Abstract: A cultivator for damaging undesirable plants in an agricultural setting is disclosed. Embodiments of the cultivator include one or more energy emitters that stress target biological material, and the energy emitters in particular embodiments stress plants in at least two different ways, such as imparting light at certain wavelengths that cause dual effect stressors to the plant, such as heat related stress and photochemical stress similar to a sunburn. Some embodiments include a focusing system that spreads out narrow light beams and/or brings multiple light beams together at a point that is outside the cultivator. Some focusing systems cause multiple light beams to initially diverge before converging. Some embodiments utilize unusually large mirrors to capture, for example, multiple light pathways, and direct them to the target. Advantages include the ability to accomplish weeding and/or thinning with very low overall power consumption while moving quickly through a field.