156 DISEASES OF THE SWEET PEA 



FIG. 32. SHOWING HOW APHIDS FEED AND THE NECESSITY 

 OF A CONTACT SPRAY TO KEEP IT IN CHECK. (COURTESY 

 OF THE KENTUCKY TOBACCO PRODUCTS CO.) 



do any males occur. This form of repro- 

 duction without the intervention of the 

 male is known as parthenogenesis. On the 

 approach of cool fall weather a generation 



