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ARS Home » Southeast Area » Fort Pierce, Florida » U.S. Horticultural Research Laboratory » Subtropical Plant Pathology Research » Research » Publications at this Location » Publication #309607

Title: Antimicrobial nanoemulsion formulation with improved penetration of foliar spray through citrus leaf cuticles to control citrus Huanglongbing

item YANG, CHUANYU - University Of Florida
item POWER, CHARLES - University Of Florida
item Duan, Ping
item Shatters, Robert - Bob
item ZHANG, MUQING - University Of Florida

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/2/2015
Publication Date: 7/24/2015
Publication URL:
Citation: Yang, C., Power, C.A., Duan, Y., Shatters, R.G., Zhang, M. 2015. Antimicrobial nanoemulsion formulation with improved penetration of foliar spray through citrus leaf cuticles to control citrus Huanglongbing. PLoS One. 10(7):e0133826. doi: 10.1371/journal.pone.0133826.

Interpretive Summary: Citrus leaf surface acts as a strong barrier against the entry of many chemical compounds. To overcome this barrier and increasing the efficacy of chemical control, we applied and optimized nanoemulsion technology along with a suitable penetrant to develop an effective delivery system for application of antibacterial compounds against the Huanglongbing (HLB) bacterium, Candidatus Liberibacter asiaticus. In this report, we evaluated a number of candidate penetrants for their efficacy on the HLB-affected citrus leaf cuticle, and optimized a nanoemulsion system for delivering effective antibacterial compounds into the citrus phloem via foliar spray. The novel formulations we developed shows more efficient elimination of Ca. Liberibacter asiaticus and relative long-lasting effect in HLB-affected citrus plants.

Technical Abstract: Huanglongbing (HLB) is one of the most serious citrus diseases that threaten citrus industry worldwide. Because Candidatus Liberibacter asiaticus (Las) resides in citrus phloem, it is difficult to deliver an effective chemical compound into the phloem for control of HLB. In this study, a transcuticular nano-delivery system was developed for enhancing permeation of the effective compound ampicillin (Amp) against HLB disease through the citrus cuticle into the phloem by foliar spray. The results demonstrated that efficiency of cuticle isolation using an enzymatic method (pectinase and cellulase) was subjected to citrus cultivar and Las-infection, and cuticles were more difficult to be isolated from Valencia orange (Citrus sinensis) and HLB-symptomatic leaves. Brij 35 was screened from a pool of eight candidate penetrants as an optimal penetrant for HLB-affected citrus cuticle, exhibiting an approximately 3-fold enhancement of cuticular permeability over water control. In vitro assay against Bacillus subtilis, the novel formulation made with Amp and loaded into nano-emulsions coupled with Brij 35 resulted in higher inhibitory zone diameters (5.75 mm and 6.66 mm), compared with inhibitory zone diameters of Amp coupled with nanoemulsions (3.02 mm and 4.90 mm), or Brij35 (4.34 mm) and Amp solution along (2.83 mm). Furthermore, the novel formulations more efficiently eliminated the Candidatus Liberibacter asiaticus in HLB-affected citrus in plants. Therefore, our research provides a useful platform for delivering a compound effective against HLB disease into citrus phloem by foliar spray.