sentences:  Registered insecticides or chemical controls are sometimes used to prevent this and labels will specify the withholding period before the forage crop can be grazed or cut for hay or silage.Alfalfa is also susceptible to root rots, including "Phytophthora", "Rhizoctonia", and Texas root rot.Alfalfa is also susceptible to downy mildew caused by the oomycete species "Peronospora aestivalis".