LOSSES IN FRESH-MARKET TOMATO PRODUCTION IN FLORIDA DUE TO TARGET SPOT AND BACTERIAL SPOT AND THE BENEFITS OF PROTECTANT FUNGICIDES

Three large-scale field tests were conducted under commercial growing conditions in southwestern Florida to quantify yield losses associated with foliar diseases of fresh-market tomatoes, document the benefits of protectant fungicides, and establish a protocol to be used in makin g yield-loss assessments for fresh-market tomatoes. The benefits of pr otectant fungicides were amply demonstrated in two of three experiment s. Marketable and extra-large fruit yields were reduced 30 and 43% in these tests, respectively, when no fungicides were used. Net returns o n investment were $7,800 to $14,800/ha greater in plots treated with c hlorothalonil than in control plots. Much of the loss in marketable yi eld was due to direct damage to fruit by the target spot fungus. As mu ch as two-thirds of the fruit had to be discarded in no-spray plots be cause of blemishes from target spot. Tank-mix sprays of copper-mancoze b provided good early season control of bacterial spot, but there was no correlation between bacterial spot damage levels and yield or monet ary losses. Little return on investment in protectant fungicides was r ecorded where target spot was not a factor in the third experiment, ev en though low to moderate levels of bacterial spot were present.