Efficacy of Putative Botanical Fumigants and Fungicides Against Soil‐Borne Fungal Pathogens in Wheat

ABSTRACT The negative effects of pesticides for humans and environment have encouraged research into natural control means to protect crops from biotic stresses. This study evaluated the antifungal activity and phytotoxicity of seven natural putative inhibitory products (PIPs), as well their persistence, under both in vitro and in vivo conditions. Six agricultural wastes (bergamot, eucalypt, false pepper, laurel, pomegranate, and sage) were tested in in vitro against 10 soil‐borne fungal pathogens at 2% (w/v). A resistance inducer product (EP5‐product) was also used to improve plant resistance against the aggressiveness of fungal pathogens used. Based on the in vitro results, aliquots of bergamot, pomegranate, and EP5‐product were applied to pots artificially inoculated with Fusarium algeriensis , F. culmorum , and F. oxysporum f.sp. dianthi and subsequently sown with wheat seeds to evaluate their in vivo inhibitory and phytotoxicity activities. Persistence was assessed by re‐sowing the same soil after the first greenhouse trial. Phytosanitary status of the roots and the second leaf, expressed as phyto‐toxicity, disease incidence, and plant growth features (seeds germination, plant height and dry‐matter) were evaluated. Additionally, re‐isolation of the inoculated fungal pathogens from the roots was determined. Bergamot, pomegranate and EP5‐product showed the highest in vitro inhibitory activity. In the first greenhouse trial, EP5‐product showed the greatest phyto‐toxicity, though re‐isolation frequency results indicated that it effectively protected the roots. In the second trial none of the PIPs showed phyto‐toxic effects, but all significantly reduced MkI on roots and the second leaf. In this case, re‐isolation frequency values were higher than in the first experiment, especially for bergamot. In conclusion, agricultural wastes as putative botanical fungicides, and the EP5‐product are promising natural alternatives to chemical pesticides. The persistence of their efficacy, contrasted with the non‐persistence of their phyto‐toxicity, suggests that they are more suitable for soil biofumigation and less for foliar application.