In vitro compatibility of Pimpinella anisum and Origanum vulgare essential oils with nematophagous fungi and their effects against Nacobbus aberrans

Abstract

The soil nematode Nacobbus aberrans (Thorne & Allen) is one of the recurrent biotic adversities in crops growing under cover, and its presence in the horticultural area of Rio Cuarto, Argentina, is reported from the 1980s to the present day. The use of botanical extracts in combination with biological control agents could be a promising method for the control of this nematode. Nematicidal effects of Pimpinella anisum (anise) and Origanum vulgare (oregano) essential oils (EOs) against second-stage juveniles (J2) of N. aberrans were evaluated in vitro. Fisher LSD tests evidenced significant nematicidal (α = 0.05) effects of the two EOs tested, with LD100 of 200 and 600 µL L−1 for anise and oregano, respectively. Compatibility assays between EOs and five nematophagous fungi were microscopically and macroscopically performed on soil extract solid medium (SESM) conditioned at different water activities (0.99 and 0.98 aw) and incubated at 30, 25 and 20 °C. Purpureocillium lilacinum SR14 was the fungal strain that showed compatibility at levels of spore germination, viability of propagules and growth rate under the different anise oil doses, temperatures and aw assayed. In conclusion, the integrated application of anise EO with the nematophagous fungus, which combines two action mechanisms, could generate, on the one hand, a rapid larval mortality effect caused by the EO and, on the other hand, a parasitic effect that has the advantage of remaining in time under variable environmental conditions.