EFFECT OF NITROGEN SUPPLY ON THE POPULATION OF EUROPEAN RED SPIDER MITE AND GREEN APPLE APHID IN AN IPM APPLE ORCHARD

Fertilizer experiments were conducted on cultivars of ‘Idared’ and ‘Jonagold’ on MM106 rootstocks with solid ammonium nitrate (dose of 0, 50, 100, and 200 kg/ha), on ‘Jonathan’ (with ammonium nitrate 0,50 kg/ha and multiple sprays – 4 times – with liquid urea 1%). In case of cv. ‘Jonathan’, the lowest green apple aphid (Aphis pomi De Geer) infestation was in the urea plot and the highest in the ammonium nitrate plots, with doses of 50 kg/ha.
In the case of cv Idared and cv. ‘Jonagold’ the results were variable: the lowest aphid level was found on the 50 kg/ha plots in 1995, this tendency was reversed in 1996. According to the available data, if the nitrogen concentration of the leaves of the fruit trees is high (1.8 – 2.6%) the egg production of the spider mites increase.
This effect is an important reason for the high population density of European red spider mite (Panonychus ulmi) in the commercial orchards.
Owing to the application of acaricides and insecticides harmless to the predatory mites, the population density of European red spider mite decreased below economical threshold levels, independently of the nitrogen concentration of the leaves.

IV International Symposium on Mineral Nutrition of Deciduous Fruit Crops

J. Papp, G. Jenser, A. Haltrich

IPM, apple orchard, nitrogen, aphid, spider mite

https://doi.org/10.17660/ActaHortic.2001.564.50