SHIKIMIC ACID MONITORING IN WEED CONTROL WITH GLYPHOSATE IN A COMMERCIAL CITRUS ORCHARD

ABSTRACT In order to check the accumulation of shikimic acid in a traditional commercial grove of citrus “Pêra” cultivar (Citrus sinensis) managed for weed control with glyphosate, a systemic herbicide with wide spectrum, samples were collected at Fazenda Jequitibá, in Santo Antonio de Posse County, São Paulo State, Brazil. The producer applied the following treatments of Roundup Original® glyphosate at 1,440 g.ha-1 a.e. of the isopropylamine salt on 19 December 2006 between rows of 15 plants, leaving five others as control. The reapplication of glyphosate at 1,260 g ha-1 was done on 2 April 2007. In both cases, immediately before application and at 3, 7, 10, 15, 20 and 35 days thereafter, 20 leaves from each treated and untreated plants were collected for analysis of the content of shikimic acid by isocratic high performance liquid chromatography (HPLC) assisted with microwave. The results showed no significant differences in levels of shikimic acid between the material from the area treated with glyphosate and that weeded manually.