Biologically based approach to controlling Pythium root rot of greenhouse cucumbers grown in rockwool system

This study aimed to examine the effect of co-cultured consortium of four Trichoderma spp., including T. asperellum, T. koningii, T. polysporum and T. gamsii on Pythium root rot of greenhouse cucumbers grown in rockwool hydroponic culture. Experiments were carried out: (1) in experimental hydroponic system constructed with reused rockwool slabs “naturally” infested with Pythium spp. and additionally inoculated with P. aphanidermatum, P. ultimum, Pythium groups G and F; and (2) in commercial greenhouse wherein cucumber plants (c. Boncanale) were grown in reused Pythium infested rockwool system. The bioagents were co-produced on autoclaved barley grain. The abundant spore mass was suspended in ready-to-use fertigation solution, filtered twice and adjusted to 5.0-7.5 x 107 spores ml-1. 150 ml of this solution were applied to the roots of treated plants zero, once, twice or three times. Treatments were performed manually in the experimentally constructed system starting at day 7th after sowing and followed at intervals of 14 days, or through the dripping irrigation system in the commercial greenhouse where the first treatment was performed immediately after planting while next two followed at 30 days intervals. Significant reduction in disease incidence was achieved through two or three subsequent treatments: total numbers of wilted and dead plants were reduced by 50% and 73%, respectively, in the experimental system, and by 60% and 40% in the commercially conducted experiments. This study suggests innovative biocontrol approach using preparation of multicomponent bioagent spore suspension directly in the fertigation solution, and application to the plants through dripping irrigation system.