37^ Diseases of Greenhouse Crops 



to be four important aphids which attack plants^ 

 The melon aphis {Aphis gossypii) is a general 

 feeder and attacks a large number of plants. The 

 green aphis {N ectorophora rosd^) seems to attack the 

 rose only. The brown aphis {Rhopalosiphum violcz) 

 attacks the violets. The black aphis {N ectorophora 

 chrysanthemicoleus) attacks the chrysanthemum. 

 The following table by Davis * is a list of plant 

 lice which are known to attack ornamentals in the 

 greenhouse : 



•Davis, G. C, Michigan Agr. Expt. Sta., Special Bui. 2: 5-43, 

 ^896. 



