Watch the Open Fields online guitar lesson by Brad Carlton from Groove Builder
Section A of this tune entitled "Open Fields" consists of a D chord over which you would use sus2, add 9, Major Pentatonic and D Mixolydian. The next chord is Am7 which accepts A Minor Pentatonic, Am Arpeggios and the Dorian mode. The next chord is G which uses sus 2, add 9, Major Pentatonic and the Major scale. Remember that the progression D Am7 G is a Vii I progression in the key of G.