Occurrence and Management of Tomato Canker

Bacterial canker recently has been one of the most important disease problems on tomatoes grown in New York. The goals of this project were to determine the sources of bacterial canker in New York and to examine the impact on disease development of management practices used in commercial settings. Canker was not observed in any of the fields, which was very surprising considering the regularity with which this disease has been occurring. Possible explanations include: 1) conditions were not favorable for canker development, 2) seed has been the source and the seed lots the cooperating growers used were pathogen-free, and 3) growers used effective management programs in 2000. However, none of these explanations seems highly likely. Valuable information was gathered during discussions with growers about implementation of recommended management practices for canker. Growers also benefited. Several decided to start using practices they had not been using. In sharp contrast with canker, bacterial spot was widespread in 2000. Infested seed is a possible source of the bacteria causing spot. Additional work is needed to obtain a better picture of the occurrence and manageability of canker and other bacterial diseases of tomatoes in New York and to investigate possible sources of the pathogens. Additional work is warranted because reducing the occurrence of canker and other bacterial diseases of tomatoes would improve grower profitability, decrease use of copper pesticides, and enable growers to resume using TOM-CAST which also can decrease pesticide use. TOM-CAST, a forecasting system for scheduling fungicide applications for early blight, was an important component of the tomato IPM program in New York until canker became important. BACKGROUND AND JUSTIFICATION Bacterial canker has become one of the most important disease problems on tomatoes grown in New York. Canker is very difficult to control once it develops. Weekly applications of copper fungicides are recommended. Consequently, when canker occurs, growers no longer use TOM-CAST for scheduling fungicide applications for early blight. The need to spray weekly for canker and other bacterial diseases has also been cited as the primary reason TOM-CAST is not longer being used in New England. Furthermore, weekly copper applications are often not adequately effective for controlling canker. Therefore it is critical to control the source. The goals of this project were to determine the sources of bacterial canker in New York and to examine the impact on disease development of management practices used in commercial settings. The