Pear rust, also known as brachypterosis, is one of the most important diseases of pear trees. It occurs in areas where there are cypress plants near Nanguo Pear Garden. Pear rust does not harm apples and hawthorn. Pear rust fungus is the main parasite, and its main host is decantation, cypress, juniper and so on. Pear rust causes dryness of pear leaves, and the fruit is deformed and easily falls, affecting pear fruit yield and quality. In the future, with the development of street and gardening, the number of planting of cypress trees will increase, and pear rust will be increasingly aggravated. .

First, illness

The disease mainly damages leaves, young fruit and shoots. The leaves suffer damage and begin to have distinctive orange-yellow round spots under the leaves. The number varies. Later when the lesions spread to 4-8 mm in diameter, the central part of the diseased part will have tiny orange-yellow needles, ie the spores of the pathogen. Device. When the weather is wet, it overflows with pale yellow mucus. This mucus is composed of a myriad of sexual spores, and the mucus becomes black after drying. The lesions became thicker, with depressions on the front, and the dorsal surface of the lesions bulging. The grayish yellow hairs grew on the bulge and were about 4–5 mm long. This was a pathogen spore. One lesion grows 10 to several dozen hairs. When the rust device matures, the tip breaks and yellow-brown powder is emitted, which is the rust spore of the pathogen. In later stages, the disease department became dark and the leaves were coked, which caused early defoliation.

The young fruit suffers an orange-yellow lesion on the fruit surface, with small black spots and hairs on it. The growth of the diseased department is stagnant, and it is easy for the pear fruit to become deformed and fall off early.

When new shoots, fruit stems, and petioles were damaged, the symptoms were almost the same as those of fruit damage. Spermatozoa and rust organs were also found on the lesions, and later the disease was cracked. Damage to petiole and stalk can easily cause defoliation and fruit drop. After the shoot is damaged, the diseased part often dies and is easily broken by the wind.

After the host host was infected, a pale yellow spot appeared on the needles, leafhoppers or twigs, which rose slightly. In March of the following year, the bacterium broke through the epidermis and gave birth to brown horns, which are the fungal winterspores. The phosporus horn is 5 mm high and 2 mm in diameter. After water swelling, it becomes a yellow lingual jelly mass.

Second, the pathogen: Pear rust is a fungus, belongs to Basidiomycotina, bacteria need to complete its life history in two different types of hosts. Sporulators and rust generators are produced on pear trees. Winter stalks are produced on the host hosts such as cypresses and cypresses. If Papaver cypress, Cypress, etc. are transferred to the host, Pear rust cannot complete the life history.

Third, the occurrence of pear rust law: Pear rust bacteria with perennial mycelium, in the winter sickle disease organizations. In March of the following year, the teliosporus angle began to appear. When the temperature is 14-15 °C, the maturation of teliospores takes about 10-20 days. The germination period of cysts in children is from late March to early May, mainly from late April to mid-April. After the rain, the winter spores can germinate, produce the burden of spores, spread by wind and rain. From the buds of pear trees to young fruits, they are all susceptible. When the basidiomycete spores fly and fall on young leaves, shoots, and young fruit, the spores enter directly from the epidermis invader after germination, and may also invade from the stomata. Infestation of the hand for 10 days caused plaque formation. Generally, leaves of 1- to 9-day-old leaves have the most affected leaves, 13-21 days of infestation are lighter, 25 days after leaf expansion, and 6 to 15 days of incubation, and then grow on lesions. Sporulator, producing spores in sexual spores, overflowing from the sporoderm orifice with mucus, and passing insects and rain to other sexual spores. After being subjected to fineness for about 25 days, a rust device is formed on the back of the leaves. . The rust spores produced in the rust device spread from the end of May to the beginning of July to the cypress, invading the cortex and wintering the mycelium in the diseased part.

Pear rust bacteria have no uredia spores stage, and no repeated infection occurs. Only a short time a year, the spearmints infected the pear trees. The severity of the disease is related to the planting of cypresses around the pear orchards, the number of grades and the distance, especially the distance between 2.5 and 5 km from Liyuan. In the presence of cypress, whether the disease can be severe or not depends on the climate. If the pears are warm and rainy during the leaf development and young fruiting period, a large number of teliospores germinate, the pear rust occurs seriously; if the weather is dry and there is no rain, the teliospores cannot germinate, and the germs are inhibited.

Fourth, pear rust prevention and control methods:

(1) Removal to the main host: Complete removal of cypress trees within 5 km from the orchard is an effective method to prevent pear rust. In the establishment of a new pear garden, consideration should also be given to the presence or absence of cypress in the vicinity. If there are sporadic cypresses, they should be completely removed.

(2) Spraying the main host: If the cypress near Liyuan is not suitable to remove, spores may be sprayed on the cypress. Spray time before the pear tree germination, Toxoplasma gondii has matured, but when the end of the gel is appropriate, you can basically control the incidence of pear trees, the use of drugs Baumi 3-5 degrees lime sulfur or 40% 100% Formamide 100 arsenic.

(3) Spraying Pear Trees: When spraying Papaveria jasminoides can not completely prevent the disease, the pears must be sprayed to prevent the infection of the basidiospores. Pear tree spraying time should be within 25 days after the sprouting of the pear tree to the exhibition leaf, that is, in the period of spores spread and infested, spray once every 10 days, and even spray three times. Pharmacy type, available 25% Trifenin WP 1000-1500 times or 65% zein Zn wettable powder 500 times, 50% sulfur suspension 200 times, 50% eutectic wettable powder 800-1000 times

(4) Clear the garden thoroughly to reduce overwintering pathogens and pests. The fruit, disease, and defoliation on pear trees often harbor a variety of pathogens and pests. Therefore, after falling leaves in autumn, combine the winter pruning to cut out the stale fruit and diseased branches of the tree, and timely clean the fallen leaves, fallen fruits and branches and burn them together.

(5) Strengthen management of pear orchards, increase tree vigor, and increase pest resistance. One is to deepen the soil in autumn and winter to remove weeds in order to improve the sanitary conditions of pear orchard and eliminate the overwintering worms and eggs. The second is to combine deep plowing with autumn and winter pears and apply base fertilizer once a year (based on phosphorus and potash fertilizer or organic fertilizer. ), Drainage and irrigation in a timely manner; Third, dry lime (diluted 1:3 lime, water), to prevent pests spawning, insect pests, no pests and disease prevention.

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