 covered with the lice, especially on the underside of the leaves 

 and on the tender leaves at the center of the plant. Badly 

 infested plants are stunted and many of them killed outright. 

 The insect is distributed from Massachusetts to California 

 southward to Louisiana and Texas and has been found in 

 South Africa. 



So far males and egg-laying females (the so-called true sexes) 

 of the turnip aphis have not been observed. In Texas the 

 aphids pass the winter mostly on turnips. In that climate 

 reproduction is considerably slower in the winter months but 

 does not actually cease except for a few days at a time. Both 

 wingless and winged forms occur at all seasons of the year but 

 the relative abundance varies with the crowding of the plants 

 and with their vitality. The wingless form when mature is a 

 little over ^V i^^'h in length, pale greenish, with the antennce 

 pale, blackish towards the tip ; the legs are pale with the tips 

 blackish. The body is slightly pulverulent, but much less so 

 than in the cabbage aphis. The winged form is a little less 



