Formulation of the Biocontrol FungusCladorrhinum foecundissimumto Reduce Damping-Off Diseases Caused byRhizoctonia solaniandPythium ultimum1

Abstract

Abstract Five isolates of Cladorrhinum foecundissimum , added to soilless mix as 10-day-old fresh bran preparations (1.0% w/w), significantly reduced ( P ≤ 0.05) damping-off of eggplant and pepper caused by Rhizoctonia solani strain R-23. After 4 weeks of growth, plant stands in the biocontrol-amended, pathogen-infested treatments (>80%) were comparable to those in the noninfested controls. Since plant stands were similar at 2 and 4 weeks, most of the disease was preemergence damping-off. The bran preparations also reduced saprophytic growth of the pathogen, and there was an inverse correlation ( r 2 = −0.94) between saprophytic growth and eggplant stand. Added to soilless mix at a rate of 2.0% (w/w), alginate prill containing 20% fermentor-produced biomass of six biocontrol isolates of C. foecundissimum reduced ( P ≤ 0.05) damping-off of eggplant caused by R. solani , but only the prill with biomass of isolates Cf-1 or Cf-2 yielded plant stands (>80%) comparable to that in the noninfested control. As with the bran preparations, there was also an inverse correlation ( r 2 = −0.80) between saprophytic growth of R-23 and eggplant stand with the alginate prills. Alginate prill with biomass of Cf-1 or Cf-2 also reduced ( P ≤ 0.05) damping-off of eggplant and pepper caused by other isolates (195, NG-2, DPR-1) of R. solani , but only the stands (>80%) of pepper were similar to that in the noninfested control. Alginate prill formulations of C. foecundissimum (Cf-1, Cf-2, and Cf-3) also reduced ( P ≤ 0.05) populations of the pathogen and damping-off of eggplant and pepper caused by Pythium ultimum (PuZ3). However, although the plant stands in the treatments were not as high as those in the noninfested controls, they were higher than those in the pathogen-infested controls. The treatments also reduced populations of P. ultimum in the soilless mix so that there were inverse correlations between the pathogen population and eggplant stand ( r 2 = −0.81) and pepper stand ( r 2 = −0.78). Extruded flour/clay granules containing 5.0% biomass of Cf-1 and Cf-2, added to R. solani -infested soilless mix (2.0%), reduced ( P ≤ 0.05) damping-off of eggplant and pepper. However, only the Cf-2 treatments resulted in stands (>80%) equal to those in the noninfested controls for the crops after 4 weeks of growth. The influence of bran and alginate prill of Cf-1 or Cf-2 on the spatial spread of R. solani and its ability to incite damping-off of eggplant showed that prill with Cf-1 or Cf-2 and bran with Cf-2 were equally effective in reducing the spread of the pathogen from the point source of the inoculum to the center of the flats.