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Pesticide dose adjustment for tree-fruit spraying

Background

In early 2006, East Malling Research held a series of HDC workshops to inform apple growers of an important new approach to dose adjustment for spray applications to dwarf dessert and culinary apple orchards.

  • Extensive work had shown that when sprays are applied at a fixed recommended dose as recommended on pesticide labels, there is a greater than 5 fold variation in average pesticide deposits between different apple orchards at different growth stages due to variation in tree size and canopy density.
  • Canopy density and tree height combined explained over 90% of deposit variation from one orchard to another.
  • So there is opportunity for making significant dose reductions in orchards with less dense canopies and/or smaller trees than the standard.

The PACE (Pesticide Adjustment to the Crop Environment) system of adjusting the dose according to tree height and canopy density was developed to give approximately constant tree-average deposit across a wide range of different orchards throughout the season (HDC Factsheet 20/05 ‘Apple orchard spraying: Opportunities for dose reduction’). The original scheme, which covered only dwarf and semi-dwarf dessert and culinary apple orchards, has been simplified and extended to cover a wider range of pome and stone-fruit orchards.

The benefits of appropriate dose adjustment are:

  • Reduced pesticides residues on fruit
  • Reduced environmental and bystander contamination
  • Reduced operational costs by more efficient use of pesticide
  • Reduced aquatic buffer zones under a Local Environmental Risk Assessment for Pesticide (LERAP). Note that ¼ full-dose applications reduce the risk of non-target contamination from drift by 75% and can be used to reduce the aquatic buffer zones according to the Defra LERAP guide for broadcast air-assisted sprayers.

Many growers already make dose adjustments based on successful practice and on ad hoc trials with different orchard/product combinations. The new webpage provides a dose adjustment system based on soundly derived scientific measurements. There is the potential to apply pesticides from full-dose down to ¼ of the full-dose depending on canopy density and tree height.

Further information

Further information can be found on the PACE website http://pjwrc.co.uk. A specific webpage has been created to guide the users of tree-fruit spraying products through the process of dose adjustment (http://pjwrc.co.uk/DoseAdjustment.htm).