Flies cause irritation to farm animals, workers and staff. They transmit many diseases. Cows get stressed by the presence of flies and cannot eat, drink and rest peacefully. This creates a negative effect on their productivity. Reducing the fly population means less stress and less disease. DeLaval offers Fly String and Fly Sheets to control flies on your farm. The flies stick to DeLaval fly string, fly sheets and get killed immediately! They need NO electric power and are not poisonous.