The invention discloses a broad-spectrum flower and fruit protector for plants and application of the broad-spectrum flower and fruit protector. An
active component of the broad-spectrum flower and fruit protector adopts
alginic acid oligosaccharide or an
alginic acid oligosaccharide derivative; the
alginic acid oligosaccharide is oligosaccharide obtained by connecting
mannuronic acid with
guluronic acid through a beta-1,4-glucosidic bond, and the molecular weight of the alginic acid oligosaccharide is 300 to 10,000 Da; the alginic acid oligosaccharide derivative comprises an alginic acid oligosaccharide
sulfuric acid derivative and an alginic acid oligosaccharide
phosphorus-containing derivative. The broad-spectrum flower and fruit protector is applied to increasing the flower protection and fruit setting rate in growing and developing processes of vegetables and fruit trees; the broad-spectrum flower and fruit protector is applied to the vegetables and the fruit trees. By the use of the broad-spectrum flower and fruit protector, the fruit setting rate can be increased by 40 to 80 percent, and particularly, the fruit setting rate of the vegetables is increased by 30 to 80 percent. A
drug with the alginic acid oligosaccharide serving as a main component has the advantages of safety, nontoxicity, low cost, small application amount, environment friendliness, durable effect and the like. The broad-spectrum flower and fruit protector for the plants is used for carrying out application, seed soaking, root dipping, root
irrigation and the like on crops such as the fruit trees, so that the flower and fruit protection capacity of the crops can be improved, and the broad-spectrum flower and fruit protector has an outstanding effect on increase of the
crop yield and improvement of the quality.