Macro- and Microelement Fertilizers Influence the Severity of Fusarium Crown and Root Rot of Tomato in a Soilless Production System

Host nutritional variables were evaluated for their effects on the severity of crown and root rot of tomato caused by Fusarium oxysporum f.sp. radicis-lycopersici . Tomato ( Lycopersicon esculentum Mill.) seedlings (cv. Bonnie Best) were grown in a pathogen-infested, soilless rockwool system in the greenhouse and were fertilized with a nutrient solution that was amended with macro- and microelements at various rates. Disease was evaluated after 2 weeks using an index of 0 to 4, and plant fresh weight was measured. Regression analysis indicated that disease severity was significantly increased by ammonium-nitrogen [NH 4 Cl, (NH 4 ) 6 Mo 7 O 24 , and (NH 4 ) 2 SO 4 ], NaH 2 PO 4 ·H 2 O, Fe-EDDHA, MnSO 4 , MoO 3 , and ZnSO 4 ·7H 2 O. Disease severity was reduced by nitrate-nitrogen [Ca(NO 3 ) 2 ·4H 2 O] and CuSO 4 ·H 2 O. Low rates of NH 4 NO 3 (39 to 79 mg·L -1 N) reduced disease, but rates above 100 mg·L -1 N increased it. Disease was not affected by MgSO 4 ·7H 2 O. In all cases, plant growth was inversely related to disease severity. Mineral fertilizers had no effect on nutrient solution pH. This information sheds new light on environmental factors that influence plant-pathogen interactions, and may be applied to develop a management strategy for Fusarium crown and root rot based on host nutrition.