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First, pear rust damage symptoms
The main damage leaves, shoots and young fruit. The leaves were affected. The front of the leaf formed orange-orange round lesions, and dense orange-yellow needles were small spots, ie sexual spores. When it is wet, spills pale yellow mucus. That is, sexual spores, and late small particles become black. The lesion corresponds to a thickening of the dorsal surface of the leaf, and grows from grayish yellow hairs, ie rust. After the hairs broke up, a yellow-brown powder was emitted, which was brown rust. Fruit, fruit stems, new shoots, petiole victims, the initial lesions are similar to those on the leaves, and later on the surface of the same lesions produce hair-like substances.
After the host was transferred to the host, Bai was infected and in March of the following year, red-brown, cone-shaped horns (ferniospores) were seen on the needles, leaves or branchlets. After the spring rain, the phosporite swelled into an orange-yellow lingual jelly mass.
Second, pear rust disease conditions
1. The host's host rust bacterium has the characteristic of turning host parasites. It must be overwintering on host trees such as cypress, cypress and European juniper to complete its life history. If there are no cypresses, cypresses, etc., within a radius of 5 km around the pear orchard, pear rust generally cannot occur.
2, climatic conditions Spring pears sprout budding leaves, if there is rainfall, the temperature is appropriate, teliospore germination, there will be a large number of spores scattered spread, the disease must be heavy. At this time, the wind force and the wind direction can affect the contact between the basidiospores and the pears, which has a great influence on the severity of the disease. If the temperature in the middle and early March is high, the teliospores will mature earlier. After the winter spores mature, if there is more rain, the winter spores will germinate. At this time, the pears have not yet germinated, and the spores produced by the teliospore germination have not invaded the young pear tissues. The chances are light. If pears are dry before they germinate and the temperature is low, the winter spores do not germinate. After the pear leaves have high temperatures, heavy rain, and large numbers of winter spores, pear rust occurs. Therefore, the level of temperature in the period from February to March and the amount of rain from late March to late April are important factors affecting the severity of pear rust.
3. The number of overwintering pathogenic bacteria in the presence of cypress, cypress and other trees, such as in the host host trees such as cypress, cypress, etc., the host bacteria on the base, the initial infestation source is sufficient, pear rust occurs, On the contrary, the incidence is lighter.
4. Different species and varieties of resistant pears have different resistance to rust. Generally, Chinese pears are most susceptible, Japanese pears are the second, and pears are the most resistant.
Third, pear rust prevention measures
1. Clear the main host to clear the host within 5 km of the orchard and clear the cypress and cypress, which is the most effective and effective measure to prevent pear rust. When constructing a new pear orchard, consideration should be given to whether there are any other nearby host plants such as cypresses and cypresses. If there are any, it should be removed. If there is a large number and it cannot be removed, it should not be used as a pear garden.
2. Eradicate overwintering germs such as pear orchard near scenic areas or green areas. When cypress and other host hosts cannot be removed, bactericidal pesticides should be sprayed on cypress trees to eliminate overwintering germs and reduce the sources of infection. That is, in the middle and early March (before the pears germinate), the host of the cypress and other hosts is first cut off the sickness, and then 4-5 Baume degree lime sulfur is sprayed to suppress the germination of the winter spores. In the heavy-infested areas, a fungicide was sprayed on the pears during leaf development and after flowering to prevent the infection of the spores. The agents were 1:2:200 Bordeaux and 15% triadimefon.
3. Humidification and Drought Resistance Each year from mid-May to the end of June, in case of continuous high temperature and arid climate, it is necessary to conduct humidification and drought relief in time. The orchards with irrigation conditions must perform irrigation in the whole garden. No irrigation conditions can be applied to each fruit tree sooner or later. Spraying water to increase the humidity of the orchard, spraying a new high-fat membrane after spraying, using film-forming substances to protect the soil and the tree's own nutrient and water is not easy to evaporate, and at the same time prevent external climate, pesticides against the fruit and reduce the disease rate of pear rust .
4. Fruit bagging The entire fruit is bagged within 40-50 days after flowering. On the one hand, this measure can improve the appearance quality of fruit and reduce the pollution of pesticides and harmful dust on fruits. On the other hand, it can effectively prevent the occurrence of pear rust.
5, pears spraying control in the pear tree spraying, should be mastered from the bud to the exhibition of leaves 25 days after the spread of infection, the proliferation of spores carried out. After the general pear tree leaves, if there is rain, and found that cypress trees produce phosporic horn, spray 1 times 20% triadimefon EC 1500-2000 times liquid, spray again every 10-15 days, can basically control the rust occur. If it cannot be controlled, it is necessary to add 20% fluorine fluoxazolium prochloraz 800 times solution. If it is not controlled in time, the lesion may appear on the surface of the leaves after the onset of disease (sexually transmitted spores), spray 20% Triadimefon EC 1000 times, plus high-tech 20% fluorosilicone prochloraz 800 times, can play a very good therapeutic effect. From the beginning of pear leaf to the end of May, it can be sprayed 1:2:200-240 times Bordeaux mixture; or 70% of Dasheng M-45800 times to protect. If the disease has already occurred, it can spray 20% triadimefon 600 times solution, 12.5% ​​diniconazole 3000 times solution, and 10% fluorosiliconazole 1200-1500 times solution to prevent and cure. Attention should be paid to the flowering period so as to avoid phytotoxicity.
Pear rust prevention and control method
Pear rust is also known as brown spot disease. Pear rust is caused by perennial mycelium forming bacillary dysentery on cypress twigs, and in late spring, phosporus horn is formed in March. The spores of cysts produce a large amount of spores. The spores spread to the weather. On the pear tree, it invades the leaves of the pear, but no longer invades the cypress. China's north and south fruit areas have occurred, but generally do not cause serious harm, only in the vicinity of the orchard planting cypress trees more scenic areas and urban suburbs are more harmful. In addition to harming pear trees, it can also harm hawthorn, avocado and paste stems.