by Gene McAvoy, 5-County UF/IFAS Veggie Agent.
Around Southwest Florida, bacterial spot has become serious in several tomato fields, starting to show up in a few pepper fields. Bacterial spot is most prevalent where infected plants came from the greenhouse and bacteria then went wild with all the rain. Where growers set clean plants most fields remain clean.
Mostly low levels of bacterial spot have been reported on tomato in the Manatee Ruskin area ranging from just a few spots to as high as 3% in a few fields.
Bacterial spot is showing up in some older tomato fields on the East Coast.
Bacterial spot is one of the most serious diseases of tomato in Florida because it can spread rapidly during warm periods with wind driven rains, and because fruit symptoms reduce marketability.
Bacterial spot is caused by several species of Xanthomonas spp. Four species have been identified on tomato: X. euvesicatoria, X. vesicatoria, X. perforans, X. gardneri. In Florida, the major species encountered is X. perforans.
Symptoms of bacterial spot appear as small, water-soaked, greasy spots on infected leaflets. On tomatoes, distinct spots with or without yellowing occur. Individual leaf spots may coalesce with each other, resulting in the browning of entire leaflets. Fruit spots often begin as dark specks with or without a white halo. As spots enlarge, they become raised and scab-like.
Entry into the plant occurs through stomata or wounds made by wind driven soil, insects, or cultural operations. Bacterial spot can be seed transmitted, but most inocula comes from volunteer plants or infected plant debris in the soil. Temperatures of 75-87°F are ideal for bacterial spot but infections can occur at higher or lower temperatures.
Xanthomonas perforans is seed-borne, which allows for the movement of strains on a global scale.
An integrated approach is needed to manage this disease.
Exclusion is the best means of managing bacterial spot on tomato. Unfortunately, even the best bactericidal treatment offers only limited protection when environmental conditions are favorable for rapid disease development, especially during periods of heavy, wind-driven rains.
Sanitation is important. Pepper and tomato volunteers and solanaceous weeds should be destroyed between crops. Transplant houses should be located away from tomato or pepper fields. Purchase only certified disease-free transplants and seed.
Since water movement spreads the bacteria from diseased to healthy plants, workers and farm equipment should be kept out of fields when fields are wet because the disease will spread readily under wet conditions.
No resistant tomato varieties are available commercially. In pepper, varieties with resistance to races 1 -10 are available.
It is important to apply sprays before and during rainy periods. If conditions are favorable, frequent spraying may not be sufficient to maintain bacterial spot below damaging levels...
Karen inserting info here: Organic home gardeners can use Copper Fungicide and Garden Friendly Fungicide to combat bacterial spot.
