Preventing and controlling seedling diseases and pests is an important part of nursery seedling cultivation technology. Strengthening the prevention and control of seedling diseases and pests during the seedling cultivation process is beneficial to improving seedling growth, development and greening effect. The prevention and control of seedling diseases and pests must adhere to the principle of " prevention first and comprehensive control " , and take comprehensive control measures from the aspects of seedling cultivation technology and nursery management to control the development of diseases and pests.

(I) Strengthen plant quarantine for seedlings entering and leaving the nursery.

Some pests and diseases have narrow distribution ranges, causing serious damage only in localized areas. However, these pests and diseases can spread to new areas and expand their scope of damage through long-distance transportation of seedling seeds, cuttings or roots used as propagation materials, logs, and other horticultural products. During the exchange and transportation of seedlings, strengthened quarantine measures are crucial. If pests or diseases are discovered, transportation must be immediately halted, and measures must be taken to eradicate them. Strengthening quarantine measures for seedling pests and diseases upon entry and exit from nurseries, as well as at the seedling production sites and during transportation, is a primary measure for the prevention and control of seedling pests and diseases in nurseries.

(II) Adopt scientific seedling cultivation techniques and prevention and control measures
    1. Select a good nursery siteAvoid raising seedlings in heavy, damp, poorly drained, or excessively saline-alkali soil. Also, ensure that the previous crop and the planned seedlings do not share common diseases or pests, and select different tree species and planting densities according to the different site conditions of the nursery.

2. Deep plowing in autumn and winterDeep plowing in autumn and winter can improve soil properties and eliminate diseases and pests that overwinter in the soil.

3. Maintain good hygiene in the nursery.Promptly remove weeds, fallen leaves, and diseased or insect-infested wood from the nursery and burn them. Remove coverings from seedbeds in a timely manner to improve hygiene and reduce pathogen and pest populations. Avoid piling straw or manure in the seedling area to prevent diseases and pests from entering.

4. Implement crop rotation and adjust the sowing period.Crop rotation can restore and improve soil fertility, enhance seedling resistance, and deprive diseases and pests of their habitats. Appropriately adjusting the sowing date can avoid periods of high disease and pest activity, preventing or reducing damage to seedlings.
    5. Rationally select and cultivate seedling varieties.Resistance to various diseases and pests varies among different tree species and even among different varieties of the same species. A variety that only possesses characteristics of rapid growth and high yield but lacks resistance to diseases and pests will be difficult to promote in production. Therefore, it is crucial to strengthen the introduction and breeding of superior landscaping tree species with strong resistance to diseases and pests.

6. Strengthen the cultivation and management of seedlings
( 1 ) Reasonable fertilization: Pay attention to the proper combination of nitrogen, phosphorus and potassium, and avoid excessive application of nitrogen fertilizer. Organic fertilizer should be fully decomposed to avoid attracting pathogens and pests.
( 2 ) Maintain reasonable seedling density: Reasonable seedling density is conducive to seedling growth and control of disease and pest development.

7. Rational irrigation

In the irrigation of flowers and trees, the method, amount, and timing of watering all affect the occurrence of pests and diseases. Sprinkler irrigation and " smothering " watering often aggravate foliar diseases; it is best to use furrow irrigation, drip irrigation, or watering along the edge of the pot. Watering should be moderate; excessive water often causes root hypoxia and suffocation, resulting in poor plant growth or, in severe cases, root rot, especially in fleshy roots. The best time to water is on a sunny morning to reduce humidity on the leaf surface.

Through the above measures, plants can grow stronger, have greater resistance to diseases and pests, and a significant increase in natural enemies such as insects, beneficial microorganisms, and birds, thereby improving the entire nursery plant system's ability to control diseases and pests.

(III) Biological Control

Using beneficial organisms to control nursery pests and diseases has advantages such as energy saving, lower control costs, no environmental pollution, no harm to natural enemies, promotion of healthy ecological development, and sustained control effects. The main methods used in nursery pest and disease control are:

1. Microbial preparationsThis involves using bacteria, fungi, viruses, or their metabolites that cause disease in pests to control pests in nursery plants. For example, Bacillus thuringiensis emulsion is used to control the looper moth on Sophora japonica; microbial insecticides mainly include Beauveria bassiana, Bacillus thuringiensis, and insect viruses.

2. Osamu IkusuiThis involves protecting and utilizing parasitic or predatory natural enemies to control pests in nursery plants. Commonly used parasitic natural enemies include Trichogramma wasps, swollen-legged wasps, ichneumon wasps, aphid wasps, and longhorn beetle borers; predatory natural enemies include Mongolian ladybugs and multicolored ladybugs. In nursery production, attention should be paid to protecting the ecological environment surrounding the nursery site to create conditions for the reproduction of natural enemies, thereby enhancing the control effect of various natural enemy insects on pests.
    3. Using birds to control pests.This involves protecting and utilizing beneficial birds to control pests on nursery plants. By hanging artificial bird nests in nursery trees to attract beneficial birds such as great tits, woodpeckers, and azure magpies, the density of leaf-eating pests and trunk-boring pests can be significantly reduced.

(iv) Chemical control

Chemical control is a commonly used method for controlling pests and diseases in nurseries, and it is also a major measure to control large-scale outbreaks of seedling pests and diseases and eliminate source areas. Provided that pest and disease forecasting in the nursery is accurate, the correct and timely use of pesticides can generally achieve good control results.

1. Seed disinfection: Disinfect seeds or treat them with pesticides before sowing to kill pathogens on the seed surface and prevent pests and diseases from invading and causing damage.
    2. Soil disinfection: When cultivating seedlings in nurseries where diseases and pests have occurred or are likely to occur, soil disinfection should be carried out first.
    3. Spraying control: Spray preventative pesticides before the seedlings show signs of disease; after diseases and pests occur, immediately take measures such as chemical control and manual removal for integrated control.

4. Pesticides commonly used for disease and pest control in nurseries can generally be divided into 6 types according to their different uses.

( 1 ) InsecticidesThese are pesticides used to control various pests, and some also have acaricidal effects, such as dichlorvos, dimethoate, methamidophos, amitraz, and cypermethrin. They mainly kill pests through four mechanisms: stomach poison, contact, fumigation, and systemic absorption.

( 2 ) AcaricidesThese are pesticides specifically designed to control mites (i.e., spider mites), such as trichlorfon, dicofol, and dicofol. Acaricides have a degree of selectivity, and their effectiveness varies depending on the stage of mite development. Some are more effective at killing eggs and larvae or larvae through contact, but less effective against adult mites.

( 3 ) BactericideThese are pesticides used to control plant diseases, such as Bordeaux mixture, zineb, carbendazim, triadimefon, and cypermethrin. They primarily inhibit the growth of pathogens, protect crops from damage, and penetrate the plant to eliminate invading pathogens. Most fungicides mainly play a protective role, preventing the occurrence and spread of diseases.

( 4 ) HerbicidesThese are pesticides specifically designed to control weeds in farmland, such as chlorpyrifos, fenvalerate, fluazinam, and chlormequat chloride. Based on their weed-killing action, they can be divided into contact herbicides and systemic herbicides. Contact herbicides can only control annual weeds that germinate from seeds, while systemic herbicides can kill perennial weeds. Some herbicides, when used at excessive concentrations, can kill both weeds and seedlings or cause phytotoxicity to crops.

( 5 ) Plant growth regulatorsThese are pesticides specifically designed to regulate plant growth and development, such as gibberellin (Gibberellin ) , naphthaleneacetic acid, chlormequat chloride, and ethylene agents. These pesticides have effects similar to plant hormones, promoting or inhibiting plant growth and development to meet their specific needs.

( 6 ) NematicidesSuitable for controlling various nematodes on vegetables, strawberries, tobacco, fruit trees, and forest trees. Nematicides have evolved from insecticides and fungicides with concurrent effects into a class of pesticides. Currently, almost all nematicides are soil treatment agents, most of which also have fungicidal and soil pest control effects, and some even have herbicidal effects. Based on chemical structure, they are classified into four categories: halogenated hydrocarbons, dithiocarbamates, and organophosphates.

(v) Physical prevention and control

In nursery seedling production, the attraction of adult insects to light can be utilized by setting up black light lamps or high-pressure insecticidal lamps to trap and kill adult insects. Methods such as ultrasonic treatment, heat treatment, and radiation irradiation can also be used to treat seeds and cuttings to eliminate pathogens or pests. For example, soaking the roots of paulownia seeds in warm water at 47–51°C for one hour can prevent paulownia witches ' broom disease.

In conclusion, during the nursery production management process, it is necessary to continuously improve and enhance cultivation techniques to cultivate strong seedlings and improve the plants' resistance to diseases and pests.

III. Major Pest and Disease Control Techniques in Nursery Production

(a) Aphids

　  The main aphids include the goldenrain tree aphid, peach aphid, peach powder aphid, cypress aphid, rose long-tubed aphid, willow gall aphid, autumn four-veined cotton aphid, white poplar aphid, and Chinese locust aphid. Aphids mostly overwinter as eggs, then migrate to other plants to continue causing damage, returning to their hosts before winter in autumn to overwinter. Therefore, controlling the first generation after the overwintering eggs hatches is extremely important and crucial.

　 Control methods: ( 1 ) Combine spring pruning to remove branches with insect eggs; ( 2 ) Spray pesticides during the budding period and the peak hatching period of overwintering eggs. Spray 6 % imidacloprid EC at 3000 to 4000 times dilution, or 5 % acetamiprid EC at 5000 to 6000 times dilution, or 50 % phoxim EC at 800 to 1000 times dilution, or 2.5 % deltamethrin at 2500 to 3000 times dilution, etc., and spray one of them on the leaves. Pay attention to safety when spraying. Oxymethoate is also a good medicine for controlling aphids, but oxomethoate may cause phytotoxicity to Rosaceae plants such as peach blossom, elm-leaf plum, and flowering quince. Therefore, extra care should be taken when using it on garden plants, and it should be avoided as much as possible. ( 3 ) Use yellow sticky insect boards to trap winged aphids. ( 4 ) Pay attention to protecting and utilizing natural enemies, such as ladybugs and lacewings. ( 5 ) Use per square meter100 grams3 % Furadan granules can also effectively control aphids when applied directly to the root zone of some flowering shrubs.

(ii) Mites

　　The main pests include apple red spider mites, hawthorn red spider mites, poplar gall mites, and wheat leaf claw mites that damage lawns.

　　Prevention and control methods: ( 1 ) Make good predictions and forecasts, check the leaf surface and leaf back in time, and it is best to use a magnifying glass to observe. When spider mites are found to be damaging a large number of leaves, spray pesticides as soon as possible. Preventing early damage is the key to controlling the rampant damage in the later stage. ( 2 ) Remove diseased and insect-infested branches and clear weeds, and burn them in a concentrated manner. The eaves of houses around the green space are often the habitat of overwintering mites, and they should be checked and controlled. ( 3 ) When the number of mites is light and does not affect the growth of trees, they can be rinsed with clean water. ( 4 ) When the pest infestation is serious, spray 1.8 % abamectin EC (also known as miticide, abamectin, miticide, abamectin, abamectin light, abamectin) at 7000 to 9000 times dilution evenly for prevention and control; or use 15 % pyridaben EC (also known as pyridaben, pyridaben, pyridabenin) at 2500 to 3000 times dilution, both of which have good prevention and control effects. Avoid using dichlorvos to kill mites, as dichlorvos stimulates the proliferation of mites. Do not use pyrethroid pesticides, as they are ineffective against mites. ( 5 ) Protect natural enemies, such as ladybugs and lacewings.

　 (III) Scale insects and other piercing-sucking pests

　　The main pests include crape myrtle scale, grass scale, Korean ball scale, apple ball scale, Euonymus arrow-point scale, spotted lanternfly, and Chinese scholar tree psyllid, among other piercing-sucking pests.

1. Scale insects

　　Control methods: ( 1 ) Strengthen plant quarantine. Scale insects have weak activity and limited spread, and their distribution is relatively concentrated. During the exchange and transportation of seedlings, strengthen quarantine. If such pests are found, stop transportation and take measures to eliminate them. ( 2 ) Before the trees sprout, spray the branches and trunks with a 50 -fold dilution of crystalline lime sulfur to eliminate overwintering insects. ( 3 ) Combine spring watering with root application of 3 % furadan granules. Before watering, use a pointed iron rod to mark the area around the plant roots every few meters.30 centimetersDrill holes on both sides, with a depth of 10 to 20 cm. Apply 4 to 6 grams of 3 % Furadan per square meter , cover and water after application. ( 4 ) During maintenance, if insect pests are found on individual branches and leaves, they should be pruned or scraped off immediately and burned to prevent the spread. ( 5 ) During the peak hatching period of nymphs, before the waxy layer is formed or just beginning to form, spray the branches and leaves with 1500 to 2000 times dilution of 40 % imidacloprid emulsifiable concentrate , 2000 times dilution of 6 % imidacloprid soluble liquid , and 2500 times dilution of pyrethroid pesticides. Use the above three agents alternately, spraying once every 7 to 10 days, and spraying 2 to 3 times consecutively to achieve good results. The key to spraying is to seize the opportunity (nymphal stage). Once the scale is formed, spraying is difficult to be effective. ( 6 ) Protect and utilize natural enemies. During the peak period of natural enemy insects, avoid using agents that harm natural enemies.

2. Spotted Lanternfly and Chinese Scholar Tree Psyllid

　　Control methods: Spraying with 1.2 % nicotine EC at 800-1000 times dilution, 6 % imidacloprid EC at 3000-4000 times dilution, or 5 % acetamiprid EC at 5000-6000 times dilution, or 50 % phoxim EC at 800-1000 times dilution, or 2.5 % deltamethrin at 2500-3000 times dilution , etc., can all achieve good control effects. For spotted lanternflies, egg masses can also be scraped off when pruning trees in spring.

　　(iv) Leaf-eating pests

　　The main species include willow leaf beetle, willow tussock moth, pear star caterpillar, yellow-tailed tussock moth, cypress tussock moth, willow leaf wasp, boxwood leaf borer, apple brown leafroller, Chinese scholar tree geometrid moth, mulberry thorn geometrid moth, elm leaf beetle, small green-flowered scarab beetle, horned tussock moth, bagworm, millipede, etc. Most of them overwinter as larvae and emerge early in spring to cause damage and activity.

1. Pests such as willow tussock moth, cypress tussock moth, boxwood leafminer, pear leafminer, yellow-tailed tussock moth, Chinese scholar tree geometrid moth, mulberry thorn geometrid moth, gray-spotted tussock moth, and bagworm.

　　Control methods: ( 1 ) Manually remove egg masses. ( 2 ) When larvae are clustered and causing damage, remove the infested leaves and manually kill the larvae. ( 3 ) Use frequency-vibration insecticidal lamps to attract and kill adult insects. ( 4 ) Before the larvae reach the 3rd instar, use biological or biomimetic pesticides, such as 500 to 700 times dilution of Bt wettable powder with a content of 16000 IU/ mg , 800 to 1000 times dilution of 1.2 % nicotine emulsifiable concentrate, 1500 to 2000 times dilution of 25 % diflubenzuron suspension concentrate , 1500 to 2000 times dilution of 20 % chlorpyrifos suspension concentrate , etc. ( 5 ) When larvae occur on a large scale, spray with 20 % methomyl at 2000 to 3000 times dilution, 2.5 % deltamethrin at 1500 to 2000 times dilution, 50 % phoxim EC at 1000 to 1500 times dilution, 20 % cypermethrin EC at 1000 to 1500 times dilution, etc. for control. ( 6 ) Protect natural enemies, such as parasitic wasps and mantises.

2. Pests such as willow leaf beetle, willow leaf wasp, and elm leaf beetle.

　　Control methods: ( 1 ) Take advantage of their feigned death behavior and shake them off and kill them when overwintering adults climb the tree. ( 2 ) Manually scrape off the eggs and newly hatched larvae and burn them. ( 3 ) Inject pesticides into the tree trunk. Use 6 % imidacloprid EC or 40 % dimethoate EC, according to the diameter at breast height per cubic meter of tree trunk.1 cm, Inject 1 ml. ( 4 ) Before the overwintering adults lay eggs, and during the overwintering of the first generation of larvae and adults, use chemical pesticides such as 50 % phoxim EC at 2000 times dilution, cypermethrin at 3000 to 3500 times dilution, or 90 % trichlorfon crystals at 1000 times dilution for control. ( 5 ) Protect natural enemies, such as ladybugs, mantises, and stink bugs.

　(v) Woodworms

　　The main pests include the larvae of the rose stem beetle, the white wax stem beetle, the sclerotium longhorn beetle, and the peach red-necked longhorn beetle.

1. Rose stem bee

　　Prevention and control methods: (1 ) Strengthen maintenance and management. During the growing season, prune any affected, wilted, or broken branches (cut until there are no borers in the pith of the stem) and burn them to kill the larvae and eggs inside. This method is the most effective and fundamental way to prevent and control rose stem beetles. ( 2 ) Properly arrange plants. Adult rose stem beetles are not good at long-distance flight. When designing planting, the varieties should not be too simple, so as to form a natural isolation zone around the perimeter to prevent their spread. ( 3 ) When pruning in spring, branches with insects must be completely eliminated. Cut off the branches with insects and cut the larvae inside in half to kill them. If the insects have been found to have burrowed into the roots, inject 5 to 10 ml of 6 % imidacloprid emulsifiable concentrate diluted 50 times into the borehole with a syringe , and immediately seal it with soil to kill the remaining larvae. The pruned branches should be disposed of and burned in time. ( 4 ) Spray with 6 % imidacloprid at 1500 to 2000 times dilution or 20 % cypermethrin EC at 1500 to 2000 times dilution during the early emergence of overwintering adults (when willow catkins are in full bloom) and during the egg hatching period to kill adults and larvae. Alternatively, bury 3 % carbofuran granules at the base of the plant. ( 5 ) Select insect-resistant varieties. For example, Mannheim roses with low branching points are more resistant to insects than hybrid roses with high branching points; rejuvenated roses are more resistant to insects than old roses; double-flowered floribunda roses are more resistant to this insect. ( 6 ) Pay attention to protecting parasitic wasps such as the golden wasp. Rose stem wasps have many natural enemies. Place the branches with insects cut during the larval stage in a gauze cage and hang it at the rose planting site. The small parasitic wasps will fly out and parasitize the larvae of other rose stem wasps. The parasitism rate is often over 50 %.

2. White wax bee Ha's stem bee

　　Control methods: ( 1 ) Combine spring tree pruning to eliminate overwintering larvae. Generally, during spring pruning, cut off branches with brown spots and burn them to reduce the number of overwintering larvae. ( 2 ) Spray to kill adults. In mid-to-late April , from the emergence period of adult white wax stem wasp to the hatching period of larvae, spray the leaves and current year branches with 40 % dimethoate at 1000 times dilution or 10 % imidacloprid at 1500 times dilution plus synergist. ( 3 ) Inject the trunk with pesticide. Inject 40 % dimethoate or 6 % imidacloprid emulsion into the trees by diluting the pesticide solution 10 to 20 times and applying it according to the diameter at breast height of the tree.1 cmInject 1 ml of the pesticide solution to kill adult insects and newly hatched larvae. ( 4 ) Apply Furadan to the roots. Dig trenches or make holes evenly around the tree pit, according to the diameter at breast height of the tree.1 cmApply 8 to 10 grams of 3 % carbofuran , and immediately water thoroughly after application.

3. Longhorn beetle pests such as the spotted longhorn beetle and the pink-necked longhorn beetle.

Control methods: ( 1 ) Manually hook out the larvae from the frass holes with wire and kill them. ( 2 ) Chemical control. At fresh frass holes, first remove the frass residue with tweezers, then pry open the bark around the frass holes with a knife, and then insert 52 % aluminum phosphide tablets or inject dimethoate with a syringe to kill the larvae. Then cover the affected area with mud to prevent air leakage. ( 3 ) Inject the trunk with chemicals. The method is to make a hole 5 to 10 cm below the ground under the trunk , with a hole diameter of 0.8 to 1 cm.0 cm3.0 to 5 meters deep0 cmThe opening should be slightly higher to prevent the pesticide from leaking out. Each plant should be planted according to its diameter at breast height (DBH).1 cmThe dosage of the drug is 1 ml, which is40% dimethoate emulsifiable concentrate or6% imidacloprid emulsifiable concentrate, and then sealed with mud. (4) Release the tragus wasp to protect natural enemies such as woodpeckers.

(vi) Underground pests

Underground pests mainly refer to a class of pests that live in the soil during their harmful period, including mole crickets, white grubs, and cutworms. These pests are diverse and affect a wide range of hosts.
Chemical control methods: ( 1 ) Phosphate. Mix evenly with the soil when preparing the bed.20cmIn deep soil layers, during the seedling stage, small sticks can be used to poke holes and inject insecticide solution. Alternatively, granular phorate can be applied to the bottom of the trench and mixed into the soil when changing beds and opening trenches. ( 2 ) Phoxim. Yellow-brown liquid, stable in neutral acidic solutions, easily decomposed by alkali, heat, light, especially ultraviolet light. Phoxim has strong contact and stomach poison effects, a wide range of insecticidal effects, very low toxicity to higher animals, and very prominent insecticidal effect in soil, with a residual effect of up to 3 months. Therefore, it is very suitable for soil treatment and control of underground pests. 50% emulsion 1 : 100 dilution at 1 (solution): 100 (seeds) for seed treatment, with good control effect on underground pests such as mole crickets, grubs, and cutworms. It is best to apply the medicine in the evening to reduce photolysis by sunlight. It is highly toxic to bees, so avoid releasing bees when applying the medicine. ( 3 ) Dichlorvos. Dichlorvos emulsifiable concentrate does not decompose over a long period of time, but it decomposes and becomes ineffective quickly after being mixed with water, especially in high-temperature alkaline environments, resulting in a short period of efficacy. At normal usage concentrations, it does not cause phytotoxicity to most plants. ( 4 ) Trichlorfon. Trichlorfon mainly has stomach poison and contact killing effects, is safe for humans and animals, but is highly toxic to pests. The reason is that in higher animals, trichlorfon is easily decomposed into trichloroacetaldehyde and trichloroethyl glucuronide by serum esterase in the blood, thus losing its toxicity and being excreted in urine; while in insects, it is relatively stable, decomposes slowly, and can be converted into the more toxic dichlorvos. Trichlorfon has a short residual period, and 90% crystal trichlorfon is used.0.075kgand5kgWheat bran can be made into poisoned bait to effectively kill underground pests such as cutworms and mole crickets. Diluted trichlorfon solution or poisoned bait should be prepared immediately before use and should not be stored for extended periods to prevent decomposition and loss of effectiveness.

Artificial control methods : The occurrence of grubs follows certain patterns. In flat nurseries, their activity is closely related to soil temperature. When the soil surface temperature of the seedbed...5cmThe deep soil temperature is15℃At this time, grubs mostly stay below the bed surface.15cmWithin the soil layer. At this time, use...20cmLong, thin steel needles in a horizontal direction1cmBy planting the grubs downwards at intervals, they can effectively kill 2nd and 3rd instar larvae. In addition, measures such as soil tilling, harrowing, or heavy irrigation during the 1st instar larval stage in autumn can also greatly reduce the grub population density.

(vii) Leaf spot diseases

Leaf spot disease is a general term for diseases that cause various shapes of spots due to localized infection of leaf tissue. However, leaf spot disease does not only occur on leaves; some diseases can occur not only on leaves but also on branches, stems, flowers, and fruits. Types of leaf spot diseases include : black spot, brown spot, circular spot, angular spot, leaf blight, and ring spot.

Prevention and control methods: ( 1 ) Strengthen cultivation management. Apply fertilizer reasonably and ensure sufficient fertilizer and water; irrigate in time during summer drought; build nurseries on well-drained soil; plant at appropriate density to allow ventilation and light penetration and reduce leaf humidity; remove weeds in the field in time. ( 2 ) Eliminate sources of infection. Sweep up fallen leaves at any time and remove diseased leaves. Prune severely diseased plants in winter to remove overwintering pathogens on diseased stems. Spray lime sulfur solution at 3-5 Baume degrees during dormancy . ( 3 ) Chemical control. Pay attention to timely application of medicine in the early stage of disease. The following agents can be selected according to the type of disease: 70% carbendazim wettable powder at 1000 times dilution, 10% tebuconazole water-dispersible granules at 6000-8000 times dilution. Spray 50% mancozeb aqueous solution at 1000 times dilution once every 10-15 days , and spray continuously for 3-4 times .

(viii) White powder

Control methods: ( 1 ) Eliminate overwintering pathogens. In autumn and winter, combine pruning to remove diseased and weak branches, and collect and burn dead branches and fallen leaves to reduce the source of initial infection. ( 2 ) Spray lime sulfur mixture at 2-3 Baume degrees during dormancy to eliminate overwintering mycelia in diseased buds or cleistothecia in diseased parts. ( 3 ) Strengthen cultivation management and improve environmental conditions. ( 4 ) Chemical control: Spray 15 % wettable powder of triadimefon at 1500-2000 times dilution, 40% emulsifiable concentrate of fusarium oxychloride at 8000-10000 times dilution, or 45 % suspension of tebuconazole at 300-800 times dilution at the initial stage of disease. 10 % triadimefon smoke agent can be used for fumigation in greenhouses . ( 5 ) Biological agents: In recent years, biological pesticides have developed rapidly. BO-10  ( 150-200 times dilution ) and antifungal agent 120 also have good control effects on powdery mildew. ( 6 ) Planting disease-resistant varieties: Selecting disease-resistant varieties is one of the important measures to prevent and control powdery mildew.

(ix) Anthrax

Prevention and control methods: ( 1 ) Strengthen maintenance and management to enhance the plant's disease resistance. Select disease-free plants for cultivation; apply fertilizer and rotate crops reasonably, and ensure appropriate planting density to facilitate ventilation and light penetration and reduce humidity; pay attention to watering methods and avoid flooding; and promptly update or disinfect potting soil. ( 2 ) Eliminate pathogens. Promptly remove dead branches and fallen leaves, prune diseased branches, scrape off lesions on the stem, and thoroughly remove diseased plant debris such as rhizomes, bulbs, and corms to eliminate the source of initial infection. Spray lime sulfur solution at 3-5 Baume degrees during dormancy . ( 3 ) Chemical control during the disease period, especially timely spraying of fungicides in the early stage of the disease. The following agents can be selected: 47% carbendazim wettable powder at 600-800 times dilution, 40% fuxing emulsifiable concentrate at 8000-10000 times dilution, 10% shigao water-dispersible granules at 6000-8000 times dilution, 10% polyoxin wettable powder at 1000-2000 times dilution, 6% lebigen wettable powder at 1500-2000 times dilution, 50 % carbendazim at 800 times dilution , 70% thiophanate -methyl at 1000 times dilution, 75 % chlorothalonil at 800 times dilution, or 80 % anthracnose mancozeb at 800 times dilution. Spray once every 10-15 days, for 4-5 consecutive times . ( 4 ) Select or use disease-resistant varieties.

(x) Damping-off and seedling blight

Prevention and control methods: ( 1 ) The prevention and control of seedling damping-off and seedling blight should be based on seedling cultivation measures, combined with chemical control measures. ( 2 ) Treat the seedbed with pesticides and disinfect the soil. ( 3 ) Strengthen seedbed management. Select plots with higher elevation, better drainage and sufficient sunlight for seedbeds. Promote seedling cultivation in nutrient pots. Select seeds carefully and cultivate seedlings in a timely manner. ( 4 ) Spray pesticides in a timely manner at the early stage of disease.

(xi) Downy mildew (epidemic)

Prevention and control methods: ( 1 ) Strengthen cultivation management. Remove diseased branches and fallen leaves in time. Use scientific watering methods and avoid flooding. In greenhouse cultivation, pay attention to ventilation and control temperature and humidity. Roses planted in the open field should also pay attention to sufficient sunlight and ventilation. ( 2 ) Chemical control. Before flowering, spray Bordeaux mixture (1:0.5:240 ), 75% chlorothalonil wettable powder ( 800 times dilution), and 50% captan wettable powder (500 times dilution) in combination with the control of other diseases. When sporadic lesions appear in the field in June , spray with 58% metalaxyl-mancozeb wettable powder at 400-500 times dilution, 69% mancozeb wettable powder at 800 times dilution, 40% pymetrozine wettable powder at 250 times dilution, 64% cymoxanil wettable powder at 400-500 times dilution, and 72% chlorothalonil wettable powder at 750 times dilution. Spray again in July to basically control the damage. ( 3 ) After the disease occurs, 50% metalaxyl-copper wettable powder at 600 times dilution and 60% aluminum phosphide - fosetyl-aluminum wettable powder at 400 times dilution can also be used to drench the roots, drenching each plant with the solution .300g。

(xii) Viral diseases

Prevention and control methods: (1 ) Propagate non-toxic seedlings by taking cuttings from healthy plants. Diseased or suspected diseased plants cannot be used as propagation material. Select healthy and vigorous plants twice ; break the cuttings by hand instead of cutting them with a knife. Diseased plants should be removed from the plant.36℃Treatment in hot air for 4 weeks can lead to recovery. Heat-treated plants can be used as materials for tissue culture to produce virus-free seedlings. However, some people hold the opposite view. ( 2 ) Chrysanthemum dwarf disease is easily spread through agricultural operations such as topping and picking flowers. Therefore, pay attention to field hygiene and the transmission of the virus through operations to reduce the occurrence of the disease. In the daily management of chrysanthemums, such as pruning, topping, and cutting, pay attention to the disinfection of tools and hands. ( 3 ) Reduce the source of infection, remove diseased dead leaves, promptly remove diseased plants and wild hosts in the field, pay attention to removing wild chrysanthemums and weeds with dwarf yellowing symptoms around the chrysanthemum cultivation area, and kill dodder, especially host plants carrying this type of virus.