Pinus patula SCHIEDE ET DEPPE IN SCHLD. ET CHAM. is susceptible to biodeterioration during outside chip storage (OCS), reducing pulp quality and tear and burst indices of resulting paper. Accelerated laboratory trials showed that chips treated with 2% (w/v) propionic acid and stored for 17 weeks, produced pulp of quality indistinguishable from fresh untreated chips. Pulp tests during field trials of 30-ton chip piles in the subtropical environment of Zululand confirmed that chips treated with 2% (w/v) propionic acid yielded acceptable pulp after 4 months' OCS. The surfaces of untreated chips were extensively colonised by fungi after 2 months' OCS. After 4 months' OCS hyphae had penetrated these chips to colonise interior elements, typical basidiomycete decay patterns were observed, and celluloytic soft rot ascomycetes including Chaetomium spp. produced ascospores on chip surfaces. In contrast, treated chips were never extensively colonised in these tests and interior elements remained uncolonised. No basidiomycete decay was observed. No soft rotters were observed and ascomycetous colonisation was restricted to staining fungi such as Penicillium spp. Quantification of microorganisms in the chips showed that when propionic acid was applied, onset of the succession pattern was delayed for 2 months.

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