Seed treatment with Trichoderma species for control of damping-off of cowpea caused by Macrophomina phaseolina

Cowpea seeds treated with three Trichoderma spp. at four inoculum doses, an d at four exposure times in three different formulations were planted in so ils amended with Macrophomina phaseolina, and assessed for stand establishm ent and post-emergence damping off. The highest percentage plant stands at 21 days after planting were 66% for T. koningii and T. harzianum, and 51% f or Trichoderma sp., at 6.8 x 10(7), 2.0 x 10(10), and 1.0 x 10(7) colony fo rming units (CFUs) ml(-1), respectively. Across sampling dates and irrespec tive of time of exposure to the formulations, the T. harzianum and T. konin gii formulations resulted in significantly greater percentage plant stands than the seeds treated with a Trichoderma sp. and the controls. Seed treatm ent formulations with Trichoderma spp. were derived from propagule suspensi ons at the most effective inoculum dose in Tween 80, in suspension with coo ked cassava starch as an adhesive, or in a slurry with uncooked cassava sta rch. At 21 days, the suspensions with Tween 80 and cooked starch resulted i n significantly higher percentage plant stands than the control, while stan ds from seeds treated in a slurry formulation and starch solutions were not different. Seed exposure to the different formulations for 10, 20, 30, or 40 min, provided mixed results. Seeds treated with benomyl at 0.5 g a.i/50 g resulted in 95 and 100% stands for the two sets of experiments, respectiv ely.