Occasionally, onion maggot and cutworms cause damage. No varieties specifically resist insects but some varieties are less affected. Beneficial predators are commercially available for thrips but do not give dependable control. There are no commercial replacements for diazinon for soil insects or methomyl for western flower thrips. Chloropyrifos is the only effective control for onion maggot, with no alternative chemicals.
Soil borne diseases include pink root.
Leaf spot diseases are partially alleviated by thinner spacings. No biological controls are available. Current studies show limited success. Weeds Problem weeds include broadleaf weeds such as ragweed and pigweed, annual grasses, and perennials such as bermudagrass and yellow nutsedge. Field rotation and mechanical cultivation are practiced.