Tomatoes can be pruned to force fruit production. In fact, tomatoes require very few leafy stems to yield an abundant crop and the fewer leaves, the less watering and summer stress that occurs for the plant. Pruning also significantly improves light and air penetration through the plant canopy, reducing disease and improving the quality of the ripening fruits. Determinate type tomatoes are generally left un-pruned, as they produce all of their fruit in a single flush. Soil borne blights can be a serious concern for tomato plants, and cross contamination occurs between tomatoes, potatoes, egg plant and peppers. To reduce the chance of blight in your tomato crop, rotate planting sites from year to year and avoid planting tomatoes where the previously listed tomato relatives have recently been grown. Blights splash up from the soil, so mulching, removal of lower stems, and attentive watering are all recommended measures to prevent blight from infecting tomato plants.