Spot It & Stop It: Leaf Spot
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Leaf spot, one of the most common diseases in ornamental, greenhouse and landscape plants, lives up to its name by leaving unsightly black or brown spots on foliage. Caused by any number of fungal and bacterial pathogens, leaf spot is difficult to control once established; prevention through a variety of cultural and chemical means remains the most effective strategy.
How to Spot Leaf Spot
Leaf spot may be one of the easiest of all plant diseases to identify. Dark brown or black spots are the telltale signs. Depending on the specific fungal pathogen involved, spots may appear as targets, may be raised above the leaf surface, or may show spores coming from the lesions. Defoliation is a possibility, as are deformities in the leaf or the growing shoot.
How to Stop Leaf Spot
As with many other plant diseases, prevention of leaf spot (as opposed to reliance on a curative treatment) is the most effective strategy. Understanding the pathogens’ life cycle is critical; disease is typically spread by air currents or splashing water, by bringing infected plants into a non-disease environment, or through plant-to-plant contact, such as in a crowded greenhouse. Pathogens also can overwinter on dropped leaves and other plant debris.
- A combination of chemical and cultural disease control methods may offer the best chance of avoiding leaf spot.
- In greenhouse environments, special attention should be paid to minimizing humidity. Ensure adequate air circulation, and minimize overhead watering when possible.
- Avoid bringing infected plants into a greenhouse; remove and destroy infected plants or debris once disease is identified. Workers should wash their hands thoroughly after handling infected plants.
- Clean tools regularly, and avoid re-using pots or planting media.
- Avoid over- or under-fertilizing.
- Use a chemical fungicide as a preventive measure. Note that while fungal leaf spot and bacterial leaf spot may exhibit similar symptoms, the pathogens and the appropriate treatments will differ. Expert analysis may be required to accurately distinguish fungal versus bacterial leaf spot.
For control of a wide range of fungal disease pathogens, including Alternaria, anthracnose, cercospora, sclerotinia and others, consider treatment with FloxcorTM fungicide. Floxcor is taken up quickly by the plant, and provides control of over 20 ornamental diseases. To help prevent fungicide resistance, rotate or tank mix applications of Floxcor with Eagle® 20EW specialty fungicide. For more information on Floxcor fungicide and Eagle 20EW specialty fungicide, contact your Corteva representative or visit https://www.corteva.us/products-and-solutions/turf-and-ornamental.html
Floxcor™ is not for sale or use in Nassau and Suffolk counties, New York. Other state restrictions on the sale and use of Floxcor apply. State restrictions on the sale and use of Eagle® 20EW apply. Consult the label before purchase or use for full details. Always read and follow label directions.
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