The red poppy, *Papaver rhoeas*, and several species of daisy of the family Compositae often co-exist as weeds of wheat fields. Fig. 5.1 shows changes in the percentage frequency of red poppies and daisies in an area of wheat fields over a six year period from 1998 to 2003. From 1985, the herbicide metsulfuron-methyl was used to control weeds in this area of wheat fields. This practice continued throughout the six year period. 1998 showed the first occurrence of a red poppy known as biotype X. This red poppy had a specific mutation not present in normal red poppies. [Figure 5.1]