CITRUS LEPROSIS IN FLORIDA, USA, APPEARS TO HAVE BEEN CAUSED BY THE NUCLEAR TYPE OF CITRUS LEPROSIS VIRUS (CiLV-N)

Abstract

Citrus leprosis (CL) is a highly destructive viral disease vectored by Brevipalpus phoenicis Geijskes (Acari: Tenuipalpidae). It was first described in Florida in 1907 and last reported in 1968. CL was found after the 1920s in South America (Paraguay, Argentina and Brazil) and presently is known to occur in most of the South American countries. After its detection in Panama in 2000, the disease spread quickly northward through Central America and is now established in Southern Mexico, threatening all of the Caribbean islands as well as the citrus growing areas within the United States. The disappearance of the CL from the United States could be attributed to the severe freeze of December 1966. Multiple spray applications of sulphur for mite control could have gradually reduced the source of inoculum by substantially reducing the Brevipalpus populations. Recent ultrastructural studies revealed that CL may be caused by two distinct viruses, respectively the rare nuclear type (CiLV-N) and the prevalent cytoplasmic type (CiLV-C). A slight difference in foliar lesions caused by these viruses was noticed. CiLV-C produces leaf lesions that become larger in size, with a pale green color and commonly having gummy rings while CiLV-N induces smaller lesions with a dark center and a bright yellow halo. Analysis of available photographic records and samples in the Herbarium of the Instituto Biologico de Sao Paulo in Brazil strongly suggest that CL in Florida was caused by CiLV-N. This helps to explain the disappearance of CL from the United States because it is now known that CiLV-N is less aggressive than CiLV-C. DOI: http://dx.doi.org/10.17525/vrr.v16i1-2.51