Production and application of the bioherbicide agent Dactylaria higginsii on organic solid substrates

Purple nutsedge and yellow nutsedge are serious weeds in Florida and in many parts of the world. Dactylaria higginsii is a promising bioherbicide candidate for these weeds. This fungus does not sporulate in liquid culture. Thus, for mass production of D. higginsii, 19 solid substrates were tested, including dried, cut culms or foliage of 14 different plants prepared as hays, sugarcane bagasse, a commercial peat-based microbe carrier (BioAPT), and two recycled papers (kraft paper and newspaper). These substrates were tested alone or amended either with 0.01% indole butyric acid (IBA), which enhances growth and/or sporulation of D. higginsii, potato dextrose broth (PDB) for nutrient amendment, or PDB. +. IBA. Yield of D. higginsii conidia produced on these substrates was measured 4 and 12. weeks after inoculation. Conidia were tested for virulence on purple and yellow nutsedges in the greenhouse. Hays without amendments or amended with PDB yielded more conidia which were also more virulent than those produced on hays amended with IBA. Conidial yields were highest when the fungus was grown on purple nutsedge hay without amendments for 4. weeks but conidia produced on this medium had low virulence. Conidia produced on sorghum × sudangrass and cogongrass hays were slightly larger and thicker walled than those produced on other substrates. Conidia produced on sorghum × sudangrass were the most virulent on nutsedge seedlings. Purple nutsedge was more susceptible to D. higginsii than yellow nutsedge. Cogongrass and sorghum × sudangrass hay substrates offer a suitable and easy medium for large-scale production of D. higginsii. © 2010 Elsevier Inc.