INFLUENCE OF WATER VOLUME AND DROP SIZE IN RASPBERRIES

The main disease in raspberries is Botrytis fruit rot. For a good control, three or four treatments with chemicals during the flowering period are needed. A questionnaire in 2010 revealed that raspberry growers use a wide range of water volumes (300 to 1000 L/ha) and also apply with different nozzles, resulting in different drop sizes. In 2010 we started a project to optimize chemical treatments in raspberries. We compared the application of 300, 600 and 900 L water per hectare with coarse and fine drop size respectively. We measured the deposition of the chemicals on leaves and evaluated the biological efficacy against Botrytis fruit rot and two-spotted spider mites. The deposition trials showed more chemicals on the leaves with the lowest water volume (300 L) and with coarse drop size. There was no correlation between the deposition on the leaves and the control of Botrytis fruit rot and the spider mites. All treatments gave a good result in controlling Botrytis fruit rot, with no differences among the variants. The spider mites live on the bottom side of the leaves. None of the water treatments controlled spider mites efficiently. In further trials, we used a water volume of 1800 L per hectare and the air volume was increased from 25500 to 35800 m³/h; these trials were more efficacious.