Plant Disease Management in Agriculture
Today, the topic is about plant disease management in agriculture.
What is plant disease? A plant disease is usually defined as abnormal growth and dysfunction of a plant. Diseases are the result of some disturbance in the normal life procedure of the plant.
Diseases may be the result of living and non-living causes. Biotic diseases are caused by living organisms, for example, fungi, bacteria, and viruses. Abiotic diseases are caused by non-living environmental conditions, for example, soil compaction, wind, frost, soil salt damage, and girdling roots. Plant diseases are of great economic value in crop production. Plant disease is the deviation from the standard state of health of the plant, resulting in the reduction of farm yield and crop failure in severe cases.
The main effect of plant diseases in crop production is a reduction in the capacity of farm produce while pests reduce both the quality and quantity of the farm produce. Both pests and plant diseases must be controlled or managed to attain a reasonable yield from the farm.
Plant diseases management:
Before we explore into methods of controlling plant diseases; it is very important, we understand the plant disease series and how plant diseases emerge.
Plant disease cycle is the succession of events that occur through the development of diseases in a plant. Plant diseases do not just manifest, there are three conditions that must be present for any plant disease to manifest. These are;
- A susceptible plant.
- A virulent pathogen.
- A favorable environment.
A plant disease will emerge if these three conditions are present.
The plant to be infected should be susceptible. Susceptible in the sense that it would have been physiologically weak either as an effect of a nutrient deficiency or water stress. This state is susceptible and the first phase of plant disease development.
Plant diseases are caused by organisms known as pathogens and they must be virulent. A virulent pathogen is a pathogen that is able of causing different plant diseases. Some pathogens can lack the ability to cause disease, probably as a result of reduced vigor. Bacterial diseases in plants happen when pathogens penetrate the plants through openings of the plant tissues; such pathogen is supposed to be virulent.
The environment where the plant and the pathogen will interact must be good for any plant disease to occur. Environment plays a vital position in plant disease management. A good environment that aids disease development is either a waterlogged area or when the plot has been overtaken by weeds. Most fungal diseases in plants are sources of the water-logging situation.
If any of these conditions is missing, the disease will not happen even if two conditions from the aforementioned conditions are present. From this analysis of plant disease management, a farm is thought to record a very negligible disease condition. Truly, plant disease cannot be entirely eradicated, but it can be controlled and reduced below an economic threshold level.
Read: Nematodes in Agriculture.
A farmer has managed over two conditions the susceptibility of the plant and the environment. Imagine a situation where the farmer focuses on only the environment, during controlled irrigation and drainage to discourage water-logging situation or normal weeding to eradicate any plant pest-host; such farm will experience a disease-free operation. Or through fortification of the plants with adequate nutrients, there is an adequate supply of water to avoid water stress. A better understanding of this plant disease management idea can make a farmer cultivates with little or no disease emergence record, equally increasing the quality and quantity and ultimately the farm profit.
Plant disease is best managed during an integrated approach, which includes a grouping of cultural, mechanical, biological practices, and chemical practices.
Some of the plant disease management methods are given below;
Cultural management includes a proper plant selection. Utilize plants that take out well in the local climate. Use disease-resistant selection when possible. Plant qualified seed or seed pieces. Place plants in a suitable environment for optimum growth. For example, develop shade-loving plants in the shade, not hot sun.
Prepare the soil before planting to develop root growth, reduce compaction in clay soils, and improve water holding of sandy soils. Apply fertilizer and water to plant needs. Prune correctly, as needed, and at the accurate time of year.
Fertilizer usage can have some bearing on the development of certain diseases. It differs with crop and every disease, but, nitrogen out of balance with nutrients enhances foliage disease growth and predisposes some plants to other diseases. Potash, on the other hand, helps decrease disease development when it is in balance with other elements.
Planting in a raised bed is helpful in preventing certain diseases such as Southern blight and definitions of the wilt diseases. This practice is advisable when raising leguminous crops such as peanuts, soybeans, and guar, and when growing vegetable crops in tight, weakly drained soils.
Burning of crop residue has been discouraged as of destruction of valuable organic matter and creation of an air pollution problem. The fact remains, however, that it is a highly efficient means of eradicating any disease-causing organisms associated with crop residue.
Time of seeding has a very important bearing on disease prevention in many cases. Delayed planting of wheat will help escape the probability of wheat streak mosaic virus. Early spring planting of cotton can effectively help escape cotton root rot.
Roguing (removal) of diseased plants as they appear is often an effective way of helping reduce the spread of a destructive disease. Virus diseases of stone fruits and bacterial wilt of cucurbits are best examples where roguing is worthy of consideration.
These cultural control practices have been originated to be economically feasible in reducing disease losses. Growers must properly identify the diseases that limit production and then use a variety of controls in combination.
Mechanical management of plant disease methods includes rototilling in the fall, which exposes pathogens, insect eggs, and weed seeds to cold winter temperatures. This action speeds the decomposition of crop residues, improving soil organic matter. Clean up or prune out infested plant materials to reduce the basis of inoculums on the property.
Rotate crops when probable to starve pathogens. For example, avoid planting solanaceous crops in the same area as pathogens specific to this group can build up in the soil and infect new crops. Apply mulch in your gardens. Not only does this maintain soil moister and cooler (helping roots thrive), it creates a splash barrier against soil pathogens or pathogens on plant debris in the soil. Use soil solarization to decrease soil pathogens and weed seeds. Pull weeds and volunteer seedlings that hog precious water, but serve as a reservoir for pathogens and insects. Core aeration turf once or twice yearly.
Chemical control of plant diseases refers to the use of fungicides, insecticides, and herbicides to manage a problem. Always recognize the cause of a plant problem first, then select and use a product appropriate for the problem and follow label directions. Apply it at the correct time using the recommended process. Always spot treat.
Exclusion principles: These exclusion principles of disease control are adopted in anticipation of the plant disease. They aim at avoiding and preventing the expansion of the disease; they involve the below cultural practices:
- Careful choice of the planting site.
- Using adequate planting distance.
- Planting improved and pathogen-free seeds.
- Use of Biosecurity and legislation to restrict group within the farm.
- Choice of healthy and vigorous seeds.
- An adequate supply of nutrients.
- Planting under favorable soil pH level.
- Biological control of plant diseases using the natural enemy of the pest.
Biological controls of plant disease include the use of compost, compost teas, and hyperparasites products, which can reduce pathogens by introducing beneficial microbes. Encourage helpful insects by planting flowering plants attractive to all stages of development. Avoid blanket applications of pesticides, which may kill beneficial in adding to harmful insects. Spot treat pest troubles instead.
Eradication principles or Reduction of the Pathogen
These principles of crop protection are adopted when plant disease has appeared. They aim at killing or eliminating and outright elimination of pathogens from the farm.
Serious disease damage to a crop or garden patch can be prevented or reduced by pulling out and destroying the first plant or the first few plants that explain the disease symptoms (roguing). This prevents the increase of the pathogen to other healthy plants (e.g., elimination of the first bean plants with mosaic symptoms).
Since some of the roots-infecting pathogens remain feasible in the soil even after the crop is harvested, avoid planting the same or similar susceptible crop in that component of the garden for the next 2 to 3 years. Suitable crop rotation in the garden is very essential to reduce the damage caused by root rot and wilt-causing pathogens and nematodes.
Eliminating the infected leaves and diseased or dead branches, as well as using fresh garden tools and similar methods of sanitation, will prevent the spread and build up of disease-causing organisms. Other cultural practices, such as increasing plants on raised beds and using composted tree bark in the planting medium for containerized nursery stock, help decrease the damage caused by certain soil-borne pathogens (e.g., damping-off, root rots, and wilts). Apply proper irrigation management can prevent some diseases (e.g., collar rot of apple).
Using the sun’s heat through the summer months to reduce some of the soil-borne pathogens can be successful in certain regions. In this procedure, called soil solarization, the soil is cultivated to a fine texture and deeply watered. The moist soil is covered with an apparent polyethylene sheet. The sheet’s edges are buried to make an airtight environment. The moist soil below the polyethylene mulch heats up and is gradually “cooked.” Under sunny weather conditions for at least 4 weeks, this procedure reduces or eliminates several soil-borne pathogens.
Marigolds interplanted with nematode susceptible crops create substances in the soil that are toxic to plant parasitic nematodes and thereby reduce the nematode damage to the crop plant. Controlling insects with insecticides can decrease the spread of some of the diseases caused by viruses that are transmitted by insects (e.g., potato leaf roll virus spread by aphids).
This suppression principle for plant disease management can be adopted in both an organic or inorganic farm as plant disease control measure. It is accepted when a plant disease has emerged. It aims to maintain the population of the pathogen below an economic threshold level, thereby making the disease unnoticed.
Lastly, plant diseases can also be controlled during integrated plant disease management. It involves the grouping of the two or more methods of plant disease management or principles.
Integrated disease management:
An effective, economical, and sustainable disease management strategy must incorporate all the available approaches to a disease management program. It must include the relevant preventive and control measures appropriate for the crop, such as selection of planting site, selection of the mainly adapted and disease-resistant variety, crop rotation, pathogen-free planting material, seed treatment, appropriate planting date, planting depth and density, irrigation and fertilizer use, weed control, sanitation, appropriate pesticide applications, suitable harvesting, and handling and storage of the produce. The integrated disease management measures selected must be effective (should control the disease), economical (should result in an economic return), and sustainable (must be environmentally sound).
The above all are the methods of plant disease management to adopt in both organic and inorganic farms. It is better to prevent and avoid them to eradicate. Prevention of plant disease management is often cheaper compared to plant disease diagnosis and disease control. As a good farm manager, you should always ensure your farm is healthy by adopting any of the aforementioned plant disease control methods.