Biocontrol of decay in seasoning utility poles. I. Growth rate and colonizing ability of bluestain and decay fungi in vivo and in vitro

Seasoning (air drying) of utility poles for 6–12 months is essential before preservative treatment can be achieved. However, during seasoning, pine sapwood is often colonized by decay fungi, thereby compromising the performance and service life of the poles. This study investigated the potential of bluestain fungi to act as short‐term biocontrol agents against decay during seasoning. An important attribute for biocontrol is rapid growth, so growth rates of common bluestain (Ceratocystis coerulescens, Ophiostoma minus, Ophiostoma piceae, Ophiostoma piliferum, Sphaeropsis sapinea) and decay fungi (Heterobasidion annosum, Phlebiopsis gigantea, Stereum sanguinolentum) were compared on agar medium and pine in logs at various temperatures. On agar, the growth temperature optimum of most bluestain fungi and all the decay fungi was ～25°C, with little growth at ≤5°C or above 32.5°C. Overall, the fastest growing were S. sapinea and O. minus. In logs, the most effective colonizers were S. sapinea and O. minus with pathogenic abilities that made them well fitted to colonize the sapwood of freshly felled pine. Within these species, certain isolates produced much larger lesions in phloem and the sapwood tangential plane than all the decay fungi. Notably, there was significant variation in colonizing ability between different isolates within a species, emphasizing the need for testing a range of isolates when selecting a potential biocontrol agent.