Control methods of apple rust

Apple rust is also called red star disease. It often causes apple trees to shed leaves, drop fruit and break branches. Because the disease is a parasitic disease, it is more serious only in areas where the host exists.

(1) Symptom Apple Rust can damage green shoots such as tender leaves, petioles, new shoots, young fruits and fruit stalks. When the leaves are sick, they begin to produce bright orange spots on the front of the leaves, and then expand. The color of the lesion is dark in the middle, shallow in the periphery, and many orange particles (sex spores) are formed in the central part. When the weather is wet, they will secrete yellowish mucus. Later, the sexual spore apparatus gradually turned black, the front of the lesion was sunken, the mesophyll of the affected area was hard, the back of the leaf lesion was raised, and clusters of yellow-brown hairy rust spore apparatus grew, containing a large number of rust spores.

Petiole, fruit stalk and twig are diseased, and the diseased part is orange and yellow, protruding into a spindle shape, on which sexual spore apparatus and rust spore apparatus are formed. In the middle and late stage of new shoots, the diseased spots are sunken, cracked and easily broken; Young fruits often occur near the calyx depression, forming orange-yellow circular spots, about 65438±0cm in size, which turn brown in the later stage, with fruiting bodies in the center and hairy rust fruiting bodies around them.

In July and August, induced spores formed on apple trees began to infect Sabina vulgaris. At first, pale yellow spots appeared on needles, axils or branchlets, then the diseased parts swelled slightly, and even spherical galls with a diameter of 3 ~ 5 mm were formed. In the next spring, the pathogen broke through the host epidermis, revealing reddish brown, conical or flat wedge-shaped angles, which showed a cockscomb-shaped fluctuation. At this time, the swelling of the affected part is more obvious, and even a nearly spherical structure can be formed around the branches, and the largest diameter can reach15 mm. After the rain, the horn absorbs water and expands, becoming an orange colloidal block, which looks like a flower. (2) Occurrence regularity: The pathogen of apple rust is a parasitic fungus. The main host is juniper, others are juniper, juniper, juniper, juniper, juniper, juniper, juniper, juniper, etc. The pathogen overwinters in the galls on the host branchlets as hyphae. The winter spore horn was formed in the following spring, and then when the air was humid, the winter spore horn swelled with water, sprouted and produced a large number of basidiospores, which spread to apple trees with wind and rain, infected apple leaves, petioles and young fruits, and formed sexual spores and rust spores on the diseased spots. When the rust spores matured, they spread to juniper branches with the wind and invaded juniper branches. The occurrence of diseases is greatly influenced by climate. Apple is warm, rainy and windy from bud stage to young fruit stage, and diseases are easy to occur and spread. (3) Prevention and control methods ① Eliminate the source of bacteria.

Thoroughly eradicate host plants such as Sabina vulgaris near the orchard. If it can't be eradicated, the diseased branches should be cut off in winter and burned centrally. When the fruit tree buds germinate to young fruits, spray 2 ~ 3 Baume sulfur mixture 1 ~ 2 times. Don't plant juniper trees as host trees within 5 kilometers outside the newly-built orchard. ② Chemical control.

Spraying bactericide 1 ~ 2 times after apple trees germinate to young fruits to prevent the invasion of germs. The better medicament is 1: 2: 200 times bordeaux solution, or 1000 ~ 1500 times triadimefon WP, or 800 ~ 1000 times 70% thiophanate-methyl solution, or 80000 times 40% Fuxing EC.