Wireless sensor networks for precise Phytophthora decision support. D. Goense 1 , J. Thelen 2 and K. Langendoen 3 1 Agrotechnology and Food Innovations BV 2 Wageningen Agricultural University 3 Delft University of Technology Daan.goense@wur.nl Background. Precision Agriculture provides the optimal treatment for each production unit that can be distinguished and which can be individually treated in an efficient way. This agricultural practise is based on detailed information on the status of crops and soil. Most of this information focuses on techniques like soil mapping, yield mapping and remote sensing, which cover the spatial domain with more or less spatial resolution. The information is incidentally sampled and is therefore valid at the time the observations are made. Some of the processes like fertilization and especially crop protection require frequent updates in information. Sensor systems that are continuously present can deliver such information. Several research groups and companies are working on the development of “Smart Dust”. “Smart Dust” stands for a sensor, a processor and a means of communication that will be packaged into a few cubic millimetres in the future. It is expected that these devices will be available in six years at a cost of around one dollar apiece, although downsizing might not have reached the intended level at that time. Such wireless sensor systems can form a dense network and provide the possibility for continuous monitoring of relevant parameters in a dense grid for a reasonable price. In the Netherlands, high capacity communication and processing infrastructure is being developed for the LOFAR astronomical observation system (www.lofar.org ). This system is based on a new generation Low Frequency Array telescope, which is made up of a large number of small antennas spread over an area with a diameter of 350 km. These antennas are coupled in real time by the communication infrastructure. Precision agriculture is, together with geophysics one of the other disciplines that can make use of this infrastructure spread over the rural area. Objective. Research started to investigate the possibility of wireless sensor networks in agriculture and particularly that of microclimate monitoring with presently available wireless sensor technology. At the same time architecture will be developed to incorporate wireless sensors in an agricultural ICT infrastructure. The research objectives are: 1) to design an architecture for decision support systems in agriculture, based on wireless sensor networks as an extension of a rural communication infrastructure, 2) to investigate the distances over which radio signals will propagate in a crop canopy under varying conditions, 3) to determine accuracy of localisation techniques for sensor networks and 4) to obtain first results on micro climate monitoring. Requirements. The first application focuses on measuring the microclimate of a potato crop to deliver detailed information for the next generation of decision support systems for Phytophthora control. This involves measuring temperature and relative humidity in the crop canopy. As a