Nachrichtenblatt des Deutschen Pflanzenschutzdienstes (2001) 53, 113-119

Verena Rappaport and Bernd Freier (2001)
Erprobung eines flexiblen Schwellenwertkonzepts für Getreideblattläuse an Winterweizen unter Berücksichtigung der natürlichen Gegenspieler
[Testing of a flexible threshold model for cereal aphids on winter wheat in consideration of natural enemies]
Nachrichtenblatt des Deutschen Pflanzenschutzdienstes 53 (5), 113-119
Abstract: The present reliable threshold model for cereal aphid control in winter wheat is based on an infestation monitoring during the end of flowering. The control threshold of 3 to 5 aphids per ear and flag leaf considers that generally the infestation evidently increases in the following and the exceeding of this threshold causes yield losses. In the present study, a flexible threshold model was used that considers different infestation trends due to various influences, in particular by beneficials. Therefore, the threshold was extended to a range from one to ten aphids per ear and flag leaf. The flexible model was tested in four locations in Germany (Flaeming, Westfalen, Magdeburger Boerde, Mitteldeutsches Trockengebiet) in 1994 to 1996 using a scenario catalogue and making weekly countings on the density dynamics of aphids and their natural enemies. While using simple threshold led to two miscalculations (one against and one in favour of a chemical control measure) in the 11 investigated fields, the application of the flexible threshold model led to right decisions in all cases. However, the aphid density increased over the injury level in only two cases, and over the economic threshold in only one case.
Farmers in all five locations successfully tested the flexible threshold model. On the base of the investigations and experience over three seasons, the methodological conception was simplified for use by farmers. It provides for both a counting in a line to the field centre and assessments of the occurrance of aphid predators by means of a 1-m² counting frame. The flexible approach is very appropriate, with regard to integrated plant protection, but, it won't be easily implemented in practise because of the special handling and low expectation of an economic effect.
(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): Bernd Freier

Research topic(s) for pests/diseases/weeds:
thresholds/decision-support systems

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Sitobion avenae	Wheat (Triticum)	Germany
	Rhopalosiphum padi	Wheat (Triticum)	Germany
	Metopolophium dirhodum	Wheat (Triticum)	Germany