Analysis of leaf wetness duration dynamics on a sunflower (Heliantus annuus L.) canopy

Leaf wetness duration (LWD) is an important agrometeorological variable, responsible for the development of many plant pests and diseases. Despite its importance, LWD is a variable which is difficult to measure since numerous sensor types exist, made in different materials and based on different principles, and its measurement procedure is not described in an official or unequivocal protocol. For this reason it is necessary to understand and firmly establish the dynamics of dew condensation and evaporation and the relations between leaf wetness and the agrometeorological variables that affect and cause this phenomenon. Comprehension of these dynamics will allow for overcoming the problems linked to the lack of a standard protocol for the use of sensors, with opportunity of setting up a model capable of determining leaf wetness duration based on the available agrometeorological and crop variables. The results of the research have demonstrated that there is a recognizable relationship between agrometeorological variables and their influence is statistically significant. Nevertheless, the relations found were not sufficient for enabling a precise determination of LWD. Moreover, the comparison between field measurements and visual inspections demonstrated that sensors tended to overestimate the number of wetness hours in comparison to the real data. These results revealed that LWD is a very critical variable and its variability is not easy to describe in detail.