Etiology and Management of a Mandarin Rind Disorder in California

ABSTRACT Recent reports of a preharvest rind disorder of Satsuma mandarin fruit resulted in severe crop losses in some growing areas of California (Butte, Fresno, Tulare, and Kern Counties). Symptoms were more frequently observed on fruit on the outer perimeter of the tree and on the exposed side of the fruit. Fungal isolations from affected fruit were inconsistent among orchard sites and growing seasons. Isolations resulted in species of Alternaria, Fusarium, Macrophomina, Ulocladium, and Cladosporium. In laboratory studies, mandarin fruit that were soaked in water for 6 h at 15 to 35°C, air dried, and incubated at 20°C for 3 days developed lesions similar to those observed in the field. When fruit were treated with an agricultural summer spray oil or the antitranspirant di-1-p-menthene prior to water soaking, the incidence and severity of the disorder were significantly reduced. Similar results were obtained in 2 years of field trials at two sites using one to three preharvest applications with the agri...