DISEASE: Pecan scab PATHOGEN: Fusicladium effusum (former names include Fusicladosporium effusum, Fusicladium caryigenum, Cladosporium caryigenum, and Cladosporium effusum) HOST AND RANGE: Host species include pecan (Carya illinoinensis) and other Carya species, … Thus, use a variety of fungicide groups for pecan scab disease control and make applications in a preventative manner before disease builds up to levels that will harm the crop and make control difficult. Pecan scab is the most economically significant disease of pecan trees (Carya illinoinensis) in the southeastern United States. Pecan Scab. Attacking in wet, humid weather, the fungus covers young twigs, leaves and developing nuts with olive-brown to black spots. Pecan scab is widely regarded as the most damaging pecan tree disease. How can one get rid of pecan scab? The Plant Health Instructor. Here's a link to the Texas Plant Disease Handbook with more information about scab and treatment. But getting the best use out of them and doing so in a manner that prevents resistance development can be confusing for some folks. Hoefnagels, M.H. These spots may have a velvety or cracked appearance. olive green to black sunken spots or. Pecan scab (Venturia effusa) Lifecycle of Venturiaeffusa, cause of pecan scab Autumn Winter Summer Spring Fungus becomes dormant as stroma and overwintering conidia (twigs and shucks) Epidemics build up on young leaves (conidia) Overwinters as stroma and conidia Epidemics build up on fruit (conidia) Polycyclic disease (rain and wind) We’re fortunate to have a wide variety of fungicide options for pecan scab management. Nut losses on unsprayed susceptible varieties can reach 50 percent to 100 percent in a year. How do I get rid of it? 1 Response. and B.D. Pecan scab, caused by the fungus Cladosporium caryigenum, forms spots or on leaves and nut shucks, expanding as the leaves expand. Leaf spots may. Infected nuts sometimes drop prematurely. become numerous, leading to … DOI: 10.1094/PHI-I-2016-0620-01. Venturia effusa is a fungal plant pathogen that causes pecan scab. Asked December 18, 2013, 8:56 PM EST. Pecan scab, caused by the fungus Cladosporium caryigenum, is generally the most damaging pe can disease. Kaufman County Texas. The fungus causes lesions and tissue death on pecan twigs, petioles, leaves, nuts and shucks beginning in early spring, with multiple cycles of infection repeating until late summer. (husks), leaf blades and leaf petioles (Figures 1 and 2). the shade value and the nut crop. The disease can be identified by the following symptoms: They may be small, circular, or have olive-green to black spots form on the lower surface of the leaf and nuts. Prevention & Treatment: The best way to reduce the overall impact that pecan scab will have is to plant scab-resistant pecan varieties. Pecan scab (PS) is the only economic disease found in Missouri orchards. 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