Introduction to overwintering places of plant diseases and insect pests

Many flower lovers feel that winter is a relatively safe season for diseases and insect pests. In fact, the overwintering places of garden plant diseases and insect pests are relatively fixed and concentrated, and winter is also a key period for the prevention and control of diseases and insect pests. The editor would like to introduce you to the overwintering place of diseases and insect pests in winter.

Melon leaf chrysanthemum (details)

1. Seedlings and other breeding materials. Diseased seeds, seedlings, bulbs, bulbs, tubers, scions and other reproductive materials are the main sources of primary infection of pathogens such as pathogens and viruses. Pathogens can be attached to the surface of these materials or latent internal overwintering, such as: hundred days chrysanthemum black spot disease, melon leaf chrysanthemum virus disease, geranium brocade disease and so on. Breeding materials with disease often become the disease center of green space and flower bed, and the growing season makes the disease spread, spread and even cause epidemic.

2. Soil. Soil is an important source of infection for soil-borne diseases or root diseases. Pathogens dormant in the soil over the winter; some can survive for several years, such as chlamydospores, sclerotia, cords and so on. The saprophytic ability of soil habitual bacteria is very strong, which can not only survive on the host residue, but also directly operate saprophytic life in the soil. Pythium and Rhizoctonia, which cause seedling blight, can live in the soil for a long time. In fertilizer, if mixed with unripe plant remains, it often becomes the source of infection.

3. The remnant of diseased plant. The pathogen can overwinter on withered branches, fallen leaves and fallen fruits, and infect the host the following year.

4. Diseased plant. The existence of diseased plants is also one of the sources of primary infection. Once perennial plants are infected, pathogens can be retained in the host, such as stem rust, canker, rot, and vegetative forms can survive the winter in the host. Greenhouse flowers due to the particularity of living conditions, their diseases are often the source of infection of flowers in the open field, such as virus disease, powdery mildew and so on.

Control of plant diseases and insect pests in winter-in winter, most of the pests overwinter in eggs, larvae, cocoons and adults (shell insects) in soil, litter, weeds, bark, cracks, bud axils, branches and so on. Bacteria are mostly overwintered by mycelium and spores in the disease residue and soil. For example, the leafhopper overwinters the eggs on the branches of sweet-scented osmanthus, yinxiang and camphor (there is a white substance on the spawning place), and the branches above wither and die; the leafy banyan planthopper overwinters with nymphs and eggs in the axils of the leaves. It is necessary to remove these overwintering diseases and insects and clean the overwintering places in time.

Withered branches, fallen leaves and weeds should be removed; diseases and insect pests and overlapping branches should be cut off, which can directly eliminate a large number of overwintering pests and pathogens, improve plant ventilation and light transmission conditions, and enhance tree potential in the coming year; artificial removal of cocoons, egg blocks, buds, scraping of overwintering scale insects; ploughing soil sun resistance to reduce overwintering diseases and pests; at the same time, pay close attention to the control of trunk borer pests.

The trunk should be whitened after falling leaves to before the soil is frozen, which can not only kill the diseases and insects overwintering on the trunk, but also effectively reduce the freezing injury. The whitening materials are raw lime, sulfur (or stone-sulfur mixture), water and salt, and the whitening height is 1.1 meters.

We should also pay attention to anti-freezing in winter. The freezing injury is caused by the cell death caused by the non-lipid gap with high permeability on the plant protoplasmic membrane and the leakage of intracellular substances caused by the sudden drop of air temperature. The twigs can be cut off in early winter to promote the Lignification and nutrition accumulation of the branches, and improve the cold resistance; stop applying nitrogen fertilizer to trees, and properly apply some phosphorus and potassium fertilizer; spray antifreeze to enhance the frost resistance of plants and reduce the mechanical damage to the membrane system caused by the formation of frozen crystals in the protoplast at low temperature; root neck soil cultivation can prevent frostbite of root neck and tree roots, and reduce soil moisture evaporation at the same time. For valuable tree species that are not cold-resistant, wind barriers can also be erected in the upwind direction of the trees. Occurrence characteristics and control strategies of plant diseases and insect pests in urban garden

With the rapid development of urban landscaping construction, a large number of flowers and trees have been planted in the corners of the city, adding a beautiful landscape effect to the city. However, in the process of growth and development of these flowers, grasses and trees, they are often attacked by various diseases and insect pests, which make them lose their ornamental value and greening effect, and even cause the death of the whole tree, so that large areas of urban greening tree species, scenic forests and other trees decline or die, resulting in significant economic losses. In view of the current problems faced by garden plants, this paper puts forward a number of comprehensive control strategies, such as strict quarantine, strengthening management, cultivation prevention, natural enemy control, biological control, artificial control, physical control, chemical control, improving pesticide application technology and so on. For the reference of colleagues in the industry.

The prevention and control of garden plant diseases and insect pests is based on plant pathology and general entomology, and is a science based on the study of the occurrence of garden plant diseases and insect pests. Taking garden plants as the object, it is a science that studies the diagnosis, identification, occurrence regularity, investigation, prediction and integrated control theory and technology of garden plant diseases and insect pests. With the increasing improvement of economy and living standards, landscaping is becoming more and more important in people's life. However, in the process of growth and development of these flowers, grasses and trees, they are often attacked by various diseases and insect pests, which make them lose their ornamental value and greening effect, and even cause the death of the whole tree, so that large areas of urban greening tree species, scenic forests and other trees decline or die, resulting in significant economic losses.

1 the importance of prevention and control of garden plant diseases and insect pests

Landscaping is an important part of urban modernization. People use rich flower resources to afforest and beautify the environment. These garden plants can not only create a beautiful environment suitable for human life, but also achieve better economic benefits. However, in the process of growth and development, these flowers, grasses and trees are often attacked by a variety of natural disasters, garden plant diseases and insect pests is a very common natural disaster. Under the same circumstances, diseases and insect pests often lead to poor growth of flowers and trees, necrotic spots on leaves, flowers, fruits, stems and roots, or deformities, wilting, decay, incomplete morphology, fallen leaves and root rot, which reduce the quality of flowers and trees, make them lose their ornamental value, greening effect, and even cause the death of the whole plant. Some diseases and insect pests can degenerate some flower varieties year by year, eventually destroy them all, or make urban greening tree species, scenic forests and trees decay or die, resulting in significant economic losses. With the development of urban modernization and the improvement of material and cultural level, people's demand for ornamental plants increases sharply, coupled with the increasing depletion of existing forest resources, they are deeply aware of the shortage of flower resources and forest resources. Therefore, while making efforts to expand national garden plants and forest resources, China and many other countries have formulated specific regulations and measures for the prevention and control of diseases and insect pests, and invested a lot of human and financial resources to reduce the heavy losses caused by diseases and insect pests to the national economy. Therefore, mastering and implementing the theory and technical measures of pest control is an important guarantee to improve the ornamental value and economic value of garden plants.

2 current problems

2.1 the introduced plant varieties are single, which creates conditions for the occurrence of diseases and insect pests.

Since the 1990s, most of the lawn plants introduced into the city are grasses (Kentucky bluegrass, ryegrass, tall fescue) and white clover, the street trees are mainly white wax, lack of native plants. This artificial ecosystem is very fragile, and it is difficult to establish the interaction, mutual restriction and coordination between plants and the environment, plants and herbivores (including a variety of organisms) and natural enemies. During this period, due to the lack of biological and abiotic factors in the ecosystem, the newly invaded diseases and insect pests will grow and breed rapidly on these abundant and continuous plant foods once they encounter suitable environmental conditions, resulting in a great occurrence. Such as 1998 and 1999 Zhengzhou cold season lawn Spodoptera litura.

2.2 single means of prevention and control

At present, the prevention and control of garden plant diseases and insect pests depends to a large extent on chemical pesticides, because of its simple use, quick effect and good effect, especially when diseases and insect pests occur, chemical control often becomes the only effective measure. However, chemical control also has many disadvantages, improper use can cause human and animal poisoning, pollute the environment, kill natural enemies, and cause drug damage. Lack of the overall concept of the ecological environment, and often ignore comprehensive management, especially biological control and other pollution-free control technologies, affecting the improvement of the overall level of control, resulting in the destruction of the ecological environment, natural enemies and other natural control functions are weakened, resulting in the emergence of drug resistance of diseases and pests and rampant again. The long-term use of a single variety of pesticides will cause varying degrees of resistance to some pests and pathogens, resulting in higher and higher drug concentration, smaller and smaller safety, and more and more difficult to control. In addition, the environmental pollution caused by outdated pesticide application and excessive use of pesticides has aroused widespread concern among the public.

2.3 the growing environment of garden plants is deteriorating day by day

The plant growth environment is deteriorating day by day. With the acceleration of urbanization, the structure of modern urban infrastructure construction is becoming more and more complex, and the problem of environmental pollution is becoming more and more serious. Flowers and trees in street trees and street green spaces are often affected by sewers, gas pipes, wires and cables, and many other underground facilities, and toxic gases or waste water emitted from cars and factories also affect plant growth all the time. Garden plants grow in a bad environment, the plant growth is not robust, and the disease resistance is poor, which provides favorable conditions for the invasion of diseases and insect pests.

3 prevention and control strategy

3.1 carry out strict quarantine

The primary task of prevention and control of garden plant diseases and insect pests is to strengthen plant quarantine and strictly prevent the invasion of dangerous diseases and insect pests. With the acceleration of urbanization in China, urban construction has entered a new stage of development, and the exchange of seeds and seedlings between domestic and foreign garden departments has become increasingly frequent. When introducing or exporting plant materials, it is necessary to take as key quarantine objects the species of dangerous diseases and pests that have not yet been discovered, have strong breeding ability, have wide adaptability, do great harm, and can spread with plant materials, and those that are found to be imported should be blocked and eliminated on the spot. Such as pine stem scale, pine stem nematode disease, root-knot nematode, root nodule disease, leaf miner and other diseases and insect pests are easy to spread with the seedlings. Therefore, strict plant quarantine should be carried out in the process of introduction and transportation of seedlings.

3.2 to strengthen conservation management and improve the stress resistance of plants, the occurrence and damage of diseases and pests are related to the growth potential of plants to a considerable extent. The plants with poor growth potential should be fertilized, watered, loosened and weeded in time to improve their own resistance to diseases and insects. And combined with autumn and winter pruning to remove disease and insect branches. This can not only regulate plant nutrients, but also reduce the sources of overwintering diseases and insects, ventilate and transparent light, enhance tree potential, and create environmental conditions that are not conducive to the overwintering, reproduction and damage of diseases and insect pests.

3.3 Prevention of cultivation and management

This is a basic measure in comprehensive control. According to the principle that the occurrence, harm and development of diseases and insect pests have certain requirements on external environmental conditions and host conditions, we should grasp the main ecological factors that affect the growth and decline of diseases and insect pests. Through a series of technical measures such as improving cultivation, conservation and management, we can change the suitable growth conditions of diseases and insect pests, create a good growth and development environment for garden plants, and improve their resistance to diseases and insect pests. To restrain the occurrence of diseases and insect pests.

3.3.1 breeding of pest-resistant varieties combined with the occurrence of local diseases and insect pests, breeding disease-resistant and insect-resistant garden plant varieties such as ginkgo biloba, Magnolia magnolia, etc., and strictly carry diseases and insect pests when raising seedlings and emergence, this is the most economical and effective way to control garden diseases and insect pests.

3.3.2 the diversity of suitable trees and garden plants uses the method of evergreen deciduous leaves to plant lawns, ground cover plants, trees and shrubs in multiple layers, and through the scientific collocation of tree species, establish a reasonable plant community structure and give full play to the role of natural control factors. promote the stability of urban garden ecosystem and improve the self-regulation ability of plants to diseases and insect pests.

3.3.3 reasonable fertilizer and water measures ornamental plants should be fully mature if organic fertilizer is used, so that the pathogens and pests in organic matter can be completely killed. When using inorganic fertilizer, the proportion of nitrogen, phosphorus and potassium should be reasonable, and proper application of phosphorus and potassium fertilizer can improve plant disease resistance. No matter the watering method, the amount and time of watering, ornamental plants all affect the occurrence of the disease. Sprinkler irrigation and water nourishing will aggravate the occurrence of leaf diseases, it is best to use furrow irrigation and drip irrigation. Watering time is best chosen in the morning on a sunny day, in order to reduce the humidity on the leaf surface in time, which can improve the disease resistance of plants.

3.3.4 strengthen the tending management and timely pruning of garden plants to enhance the tree potential, combined with pruning to remove plants, diseased branches and residues infected by diseases and insect pests, so as to reduce the source of diseases and insect pests.

3.3.5 the pathogens (bacteria) or overwintering eggs of most diseases and insect pests in the clean garden overwinter in the litter or weeds in the garden, so the litter, leaves and weeds in the garden are thoroughly removed and destroyed in winter to improve the hygienic condition. can greatly reduce a variety of disease and insect sources. Many weeds are wild hosts of plant diseases, such as plantain and other weeds are wild hosts of root-knot nematodes. Overgrowth of weeds also increases the humidity of the microclimate, which is beneficial to the infection of pathogens.

3.3.6 White trunk painting can not only effectively prevent frost injury and sunburn of trees in winter, improve the disease resistance of trees, destroy the overwintering places of diseases and pests, kill mites and scale in the bark, but also prevent adult longicorn beetles from laying eggs in the following year, which plays the dual role of anti-freezing and killing insects.

3.4 popularizing and applying the technology of pollution-free control of natural enemies will not destroy the ecological balance, pollute the environment and do not harm natural enemies, which is the main direction of pest control research in the future. Research in this aspect should also be strengthened in the prevention and control of insect pests in garden plants, such as pest control with insects, bacteria, birds, etc., as well as the use of black light, extra-sex hormones, laser and other modern science and technology to eliminate pests, or cause hereditary physiological defects, resulting in male infertility and improving the level and effect of pest control.

3.4.1 Pest control through the protection and use of parasitic or predatory natural enemies, such as the use of Turkish flat grain beetle to control cypress beetle, the use of Trichogramma to control acacia inchworm, the use of red ladybug to control paramecium and so on.

3.4.2 use birds to control pests and use beneficial birds to control pests, such as using woodpeckers to control longicorn beetles, gray magpies to control pine caterpillars, and poultry, such as raising chickens to control acacia inchworm.

3.5 the choice of biological pesticides can effectively protect natural enemies and eliminate pests in the process of pest control, with little pollution to the environment, and has a lasting control effect on diseases and insect pests compared with chemical pesticides. For example, using BT emulsion to control acacia inchworm can control its harm by spraying twice a year, while chemical pesticides must be used to control each generation of pests more than twice. In addition to Bt emulsion and urea, Huabao and nicotine produced in recent years are the first choice of plant insecticides to control garden diseases and insect pests.

3.6 physical and mechanical control methods according to some habits of pests, the use of tools, equipment or the creation of material conditions preferred by pests, the use of light, heat, radiation and other mechanical, physical and artificial methods to control pests. Because of its simplicity and pollution, this method is especially suitable for urban gardens.

3.6.1 Light trapping takes advantage of the phototaxis of pests such as nocturnal moth, diamondback moth, poisonous moth, borer moth, withered leaf moth, leafhopper and beetle adults, and sets a black light to trap and kill them during the peak period of adult occurrence.

3.6.2 latent traps make use of the overwintering characteristics of pests (such as Salix moth larvae, pine caterpillars, leaf mites, etc.) in autumn to bind grass ropes on the tree trunk to lure pests to overwinter, and the following spring can kill pests.

3.6.3 use hormones to control insects and use extra-sexual hormones of insects as attractants to trap and kill pests. At present, more than 1000 kinds of insect sex hormone compounds have been synthesized, of which 280species are commercialized. Extra-sex hormones such as cotton red bollworm, cotton bollworm and pear heart borer have been widely used in pest prediction in China.

3.7 artificial control

Scrape off the eggs of the dance moth on the tree trunk or building, dig up the pupae of the locust inchworm in the pine soil near the locust tree, pick the insect bag of the poplar moth, shock and kill the larvae of the locust inchworm, Pinus tabulaeformis caterpillar and Dendrolimus punctatus, scrape off the shell insects on the tree trunk, cut off the diseased branches and leaves, and so on.

3.8 correct use of chemical pesticides

Chemical control should be carried out only in case of emergency, target control should be carried out, and agents with strong selectivity, low toxicity and little environmental pollution should be selected as far as possible. The method of using chemicals to control diseases and insect pests is mainly used to solve the sudden or serious occurrence of diseases and insect pests in a large area. It has the advantages of fast efficacy, convenient mechanization and large-scale application, and less affected factors, but it also has obvious side effects such as killing natural enemies, producing resistance, polluting the environment and so on. Therefore, the correct use method must be mastered when using chemical pesticides. First of all, we must have a correct understanding of pesticides and their dosage forms, prevention and control objects, various means of use of pesticides, toxicity of pesticides, etc. Secondly, it is necessary to be familiar with and master the performance of all kinds of pesticides, to clarify the effects of pesticides on protected plants (such as stimulating growth and development, plant drug resistance and conditions for drug damage, etc.), and to investigate and analyze the occurrence regularity of diseases and pests in different areas, as well as meteorological conditions (light, temperature, humidity, wind and other diseases and insects, etc.) and the impact on the role of pesticides. Third, we must prepare the necessary conditions and safety measures for the use of pesticides, and at the same time carry out strict technical training for operators.

3.8.1 grasp the meteorological conditions conducive to pesticide application, meteorological changes directly affect the effect of pesticide use. As far as temperature is concerned, the suitable temperature for most pesticides is 2O~3O ℃. Too high or too low temperature will affect the efficacy of pesticides. Generally speaking, the pesticide should be applied on a sunny day before 10 o'clock in the morning or after 15:00 in the afternoon. rainfall has a great influence on the use of pesticides. Rain Water can dilute and wash off the chemicals on the leaves, such as re-spraying if it rains within 24 hours after spraying.

3.8.2 seize the weakest link of diseases and insect pests and the most favorable opportunity for mass killing. General diseases have significant differences in response and sensitivity to pesticides in the whole infection cycle or at different stages of life history. the disease in the early stage of the disease or the stage of spore germination and invasion of plants is the weakest link in his life history, sensitive to pesticides and the weakest ability of drug resistance, which is the key period of control. The resistance of insect pests is the weakest before the first hatching to the third instar, especially the egg hatching period and the molting stage of larvae are the best periods for pesticide application.

3.8.3 it is necessary to pay attention to the different growth stages of plants applied in the insensitive period and different plants have different responses to pesticides, the resistance of seedlings and flowering stage is poor, and the plants with weak growth and malnutrition are more likely to produce drug damage.

3.8.4 in order to maintain the ecological balance, we should pay attention to the protection of natural enemies in the prevention and control of diseases and insect pests. For example, the application of pesticides in the egg stage or pupal stage of natural enemy insects can achieve the purpose of controlling pests and protecting natural enemies.

3.8.5 For diseases and insect pests that can be treated concurrently. It is necessary to implement simultaneous treatment, minimize the frequency of application to avoid environmental pollution and the generation of pest resistance, and accurately grasp the use concentration and limit concentration of each agent for each control object.

3.8.6 Pay attention to the alternate use of drugs, try to slow down the occurrence of drug resistance of control objects, and at the same time, according to the purpose of prevention and control, select appropriate pesticide formulations to improve the control effect. Such as the control of leaf-eating pests, generally use emulsifiable concentrate, wettable powder; control of underground pests generally use powder, emulsion, etc. to prepare toxic soil treatment soil and so on.

3.9 Improved application techniques

At present, most of the urban pest control methods use conventional spraying. It is estimated that only 25%-50% of pesticides sprayed from conventional spraying equipment are deposited on plant leaves, less than 1% of pesticides are deposited on target pests, and only 1%-3% of pesticides can play an insecticidal role. This pesticide application method is not only inefficient, causing pesticide waste, but also causing a large number of pesticides to be lost to non-target environments, causing human and animal poisoning and environmental pollution. Therefore, it is necessary to improve the application technology of chemical pesticides (especially spraying), improve the utilization rate of pesticides, reduce the amount of pesticides in non-target environments, and protect the environment on which we live.