Budwood as a source of wilt in greenhouse roses

VERTICILLIUM wilt, a serious disease resulting from infection by a soil-borne fungus, is important in California on many crops including potatoes, strawberries, cotton, cherries, apricots, chrysanthemums, and roses. Although it is a more important disease in greenhouse roses grown for cut flowers, it does not cause much trouble in roses grown for the home garden. This phenomenon has been difficult to understand because they are both propagated by budding into young, rooted cuttings of rootstocks grown under the same cultural conditions, and in the same soil types, and frequently in the same fields. Another point of confusion is that greenhouse roses are commonly grown on Manetti rootstock, which is resistant to Verticillium fungus, whereas garden roses are grown on Odorata, Dr. Huey (also called Shafter), Burr Multi-flora or Ragged Robin, all of which are more susceptible than is Manetti.