A method and apparatus for controlling weeds using concentrated solar energy is disclosed. Solar energy may be concentrated by Fresnel lens and directed by manual or automated methods at surfaces of weed plants to heat portions thereof causing damage. Shutters or other devices may be used to direct, and control intensity of concentrated, solar energy, such control preferably applied before significant concentration. In some embodiments, solar energy concentration apparatus may be integrated with ground, air, or water vehicles which may use solar photovoltaic cells for electric power for propulsion and other purposes. Vehicles may use global positioning satellite (GPS) receivers or other methods and apparatus, including video cameras, for navigation and selection of areas (e.g., row middles), plants, or portions of plants to be exposed to concentrated solar energy. Air vehicles may use hydrogen gas electrolyzed from water condensed from humid air to replenish hydrogen gas lost from containment vessels.