Ectomycorrhizal development on pine by Pisolithus tinctorius in bare-root and container seedling nurseries

Vegetative inoculum of Pisolithus tinctorius (Pt) produced by Sylvan Spawn Laboratories (C:N 50) and by research methods (IMRD), spore-encapsulated seeds, spore pellets, and sprayed spores were compared for efficacy in forming Pt ectomycorrhizae on pines in operational bare-root nurseries in South Carolina, Florida, and Indiana and in microplots and containers in Georgia. Two rates of application (0.33 and 0.16 liter/m² of soil) of both sources of vegetative inoculum were similar in effect and formed abundant Pt ectomycorrhizae (Pt index > 50) and fruit bodies in all studies. Spore treatments formed consistently fewer Pt ectomycorrhizae than vegetative inoculum. The most effective spore treatment was spore encapsulated seeds. These results indicate that at a bed density of 270 seedlings/m², 0.6 to 0.7 liter of vegetative inoculum is needed to obtain Pt indices > 50 on 1,000 pine seedlings.