peer reviewedLeaf wetness duration (LWD) is an important factor influencing the occurrence of plant disease
epidemiology. Despite considerable efforts to determine LWD, little attention has been given to
study its variability within the canopy. The objective of this study was to evaluate its
spatiotemporal variability in wheat fields in a heterogeneous landscape. The spatiotemporal
variability of LWD was evaluated in a site close to Arlon (Belgium) during the period May to July
2006 and 2007. LWD measurements were made using a set of flat plate sensors deployed at
five different distances from a 18 m high hedge (5, 10, 20, 50, 100 m). Each set of two
sensors was placed horizontally close the flag leaf. In addition, we collected the amount of
dew water that deposited on rigid epoxy plates placed next to each sensors. Experimental
results showed that LWD measurements revealed substantial heterogeneity among sensor
positions. LWD is longer for sensors closer to the hedge mainly because of its shadowing
effect. 3 to 4 hours of difference was observed between sensors located at 5 m and those
located at 100 m, and besides, a significant quantitative difference (p < 0.0001) of dew
deposit was observed between area beside hedge and those placed at 100 m. In summary, this
study provides new information on how wetness is distributed on wheat leaves according to
the distance from a hedge. This leads to local microclimate conditions that will contribute to
the disease spatial heterogeneity