Disease Note.

Citrus Chlorotic Dwarf: A New Whitefly-Transmitted Viruslike Disease of Citrus in Turkey. S. Korkmaz, Subtropical Fruits Research and Experimental Centre, University of Cu-kurova, 01330 Adana, Turkey. A. Cinar, and U. Kersting, Subtropical Fruits Research and Experimental Centre, University of Cu-kurova, 01330 Adana, Turkey; and S. M. Garnsey, USDA, ARS, Horticultural Research Laboratory, 2120 Camden Road, Orlando, Fla. 32803. Plant Dis. 79:1074. Accepted for publication 11 August 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/PD-79-1074C.

A viruslike disorder of citrus has rapidly spread in citrus plantations along the south coast, where about 85% of (he country's total citrus production is concentrated. Citrus infectious variegation virus (CIVV) was first suspected but extracts from diseased tissue failed to react with CIVV-specific antisera in enzyme-linked immunosorbent assay, and mechanical transmission by leaf inoculation, readily accomplished with CIVV, was unsuccessful. The causal agent was transmissible by grafting and stem-slash inoculation with buffered leaf extracts (1), with infection rates ranging from 5% for 5 cuts to 72% for 100 cuts. In laboratory tests, the disease agent was repeatedly transmitted from citrus to citrus by Ihe Japanese bayberry whitefly, Parabemisia myricae (Kuwana). When 15 to 20 whiteflies per receptor plant were used, transmission rates were 18 and 46% with inoculation access periods of 24 and 48 h, respectively. On all susceptible varieties, the first distinct symptom of this new whitefly-transmitted disease, "Citrus Chlorotic Dwarf" (CCD), is a V-shaped notch on one or both sides near the lip of young leaves. In mature leaves, symptoms are crinkling, warping, inverted cupping, and variegation. Symptoms occur at 20 to 25°C and are more pronounced at 30 to 35°C. The first symptoms are observed on Ihe first or second new flush of growth, 5 to 8 weeks after inoculation. Systemically infected plants are also stunted. In a disease survey of Icel, Adana, and Hatay provinces, 55 orchards (total area, 350 ha) were checked, and 20.3% of 4,407 randomly selected trees were affected: 30.7% of lemon, 18.2% of grapefruit, 17.4% of mandarin, and 6.2% of sweet orange trees had CCD symptoms. Incidence of this graft-transmissible, whitefly-vectored pathogen is increasing in the East Mediterranean region of Turkey.