Crop-Safe Pyraclostrobin-Loaded Multiwalled Carbon Nanotube Delivery Systems: Higher Fungicidal Activity and Lower Acute Toxicity

Carbon nanotechnology is a growing research field with applications in electronics, medicine, and engineering. The application of carbon nanomaterials in agriculture has also been explored because of population growth and resource depletion. In this research, fungicide pyraclostrobin (Pyr) was successfully loaded on multiwalled carbon nanotubes (MWCNTs) via a physisorption process, with drug loading up to 16.64% (w/w). Compared with the 97% Pyr technical concentrate (97% Pyr TC), prepared Pyr-loaded MWCNTs had a longer period of sustained release (360 h). The indoor bioassay results showed that the MWCNTs carrier had a certain fungicidal activity against Pyricularia oryzae, and the EC50 of Pyr-loaded MWCNTs against P. oryzae was 0.054 mg/L, which was close to that of 97% Pyr TC (EC50 = 0.065). The nanoparticles could be widely and uniformly distributed on the surface of mycelium and absorbed by the roots of rice. There is a synergistic effect between the carrier and drug molecules. The results of pot experiments showed that the efficacy of the drug-loaded system against rice blast was 86.16% at a concentration of 300 mg/L, which was comparable to the control effect of commercial preparation 9% pyraclostrobin microcapsule suspension (9% Pyr CS). In addition, compared with 97% Pyr TC, its acute toxicity to zebra fish was reduced to 1/80, and the nanocarrier had no negative effect on the germination of rice seeds and the growth of rice seedlings. To sum up, these results suggest that MWCNTs are expected to be a vehicle choice for pesticide delivery systems.