Jujube rust mite

Also known as jujube rust mite, jujube bud mite, and jujube gray leaf. This pest is distributed throughout the winter jujube producing areas of Shandong Province and has become one of the main pests on jujube trees.

After jujube trees are damaged, the leaves curl, the leaf color turns gray, flowers and fruit drop heavily, and then the leaves fall, causing a second flush of leaves; the fruit surface develops rust spots, causing substantial yield reduction and declining quality.

The number of generations of this pest varies with geographic location. In the Zaozhuang area of Shandong, there are about 10 generations per year. It overwinters as adult mites and nymphs in the scales of jujube spurs or in the bark crevices of jujube branches. It is characterized by many generations, rapid reproduction, high mortality, strong stress resistance, rapid spread, wide distribution, and being difficult to control.

In spring, when jujube buds sprout, the overwintering mites begin to become active and gather to feed. When their density is low, they mostly concentrate on the underside of jujube leaves along both sides of the three main veins. Their activity radius is extremely small, but they have the habit of migrating with the wind, so they spread relatively quickly. In mid-June, the damage peak is reached. One 8 cm jujube leaf can have 100 to 200 mites, and individual leaves can have nearly 400 adult mites and nymphs. Mite activity can be found on both sides of the leaf, but mainly on the underside. This forces the leaves to curl upward longitudinally, and the leaves turn from green to gray and become brittle. According to data from relevant jujube research institutes, when the temperature is high and atmospheric humidity is relatively low, it is unfavorable for the development of this center. In July and August, the mites move from the leaves to the bud scales to pass the summer and then overwinter. On jujube trees with severe jujube bud mite infestation, the leaf graying rate reaches 70%, the leaf curling rate 50%, the rusted fruit rate 20%, the fruit drop rate 10% to 15%, and yield reduction 30% to 70%. Therefore, the jujube bud mite has become one of the only mite species in jujube areas that is difficult to control.