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Abstract

Control of bottom rot on lettuce caused by Rhizoctonia solani with commercial biocontrol agents and a novel fungicide.

Bottom rot, caused by Rhizoctonia solani, is a problem in commercial letttuce production in Germany. Chemical fungicides can control the pathogen, however the efficiency is often low and the legal regulations restrict use. The objective of the study was to test the effectiveness o the biological control agents (BCAs) FZB24®, Phytovit®, Mycostop® and Prestop® against R. solani on lettuce. A new fungicide (BAS 516 00 F) was included in the experiments. The effects of the BCAs and the fungicide were tested in a leaf-disc bioassay, in climate chamber experiments and in a field trial.
In the climate chamber experiments, the disease Inhibition effect of the bacterial BCAs FZB24® and Phytovit® varied with disease pressure and application frequency. Both products were able to reduce significantly the disease incidence (Dl) only under conditions, which limited pathogen development. In consideration of all experiments, the fungal agent Prestop® provided the best control effect in
comparison to the BCAs. In the field, the level of disease suppression by Prestop® was as high as provided by a single application of BAS 516 00 F. However, the reduction ofthe Dl and the disease severity (DS) were not acceptable under conditions favourable for the pathogen. The fungicide BAS 516 00 F effectively controlled bottom rot in all tests. In the field experiments, two applications were more effective than a single application and provided acceptable control of the pathogen. The results indicated that treatment with BAS 516 00 F is a solution to suppress R. solani in the production of lettuce.



Grosch, R.; Koch, T.; Kofoet, A. 2004. Control of bottom rot on lettuce caused by Rhizoctonia solani with commercial biocontrol agents and a novel fungicide. Zeitschrift für Pflanzenkrankheiten und Pflanzenschutz 111 (6), 572-582.