We should be past any hard freezes now, but there is still a chance for a light frost this spring, particularly those in low lying areas.
Many folks in the area are now out vigorously planting gardens and flower beds.
Most years, several calls come into the office asking about tomato diseases and wilt problems during August. Now, when planting tomatoes is the time to take care of these issues. Fusarium and Verticillium wilts are common wilt diseases of tomatoes. Yellowing of the lower leaves that progress upward throughout the plant is a distinguishable characteristic of the problem. These two diseases are very difficult to distinguish between each other. There are no chemical controls, thus requiring prevention and sound cultural practices. Resistant cultivars that have the letters V or F following the cultivar name should be selected to help prevent the wilts from starting. Destroy infected plants as soon as possible. You might also find it necessary to rotate an infected garden to plot out of tomatoes for three-five years.
Avoid planting tomatoes near walnut trees where toxicity from tree roots also causes similar foliage yellowing. Tomato plants are particularly susceptible to juglone, a chemical given off by walnut trees. Juglone is also present in the leaves, bark and wood chips of walnut trees which should not be used as mulch or compost in the garden.
Bacterial canker is an infectious disease of tomatoes causing reduced yield and premature fruit drop. It is most easily recognized by white blisters that occur on infected tomatoes. Symptoms can occur on all of the above ground portion of the plant but typically appear first on older leaves at the base of the plant. Margins of infected leaves appear brown and scorched; they are curled upward and inward. Borders between the brown and green areas of the leaves are abruptly distinct, often separated by a thin line of yellow tissue. Light streaks usually develop on infected stems and shoots. These streaks eventually become darker and split, forming a shallow canker. Internal tissue of infected plant stems is discolored, usually yellow or tan. Interference with water transport in this vascular tissue caused by the cankers will result in wilting of all or part of the plant.
Bacterial canker is introduced to previously uninfected areas through infected seeds or transplants. Once established in the garden, the bacteria may survive on infected plant residue for up to three years, thereby making it necessary for rotating tomatoes out of that particular area of the garden for at least that period of time. Prevention of bacterial canker; using disease-free seeds and disease-free transplants is the only acceptable strategy for control. Once bacterial canker becomes established, repeated application of copper compounds may reduce the rate of disease spread, but should not be considered a reliable control measure. Bacterial canker infected gardens should be rotated out of tomatoes for at least three years. Remember Eastern black nightshade is a wee that is very closely related to tomatoes. It should be controlled at all times, but especially in infected areas set aside for future tomato planting to assure breaking the bacterial life cycle.
You can contact the local Purdue Extension Office by calling 829-5020 Ext. 14 in Owen County or 448-9041 in Clay County for more information or publication copies regarding this week's column topic or to RSVP for upcoming events. Please call first to assure items are ready when you arrive and to RSVP for programs.
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