Atrazine nanoencapsulation improves pre‐emergence herbicidal activity against Bidens pilosa without enhancing long‐term residual effect on Glycine max

BACKGROUND Poly(ϵ‐caprolactone) nanocapsules (NC + ATZ) are an efficient carrier system for atrazine and were developed as an alternative to reduce the harmful environmental effects of this herbicide. Here, we analyzed the pre‐emergence herbicidal activity of NC + ATZ against Bidens pilosa and evaluated its residual effect on soybean plants after different periods of soil treatment with the formulations. RESULTS In contrast to non‐nanoatrazine, NC + ATZ treatment led to very high mortality rates of B. pilosa seedlings even after a tenfold dilution, which suggests that atrazine nanoencapsulation improved its pre‐emergence herbicidal activity. In a short‐term assay (17 days), soil treatment with all atrazine‐containing formulations resulted in intense toxicity to soybean plants. NC + ATZ at 200 g ha−1 had the same inhibitory effects on the physiological and growth parameters of soybean plants compared with non‐nanoatrazine at 2000 g ha−1, which suggests that atrazine nanoencapsulation increased the short‐term residual effect of the herbicide. In a long‐term assay (60 days), a gradual recovery of soybean plants from atrazine phytotoxicity was observed. When comparing the effects of nano‐ and non‐nanoatrazine at the same concentrations, the growth and physiological parameters of soybean plants were mainly affected to the same extent. This indicates that encapsulation of atrazine into poly(ϵ‐caprolactone) nanocapsules did not enhance the long‐term residual effect of the herbicide on soybean. CONCLUSION NC + ATZ could be applied for efficient weed control without additional phytotoxicity to susceptible crops compared with non‐nanoatrazine, provided that a safe interval is respected from atrazine application to sowing. © 2019 Society of Chemical Industry Nanoatrazine provides an efficient pre‐emergent control of Bidens pilosa without additional phytotoxicity to Glycine max compared with non‐nanoatrazine, if a safe interval is respected from atrazine application to crop sowing.