See: Varietal Publication No.
CXXIII, April, 1987
Yolo has high resistance to spotted
alfalfa aphid, pea aphid, Southern root--knot nematode, and Fusarium wilt;
resistance to blue alfalfa aphid; moderate resistance to Phytophthora root
rot and stem nematode; and low resistance to bacterial wilt, Verticillium
wilt and anthracnose.