A vine grower is cultivating grapevines in an outdoor vineyard. One of the vines, Vine E, has become infected with powdery mildew, a disease caused by a wind-dispersed fungus.
Figure 1 shows the layout of five key grapevines in the vineyard.
a.[2]
Which vine in Figure 1 is the fungus likely to spread to first from Vine E? Give a reason for your answer.
b.[1]
Suggest one physical action the grower could take to reduce the spread of this fungal disease to the other grapevines, without using chemical fungicides.