What are the methods for controlling flower diseases?

Flower diseases fall into two major categories: physiological diseases and infectious diseases. Physiological diseases are caused by unsuitable environmental conditions; infectious diseases are caused by biological infection. The organisms that cause flower diseases are mainly fungi, bacteria, viruses, and so on.

1. Control of fungal diseases

Diseases caused by fungal infection are called fungal diseases. Fungal diseases are the largest category among flower diseases, accounting for about 90% of flower diseases.

Fungal diseases of flowers generally have obvious symptoms, such as powdery substances (white powdery mildew, etc.), moldy substances (black mold, gray mold, blue mold, green mold, etc.), rust-like substances, granular substances, filamentous substances, nuclear substances, and so on. These characteristics are one of the main bases for identifying fungal diseases.

Common fungal diseases of flowers include powdery mildew, anthracnose, gray mold, rust, damping-off, seedling blight, black spot, brown spot, root rot, sclerotinia rot, and many others. Here we mainly introduce four of the most widely distributed and most serious fungal diseases of flowers.

(1) Powdery mildew is one of the most common diseases of flowers, occurring throughout the country. It mainly harms Chinese rose, rose, climbing rose, plum blossom, tree peony, herbaceous peony, chrysanthemum, dahlia, hydrangea, gardenia, cotton rose, crape myrtle, begonia, fuchsia, cineraria, balsam, gerbera, and other flowers.

Powdery mildew mostly occurs on young buds, young leaves, young shoots, flower buds and flower stalks. In the early stage of the disease, chlorotic spots appear on the affected parts, which later gradually turn into white powdery patches, and the surface of the diseased part is covered with a layer of white powdery mold; in the later stage the spots turn gray, and small black granules are produced on the affected branches. The diseased plant is short, the young shoots are bent, the leaves curl and become uneven, the flowers are few and small, or the flower shape is deformed, or the flowers cannot open; in severe cases the leaves curl up and dry out, and even the whole plant dies.

Disease pattern: the pathogen overwinters as mycelium or conidia on the remains of diseased plants; multiple repeated infections can occur during the growing season, with the disease being more severe in summer and autumn.

Control methods: (1) Pay attention to ventilation and air permeability, and remove diseased leaves. (2) Spray 20% triadimefon emulsifiable concentrate at 4000 times dilution, 50% sulfur suspension concentrate at 3000 times dilution, or 50% carbendazim at 700 times dilution, spraying once every 10 days, for a total of 2 to 3 sprays.

(2) Anthracnose is a disease that occurs commonly throughout northern and southern China. It mainly harms orchids, clivia, Michelia alba, camellia, magnolia, plum blossom, Aglaia odorata, fig, rubber tree, palm, rose species, cyclamen, cacti, tree peony, herbaceous peony, hydrangea, Rohdea japonica, southern magnolia, jasmine, kumquat, banana shrub, kapok, cockscomb, dianthus, daylily, Calendula officinalis, winter coral, fishtail palm, and other flowers.

Anthracnose mainly harms leaves, and also infects stems, young shoots, flower buds, fruits and other parts. The disease starts from the leaf tip and leaf margin. In the early stage of the disease, round or oval reddish-brown small spots appear on the leaves, which later expand into brown spots; the center of the spot changes from grayish-brown to grayish-white, while the margin is purplish-brown, and finally the spot turns dark brown with small black dots arranged in concentric rings. In severe cases the leaves die.

Disease pattern: the pathogen overwinters as mycelium in the host and in the soil; the disease begins in April, with the peak period from May to June.

Control methods: (1) Pay attention to ventilation and air permeability. (2) Spray 75% chlorothalonil at 800 times dilution, or 50% Shujunwei suspension concentrate at 800 times dilution, spraying once every 7 to 10 days, for 2 to 3 consecutive sprays.

(3) Gray mold This disease mainly harms tree peony, herbaceous peony, cyclamen, begonia, Primula obconica, China aster, dahlia, fuchsia, Calceolaria, gloxinia, Calendula officinalis, geranium, hydrangea, gardenia, cineraria, chrysanthemum, Chrysanthemum paludosum, gladiolus, rhododendron, Chinese rose, rose, camellia, poinsettia, iris, banana shrub, trollflower, lily, tulip, and other flowers.

Gray mold harms the leaves, stems, flowers and fruits of flowers. Depending on the host, the affected parts and degree vary. Generally, water-soaked spots appear in the early stage of the disease, then gradually expand and become brown or purplish-brown spots; in humid conditions a gray or earthy-yellow mold layer appears, and in severe cases the whole plant dies.

Disease pattern: the pathogen overwinters in the soil and often occurs in greenhouses. It is prone to occur when ventilation is poor and the temperature is too high.

Control methods: (1) Keep the interior ventilated and air-permeable, with dry air. (2) Spray with 50% carbendazim at 500 times dilution and 70% thiophanate-methyl at 800 times dilution, spraying once every 7 to 10 days, for 2 to 3 consecutive sprays.

Methods for controlling flower pests and diseases

Methods for controlling flower pests and diseases

For the control of flower pests and diseases in protected cultivation, the principle of "prevention first, integrated control" should be implemented, taking horticultural control as the foundation, strengthening manual control, giving full play to the controlling role of natural enemies, and combining with chemical control to carry out integrated management of pests and diseases.

There are mainly three aspects to the approach of prevention first: (1) Eliminate the sources of pests and diseases or reduce the base population of pests and diseases. For example, plant quarantine is an effective measure adopted to prevent dangerous diseases and pests from spreading along with seeds and seedlings. Reducing the base population of pests and diseases means reducing the number of overwintering pathogens and pests; (2) Worsen the environmental conditions for the occurrence and damage of pests and diseases, that is, create or make full use of conditions unfavorable to pests and diseases, and change or eliminate conditions favorable to pests and diseases; (3) Take effective measures in time to eliminate pests and diseases before they break out in large numbers and cause significant damage. For example, the rational use of pesticides and the adoption of effective manual and physical measures.

Integrated control means taking agricultural technical control as the foundation, adapting measures to local and temporal conditions, rationally applying chemical control, biological control, physical and mechanical control and other measures, giving full play to the positive role of various control methods, and combining them organically and coordinating them with one another,

making up for each other's shortcomings, so as to achieve the goal of economically, simply, safely and effectively controlling and eliminating pests and diseases.

Take effective measures to protect flowers from the invasion of pathogens and pests, and control the numbers of pathogens and pests; improve environmental conditions so that they are favorable to the growth and development of flowers and unfavorable to the survival and infection of pathogens and pests, and improve the ability of flowers to resist pests and diseases. The specific control methods are the following five:

1. Plant quarantine

The frequent exchange and transfer of flower species and varieties between countries or regions has allowed some pests and diseases to spread, causing great losses to flower production. The South American leafminer and the American leafminer now widespread in our country were introduced from abroad into China in 1994 because of lax quarantine, causing great losses to flower and vegetable production in our country. Therefore, blind introduction and transfer of seeds should be avoided, and quarantine regulations should be strictly enforced.

Plant quarantine includes three aspects: diseases, pests and weeds. It is a series of regulatory measures adopted by the state to protect agricultural production from the invasion of foreign dangerous diseases, pests and weeds. According to legal provisions, for the types of plant products subject to quarantine and the lists of prohibited diseases, pests and weeds to be brought in or taken out, if quarantine objects are found, they are not allowed to be imported or exported, or may only be exported or imported after disinfection treatment has eliminated the quarantine objects, so as to prevent them from spreading and causing disaster. Plant quarantine is an important part of pest and disease control, especially at a time when transportation tools are highly developed and exchanges with foreign countries are constantly expanding, strengthening quarantine work is particularly important. At the same time, the transfer of seeds, seedlings and other cultivation materials between different regions within the country must also be quarantined, and quarantine objects must be strictly prohibited from entering new areas.

2. Horticultural control methods

Agricultural technical control methods use a series of cultivation and management technical measures in the process of flower cultivation to purposefully change certain environmental conditions so that they are unfavorable to the occurrence and development of pests and diseases and favorable to the growth and development of flowers, thereby avoiding or reducing the occurrence of pests and diseases and achieving the goal of improving flower quality. Since most agricultural measures are themselves a means of high flower yields and do not require additional manpower and materials for pest and disease control, they often achieve multiple benefits at once and meet economic requirements; at the same time, agricultural control has no adverse side effects such as polluting the environment or killing natural enemies. The specific measures of agricultural technical control are:

1.    Rational fertilization and scientific watering The organic fertilizer applied should be fully decomposed. Before application, the pathogens and

pests in it should be thoroughly killed, and pests should be prevented from laying eggs on the organic fertilizer after application. When applying inorganic fertilizer, the ratio of nitrogen, phosphorus and potassium should be reasonable; do not apply too much nitrogen fertilizer, should appropriately increase the application of phosphorus and potassium fertilizers, and advocate formula fertilization. The watering method should be appropriate; avoid spray irrigation and preferably use furrow irrigation or watering along the edge of the pot. Watering should be moderate. Choose to water in the morning on sunny days, and after watering, ventilation should be carried out in time to remove moisture.

2.    Keep greenhouses and conservatories clean and hygienic

Promptly remove diseased and pest-infested flower branches and leaves, pull out diseased plants, clear away dead branches and fallen leaves, and thoroughly eradicate weeds inside and outside the greenhouse, so as to reduce sources of pests and diseases. Diseased plant residues should be buried deep or burned.

3. Improve environmental conditions

Ventilate and exchange air frequently to reduce humidity, so as to reduce the occurrence of high-humidity diseases such as gray mold on flowers. Planting density and the density of pot placement should be appropriate, so as to facilitate ventilation and light transmission between plants and reduce the damage of scale insects and others. Control the temperature well; do not let it fluctuate between hot and cold. In winter and spring, special attention should be paid to keeping warm, while in the hot summer, shade nets should be used for covering. Adjust the light intensity according to the needs of flower growth. Ventilation and cooling can control the development of many diseases; while high-temperature greenhouse sealing can control the occurrence of low-temperature diseases such as downy mildew.

4. Winter plowing and deep turning

Winter plowing and deep turning for flowers cultivated in the open field has a significant effect on eliminating pests in the vast areas of our country, especially in cold regions. Winter plowing and deep turning can expose most of the
larvae, pupae, eggs and so on lurking in the soil to the surface, where they freeze to death or are pecked by beneficial birds, and manual capture can also be carried out. Deep plowing can bury pathogens and crop residues in the shallow soil into deep soil layers, causing them to lose their vitality, and at the same time can turn pathogens originally in deeper soil layers up to the surface, increasing their death due to the influence of other natural factors such as light, temperature and humidity.

5. Handle affected plants

The remaining plants after flowering and the affected plants of annual and biennial herbaceous flowers should be immediately pulled up and burned or buried deep in the soil; after perennial and woody flowers wither in late autumn or shed their leaves, dead branches and fallen leaves should be promptly cleared and destroyed in a centralized manner. This measure can also reduce the number of some pathogens and pests.

6.    Timely weeding

Overgrown weeds not only compete with flowers for nutrients, affect ventilation and light transmission, and cause poor plant growth, but weeds are also breeding grounds for some pathogens and pests. Some viral diseases and pests often use weeds as hosts. Weeds are also overwintering sites for some pests and diseases. Therefore, timely removal of weeds is of great significance in pest and disease control.

7.    Timely pruning

In combination with the pruning of flowers and trees, cut off diseased buds, diseased branches, diseased roots and so on to reduce the number of pathogens, and at the same time also eliminate eggs, larvae and adults of insects that overwinter and oversummer on the branches, reducing the source of insects.

8.    Adjust the sowing period

The occurrence of many kinds of pests and diseases has a certain disease period and pest occurrence period due to the influence of temperature, humidity and other environmental conditions, and is most severe in a certain period. If sowing is advanced or delayed, the disease period and occurrence period can be avoided and the damage reduced. For example, China aster seedlings are most susceptible to damage by squash beetles; if sowing can be advanced, the degree of damage can be reduced. Adjusting the sowing or transplanting period has a certain control effect on pests that have one generation per year, have a single feeding habit, and occur uniformly.

9.    Rational crop rotation

As far as possible, avoid continuous cropping with mutually infecting flowers, so that pathogens and pests in the soil cannot get suitable hosts, thereby reducing the numbers of pathogens and pests.

10.    Scientifically carry out the harvesting and post-harvest management of bulbs and other organs During digging, wounds should be reduced as much as possible; after digging out, bulbs with diseases

and pests should be promptly removed, and they may only be put into storage after being fully dried in the sun. Wounds caused during digging easily allow various molds to invade. Too high a temperature, too high humidity, and poor ventilation at the storage site are important causes of rot in bulbs. Therefore, care should be taken during digging to reduce wounds as much as possible. The storage cellar should be kept clean and hygienic; after being put into the cellar, the cellar temperature should be controlled at about 5 degrees Celsius, and the relative humidity should be controlled below 70%.

11.    Pay attention to the rational arrangement of flower species

According to the characteristics of flower species and the conditions of the site, arrange them rationally so that the cultivated flowers are distributed in an orderly manner, with appropriate spacing, receive the space and sunlight they should have, and are in an environment with smooth air flow, thereby benefiting the growth and development of flowers and being unfavorable to the occurrence of pathogens and pests.

12.    Select healthy, disease- and pest-free propagation material

Viral diseases of flowers occur commonly, and many propagation materials carry viruses. Therefore, virus-free tissue-cultured seedlings should be used in production. It is best to establish disease-free seed fields and collect seeds or obtain propagation materials from healthy mother plants.

13.    Select and breed disease- and pest-resistant varieties

Breeding pest- and disease-resistant flower varieties and cultivating flowers with strong disease resistance can protect flowers from pest and disease damage or reduce the degree of damage. This is one of the important methods for effectively controlling flower pests and diseases.

3. Biological control methods

Biological control is the use of natural enemies to control pests and diseases. Natural enemies are organisms that feed on pests or pathogens. Under natural conditions, natural enemies are widespread and control the damage of pests and diseases, especially pests. In flower care, the role of natural enemies should be consciously strengthened; for example, place pruned pest-infested branches for a few days before burning them, so as to protect the parasitic natural enemies inside the insects.

4. Physical and mechanical control methods

1.    Heat treatment of propagation material

Soaking seeds or other propagation materials in water at a certain temperature can kill pathogens and pests on the surface and inside, but the temperature and treatment time must be well controlled. Too high a temperature and too long a treatment time will both affect the vitality of seeds and other propagation materials.

2.    Soil heat treatment

If conditions permit, soil can be treated with hot steam to kill pathogens, nematodes and pests in the soil. Soil heat treatment should be carried out before planting, and the heated soil should reach a certain depth, with the soil temperature at a depth of 20 cm reaching 75 degrees Celsius as appropriate.

3.    Mechanical barriers

Covering with agricultural film can play a certain degree of mechanical barrier role against the entry and spread of pathogens and pests, and can also inhibit the formation of spores of gray mold and sclerotinia.

4.    Trapping and killing insects and nematodes

Use the tropism of insects and nematodes to control pests and nematodes. For example, use yellow sticky boards to trap and kill adult whiteflies, use flypaper to trap and kill adult leafminers, and plant trap plants to trap nematodes, so as to reduce their damage to flowers.

5. Chemical control methods

Chemical control is pesticide control. It has the advantages of good control effect, quick results and simple methods of use. But at the same time it also pollutes the environment and causes pesticide damage, and after long-term use pathogens and pests will develop resistance. Chemical control is an important part of integrated pest and disease control, but attention must be paid to the scientific use of pesticides.

1.    Correctly select the type of pesticide

Understand the functions of the pesticide and the protection target, and apply the right pesticide according to the type of pest or disease. For example, the fungicide metalaxyl has a very good control effect on downy mildew of various flowers, but cannot control powdery mildew. The insecticide pirimicarb has a relatively good control effect on the vast majority of aphids, but is almost ineffective against cotton aphid.

2.    Rationally select the pesticide formulation

High humidity favors the occurrence of gray mold; therefore, choosing procymidone smoke agents or dust formulations has a better control effect on this disease. To control scale insects, systemic granular formulations can be applied to the soil and systemic liquid formulations can be poured on, so as to achieve the goal of applying pesticide underground to control pests above ground.

3.    Apply pesticide at the right time

Fully understand the occurrence patterns of pests and diseases, find the weak links, and apply pesticide in time. For example, before sowing or transplanting flowers, pesticide disinfection can be applied to seedling rooms and greenhouses, the soil can be treated with pesticide and seeds can be dressed, and disinfectants such as formalin can be used to disinfect agricultural operation tools and containers such as flower pots. Eliminating pests and diseases outside the flower garden and before damage is the best policy. For example, eliminating pathogens and pests on overwintering hosts, or eliminating them during the overwintering stage, are both proactive approaches. For diseases, the favorable time for control is the moment before the pathogen infects, or eliminating the pathogen at the initial stage of occurrence before the next spores reproduce and spread. Applying pesticide too early means its potency will decompose under sunlight and rain and it will not play its due role; applying pesticide too late means the pathogen has already invaded, making it a "belated shot." In controlling pests, the resistance to pesticide of different pests or of the same pest at different developmental stages must be taken into account. For example, the larvae of ordinary pests are divided by the 3rd instar: before the 3rd instar their resistance is poor, and after the 3rd instar their resistance increases significantly, while newly hatched larvae have the lowest resistance. Generally speaking, the resistance of Lepidoptera insects to pesticides is egg > pupa > larva > adult, so the favorable period for controlling larvae is generally before the 3rd instar, and controlling adults is even more favorable. However, controlling boring pests is different; generally it should be done at the peak of egg laying.

4.    Alternation and mixed use of pesticides

Long-term single use of the same pesticide for pest and disease control in the same area may produce resistance within pathogen and pest populations. Therefore, rational alternating use or mixed use of different types of pesticides is advocated, so as to avoid the development of resistance.

5.    Safe use of pesticide to avoid pesticide damage

Some flowers, or a certain growth stage of theirs, may be sensitive to a certain pesticide or certain pesticides; in such cases the pesticide should be used with caution. Even if not sensitive, the pesticide concentration and dosage must be strictly controlled; do not arbitrarily increase the concentration and dosage, so as to prevent pesticide damage. If the pesticide used is a new one, a test of the pesticide concentration and dosage should first be carried out on a small area, and it may only be used on a larger area after it is confirmed to be safe. In addition, highly toxic pesticides should be used with caution, and high-residue pesticides that seriously pollute the environment and water sources should be restricted or prohibited.

(1) Inappropriate pesticide application amount.

Too high a pesticide concentration often causes pesticide damage to flowers, and this is the most easily occurring problem. To prevent pesticide damage, the concentration of the liquid must be appropriate. Different pesticides used in different seasons for different pests and diseases and on different types of flowers all require different concentrations, and preparation must be strictly carried out according to the concentrations specified in relevant pesticide manuals.

(2)    Different types and varieties of flowers, or flowers of the same variety at different developmental stages, react differently to pesticides.

For example, Bordeaux mixture and other copper-containing fungicides easily cause pesticide damage to peach, plum and so on; dimethoate emulsifiable concentrate easily causes pesticide damage to plum blossom, elm-leaved spirea, peach, ornamental peach, Chaenomeles speciosa, cherry blossom and so on; dichlorvos emulsifiable concentrate also easily causes pesticide damage to rhododendron, cherry blossom, plum blossom and so on. For the same flower, generally speaking, the seedling stage, young shoots and young leaves are prone to pesticide damage. The flowering period is even more sensitive to pesticides; therefore, spraying pesticide during flowering easily causes flower and fruit drop.

(3)    The influence of environmental conditions.

Applying pesticide at high temperature gives good results, but too high a temperature easily causes pesticide damage. For example, lime sulfur mixture used in summer at high temperature (above 30 degrees Celsius) very easily causes pesticide damage. Humidity also has an obvious influence on some pesticides; for example, arsenic preparations and Bordeaux mixture easily cause pesticide damage under rainy and high-humidity conditions. Therefore, pesticide application must depend on the weather and be used flexibly.

(1)    Toxicity to natural enemies After many broad-spectrum pesticides are applied, they not only kill pests and pathogens, but also kill natural enemies of pests, thereby causing pest resurgence. The ways to solve this:

Use selective pesticides. For example, ovotran, dicofol and so on have no effect on general insect natural enemies (such as ladybugs, hoverflies, predatory mites, Trichogramma and so on), so using such acaricides to control mites is very safe for natural enemies. Trichlorfon has very low toxicity to ladybugs and their larvae and eggs, and is also relatively safe for parasitic wasps and braconid wasps. Plant-based pesticides also mostly have relatively low lethality to natural enemies. Applying tobacco water is relatively safe for ladybugs, mirid bugs, green lacewings, predatory mites, parasitic wasps and so on. Derris extract has relatively little influence on adult ladybugs and parasitic natural enemies.

Choose a suitable time for pesticide application. For example, applying pesticide while parasitic wasps are still inside the host body will then kill only the pests. Another example is that before artificially releasing natural enemies, first apply a pesticide with a short residual period, and after the pesticide's toxicity has disappeared, then artificially release the natural enemies.

(2)    Toxicity to humans Most pesticides are more or less toxic to humans and livestock; therefore, the safety of humans and livestock must be noted. Before applying pesticide, on the one hand, learn and master the toxicity of various pesticides and the precautions for use; on the other hand, do protective work well. When applying pesticide, the original pesticide or pesticide liquid must not get on the skin; if it does, immediately wash it off with soapy water. Wear a mask when spraying, spray in the downwind direction to prevent the liquid from splashing on the face and inhaling toxic gas, and do not rub the eyes during operation. The tools used should be washed immediately after use and properly kept for future use. After each pesticide application, wash hands with soap as a precaution. If poisoning symptoms appear due to carelessness, immediately take detoxification measures and, if necessary, send the person to hospital for treatment as soon as possible.

Methods for controlling flower diseases

  Flower (Flower ['flauə]; plural: Flowers) is a general term for plants grown for appreciation, with modified short branches that have a reproductive function, and there are many kinds.

A typical flower, on a short axis of limited growth, bears the calyx, petals, and the stamens and pistils that produce reproductive cells. A flower is composed of the corolla, calyx, receptacle and stamens and pistils; it comes in all kinds of colors, and some grow very brightly colored and fragrant.