Environmentally-benign wood preservatives based on an organic biocide:antioxidant combination: Ground-contact efficacy ratings and BHT depletion after four years of exposure

As part of a larger project aimed at the development of leach resistant boron-based wood preservatives, the anti-fungal and termiticidal activities, and the resistance to leaching from timber, of three related tetra-n-butylammonium spiroborates, tetra-n-butylammonium bis(ortho-hydroxymethylphenolato)borate 2, tetra-n-butylammonium bis[catecholato(2–)-O,O′]borate 3, and tetra-n-butylammonium bis[salicylato(2−)-O,O']borate 4, have been examined. All three borates are found to be active against test organisms, with the following orders of activity being observed: 2 > 3 > 4 > boric acid against wood decay fungi, and 2 > 3 ≈ 4 > boric acid against termites. The most active compound in both assays 2 also has the highest calculated lipophilicity. In a test for permanence in wood, the following order of leach resistance is observed: 4 >> 3 ≈ 2 > boric acid. This order appears to correlate more closely with the stability constants of the borate esters, as determined using 11B NMR spectroscopy, rather than calculated lipophilicities.

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Evaluation of Heartwood Extracts Combined with Linseed Oil as Wood Preservatives in Field Tests in Southern Mississippi, USA

Insects ◽

10.3390/insects12090803 ◽

2021 ◽

Vol 12 (9) ◽

pp. 803

Author(s):

Babar Hassan ◽

Mark E. Mankowski ◽

Grant T. Kirker

Keyword(s):

Wood Species ◽

Linseed Oil ◽

Ground Contact ◽

Wood Preservatives ◽

Southern Pine ◽

Decay Fungi ◽

Contact Test ◽

The Individual ◽

Heartwood Extracts

Heartwood extracts of naturally durable wood species are often evaluated as alternatives to chemical wood preservatives, but field data from long-term performance testing are lacking. The current study evaluated the long-term (five-year) performance of two non-durable wood species treated with heartwood extracts of either Tectona grandis, Dalbergia sissoo, Cedrus deodara, or Pinus roxburghii alone or combined with linseed oil. Stakes (45.7 × 1.9 × 1.9 cm) and blocks (12.5 × 3.75 × 2.5 cm) cut from the sapwood of cottonwood and southern pine were vacuum-pressure impregnated with the individual heartwood species extract, linseed oil, or a mixture of each individual wood extract and linseed oil. For comparison, solid heartwood stakes and blocks of the wood species used to obtain extracts were also included in the tests. All samples were exposed for five years to decay and termites at a test site in southern Mississippi using ground contact (AWPA E7) and ground proximity (AWPA E26) tests. Results showed that extract-oil mixtures imparted higher termite and decay resistance in cottonwood and southern pine than linseed oil only or the individual heartwood species extract in both tests. However, these treatments were as not effective as to commercially used wood preservatives, copper naphthenate (CuN) or disodium octaborate tetrahydrate (DOT) in either test. Moreover, solid heartwood P. roxburghii stakes were completely decayed and attacked by termites after five years in the ground contact test. In contrast, C. deodara stakes were slightly attacked by termites and moderately attacked by decay fungi. However, T. grandis and D. sissoo stakes showed slight to superficial attack by termites and decay fungi in ground contact test. In contrast, T. grandis and D. sissoo blocks showed slight decay fungi attack in above-ground tests. However, termites did not attack T. grandis, D. sissoo, and C. deodara blocks. However, decay fungi moderately attacked C. deodara blocks, and P. roxburghii blocks were severely attacked by decay fungi and termites in the above-ground test.

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