Leaf Wetness Recorders

Leaf wetness recorders

The occurrence of infections caused by the scab fungus is not only effected by the temperature, but also by the duration of the leaf-humidity period. It is not so easy for market gardeners to determine this period ‘by eye estimation’. Consequently they will start spraying when ‘it would seem’ that the leaf have been wet for too long, just for the sake of assurance, but… expensive assurance indeed!

The DE WIT leaf-humidity recorder records the duration of the leaf-humidity period in the orchard, reliably and leaves no room for doubt, regarding when to spray and when not. That means:

  • Scab is combatted effectively – spray only when necessary!
  • Costs of spraying are saved because you don’t spray when it is not required!

The leaf-humidity recorder was developed in close consultation with :

  • The Royal Dutch Meteorological Institute
  • The Phytopathological Service
  • The Institute for Horticultural Engineering


The chart revolves in a clockwise direction. If the weather is dry, the stylus records on the margin of the chart.
The beginning of a rainy period (leaf-humidity) is indicated by a clear kink in the line. The fact is that the sensor shrinks when moistened; the sensor dries again (more or less quickly, depending on the weather conditions) and the stylus returns to its former position. The period ‘dry’ can now be read from the chart.

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