When pathogenic fungi are found growing on the roots of grape vines, grape farmers sometimes respond by covering the ground around their vines with plastic sheeting and pumping a gaseous fungicide into the soil. The most important concern of grape farmers who engage in this practice should be that the .

A) fungicide might also kill the native yeasts residing on the surfaces of the grapes
B) fungicide might also kill mycorrhizae
C) lichens growing on the vines' branches are not harmed
D) sheeting is transparent so that photosynthesis can continue
E) fungicide isn't also harmful to insect pests