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Poster: Biology & Disease Mgmt: Chemical Control


Citrus Canker as a bioassay for systemic bactericidal activity of Zinc nanoparticles
S. COMMERFORD (1), K. Gerberich (1), P. Rajasekaran (2), M. Young (3), S. Das (3), J. Graham (4), S. Santra (3), E. Johnson (1) (1) Citrus Research Education Center, University of Florida, U.S.A.; (2) University of Central Florida, U.S.A.; (3) University

Huanglongbing (HLB) is caused by the phloem-limited bacterium, Candidatus Liberibacter asiaticus (Las), transmitted by the Asian citrus psyllid. Since August 2005, when HLB was first discovered in South Florida, citrus production has declined by more than 60%. HLB symptoms include vein yellowing, blotchy mottle, zinc deficiency, tree decline and fruit drop. Like most systemic diseases, HLB is difficult to control because foliar applied materials cannot enter the vascular tissue due to the leaf cuticle and selective permeability of cell membranes. Zinkicide™ is a plant nutrient-based nanoparticle with bactericidal activity that is designed to be translocated systemically. Prior to HLB, citrus canker was the most serious disease threat to Florida citrus. The causal agent, Xanthomonas citri subsp. citri (Xcc), incites leaf and fruit lesions within 2-3 weeks after infection. The goal was to investigate systemic movement of Zinkicide™ via soil drench using canker as a model for bactericidal activity because of the short evaluation time compared to HLB. In replicate greenhouse trials, soil drench and spray applications of Zinkicide™ were applied prior to leaf infiltration with 104 cfu ml-1 of Xcc. Two weeks post inoculation lesions per leaf were counted. Zinkicide™ spray and drench applications significantly reduced lesion number. Reduction of lesions by the drench treatment indicates that systemic activity of Zinkicide™ will be useful for further evaluation against HLB.