Citrus Blight and Wood pH in Cuba and Florida

Abstract

Sweet orange [Citrus sinensis (L.) Osbeck], grapefruit (C. paradisi Macf.), mandarin (C. reticulata Blanco), and ‘Persian’ lime (C. aurantifolia hybrid?) trees in 6 locations in Cuba were tested for blight with water injections into the trunk and analysis of the outer trunk wood for Zn, water-soluble phenolics, K, Mg, Na, and Cl. Trees with visual symptoms of blight absorbed < 60 ml water in 24 hours; their Zn, water-soluble phenolics, K, Mg, and Cl levels in the wood were higher than those of healthy trees, as in blighted trees in Florida. Trees on rough and Volkamer lemon (C. limon L. Burm. f.), Cuban Shaddock (C. limon hyb.?), Rangpur lime (C. reticulata hyb.?), and Troyer (Poncirus trifoliata × C. sinensis) rootstocks were very blight-susceptible; trees on sour orange (C. aurantium L.) had blight in some areas, but the disorder was not widespread among trees on this rootstock. Slurries of dry wood (1 : 3,w/v) from blighted trees were about 0.1 unit higher in pH than wood slurries from healthy trees. A similar pH difference was found in Florida, but only between moderately blighted and healthy trees; severely affected trees had the same wood pH as healthy trees. The pH difference in Florida was expressed more strongly in fresh than in dried wood.