Key Features
- Defoliation or browning canopy
- Irregular or round leaf spots
- Spots with tan centers
Symptoms
Phyllosticta fungi cause leaf spots on a wide range of host plants. While symptoms vary depending on which Phyllosticta and host species are involved, typical leaf spots are light brown or tan with a purple edge. Individual spots are usually small (under 1/2 in diameter) though spots may grow together giving the appearance of larger lesions. Severely infected plants appear brown and drop their leaves prematurely. In perennials, host vigor may be reduced after consecutive years of heavy infection resulting in sparse growth and increased susceptibility to stresses.
Biology
There are many different species of Phyllosticta and few attack more than one host. Phyllosticta spores are produced in the spring on previously infected leaf litter and plant debris. Spores are produced within black, erumpent pustules called pycnidia. Infection will occur when relative humidity is high or leaves are wet. If weather conditions are conducive, these new infections will produce spores that will cause leaf spots on nearby susceptible plants. Phyllosticta overwinters on previously infected leaf litter and plant debris.
Management Recommendations
Whenever possible, reduce overhead water, and keep leaves as dry as possible. Correct fertilization, irrigation, and soil drainage will increase plants' natural defense against the disease. Remove and destroy all Phyllosticta infected plants and plant debris to reduce the spread of disease and the number of overwintering spores. Several fungicides are labeled for homeowner use for the control of Phyllosticta leaf spot. However, these fungicides can only prevent new infections. Always read and follow the directions on the product label.
Effective Pesticides
Active Ingredients include: Chlorothalonil, Propiconazole, Sulfur
Resources
- Not satisfied with ID? Contact the Purdue Plant and Pest Diagnostic Lab
- Sign Up for the Purdue Landscape Report
