Micronized Copper Wood Preservatives: Efficacy of Ion, Nano, and Bulk Copper against the Brown Rot Fungus Rhodonia placenta

Abstract

Recently introduced micronized copper (MC) formulations, consisting of a nanosized fraction of basic copper (Cu) carbonate (CuCO3·Cu(OH)2) nanoparticles (NPs), were introduced to the market for wood protection. Cu NPs may presumably be more effective against wood-destroying fungi than bulk or ionic Cu compounds. In particular, Cu- tolerant wood-destroying fungi may not recognize NPs, which may penetrate into fungal cell walls and membranes and exert their impact. The objective of this study was to assess if MC wood preservative formulations have a superior efficacy against Cu-tolerant wood-destroying fungi due to nano effects than conventional Cu biocides. After screening a range of wood-destroying fungi for their resistance to Cu, we investigated fungal growth of the Cu-tolerant fungus Rhodonia placenta in solid and liquid media and on wood treated with MC azole (MCA). In liquid cultures we evaluated the fungal response to ion, nano and bulk Cu distinguishing the ionic and particle effects by means of the Cu2+ chelator ammonium tetrathiomolybdate (TTM) and measuring fungal biomass, oxalic acid production and laccase activity of R. placenta. Our results do not support the presence of particular nano effects of MCA against R. placenta that would account for an increased antifungal efficacy, but provide evidence that attribute the main effectiveness of MCA to azoles.

Integrated control of wood destroying basidiomycetes combining Cu-based wood preservatives and Trichoderma spp.

“…R . placenta (EMPA 45) was used as a positive control because of its high Cu-tolerance as demonstrated by Civardi et al [2] and Ribera et al [3]. In total, nine containers per wood destroying basidiomycete were prepared (three biological repetitions per fungal treatment).…”

“…The p -values obtained rejected the normality at a 95% confidence level for growth measurements, sporulation rates and wood mass losses. Therefore, and following previous studies by Civardi et al [2], a logarithmic transformation for growth and sporulation data and an arcsine transformation for wood weight losses were applied to obtain normality. All data was back-transformed to numerical values for presentation (expressed as mean ± SD).…”

“…Copper (Cu) is the primary biocide component presently used to protect wood against soft-rot fungi in ground contact [1], but fails to protect against a range wood destroying basidiomycetes [2, 3]. Diverse mechanisms involved in the Cu-tolerance process of basidiomycetes have been described such as the ability to absorb Cu into cell wall components, extracellular chelation by metabolites and intracellular complexion with metallothioneins [4–9].…”

Release of copper-amended particles from micronized copper-pressure-treated wood during mechanical abrasion

“…This is the same as the formulation with high amount of tebuconazole MCA_HTBA we used in a previous investigation [31]. A full characterization of the Cu particles in the MCA formulation is available from the latter study.…”

Aging of Dissolved Copper and Copper‐based Nanoparticles in Five Different Soils: Short‐term Kinetics vs. Long‐term Fate

“…Bordeaux mixture (copper hydroxide and calcium sulfate) has been used as an agricultural fungicide since the 1800s (Flores‐Vélez et al, 1996), and chromated copper arsenate (CCA) has long been used to treat timber, as it provides highly effective protection against termites and fungi (Hingston et al, 2001). While CCA itself is no longer widely used due to its potential to leach toxic arsenic and chromium (Hingston et al, 2001), other copper‐based materials, and increasingly Cu‐NMs, (Evans et al, 2008; Civardi et al, 2015), are still used to treat timber. They also continue to be used as active ingredients in agricultural fungicides (e.g., Kocide), as copper‐based fungicides are accepted for use on organically certified products in many countries (van Bruggen and Finckh, 2016).…”