Benzaldehyde as a soil fumigant, and an apparatus for rapid fumigant evaluation

摘要

An apparatus was developed for the rapid and facile evaluation of soil fumigants in a controlled manner using small volumes of soil. The apparatus consisted of a manifold to which were attached 6 canisters containing a loamy sand soil (adjusted to -100 kPa soil water potential). The soil was infested with either conidia of Fusarium oxysporum or Trichoderma harzianum; sclerotia of Sclerotinia minor; ascospores of Talaromyces flavus; vermiculite colonized with Pythium aphanidermatum; or beet (Beta vulgaris cv. Detroit Red) seeds colonized with Rhizoctonia solani. Using N2 as a carrier gas, either N2 or N2 + benzaldehyde was passed continuously through the soil for 24, 48 or 72 h. At all 3 exposure times, benzaldehyde + N2 reduced viability of R. solani and S. minor, and reduced populations of P. aphanidermatum and Trichoderma harzianum. Populations of F. oxysporum were reduced after 48 and 72 h of exposure to benzaldehyde, whereas populations of Talaromyces flavus were reduced only after 72 h of exposure. Fumigation with benzaldehyde + N2 for 24 h did not affect soil pH 1 week after exposure, but fumigation for 48 or 72 h temporarily lowered pH from an average of 6.86 to 5.57 and 5.32, respectively. The biocontrol fungus, Talaromyces flavus, was less sensitive to benzaldehyde than the pathogens or the biocontrol fungus, Trichoderma harzianum. Thus, combining Talaromyces flavus with benzaldehyde to enhance biocontrol may be possible.