The use of organic certified compost to control soilborne diseases caused by Phytophthora spp.

Summary

Soilborne pathogens can cause serious damages to economically important crops. Control of these diseases has traditionally depended upon rotations and soil quality improvement strategies. Compost has shown a suppressive activity against soilborne pathogens, and its use may decrease the severity of root rot diseases, optimize waste recycling and increase yields in organic farming. An organic certified compost produced from biowaste, green and yard wastes in a composting plant in the North-West of Italy, has been analysed for its suppressiveness against Phytophthora disease. The organic certified compost has been compared with a conventional compost produced in the same composting plant and with a peat substrate. In the first group of trials, composts maturity and quality have been estimated using Wood’s End Lab’s “Solvita” Compost Maturity Test Kit, and germination and plant grown bioassays. In a second group of trials, the organic certified compost, has been assessed for its suppressive activity in greenhouse against Phytophthora nicotianae on tomato and Phytophthora capsici on zucchini. In a third group of trials, compost was used alone or enriched with microorganism of the fungal genus Trichoderma and the suppressiveness in open field towards Phytophthora capsici on pepper has been evaluated. Organic certified compost quality was comparable to peat quality. Organic certified compost showed to have a disease suppressive activity in greenhouse, compared to peat amendment, against Phytophthora spp.. The disease suppresiveness of certified compost reached 76% in the case of tomato. The results were not confirmed in open field, even when compost was enriched with Trichoderma spp.