Abstract: An infrared thermometer has a field of view selected so that the temperature of the crop growing in a field is accurately measured. The infrared thermometer may be mounted on a support pole in a field to substantially continuously monitor the foliage temperature of the growing crop. In one preferred embodiment, the infrared thermometer comprises and instrument housing structure provided with an infrared telescope mounted on a turntable that scans through an angle of the field, while an electronic circuit simultaneously integrates the output of the infrared telescope. The angle to be scanned is selected by the user in accordance with his needs. In another embodiment, the infrared thermometer comprises a novel sensor head block including an aperture which provides a wide, elongated oval field of view for an infrared sensor provided therein. In both embodiments, the elongated oval field of view has a width that is at least four times its height.