P.M. Rogers, W.R. Stevenson, J.A. Wyman, Ken Frost, Russell Groves
Each year three major foliar diseases invade Wisconsin commercial carrot fields—alternaria leaf blight, cercospora leaf spot, and aster yellows. The first two are caused by fungi, the third by bacteria, and all three are costly to carrot growers. The authors present a detailed description of how these diseases are introduced and spread in a field, how they traditionally have been controlled, and how Integrated Pest Management can cut spray costs by basing spray schedules on disease resistance of the cultivar being grown and on results of careful monitoring—monitoring of weather conditions and foliar symptoms for the fungus diseases, monitoring of the number of infective insects for the bacterial disease.
Included are color pictures to help field scouts distinguish the aster leafhopper (which spreads aster yellows infection) from the potato leafhopper (which doesn’t). Methods of scouting for foliar damage and for aster leafhoppers are described. Several tables present the levels of foliar disease resistance of various carrot varieties.
This is a comprehensive look at carrot foliar diseases in Wisconsin and how best to control them (8 pages, 2011).