Synthesis and Evaluation of Copper Oleate Nanoparticles Against Citrus Anthracnose Caused by Colletotrichum gloeosporioides: In Situ Experiments, In Vitro Bioassays, and Field Trials

Abstract

AbstractAnthracnose in citrus is a severe disease caused by Colletotrichum species. Synthetic fungicides have been used to combat this citrus disease; however, they may have adverse health effects on humans and cause harmful environmental impacts. During a search for environmentally friendly fungicides, we successfully prepared organic copper (copper (II) oleate) nanoparticles by using natural chitosan polymer as a coating agent and stabilizer and by combining an exchange reaction and in situ coating method. Organic copper nanoparticles coated with chitosan polymer (Cu‐oleate@CS NPs) with Cu contents ranged from 5.0 to 6.0 % by weight. The nanoparticles have an average particle size ranging from 50 nm to 60 nm (TEM), covered by a layer of polymer with a thickness of about 10 to 12 nm. The analytical results of zeta potential and dynamic solution size showed that the nanoparticles are uniformly dispersed (90–120 nm by DLS), with high stability (zeta potential=−61.7 mV) and low cytoxicity to Vero healthy cell line. Cu‐oleate@CS NPs significantly inhibited the mycelial growth of C. gloeosporioides in vitro at 500 and 1000 μg/mL. In field trials, the best antifungal efficacy of Cu‐oleate@CS NPs against citrus anthracnose on orange plants was found at a spray concentration of 0.33 % with a disease control efficacy of 54.18 % at 14 days after the second spraying. Our study results demonstrated a novel preparation of Cu‐oleate@CS NPs and suggested that it could be used as a promising nanoformulation to control citrus anthracnose in vitro and in vivo.