synonymphomopsis asparagi (Asparagus stem blight) generally refers to asparagus stem blight
Asparagus stem blight is caused by Asparagus pseudostem spot fungus and occurs inasparagusDisease.It mainly damages stems, young shoots, lateral branches and pseudo leaves.The primary disease spot on the stem is spindle shaped or line shaped dark brown spots, and the periphery is watery. With the aggravation of the disease, the disease spot gradually expands, and the central reddish brown depression is scattered with many black small particles.After a circle of disease spots around the stem, the stem is dry and burning like fire.[1][4]
Asparagus stem blight is a Chinese diseaseasparagusIt is a destructive disease with wide distribution and serious harm in production.It often occurs together with asparagus root rot, asparagus virus disease and asparagus brown spot disease in rainy seasons in summer and autumn, and is one of the diseases that cause large-scale seed destruction.The disease can seriously affect the yield of asparagus, and even cause crop failure.[5]
Asparagus stem blight is a serious disease with great harm. The conventional control mainly focuses on chemical pesticide control, and the control effect is not ideal. Comprehensive control measures such as strengthening cultivation management should be taken.[3]
The pathogen of asparagus stem blight is Asparagus officinalis (scientific name:Phomopsis asparagi(Sacc.) Bubak), ofSeminaria, Glomerosae, Sclerotiniafungus。ConidiaIt is formed in the ovary, single or 2-3 aggregated, oblate to nearly spherical, black, with prominent orifice, and the wall thickness near the orifice is 75-225 microns in diameter.In wet conditions, a large number ofConidiaOverflow from the orifice to form milky white spore horn, which is yellow white or dirty white after drying.Under certain conditions, the pathogen has three types of conidia: mouth shaped spores are oval, colorless, unicellular, with 2-3 obvious oil balls, most of which are 2, distributed at both ends of the spores, with a size of (5.0-12.5) μ m × (1.75-3.75) μ m, and an average of 7.5 μ m × 2.5 μ m;β - type spores are linear to lanceolate, occasionally hook shaped or wavy, colorless, without separation, and there is no fat ball in the spores, with a size of (17.5-26.0) μ m × (1.0-2.0) μ m;The intermediate spores are (12-16) μ m × (2.5-4.5) μ m.[4]
On the potato sucrose agar medium, the colony morphology is white flocculent or fluffy at first, with neat edges, and then turns to grayish green or yellowish green. The medium under the colony is light brown to dark brown, forming black stroma and overflowing milky white spores.myceliumThe optimum temperature for growth is 24-26 ℃, and the growth stops when the temperature is lower than 15 ℃ or higher than 33 ℃. The growth can be achieved within the range of pH 5-10, and the optimum pH is 6-7.[4]
Harmful symptoms
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Asparagus stem blight mainly damages stems, young shoots, lateral branches and pseudo leaves.The young stem will show symptoms 5-7 days after being unearthed, and chlorotic water stains will appear, which will hinder the growth or cause the young stem to rot.After the infection of stems, small brown spots with rapid expansion appeared under low temperature or high temperature and dry conditions, and acute disease spots with rapid expansion under moderate temperature and high humidity conditions.The stereotyped chronic disease spots are long oval or spindle shaped, small, with clear edges, brown to dark brown, sunken in the middle, and no or occasional few small black particles.The acute type of disease spots expand rapidly, with watery and light brown edges. The length of the disease spots ranges from several centimeters to more than ten centimeters. The middle is yellowish brown to grayish white, slightly concave, and the upper part is densely covered with grayish black to black small particles, scattered or arranged in whorls. Under wet conditions, there are grayish white velvety hyphae at the edge of the disease spots.The pathogen quickly invaded the xylem and stem pith, leading to hollow and easily broken stems and withered upper parts.The lateral branches and pseudo leaves were infected, and the disease spots were light brown. The lateral branches were quickly circumcised, and the disease spots and pseudo leaves died, with scattered black small grains.[4]
Asparagus stem blight
Infection cycle
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The pathogen overwinters on the diseased stump with conidia or conidia. The conidia released from the field or the conidia on the withered and old stump stacked on the ridge under high humidity conditions for infection, becoming the main source of initial infection in the next year. The conidia produced on the stems, branches and diseased spots flow down along the stems and branches with rain, causing disease at the base of the stems, which is prevalent after repeated infection.[5]
Epidemic law
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The epidemic of the disease depends on the cooperation of temperature, humidity, rainfall and the vegetative growth stage of asparagus plants.When young stems are unearthed in peak season, the temperature is 20-30 ℃, it is rainy and foggy, and the field humidity is high, so the disease can spread.With the extension of the time when young stems are unearthed, the degree of stem tissue corking increases, and the ability to resist invasion increases, but the new branches and leaves at the top of the plant are vulnerable to disease.In terms of cultivation,InterplantingThe occurrence and prevalence of favorable diseases of cotton, corn, soybean, potato, sesame and other crops.Excessive application of nitrogen fertilizer and insufficient phosphorus and potassium fertilizer led to the decline of plant disease resistance.The favorable diseases, such as low-lying terrain, poor drainage, sticky soil, high and dense plant growth, are prevalent.In addition, the occurrence and prevalence of the disease will be aggravated by the adjacent or mixed fields of shoot picking, seedling raising and non shoot picking.[4]
Prevention and control methods
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Agricultural control
Parcel selection:Asparagus officinalis shall be planted on the land with convenient drainage and irrigation, fertile soil and flat terrain.It is not suitable to plant on low-lying, sticky and waterlogged land.[2]
Variety selection:The resistance to stem blight of asparagus varies among varieties, so it is necessary to select varieties with strong resistance when planting asparagus, such as "Atlas", "UC800", etc.[2]
Removal of disease strains:During the growth of Asparagus officinalis, the diseased plants should be removed in time, put into plastic bags, taken out of the field and buried deep, and cut off the source of infection.[1]
Qing Garden in late autumn:After the natural yellowing of asparagus stems and leaves in late autumn, the above ground parts should be cut off from the ground and used as fodder or burned.Be careful not to cut it too late, otherwise the stems and leaves will become brittle and the branches and leaves scattered in the field will increase the number of overwintering pathogens.The stubble left after cutting should be covered with soil, or the plant can be cut off from 3-5 cm below the ground with a spade or hoe.After the plants are cut or uprooted, the scattered branches and leaves on the ground shall be collected with a rake and taken out of the shoot garden to burn.[1]
Scientific fertilization:Apply more organic fertilizer, increase the application of microelement fertilizer, and reasonably match nitrogen, phosphorus and potassium fertilizers to avoid excessive application of nitrogen fertilizer, cultivate healthy plants, and enhance the ability of plants to resist diseases.[2]
strengthen management:In spring, the seedlings in the field shall be pulled out in time to prevent the pathogen from infecting the young seedlings.After the spring bamboo shoots are harvested, 3-5 mother stems should be left in each hole, which should not be too many, so as to prevent the field from being shaded.The drainage ditch shall be dug and timely drained in rainy season to prevent ponding in the field.[2]
Chemical control
Ground sterilization:After the garden is cleaned, the ground shall be sprayed and disinfected.The method is to spray the liquid medicine evenly on the ground, and spray the medicine before harvesting and during autumn head changing. 50% carbendazim wettable powder can be used 500 times liquid, 70%Thiophanate methylWettable powder 500 times liquid, 40% Jiaobanling wettable powder 500 times liquid, 25%BenomylWettable powder 500 times liquid, etc.[3]
Seed disinfection:The combination of warm scalding seed and liquid medicine immersion can be used.Dry seeds can be soaked in 60-65 ℃ hot water for 5-10 minutes, then transferred to cold water for cooling, and then soaked in 400-500 times of 25% carbendazim wettable powder for 2-3 days before germination and seeding.[4]
Reagent coated stem:When the tender stem of the parent plant is about 30cm long, the stem shall be coated with chemicals at the lower part of the branch. When the stem is coated, rubber gloves shall be worn, and a sponge shall be dipped in the liquid medicine to coat the skin around the tender stem.Once more when the stem height is 55-60cm.50% carbendazim 40 times solution is mainly used to coat the stems, which is used in summer and autumn when the stems are retained.When painting stems, pay attention to evenly painting around the tender stems without omission.The concentration shall be strictly controlled to prevent drug damage.[3]
Spray:The tender stem with mother stem will be sprayed 3 days after being unearthed, and then once every 5-7 days.With the growth of tender stem, the interval can be increased.Generally, after the tender stem grows for 40 days, the spraying focus will be shifted to the tender part of new shoots.It is rainy, foggy and humid in summer and autumn, and the air humidity is high, which is suitable for disease occurrence.The acute stem blight can spread in a large area in two days, so we should seize the opportunity to use drugs, not only more times, but also due to the high water content in the air, we should appropriately increase the concentration of drugs.Before the rain, it is necessary to seize the time to spray, and after the rain, it is necessary to spray again in time. In sunny days and dry days, when the disease occurs slightly, the drug concentration can be reduced, and the number of drugs can be reduced accordingly.Attention shall be paid to mixed and alternate application of drugs, and the spraying shall be uniform and thoughtful, focusing on the parts that have not been lignified, such as tender branches and new shoots.50% methyltobuzin wettable powder, 50%CarbendazimWettable powder, 75%ChlorothalonilWettable powder 600 times liquid, 64%Antitoxic alum500 times liquid spray prevention.[3]
