Use of mixed populations of microflora to control sapstain on radiata pine
C Chittenden, R Wakeling, B Kreber
Most methods of biological control in the wood products field have focused on the use of single species of fungi or bacteria to control sapstain or decay. The approach taken in this study involved applying soil microorganisms, in combination with nutrients and various adjuvants that collectively form the biological control system.
Radiata pine branch discs, autoclaved or fresh, were dipped in a forest soil suspension (FS) or FS plus a cocktail containing alkaline adjuvants (ammonia, ethanolamine and lime) and nitrogen rich (urea and DIFCO nutrient media) compounds (AC). Treated discs were pre-incubated for either 48 or 72 hours prior to spray application of challenge sapstain fungi and subsequently assessed at weekly intervals for sapstain. The effects of FS alone, adjuvant concentration, autoclaving the radiata pine discs, and the difference in time interval prior to challenge with staining fungi were determined. A commercial antisapstain product was included as a benchmark.
After three weeks, fresh wood pre-incubated for 48 hours with FS plus 5.0 % w/w AC gave the best performance out of the experimental treatments. This treatment had a mean surface
coverage of 31.5%, compared to 24.5% for the lower and 10.2% for the higher concentration of the commercial benchmark and 88% for the controls. However, for similarly treated discs incubated for 72 hours prior to spraying with the challenge fungi, mean surface coverage was reduced to 17.5%. In general, a 72 hour interval between treatment and challenge with staining fungi reduced surface coverage regardless of treatment. Overall, the experimental treatments on fresh wood discs were more effective than on autoclaved discs but a reversed trend was seen for the commercial benchmark product. These results are discussed within the context of fungal ecology.