EFFECT OF PHYTOSANITARY METHODS ON PHYTOSEIIDAE IN WALNUTS ORCHARDS IN THE SOUTH EAST OF FRANCE

A scientific investigation was made in 1996 and 1997, by the Walnut Experimental Station in Rhône-Alps (S.E.Nu.R.A) and the French Plant Protection Service in Rhône at Lyon (S.R.P.V.), of more than 80 orchards in Rhône-Alps area (France). This investigation aimed to know the mite populations (phytophagous and his predator) and to confirm the impact of the insecticide treatments on these populations. Five classes of orchards were made according to the type of product which has been used on the main pest (codling moth) : Class 1 : Economic orchards : no treatment ; Class 2 : Organic orchards : they respect the organic rule and they use the granulosis virus ; Class 3 : Classic chemical products ; Class 4 : Classic chemical product and chemical product against spider mite ; Class 5 : Corrosive treatment: At least once with chloropyriphos ethyl + dimethoate.
During the season, we counted the total of Panonychus ulmi and the phytoseiid mites on the leaves. We collected the phytoseiidae and the identification of them were realised by the S.R.P.V. The result showed that :
– Over 90 % of the phytoseiidae are Euseius finlandicus, specific to the walnut tree.
– We can find them in all orchards groups.
– The number of phytoseiidae is inverse ratio to the number of P. ulmi. The increasing of P. ulmi population is more important when the treatments are noxious.
– Orchard groups one and two have any hardly problems with spider mite.
The phytoseiidae take care naturally of the P. ulmi population. When the treatments are appropriate and the active ingredients are well adapted, the mite problem seems to disappear or appear rarely.

IV International Walnut Symposium

A. Verhaeghe, D. Breniaux, C. Brazier

phytosanitary methods, walnut, codling moth, phytoseiidae, Euseius finlandicus,Panonychus ulmi, Phyllocoptes unguiculatus

https://doi.org/10.17660/ActaHortic.2001.544.46