Prevention and control of pear diseases and insect pests

pear scab

Symptoms can occur from flowering to fruit near maturity, which mainly harms all green tender tissues on pear trees, such as scales, leaves, petioles, leaf scars, new shoots, flower organs and fruits. Its main feature is the formation of obvious black mold layer in the affected area, much like mold smoke. Moldy spots are produced at the base of infected calyx and pedicel. The disease at the base of leaf cluster causes inflorescence and leaf cluster to wither and die. When the leaves are infected, polygonal or nearly round faded macula will appear on the front, and radial mildew layer will be produced on the back of the leaves. Small veins are the easiest to grow, and when the disease is serious, it will cause a lot of leaves. The new shoots were infected with spindle-shaped lesions, and the cortex of the affected parts cracked in the later stage, showing rough scabs. Most young fruits fall off early or the diseased parts lignify to form deformed fruits. Many scabby pits are formed when the big fruit is infected, and cracks often appear. Some diseased spots are radial black spots, and the wounds of diseased spots are often infected by other saprophytic bacteria, which leads to the whole fruit rot.

The pathogen Venturia Nashikola Tanaka et Yamamoto is called pear scab and belongs to Ascomycetes. It mainly harms China pears and Japanese pears, while pear black shank mainly harms western pears. Ascomycetes of pear scab were formed on the overwintering diseased leaves, which became the primary infection source of the following year. Ascomycetes are oblate or round and black. The neck is fat and short, with pores and no bristles, with a size of 52.5 ~ 138.7 (micron), and the shell wall is black and leathery, consisting of 2 ~ 3 layers of cells. Ascomycetes are rod-shaped and clustered at the bottom of the shell of Ascomycetes. They are colorless and transparent, 35 ~ 60 (microns) long and contain 8 ascospores. Light brown, twin, dumbbell-shaped, big and small (as opposed to apple black star), with the size of 10 ~ 15× 3.8 ~ 6.3 (micron). The asexual state is filamentous fungi. Fuck, it's called pear scab, which belongs to semi-conscious fungi. Auricularia auricula growing on diseased spots is the conidiophore and conidia of fungi. Conidiophore is solitary or clustered, protruding from the host stratum corneum, inverted rod-shaped, dark brown, upright or curved, with many obvious spore marks. Conidia are light brown, oval or spindle-shaped, slightly pointed at the end, and are single cells with a size of 7.5 ~ 22.5× 5 ~ 7.5 (microns).

The pathogen of pear scab grew well on wort agar medium. It grows rapidly at 18 ~ 22℃, and spores can be produced in 6 ~ 7 days. If it exceeds 24℃, it is difficult to cultivate. Conidia germinate well in water droplets, and can germinate at 2 ~ 30℃. The optimum temperature is15 ~ 20℃, and the germination rate drops sharply above 25℃. The temperature of conidia formation is 65438 02 ~ 20℃, and the optimum temperature is 65438 06℃. In autumn and winter, ascomycetes form on fallen leaves.

Transmission route and pathogenic conditions: the pathogen overwinters on diseased bud scales, diseased fruits and diseased leaves or overwinters on fallen leaves in the form of hyphae or ascomycetes. In case of bad weather in winter, the germination ability of conidia is low, which is beneficial to the formation of sexual generations, and ascospores become the main source of infection. Spores of pathogen spread mainly through rain erosion and in pear orchards. The susceptible varieties, such as Yali pear, get sick first on the new shoots in early spring, and the diseased shoots are important reinfection centers. The fruits and leaves in the conical space under the diseased branches were seriously infected, and the "diseased bud branches" were the main infection sources of pear scab in the early stage.

Humidity is an important condition affecting the occurrence and prevalence of diseases. The spring rain is early and plentiful, and it rains in summer, causing serious diseases. In dry years, the disease is mild. The invasion of pathogen spores requires precipitation of about 5 mm or rainy days of more than 5 ~ 48 hours. The suitable temperature for conidia germination is 22 ~ 23℃, and the suitable range is 5 ~ 30℃. Pear trees have weak disease resistance at lower temperature. The lowest daily average temperature of pathogen invasion is 8 ~ 10℃, and the suitable temperature for epidemic is 1 1 ~ 20℃. The incubation period is 20 ~ 25 days in spring and 14 ~ 20 days in summer, and it is shortened at high temperature. Generally, diseased branches appear shortly after flowering, spread on leaves or fruits after 4-5 cycles, reach the peak in rainy season in July, and stop spreading after 10 months.

In addition, orchards or trees with low terrain, dense crown, poor ventilation and high humidity are prone to scab.

Selection of disease-resistant varieties by control method (1). There are great differences in disease resistance among pear species and varieties. Generally speaking, pears from China system (Pak Lei system and Qiu Zi system) are the most susceptible to diseases, followed by Japanese pears and western pears. The varieties with serious diseases are Yali pear, QiuPak Lei pear, Beijing pear, Gai Hua pear and Anli pear, followed by Laiyang pear, Changshan crisp pear and Xuehua pear. Honey pear, perfume pear, fetal yellow pear, western pear and Bali pear have strong disease resistance. (2) eliminate the source of the disease. In late autumn and early winter, leaves and fruits are removed, and diseased branches are removed by pruning before pear germination in early spring. During pear bud expansion, 5-7% urea solution or sulfuric acid plating solution plus 0. 1-0.2% amobam solution is used for centralized burning or spraying branches. Remove diseased branches and clusters at the early stage of the disease. In mid-May, the ratio of width to branch diameter is 1: 10, and it reaches xylem. The prepared medicinal tetracycline tablets can be canned and peeled, and then wrapped tightly with plastic strips, which can effectively prevent and control pear scab. (3) chemical control. Spraying 3000 times of 12.5% diniconazole wettable powder before and after flowering or bagging of pear trees has obvious control effect. You can also spray 2500 times of 10% world high water dispersible granules before and at the beginning of the disease, and spray 3000 times or 4000 times or 600-800 times of 80% basic copper sulfate wettable powder or 350-500 times of 30% and 35% basic copper sulfate suspending agents every 10 day in years with less rain. Oil emulsion (acaricide): mancozeb: water = 10: 1: 500 can be selected for varieties sensitive to bordeaux mixture and copper preparation, which can effectively control pear scab and pear psyllid. In addition, 70% Guoerkang superfine wettable powder1500 ~ 2 (target solution or 800 times solution of 50% carbendazim wettable powder and 250 times solution of 25% carbendazim wettable powder) can also be selected. When the rainfall is greater than 10mm after pear fruit dropping, 800 times of Pujunke wettable powder or 2000 times of 12.5% Teflon wettable powder can also be sprayed. Or/kloc-0.000 times of 25% oxycodone EC,/kloc-0.000 times of 30% encyclopedia EC, 75% chlorothalonil WP and 600 times of 65% zineb WP. In order to increase the adhesiveness of the liquid medicine and reduce the rain erosion, we can add the leather glue equivalent to 1/3000 ~ 1/4000 to 500 kg of liquid medicine, or add 0.5 kg of rosin soap or 0. 1 ~ 0.2% of "650 1" developer. Spray the medicine evenly, so that the surface of the fruit and the front and back of the leaves are covered with medicine. Recently, it has been reported that spraying 40% Nova emulsion 7000 times at the initial stage of the disease has an outstanding effect on the control of pear scab.

Pear tree diseases mainly include scab, ring rot, rot and black spot, rust, powdery mildew, brown rot, root rot and yellow leaf disease also occur in some orchards, some orchards occasionally have epidemic rot, and old pear trees often have wood rot. In order to effectively control pear diseases, comprehensive control of pear orchard diseases must be done. Specific measures are as follows:

1, do a good job in orchard sanitation. After defoliation of overwintering bacteria is eliminated, plant before germination, thoroughly clean up defoliation and diseased fruits, and bury or burn them centrally (diseased fruits cannot be buried in soil). Cut off all kinds of dead branches on the tree and destroy them centrally. Before germination, spray the whole garden with 40% thiram 100 times solution plus 500 times solution assistant or 200 times solution of 75% sodium pentachlorophenol. So as to eradicate all kinds of overwintering bacteria remaining on the tree. In areas where pear rust occurs, completely cut off Sabina vulgaris as the host, or completely cut off before the germination of winter spore horns on Sabina vulgaris, or spray 2-3 Baume sulfur mixture or 1 Baume sulfur mixture and 75% sodium pentachlorophenol 300 times mixture on Sabina vulgaris before the spring rain to prevent the germination of winter spore horns. Thoroughly scrape off all kinds of germ fruiting bodies on wood rot trees and destroy them centrally. From the end of April to the end of May, the patrol found the diseased tip of Black Star, which was cut off in time and burned or buried deeply.

2. Strengthen cultivation management, strengthen disease prevention and rational fertilization, increase the application of organic fertilizer and avoid partial application of nitrogen fertilizer; Reasonable irrigation, pay attention to timely drainage in rainy season, timely irrigation in early spring, increase the water content of trees and improve the anti-corruption ability of trees; Reasonable fruit yield and enhanced tree potential. Orchards with serious yellow leaf disease and lobular disease should be fertilized in autumn with appropriate amount of ferrous sulfate and zinc sulfate. Pay attention to applying medicine to protect all kinds of large mechanical wounds, such as cutting, sawing and splitting wounds, to prevent the infection of wood rot fungi. Bagging after fruit setting can prevent fruit diseases.

3. The treatment of trunk diseases began in late March. Pay attention to the examination and treatment of rotten spots and apply drugs to protect them in time. See above for specific methods and effective drugs. Before germination, scrape off the ring marks in time and apply medicine. After scraping off the fruiting body of the pathogen, pay attention to taking medicine to protect the wound.

4. Timely detection and treatment of root diseases. After pear trees germinate and bloom, root diseases are found in time and treated in time.

5. The main diseases controlled by spraying chemicals before wheat harvest are scab, ring rot, black spot, rust and yellow leaf disease. Other minor illnesses can be treated at the same time. In general, scabs need to be sprayed three times, that is, at the end of April or early May, in the middle and late May and early June; When it is dry, it needs to be sprayed twice, that is, in mid-May and early June; It needs to be sprayed four times in rainy years, namely in late April, early May, late May and early June. The application time depends on the specific conditions such as climate and illness. For ring rot, it should be sprayed about 10 days after flowering, once every 15-20 days, and it needs to be sprayed 2-3 times. The specific spraying time should be timely spraying after rain, spraying more when it rains, spraying less when it rains and spraying when it doesn't rain. Black spot usually needs to be sprayed twice, that is, in the middle and late May and early June. 10- 15 spray rust once a day and twice continuously. Yellow leaf disease: spraying medicine every 7- 10 days after the leaves are unfolded until the leaves turn green. If you need to spray drugs to prevent and treat more than two diseases at the same time, you should choose drugs that are effective for both and consider treating other diseases. At the same time, try to avoid using copper preparations in the early stage to avoid phytotoxicity.

6. Spraying control in the middle growth period The diseases that need spraying control in this period mainly include scab, ring rot, black spot, epidemic rot and powdery mildew. Other minor illnesses can be treated at the same time. Generally speaking, scabs need to be sprayed 2-3 times, that is, in late June, mid-July and late July. Ring rot generally needs to be sprayed 2-3 times, that is, in late June, early July and late July. The specific spraying time and frequency still depends on the rainfall. Black spot disease generally needs to be sprayed 2-3 times, that is, in late June, mid-July and late July. The specific spraying time and frequency should be determined according to the severity of the disease and rainfall. Plague generally needs to be sprayed 1-2 times, that is, in the middle and late July. Powdery mildew generally needs to be sprayed 1-2 times, that is, in the middle and late July. Copper preparations can be used as much as possible during this period, and the treatment of different diseases should be considered.

7. Spraying before harvest to prevent and control the diseases that need spraying at this stage are mainly scab, brown spot and blight. Generally, scabs need to be sprayed 2-3 times, that is, in mid-August, late August and early September. The specific spraying time and frequency depend on the severity of the disease and rainfall, but in any case, spraying should be done on time in early September. Brown rot usually needs to be sprayed twice, that is, in the middle and late August and late September. Epidemic rot usually needs spraying 1 time, that is, in the first half of August. During this period, we should try our best to choose internal inhalation therapy drugs; At the same time, Bordeaux mixture should be avoided to avoid polluting the surface of fruit.