Organic farmers should practice best cultural management to manage this disease. Late blight (causal agent Phytophthora infestans) is a very difficult disease to control organically in regions where potatoes are grown on large acreage and rain occurs during the production period. New York State Agricultural Experiment Station. ![]() Cornell University College of Agriculture and Life Sciences. Resource guide for organic insect and disease management. We’ll post the survey results in an upcoming edition of the Vegetable Gazette newsletter.Excerpts from: Brown Rosen, E., E. Which disease did you think we had based on the photos? An up-to-date list of fungicides is in the tomato section of the current edition of the Mid-Atlantic Commercial Vegetable Recommendations guide. You can also spray fungicides when symptoms first start to appear on the lower leaves, usually around fruit set. Leaf moisture or high relative humidity is needed for the pathogens to infect the plant, so the longer the leaves are dry, the less likely disease will develop.Īlso, depending on the size of the outbreak, the symptomatic leaves could be removed to reduce inoculum (spores) in the field. Maximize airflow through the plant canopy. ![]() Tomato cultivars are available with resistance to Early Blight. The pathogens survive on crop residue, so disease pressure is reduced once the crop residue is broken down and decomposed. Wait at least 2 to 3 years between planting tomatoes or other solanaceous crops (peppers, eggplant, potato, etc.) in a field. Management of Septoria Leaf Spot and Early Blight starts with good crop rotation. Instructions for submitting a sample can be found on the Plant Disease Clinic website. This is a good reminder to send several representative samples to the Plant Disease Clinic. The sample we sent to Sara only had Septoria Leaf Spot, but Beth saw symptoms of Septoria Leaf Spot and Early Blight in the photos. According to Penn State’s Vegetable Pathologist, the lesion with the tear in this photo is characteristic of Early Blight. Beth said that the lesion with the tear in the photo below is characteristic of Early Blight.įigure 9. Photo: Beth Gugino, Penn Stateīeth looked at the photos and saw symptoms of both diseases. They are easily splash-dispersed within and between adjacent plants. Note the spores coming out of the pycnidia in the center of the Septoria lesions. Note the small black pycnidia on some of the leaf spots. Pycnidia aren’t always visible with Septoria Leaf Spot, but when they are, you can be sure you have it.įigure 7. Can you see the small dark spots within each leaf spot in the picture below? Those are called pycnidia and are characteristic of Septoria Leaf Spot. ![]() Septoria Leaf Spot does not affect fruit Early Blight does. ![]() There are several ways to distinguish Septoria Leaf Spot from Early Blight in the field. Sara said the disease was Septoria Leaf Spot.We took several infected leaves to Plant Pathologist Sara May at Penn State’s Plant Disease Clinic and showed pictures to Penn State’s Vegetable Pathologist Beth Gugino to find out. The symptoms point to Septoria Leaf Spot (caused by the fungus Septoria lycopersici) and Early Blight (caused by the fungus Alternaria solani). As leaf spots grew, they overlapped with other leaf spots, creating large lesions. We noticed the spots were made up of concentric circles appearing as a target or bullseye. When we looked closer at the leaves, we saw small dark spots surrounded by yellow halos. The symptoms had started at the bottom and quickly moved up the plants. In late July/early August, we started noticing disease symptoms on several plants.
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