Zinc nanoparticles for potential control of Huanglongbing on citrus
Mayara Mari Murata: University of Florida
<div>Huanglongbing (HLB), caused by the phloem-limited fastidious bacterium <em>Candidatus</em> Liberibacter asiaticus (CLas), has caused tremendous economic losses for citrus industries worldwide. It is considered the most destructive disease in citrus and no cure is available for growers. The development of affordable and sustainable chemicals for HLB management is essential for the future of citriculture. We aim to test the antimicrobial activity of the nano-zinc oxide material, Zinkicide<sup>TM</sup>, against CLas. This product is a plant nutrient-based nanoparticle with bactericidal activity that translocates systemically after spray or soil drench application. Preliminary HLB data from citrus canker field trials showed some efficacy, but efficacy correlated with application rate and interval. Application rate and timing needs optimization. Phytotoxicity was assessed in Sour orange seedlings and wilt symptoms were observed only at high Zinkicide<sup>TM</sup> concentration (above 3,000 ppm). Three-year old grafted inoculated CLas-positive Hamlin sweet orange plants were treated with Zinkicide<sup>TM</sup> at 1,600 ppm every 7, 14, and 28 days under greenhouse conditions. Antimicrobial activity against CLas was evaluated by transcriptional activity in leaves. Zinkicide™ spray and drench applied weekly or biweekly significantly reduced Clas activity. These results showed that Zinkicide nanoparticles are a promising tool against HLB and that the current field trial application schedules need to be modified.</div>
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