The UK PACE Scheme for Adjusting the Dose to Suit Apple Crops

C. V. Cross, P. J. Walklate


Our research has shown that when sprays are applied at a fixed recommended dose rate as prescribed on pesticide labels, there is a greater than 6-fold variation in average pesticide deposits between different apple orchards at different growth stages due to variation in tree size and canopy density. In the work, LIDAR (Light Detection and Range) was used to rapidly characterise tree canopies, a breakthrough which enabled such relationships to be investigated and quantified. The work showed that canopy density accounts for 80% of this variation and canopy density and tree height combined account for over 90% of the variation. If the label recommended dose rate gives a certain average deposit which is effective on taller trees with a denser canopy, designated as a standard, then the same average deposit which can be achieved with a lower dose rate on smaller or less dense trees will be equally effective. Thus, there is an opportunity for making significant dose rate reductions in orchards with less dense canopies and/or smaller trees than the standard. In spring 2006, the PACE (Pesticide dose rate Adjustment to the Crop Environment) system of adjusting the dose rate according to tree height and canopy density so that constant average deposits are achieved in a wide range of different orchards throughout the season was launched in the UK. A series of seminars and training courses for growers were held which were attended by over half the industry. In this paper, the five steps that growers were instructed to follow to determine an appropriate dose adjustment are given including the crucial step where pictograms of apple trees of varying canopy density, reconstructed from LIDAR scans, are used to visually assess canopy density. Attendant advice on water volumes, spray quality and spray cover is also presented together with a worked example. Further work is being done currently to extend the scheme to cider apples and other fruit tree crops.

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