Do you love plants? Do you want to grow them in your garden, balcony, or indoors?
If so, you probably know how frustrating it can be when your plants get sick and die.
Plant diseases can ruin your hard work and spoil your enjoyment of nature. But don’t despair! You can take steps to prevent and manage them.
This article will explore the nature, causes, and control of plant diseases and the various methods you can use to prevent or treat them.
We will also give you some advice on how to make your plants stronger and more resilient to diseases.
What Are Plant Diseases?
Plant diseases are disorders that affect the normal functioning of plants. It can be caused by various factors, such as weather, bugs, worms, germs, or molds.
Any part of the plant can be affected by diseases, such as the blossoms, fruits, leaves, branches, or roots. They can cause symptoms such as wilting, yellowing, spotting, blighting, rotting, or deformity.
Some examples of common plant diseases are:
- Powdery mildew: a disease caused by fungi that makes the leaves and stems of many plants, such as roses, grapes, cucumbers, and squash, turn white or gray.
- Black spot: a fungal disease that causes black or brown spots on the leaves of roses and other plants.
- Fire blight: a bacterial disease that causes the shoots and branches of apple, pear, and other fruit trees to turn black and die.
- Tomato spotted wilt: a viral disease that causes yellow or brown spots on the leaves and fruits of tomato, pepper, and other plants.
- Root rot: a fungal or bacterial disease that causes the roots of plants to decay and die.
- Anthracnose: a disease caused by fungi that makes the leaves and fruits of many plants, such as avocados, mangoes, strawberries, and beans, develop dark spots.
How Do Plant Diseases Spread?
Plant diseases spread by different means depending on the type of agent that causes them. Some common ways of disease transmission are:
- Spores: many fungi produce microscopic spores that can be carried by wind, water, insects, animals, or humans. These spores can land on susceptible plants and germinate to infect them.
- Tools: some diseases can be spread by using contaminated tools or equipment that have come in contact with infected plants. For example, pruning shears can transmit fire blight or black knot. However, you should be careful when using tools such as a watering can, a hand trowel, or even handy tools such as a cordless backpack sprayer, as they can also spread diseases if they are not cleaned and disinfected properly before and after using them on different plants.
- Insects: some insects can act as vectors of plant diseases by feeding on infected plants and transferring the pathogens to healthy plants. For example, aphids can transmit viruses such as cucumber mosaic virus or potato leafroll virus.
- Seeds: some diseases can be transmitted through infected seeds that are planted in the soil. These seeds can harbor pathogens that can infect the seedlings or the soil.
- Water: some diseases can be spread by irrigation water that contains pathogens or spores. For example, root rot or damping off can be caused by overwatering or poor drainage.
How Can You Prevent and Control Plant Diseases?
The best way to prevent and control plant diseases is to use a combination of strategies that aim to reduce the chances of infection and limit the spread of pathogens.
These strategies include:
Choose a time or a site where there is no disease or favorable conditions for infection. Try:
- Planting crops at the right time of the year when the weather is not too hot or humid for fungal diseases or too cold for bacterial diseases.
- Choosing a location that has good air circulation, sunlight exposure, and soil drainage for your plants.
- Rotating crops every year to avoid planting the same type of plant in the same spot where pathogens may have accumulated.
In order to prevent the introduction of disease-causing agents into your garden or home, you should:
- Buy certified disease-free seeds or plants from reputable sources.
- Inspect new plants for signs of disease before bringing them home.
- Quarantine new plants for a few weeks before planting them with your existing plants.
- Disinfect tools and equipment before and after using them on different plants.
Eradication is one of the best ways to prevent and control plant diseases. It involves completely eliminating or reducing the pathogen population that causes the disease.
Eradication can be achieved by using chemicals such as eradicants, protectants, therapeutic chemicals, soil treatments, and seed treatments.
These chemicals can stop or slow down the growth of other plant pathogens, such as nematodes, fungi, bacteria, and others. Eradicants are applied to seeds, bulbs, corms, tubers, or soil before planting to kill any existing pathogens.
Protectants form a barrier between the plant and the pathogen and prevent infection. Therapeutic chemicals are used to treat an ongoing infection.
Soil treatments use steam or chemical fumigants to kill soil-inhabiting pathogens. Seed treatments use systemic fungicides that are absorbed by the seeds and protect the seedlings.
Besides chemical methods, eradication can also be achieved by using biological methods that involve the use of organisms that are antagonistic to pathogens.
These organisms may produce antibiotics, parasitize, or compete with the pathogens for food and reduce their numbers. Biological control can be enhanced by using cultural practices that favor the antagonists.
- Bacteria: Using beneficial bacteria such as Bacillus subtilis or Pseudomonas fluorescens to compete with or inhibit pathogens on plant surfaces or in the soil.
- Fungi: Using fungi such as Trichoderma harzianum or Gliocladium virens to parasitize or antagonize pathogens in the soil or on plant roots.
- Insects: Using beneficial insects such as ladybugs, lacewings, or parasitic wasps to prey on or parasitize insects that transmit plant diseases.
- Plants: Using companion plants such as marigolds, garlic, or basil to repel or deter insects or pathogens from your plants.
- Using physical barriers such as row covers, nets, or mulches to prevent insects or spores from reaching your plants.
- Pruning your plants to remove any dead, damaged, or diseased wood and to improve air circulation and light penetration.
Cultural methods mean using practices that reduce disease incidence or severity, such as:
- Crop rotation: Changing the type of crop you plant in a given area every year to avoid building up pathogens in the soil or on the plants.
- Sanitation: keeping your garden or home clean and free of weeds, pests, and debris that may harbor pathogens.
- Pruning: Cutting back your plants to remove any dead, damaged, or diseased wood and to improve air circulation and light penetration.
You can use physical methods like:
- Heat: Using hot water or steam to treat seeds or tools before planting or using them.
- Cold: Using cold storage or freezing to preserve seeds or plants from pathogens.
- Radiation: using ultraviolet light or gamma rays to sterilize seeds or tools.
- Mechanical: using filters, screens, or traps to exclude insects or spores from your plants.
How Can You Make Your Plants More Resistant to Diseases?
Another way to prevent and control plant diseases is to make your plants more resistant to them. Resistance means the ability of a plant to withstand or overcome the effects of a pathogen. Resistance can be natural or induced.
Natural resistance means the inherent ability of a plant to resist a disease due to its genetic makeup. Some plants are naturally resistant to certain diseases because they have genes that code for proteins that can recognize and fight off pathogens.
For example, some tomato varieties are resistant to the tomato spotted wilt virus because they have a gene that blocks the virus from entering the plant cells.
Induced resistance means the acquired ability of a plant to resist a disease due to external factors. Some plants can become resistant to certain diseases after being exposed to them or after being treated with chemicals or biological agents.
For instance, some plants can become resistant to powdery mildew after being sprayed with a solution of baking soda and water.
To make your plants more resistant to diseases, you can:
- Choose disease-resistant varieties of plants when buying seeds or plants. Look for labels that indicate the level of resistance of a plant to a specific disease. For example, VFN means resistant to verticillium wilt, fusarium wilt, and nematodes.
- Use grafting techniques to combine a disease-resistant rootstock with a desirable scion. Grafting is a method of joining two different plants together so that they grow as one. You can graft a tomato scion onto a potato rootstock to create a tomato-potato plant that is resistant to nematodes.
- Apply elicitors to your plants to induce resistance. Elicitors are substances that trigger the defense mechanisms of plants against pathogens. You can apply salicylic acid, jasmonic acid, chitosan, or seaweed extract to your plants to induce resistance against various diseases.
Plant diseases are a common problem for gardeners and plant lovers. They can cause significant losses in yield and quality of your plants.
However, you can prevent and control plant diseases by using different strategies we mentioned in this article that aim to reduce the chances of infection and limit the spread of pathogens.
So, don’t worry. Do your research before planting, and your plants should be just fine!