Effect of sclerotial distribution pattern of Sclerotinia sclerotiorum on biocontrol efficacy of Trichoderma harzianum

Field studies were conducted over two seasons to investigate effects of random versus highly aggregated spatial arrangements of sclerotia of S. sclerotiorum, and effects of biocontrol agent density and formulation additives, on colonization of sclerotia by Trichoderma spp. Application of T. harzianum encapsulated in alginate pellets with either bran or polyethylene glycol additives increased the percentages of sclerotia colonized in both years, but there was no difference between additives in either year. Higher pellet densities (200 pellets/m2 versus 40 pellets/m2) resulted in higher proportions of sclerotia colonized by Trichoderma spp. in one season but not in the other. However, when sclerotia were in highly aggregated spatial patterns, significantly higher percentages were colonized in both years, compared to sclerotia in random distributions.