Fungicides influence growth and development of specific ectomycorrhizae on loblolly pine seedlings [Pinus taeda]

Four fungicides-captan, benomyl, PCNB, and benodanil-in single (1x) and double (2x) applications were used as soil drenches on fumigated nursery soil infested with Pisolithus tinctorius or Thelephora terrestris after sowing seed of Pinus taeda . Control soil was naturally colonized. Seedlings were lifted 8 months after sowing. Ectomycorrhizal development on seedlings and basidiocarp production by P. tinctorius was significantly greater than fungicide-free controls in plots treated with benomyl and captan at either rate and less in plots treated with benodanil: PCNB had no effect. Ectomycorrhizal development by T. terrestris was greatest in plots with 2x rates of benomyl and captan. PCNB and benodanil had no effect on Thelephora development but both fungicides decreased basidiocarp production. Considerable seedling mortality occurred shortly after applications of PCNB, which reduced plot density and resulted in larger seedlings in those plots. The incidence of fusiform rust galls was reduced by benodanil in all fungus treatments.