Preventing an increase in Verticillium wilt incidence in spinach seed production

A semifield assay was conducted from 2009 to 2011 to distinguish between different preventive methods of reducing Verticillium spp. in spinach seed production. The seed treatments for controlling seed infection levels included Thiram, Signum, Trichoderma harzianum, Gliocladium roseum and Natural II, and these were tested in naturally infested and uninfested soil. Even though seed treatment by Thiram and Signum in all cases reduced the incidence of Verticillium spp. on the harvested seed, the soil type had a large influence on the subsequent disease pressure as a significant effect of soil was seen in 2010 and 2011 and a non-significant effect of seed treatment on Verticillium spp. was observed in all experimental years. As no interaction between soil and seed treatment was observed, the seed treatment had no effect on the disease pressure on the seeds subsequently harvested from the infested soil.