Harmful symptoms and control methods of peanut brown spot

Peanut brown spot is a fungal disease, which is caused by Cercospora infestans, which harms peanut leaves. At first, it is a chlorotic spot, then it expands into a near round or irregular spot, the disease spot is larger and lighter than black spot, the leaf front is dark brown or tea brown, the back is brown or yellow brown, and there is a bright yellow halo around the disease spot. Let's take a look at the prevention and control methods of peanut brown spot.

Symptoms of peanut brown spot

Peanut brown spot is mainly harmful to peanut leaves, which is chlorotic at first, and then expands into near-round or irregular spots, which is larger and lighter than black spot, dark brown or brown on the front, brown or yellow on the back, and a bright yellow halo around the spot. The grayish brown powdery mildew layer can be seen on the disease spot with high humidity, that is, the conidiophores and conidia. The petiole and stem are infected with long oval, dark brown spots.

Incidence conditions of Brown spot in Peanut

The pathogen overwintered on the diseased body with ascomycetes, mycelia or ascomycetes. The following year, the conidia were produced under suitable conditions, and the initial infection and re-infection were carried out by means of wind and rain transmission. The hyphae extended directly into the intercellular space and cells to absorb nutrients, and generally did not produce haustorium. The growth temperature of the pathogen ranges from 10 to 33 ℃, and the optimum temperature is 25 to 28 ℃. The climate is rainy and humid, and the disease is serious. The disease occurred earlier, and the disease of young leaves was more serious than that of old leaves.

Control methods of Peanut Brown spot

1. Some resistant varieties were selected, such as Hua 39, 68-4, 8130, Luhua 11, Luhua 13, Luhua 9, Qunyu 101, P12, Hua 17 and so on.

2. At the initial stage of the disease, 25% manganese zinc wettable powder 375 g / ha and 70% methyl thiophanate wettable powder 263 g / ha can be sprayed, once every 7 days, twice in a row, and used alternately.

Symptoms and control of sweet-scented osmanthus brown spot is a common term for many trees of the genus Oleacea in China, which represents the species Osmanthus fragrans (Thunb.) Lour.): also known as rock cinnamon, it is an evergreen shrub or small tree of Oleaceae, with thin hard skin, long oval leaves, pointed face, opposite and unwithered by winter. Between the leaves and organs of peanuts, the Corolla is four-lobed and small in shape, and its horticultural varieties are various, the most representative of which are cinnamon, silver cinnamon, cinnamon, laurel and so on.

Sweet-scented osmanthus brown spot pathogen is mainly harmful to sweet-scented osmanthus leaves. The damaged leaves begin to appear small macula, and then gradually become yellowish brown to grayish brown, the disease spot is nearly round or irregular, or limited by the veins of the leaves can also be angular spots. The diameter of the lesion is 2-10 mm. There is a yellow halo on the outside. The disease part produces black mildew when it is wet, that is, the conidiophores and conidia of pathogens. The brown spot of sweet-scented osmanthus is caused by Cercospora, Trichospora, Trichospora, Cercosporaceae and Cercospora. The conidia of the pathogen are born on the conidiophores, and the conidia are inverted rod-shaped, so as to infect and spread. The pathogen of sweet-scented osmanthus brown spot overwintered on diseased plants and fallen leaves with hyphae and became the source of infection at the beginning of the second year. Conidia were produced in late March, which were spread by wind and rain and infected. The disease occurred from April to October, and the disease decreased after October. High temperature and humidity are beneficial to the disease, and the disease of old leaves is more serious than that of young leaves. There are also some differences in disease resistance among varieties. generally, the disease resistance of Dangui is stronger than that of Jin Gui and Yingui. Prevention and control methods 1, combined with pruning, carefully remove the diseased leaves of the plant, remove the fallen leaves of the underground disease, concentrate on burning, and reduce the source of primary infection. 2. Strengthen cultivation management and avoid stagnant water in soil. Increase the application of humus fertilizer and potash fertilizer to improve plant disease resistance. 3. During the onset of the disease, one can be sprayed with Bordeaux solution of 100-200 times of lime, or 1000-1500 times of 50% benzoate wettable powder, or 500 times of azinoling, or 50 times of Dysenamine. Symptoms and control techniques of jujube brown spot

With the gradual expansion of jujube planting area, the occurrence of diseases is becoming more and more serious. Among them, diseases such as jujube brown spot have seriously affected the yield and quality of long jujube, and caused certain economic losses to fruit farmers. In this paper, the symptoms, occurrence regularity, disease conditions and prevention and control techniques of jujube brown spot were summarized for your reference.

Harmful symptoms of jujube brown spot

The disease usually starts from the white mature stage (the earliest in early August), and does not occur before the white mature stage. The disease spot mostly occurs at the top of the fruit or waist, the initial stage is yellow or light red, irregular edge, irregular shape of small disease spot, diameter 3-5mm, slow expansion, the occurrence rate is very low. When it rained from late August to late September, a large number of diseased fruits appeared, the disease spots expanded rapidly, and the diseased tissue was inverted hemiform, deep into the pulp of 3-5mm. The junction of diseased fruit is easy to peel off, the taste of diseased fruit is bitter, the occurrence proportion is very high, the black-red spot is not convex and concave, and the size of the later stage is 5-15mm. The remarkable feature of the disease is that the diseased fruit does not fall off.

Occurrence regularity of jujube brown spot

The pathogen of jujube brown spot overwintered on the diseased fruit and dead branches with hyphae, conidia and conidia. After the jujube tree germinated the next year, the conidia spread by wind, rain, insects and so on. Invade from insect wounds, natural orifices or directly penetrate the epidermis of jujube fruit. After falling flower and early stage of young fruit, the pathogen began to infect, but did not get sick, and the pathogen was in a latent state after invasion. When the fruit is close to the ripening stage and the sugar content in the pulp increases significantly, the latent hyphae expand rapidly and induce fruit disease. With the ripening and senescence of the fruit, the wax and horny membrane of the pericarp thickened, the air permeability decreased, the respiration of the fruit itself was strengthened, and the fruit was easy to release ethylene, which promoted the softening and accelerated decay of the fruit. When the humidity is high during the fruit ripening period, conidia will infect the fruit again in the same year. The artificial inoculation in the laboratory and field shows that the incubation period of the disease in this period is only 2-7 days, so the disease occurs rapidly.

Incidence conditions of jujube brown spot

According to the investigation and analysis, the occurrence of jujube brown spot is mainly related to rainfall, the use of gibberellin and tree strength: (1) the disease is related to rainfall. The morning, evening and severity of the disease are closely related to the rainfall times of the year and the relative humidity in the air of the jujube orchard. Rainy fruit ripening is an important inducement and a necessary condition for the occurrence of fruit brown spot. In years with many overcast and rainy weather, especially from mid-June to early August, if the continuous overcast and rainy days are long, the disease will occur early and seriously; on the contrary, it will occur late and light. (2) the disease is related to gibberellin and other plant hormones. Red jujube fruit brown spot is a fungal disease and a weak parasite. The use of gibberellin and other plant hormones increases the yield and reduces the ratio of fruit to leaf, resulting in fruit malnutrition and decreased immunity, which is the internal cause of brown spot disease. (3) the disease is related to the strength of the tree. The disease of weak tree is early and severe, while that of strong tree is late and light. The field investigation found that the jujube orchard, which is located at the edge of the east hillside, is irrigated with well water all the year round because of its high topography, and the sanitary condition of the orchard is poor. Melons, beans and vegetables are planted between the rows of jujube trees, resulting in thin leaves, light leaves and weak trees, so the disease is early and serious.

Control measures of jujube brown spot

(1) Agricultural prevention and control. Do a good job in clearing the garden, remove the dead fruit and bury it deeply, cut off the withered branches and burn the disease and insect branches in order to reduce the source of the disease. Strengthen comprehensive management, increase the application of organic fertilizer and phosphorus and potassium fertilizer, enhance tree potential and improve disease resistance. Low-stalk crops such as peanuts and beans were planted in the jujube orchard, while corn and other tall-stalk crops were not planted in the jujube orchard, so as to keep the jujube orchard ventilated and transparent, reduce the air humidity and reduce the disease. (2) spray protection. 5-10 days before germination, 3-5 °be stone-sulfur mixture was sprayed in the whole garden to eradicate overwintering pathogens. During the young fruit stage, 2000-3000 times of 25% triadimefon wettable powder was sprayed 1-2 times in the orchard 3-5 days before the rainy weather, or 50% chlorothalonil wettable powder was sprayed 1-2 times every 10-15 days.