The Effects of Benomyl and Pisolithus Tinctorius Ectomycorrhizae on Survival and Growth of Longleaf Pine Seedlings

Abstract Benomyl applied to roots of longleaf pine (Pinus palustris Mill.) seedlings at planting significantly reduced brown-spot disease and increased survival, root collar diameter, and early height growth on two sites in Mississippi. Seedlings with half or more of all ectomycorrhizae formed by Pisolithus tinctorius (Pers.) Coker and Couch in the nursery had significantly better survival and growth; Pisolithus ectomycorrhizae did not appreciably affect brown-spot disease. The benefits of benomyl and Pisolithus ectomycorrhizae were most obvious when combined. More than 75 percent of seedlings treated with benomyl and with more than half of all ectomycorrhizae formed by Pisolithus initiated height growth after 3 years. Forty-seven percent of seedlings with only Thelephora terrestris ectomycorrhizae and without benomyl exhibited height growth. The combined use of benomyl to control brown-spot disease and Pisolithus ectomycorrhizae to stimulate early height growth may overcome the major handicaps that have limited artificial regeneration of longleaf pine in the South.