Nachrichtenblatt des Deutschen Pflanzenschutzdienstes (2007) 59, 107-112

Peter F.J. Wolf, Ricarda Lenz, Katja Baron and Joseph-Alexander Verreet (2007)
Quaternäres Integriertes Pflanzenschutz-System für den Echten Mehltau der Zuckerrübe. II. Prüfung von epidemieorientierten Bekämpfungsschwellen als Indikatoren des Fungizideinsatzes
[Quaternary Integrated Pest Management concept for powdery mildew in sugar beet II. Evaluation of epidemic oriented thresholds as indicators of fungicide treatments]
Nachrichtenblatt des Deutschen Pflanzenschutzdienstes 59 (5), 107-112
Abstract: Powdery mildew, caused by Erysiphe betae (Vanha) Weltzien, may be assumed as an important leaf disease in sugar beet growing areas of Germany. Although the causal agent is mainly adapted to arid climatic zones, the disease is appearing every year, where the extent of infection is mainly dependent on weather conditions and susceptibility of cultivar.
Next to the prediction of disease onset and loss prediction, the evaluation of epidemic oriented thresholds is a main part of the Quaternary IPM-concept to control powdery mildew in sugar beets. For evaluation of thresholds, field trials were conducted in Germany (n = 49), particularly in growing regions of Lower Saxonia and Bavaria. The field trials were arranged in randomized plot design with four replicates per treatment. The evaluation of treatments was aimed to pinpoint fungicide sprays most effective. Therefore efficacy of treatment timing was assessed in relation to the epidemic development. Comparison of treatments comprised fungicide sprays carried out from disease initiation till later stages of the epidemic. Additionally, the assessments were performed in relation to an untreated and a healthy control - the latter was three times treated according to a spray regime with three to four week intervals. The effect of different spraying timings was measured by the potential of disease and yield loss control.
Loss of recoverable sugar yield was 10-15 % at the maximum and occurred after early disease onset at the end of July resp. beginning of August. Disease control was most effective after timing of fungicide sprays during the period of disease initiation. This result was confirmed by loss reductions on the level of the healthy control. Thus, as a threshold for a first treatment, the stage of a 50 % plant infection frequency is defined, or in other words, when every second plant is showing symptoms of powdery mildew.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
(original language: German)
Database assignments for author(s): Joseph-Alexander Verreet

Research topic(s) for pests/diseases/weeds:
control - general
damage/losses/economics

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Erysiphe betae	Beet/sugarbeet (Beta vulgaris)	Germany