Effect of IPBC/DDAC on Spore Germination and Hyphal Growth of the Sapstaining Fungus Ophiostoma piceae

Abstract

Summary Fungicide interactions were investigated using Ophiostoma piceae (Münch) H. and P. Syd, unseasoned radiata pine (Pinus radiata D. Don) and an antisapstain formulation based on 3-iodo-2-propynyl butyl carbamate (IPBC) and didecyl dimethyl ammonium chloride (DDAC). Treated and untreated wood samples were inoculated with O. piceae and then periodically examined over an incubation period of one month using light microscopy and scanning electron microscopy. Additional treated and infected wafers were removed after 8 and 15 days, rinsed with distilled, sterile water and then further incubated on malt agar nutrient media before examining microscopically. The results of the study showed that prolific spore germination and mycelial growth of O. piceae occurred on untreated radiata pine within 24 hours whereas the majority of spores did not germinate on treated wood. However, in some spores the process of germination was only delayed, occurring after 20 days of incubation. Furthermore, it was noticed that once spore germination occurred hyphae rapidly colonised treated wafers possibly indicating that mycelium of O. piceae is more tolerant to IPBC/DDAC treatment, than spores. The possible mode of action of IPBC/DDAC on spores and mycelium of O. piceae is discussed.