Infection is more of a problem in the spring and fall, when temperatures are lower. Sooty mold is considered a cosmetic condition and does not usually harm petunias. Though overhead irrigation is typically discouraged due to its tendency toward promoting the development of fungal diseases, powdery mildew is an exception. Symptoms include the development of a white-hued powder-like growth on the surfaces of leaves and, less commonly, on flowers. © 2020 The Scotts Company LLC. Grow your flowers in full sunlight as shaded conditions lead to poor flowering. Your pretty petunias do not look quite so nice when they are suddenly spotted with unsightly mildew. Later, a fuzzy brown or grayish mold may form on the infected tissue. The fungus is spread by the wind, splashing water, or infected pieces of plant tissue contacting healthy tissue. As the disease progresses, you may also notice tiny black growths on leaves and petals. Once gray mold has become established on plant debris and weak or dying leaves and flowers, it can invade healthy plant tissue. Brown spots and blotches may appear on the leaves and stems. Mildew on Petunias Preventive Care. Damage includes stunted, distorted growth, yellowed leaves and premature leaf drop. Maintain extremely well-drained soil; waterlogged conditions cause decline. The fungus initially attacks foliage and flowers that are weak or dead, causing spotting and sometimes mold. Fungus That Attacks Petunias Verticillium Wilt. This widespread plant disease is caused by a fungus (Botrytis) that is found on most dead plant tissue. Crowded plantings, rain, and overhead watering also enhance the spread of the disease. Remove infected flowers and leaves, and clean up plant debris. Bloom failure may occur when powdery mildew develops on buds. University of California Integrated Pest Management Online: Petunia—Petunia x Hybrida, University of California IPM Online: Powdery Mildew on Ornamentals. In warm-winter areas where freezing is rare, gray mold can be a year-round problem. Fortunately, powdery mildew rarely leads to the death of petunias. The fuzzy mold that may develop is composed of millions of microscopic spores. Verticillium wilt is a fungal disease that attacks petunias among approximately 300 other host plants. Choose control options such as horticultural oil, sulfur-based products or neem oil. Remove and destroy affected plant parts. The occurrence of mildew on your petunias is the result of a fungal infection called powdery mildew. In the greenhouse, Botrytis spores are always present, being picked up by air movement and landing on crop surfaces. Powdery mildew fungi attack petunias with a display of easy-to-recognize symptoms. The occurrence of mildew on your petunias is the result of a fungal infection called powdery mildew. about Ortho® MAX® Garden Disease Control Concentrate, Common Outdoor Bugs and How to Deal with Them, Controlling Pests on Flowers, Roses & Ornamental Plants, Ortho® MAX® Garden Disease Control Concentrate. This environment may occur inside the greenhouse when the outdoor weather is cloudy and r… Become familiar with the problem that lies behind the development of mildew on petunias and act quickly the moment symptoms appear. Apply a fungicide labeled for this disease, following label directions. Black sooty mold is a condition that occurs on a variety of landscape plants, including petunias. Damask holds a Master of Arts in English and creative writing from the University of North Texas. The spores germinate when environmental conditions are favorable, for example, when the relative humidity is 94% and higher or when the duration of leaf wetness is 12 hours or more at moderate temperatures (64°F to 77°F). Cool temperatures and high humidity favor gray mold growth. Overhead watering will wash spores from your plants, according to the University of California Integrated Pest Management Online. Gray or brown spots appear on the flowers, especially in wet weather. © Copyright 2020 Hearst Communications, Inc. Petunias perform best in soil with a pH of 6.0 to 7.0, according to the Clemson Cooperative Extension. Tarah Damask's writing career began in 2003 and includes experience as a fashion writer/editor for Neiman Marcus, short fiction publications in "North Texas Review," a self-published novel, band biographies, charter school curriculum and articles for various websites. Apply low-toxicity fungicides to your petunias. Though your petunia plants will most likely survive, they can experience severe disfigurement and diminished health. Caused by a variety of fungal pathogens, the disease spreads sporadically on wind and may infect other desired plants such as flowers and vegetables. This widespread plant disease is caused by a fungus (Botrytis) that is found on most dead plant tissue. Unlike many fungal diseases, powdery mildew can develop without water and develops with the greatest intensity during dry, warm weather. Even worse is the potential health damage that may occur on your garden plants when disease strikes. Powdery Mildew. … This condition is easily recognized by the growth of black, crusty fungus on the leaves, stems and flower heads. The fungus initially attacks foliage and flowers that are weak or dead, causing spotting and sometimes mold. Once gray mold has become established on plant debris and weak or dying leaves and flowers, it can invade healthy plant tissue. Spores can survive on plant debris and may reinfect your petunias or spread through your garden. Damage. While the cosmetic damage is unpleasant, a plant may lose "up to 25 percent of its leaves without problems," according to a Washington State University Extension publication. The fuzzy mold that may develop is composed of millions of microscopic spores. World rights reserved. Healthy petunias have a greater chance of avoiding and recovering from diseases than weakened petunias. Provide optimal care for petunias as a preventive measure against disease problems like mildew. Provide optimal care for petunias as a preventive measure against disease problems like mildew. Try to avoid wetting the flowers when watering. An immediate attempt to control mildew problems offers your petunias the greatest chance for good health. Symptoms.