Septoria lycopersici is the fungus that is associated with the transmission of the devastating disease Septoria leaf spot on tomatoes. According the University of Maine, the disease can infect the plants at any stage during growth, and has been known to cause complete crop failure. In this article, we will examine the conditions, symptoms and control for Septoria leaf spot on tomatoes.
What is Septoria Leaf Spot?
Septoria leaf spot is a fungal disease that affects the foliage on tomato plants. The disease can occur anywhere where optimal growing conditions allow it to flourish and if not treated immediately can severely decrease crop yield.
Conditions for Septoria Leaf Spot
According to the University of Maine, most favorable temperatures for the infection to occur are between 68 and 77 degrees F. Like many other harmful fungal related infections, Septoria lycopersici flourishes best during periods of heavy rain or periods of heavy moisture for a period of 48 hours. Although moderate to heavy periods of natural rain contribute greatly to the spread and infection of the fungus, man made mistakes also contribute greatly. Watering plants in the evening or even as early as midday makes it hard for water to evaporate off foliage, which if not evaporated can make a good host for fungal related pathogens.
Symptoms of Septoria Leaf Spot
Septoria leaf spot can occur during any stage of plant development and can occur on young seedlings before ground transplant, states the Cornell University. Symptoms generally occur during mid August when the tomato plants start to reach peak foliage, but it can also occur earlier or later depending on environmental conditions. The small circular lesions with dark borders and gray centers easily spot symptoms of Septoria leaf spot, states the University of Maine. The disease causes the foliage on the plant to wither and die. This greatly reduces crop yield on individual plants, and if the infection spreads, it can devastate all tomato crops grown in the same general area.
Plant diseases are often controlled by using disease resistant strains of plants to prevent infection; however, there are currently no available tomato varieties that have a resistance. Cornell University recommends that susceptible plants and weeds are removed from greenhouses and planting areas prior to the growing season. Crop rotation of one to three years is recommended for preventing infection from previous years of infection. Fungicide use is the most common method of control and should start in late June to mid July and last until the growing season is finished. Cornell University recommends that growers use fungicides when the conditions as stated previously are right for disease transmission.