Napa cabbage
Yellows, also called Fusarium wilt, is another "Brassica" disease that infects oilseed rape, cabbage, mustards, Napa cabbage and other vegetable brassicas. It is only a problem in regions with warm growing seasons where soil temperatures are in the range of 18 to 32 °C. The causal organism is "Fusarium oxysporum "f. sp." conlutinans". Napa cabbage is relatively tolerant to the disease; mostly the only external symptoms are yellowing of lower, older leaves. The disease is soil borne and can survive for many years in the absence of a host. Most cruciferous weeds can serve as alternate hosts.