Control of brown root rot caused by Phytophthora cryptogea in the hydroponic forcing of witloof chicory (Cichorium intybus var. foliosum) by means of a nonionic surfactant

The surfactant Atplus MBA1301, a monobranched C13 alcohol alkoxylate, was tested for its efficacy to control brown root rot, caused by the zoosporic pathogen Phytophthora cryptogea in the hydroponic crop production (forcing) of witloof chicory. In in vitro experiments, 4 μg ml−1 Atplus MBA1301 inhibited sporangia development, while motile zoospores of P. cryptogea ceased motility and lysed within 1 min upon exposure to 10 μg ml−1 surfactant. When the pathogen was artificially introduced in pot assays or in a mini hydroponic system using a mycelial suspension and/or zoospores as an inoculum, a concentration of 10 μg Atplus MBA1301 ml−1 nutrient solution was sufficient to obtain a good control. Root hair development appeared to be negatively correlated with disease incidence and disease severity and can be used to monitor the brown root rot disease in a nondestructive way. The surfactant Atplus MBA1301 was also tested in a commercial setting under growers' conditions. Organically grown witloof chicory roots of the cultivar Vintor were artificially infected with 102 zoospores ml−1. A disease incidence of 90.8% was recorded in the infected control. Only 1.3% of the roots showed symptoms in a treatment with 10 μg ml−1 Atplus MBA1301. This is not significantly different from the healthy control, which remained free of symptoms. It can be concluded that Atplus MBA1301 has excellent potential to control Phytophthora brown root rot in witloof chicory hydroponic forcing.