1), very similar to those caused by Xanthomonas, a bacterial pathogen of zinnia. 1), very similar to those caused by Xanthomonas, a bacterial pathogen of zinnia. Cultural control measures include rotation to non-susceptible crops for two years, control of susceptible weeds, and removal of crop debris from the planting area or prompt incorporation of refuse after harvest. Most common zinnia cultivars and Z. haageana are susceptible. 48-hr reentry. Group M1 fungicide. zinniae strains. REC, Western Maryland Numerous yellow or tan spots can develop across the leaf forming irregular dead areas. Plants with leaf spots should be discarded. Some started indoors and some direct seeded. Alternaria is a fungal leaf spot that produces lesions start out as small dark spots (Fig. 2). Erysiphe) cichoracearum. Bacterial Leaf Spot: Spots reddish brown to dark brown, angular and with a prominent yellow halo form on leaves. Diseased plant debris should be removed from the growing area. As soon as that microscopic spore gets comfortable in its new home, sporulation (the fungal method of reproduction) occurs and the tiny brown fungal leaf spot begins to grow. … REC, Landscape Management & Nursery Production, Pest Predictive Calendar-Landscape/Nursery, Commercial Greenhouse Production: Ornamentals, Diseases on Greenhouse and Cut Flower Crops. Brown spots on zinnia leaf. Cultural control Practice strict sanitation and rigorous scouting to identify and remove infected plants in the early stages before the pathogen spreads. Xanthomonas campestris pv. Blights are potentially serious fungal diseases that can quickly turn entire plants unsightly. Blights. There are several popular zinnia varieties you can consider for your garden. zinniae: No sprays are effective. Plant Dis Rep 63(6):449–453. Chemical control Bactericides are only marginally effective so focus on cultural control tactics. Alternaria leaf spot is a fungal disease that affects zinnias and several other plants, including... Bacterial Leaf Spot. (field bean, kidney, lima, navy, and pinto), Garbanzo Bean (Chickpea), Cicer arietinum, Control of Some Common Aquatic Weeds with Herbicides, Treated Water Use Restrictions (Number of Days), Effectiveness of Major Forestry-registered Herbicides during Seasons of Optimum Usage, Oregon Basis, Recommendations for Broadcast Spraying for Control of Listed Species, Recommendations for Directed Spot Spray, Tree Injection, and Basal Bark Treatment, Hybrid Cottonwood (Hybrid Poplar) Grown for Pulp, Vegetation Management in Orchards, Vineyards, and Berries, Blueberry, Gooseberry, Currant, and Elderberry, Important Preharvest Intervals (PHIs) for Vegetables, Site Preparation, Stale Seedbeds, and Burndown Applications, Registered Uses of Carfentrazone (Aim) Herbicide in Food Crops, Crop Rotation Intervals (months) for Common Soil-active Herbicides, Herbicide Effectiveness in Christmas Trees, Weed Control in Container-grown Nursery Stock, Weed Control in Field-grown Nursery Stock, Ornamental Bulb, Rhizome, Corm, and Tuber Crops, Established Tree, Shrub, Rose, and Ground Cover Landscapes, General Maintenance around Ornamental Plantings, Susceptibility of Broadleaf Weeds in Turf to Common Herbicides, Weed Treatments and Available Products for Home Gardens and Landscapes, Managing Unwanted Vegetation in Riparian Restoration Sites, What to Do in Case of Pesticide Poisoning, Personal Protective Equipment (PPE) Definitions, Cleaning, Recycling, and Disposing of Agricultural Pesticide Containers, Disposing of Unusable Pesticides and Agricultural, Household and Residential Pesticide Products, Pesticides, Endangered Species, and Mandatory No-spray Buffer Zones, Worker Protection Standard (WPS) for Agricultural Pesticides. Spotted leaves occur when fungal spores in the air find a warm, wet, plant surface to cling to. Whenever possible, water in a manner that keeps the leaves dry to inhibit this seedborn disease. Spots turn brown and angular which could then be confused with Alternaria leaf spot. I have attached pictures to this email. Asked August 8, 2015, 12:11 AM EDT. The spots have grown with the leaves and gotten slightly worse. Numerous yellow or tan spots can develop across the leaf forming irregular dead areas. Phenotypic and genotypic characterization of Xanthomonas campestris pv. Symptoms Spots begin on lower leaves as dull gray water-soaked areas on the leaf. Two leaf spots are often found on zinnias. The spots may vary from 2 to 10 millimeters or more in diameter, are reddish brown, and have grayish-white centers on the upper leaf surface. Those spots are infections of the second zinnia disease, Alternaria Leaf Spot, also called Alternaria Blight, caused by the fungus ALTERNARIA ZINNIAE. All three di seases a re favo red by warm, wet or very humid weather, overhead sprinkling, excess shade, and crowding of plants.