Cultural Practices to Reduce Early Blight Table 1 lists a range of cultural practices that can reduce the incidence of early blight –as well as other key diseases such as Septoria leaf spot and bacterial canker.
EARLY BLIGHT ON TOMATO PLANTS FULL
No single practice will give you adequate control, but an integrated approach from start to finish will shift the balance in favor of healthy, productive tomatoes for the full season. Managing disease in tomato, or any crop, starts with your selection of seed and your overall farm plan for crop rotation, and doesn’t end until you have turned under the last of your crop debris and planted a cover crop. However, it will not survive in the soil during a rotation of 3 years or more into a non-host crop. We know that the fungus overwinters in infected crop debris and can persist from one season to the next in the same field. Alternaria solani is so widespread that it is difficult to escape it completely, but several cultural practices can help. The fungus can be seed-borne, so it is important to start with clean seed.
EARLY BLIGHT ON TOMATO PLANTS FREE
The first line of defense against any disease is producing healthy plants and growing them in an environment that is as free of the pathogen as possible. Early varieties tend to be more susceptible. Genetic resistance also can be important. Maintaining good crop vigor throughout the season, with adequate water and nitrogen, helps plants resist early blight. Early blight invades the older, less vigorous leaves first, and moves up the plant to younger leaves. As plants age and the fruit load grows, nutritional demands are higher, and tomatoes become more susceptible to early blight. Susceptibility is also a factor in how successfully and rapidly the pathogen grows and reproduces in the plant. Generally, the same conditions that are good for early blight also favor another key fungal disease, Septoria leaf spot. Long periods of rain also favor the disease, if temperatures are warm. In New England, these conditions occur most often during July and August. Weather conditions that create long periods of dew at night, with night temperatures above 65☏ - and especially, above 70 ☏ - are the most favorable. Below 60☏, development is slower, and below 55☏, very little activity occurs. The fastest development occurs in the range between about 65 ☏ and 85☏. Temperature determines how fast these events happen. In both cases, the longer the period that leaves are wet, the better - for the pathogen. Growth of lesions and production of new spores are also favored by leaf moisture. The leaf surface must be wet in order for spores to germinate. What constitutes “favorable conditions”? There are two key factors: temperature and leaf-wetness. This rapid reproductive cycle explains why the disease can expand so rapidly and defoliate a crop within a matter of weeks. Under favorable conditions, this complete cycle - from a spore landing on a leaf to production of thousands of new spores - takes about one week. These lesions produce new spores, which are spread by wind or running water, or carried by workers or implements onto new foliage. Fungal mycelia grow and expand, producing characteristic brown, circular lesions with dark concentric rings like a target board. Early blight disease begins when Alternaria spores (conidia) land on the leaf surface, germinate, and penetrate the leaf tissue. In four years of trials, we have seen reductions of 9% to 52% in the total marketable fruit due to early blight, in unsprayed plots.Īlternaria solani, the organism that causes early blight, is a fungal pathogen that attacks several solanaceous crops including potato and eggplant. Uncontrolled, early blight can completely defoliate tomato plants and cut short the harvest. However, it is not until mid- to late August that we see rapid expansion of the disease throughout the foliage. In our disease management trials at the University of Massachusetts, and in farm fields, the first symptoms usually develop in mid to late July. Contrary to what its name suggests, this disease normally appears late in the season, as plants develop a full load of ripening fruit. Early blight is probably the most common and widespread of foliar diseases in field-grown tomatoes in New England.
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