Control of phytopathogen organisms using bioactive compounds contained in orange wax

Abstract

Orange wax (OW) is a waxy waste generated in the essential oil purification process (winterization). It has no commercial value. It is discarded or burnt, polluting the environment. The present study demonstrates the possibility of applying it to control phytopathogens. The ethanol-soluble bioactive compounds of OW were identified and quantified. The effect of orange wax extracts on the growth inhibition of phytopathogenic fungi (Fusarium oxysporum and Colletotrichum gloeosporioides) and Spodoptera frugiperda larvae was evaluated. High-performance liquid chromatography–mass spectrometry (HPLC-MS) and gas chromatography–mass spectrometry (GC–MS) quantified 22 bioactive compounds representing 23% (w/w) of OW. Terpineol, limonene, and eremophilene were the most abundant bioactive substances in this material. The distortion of the radial growth of the fungal hyphae was measured in a potato dextrose agar (PDA), and all tested concentrations (6.3, 12.5, 25, 50, and 100 mg/mL) inhibited the radial expansion of C. gloeosporioides. In contrast, only the OW extracts at 50 and 100 mg mL−1 inhibited F. oxysporum. Spray treatments were performed using a Potter spray tower on third-instar Spodoptera frugiperda larvae. Spraying OW extract at 50 mg mL−1 for 10 s caused the highest larval mortality. However, third-instar larvae were attracted to consume corn leaves moistened with extract at lower concentrations. Up to 93% of the first-instar larvae died after eating corn leaves moistened with the extract at 50 mg mL−1. As far as the authors are aware, this is the first scientific report about the use of bioactive compounds of orange wax to control fungi. Spodoptera frugiperda could form the basis for the manufacture of new biopesticides.