The onset of plant disease is one of the most puzzling events that can occur in your garden Plant. How did it take place? Will it grow more? Will every plant I have to die? How do I remove it? The health triangle is a concept that is important to understanding disease prevention (see drawing, right). Three events must occur simultaneously for the disease to occur.
You have a plant that can get sick (the host), a pathogen that can infect the plant (like a fungus, bacteria, or virus), and environmental factors (such as humidity or drought) that encourage the sickness. Cancer cannot exist without any of those factors, so removing even one of them is important for prevention.
The best protection against disease is a good offense, so consider this before you wait for a problem to develop in your garden.
Here are some tips for keeping your plants healthy and removing at least one-half of the disease triangle.
1. Examine plants carefully before purchasing
Avoiding the introduction of disease at its source is the best strategy to reduce its impact on your garden. No one wants the added benefit of getting a disease from a new plant. Understanding what a healthy plant must look like is one of the hardest things to learn, making it more challenging to determine whether the plant you want is sick.
A few books, journals, and catalogs that display images of healthy samples are a wonderful idea to gather. Avoid taking home a plant that has insects, rotten stems, or dead patches. Once established, these problems can easily spread to your plants and are sometimes difficult to remove.
Always check the plant's roots in contrast to the crowns for quality. Although it ought to be common, one does not frequently see consumers doing this in a garden center. Put the plant stem in your fingers and place your palm on the earth.
Shake the plant loose by gently turning the pot upside down. To remove the roots from the pot, you may need to tap the pot's edge on a hard surface. The root ball must have firm, often white, evenly spaced roots. Roots that are very dark or mushy are not a good sign. It won't be long before a plant with a rotting root system dies, even if the tops seem healthy.
2. Use fully composted yard waste
A compost pile contains a variety of things that degrade at various rates. Other materials may not have rotted sufficiently to be put in the garden. Completing the composting process completely generates high temperatures that last for a long time and truly remove any germs present in the material.
Infected plant debris that has not undergone this process may likely propagate diseases in your yard. Avoid putting yard waste as mulch near delicate plants, and do not add infectious materials or debris to your compost pile if you are unsure of the health of the pile.
3. Keep an eye on your bugs
Damage from insects to plants goes well beyond simple economics. Bug damage creates the opening that viruses and bacteria frequently need to infect a plant. By moving viruses from one plant to the next, these insects actually serve as carriers for viruses.
Trips also carry the impatiens dry spot virus, which has been a significant issue for growers over the past ten years. Aphids are one of the virus' most frequent carriers. Aster yellows (photo on the right) affect a large variety of host plants and are spread by leafhoppers. Another factor that might stress out a plant and impair its ability to resist disease is insect infestation.
4. Clean up in the fall
Even if you live in a climate with mild temperatures, it is always better to clean up the garden in the fall. This is not only a wonderful approach to preventing sickness, but it's also a good strategy to manage diseases that are currently present in your garden.
On dead leaves and other debris, diseases can overwinter and then attack new leaves when they grow in the spring. If the old leaves are removed each fall, diseases like lily leaf spots, daylily green streaks, and black spots on roses can be greatly diminished. If you left stems and foliage to add interest in the winter, make sure to get rid of them before springtime new growth begins.
5. Use the right fertilizer
It's important to use care while fertilizing plants because too much fertilizer can burn the roots and reduce the plant's ability to absorb water. As a result, hunger, cold, and heat stress on the plants are increased.
A larger plant can fend off illnesses, whereas nutrient-starved plants are smaller and are more subject to leaf spots. Another way to stress out a plant is to have too much of a certain nutrient.
Your local extension office may do a soil test to provide you with accurate data on the nutrient levels in your soil. Without it, you would likely have to rely on guesswork when feeding your plants, which could lead to too much of one vitamin or too little of another.
6. Plant disease-resistant types
Plants that are disease-resistant are ones that could contract a particular disease but will resist it rather than die from it. For instance, certain tomato types are designated as "VFN resistant," meaning they are resistant to nematodes, Verticillium, and Fusarium.
Because disease resistance is rarely found on plant tags, you will most likely be disappointed if you start hunting for these codes on flowers. This does not suggest that all flower varieties have disease resistance. Many rose growers offer plants that are impervious to maladies like black spots and powdery mildew.
You can get assistance in identifying which types of various plants are the best or most hardy from nursery workers and other gardeners. Reference books and guides may also include a list of cancerous plant cultivars and species.
7. If needed, remove damaged limbs
It is best to trim trees and shrubs in the late winter as compared to the spring. Infected limbs can spread illness over the winter, which will allow it to grow while the plant is dormant. Pruning in the late winter prevents the disease from spreading into new growth.
Because although late-winter rains can result in more damage, it is still better to remove a damaged limb now rather than wait until spring to do so. Always make clean, quick cuts with sharp instruments, and make sure you only remove healthy, living tissue.
8. Water properly
It's a good idea to water your garden, but since many diseases require water as much as plants do, how you go about it matters a lot. Water is required for many diseases in the soil and air to travel, grow, and reproduce. Select watering techniques that limit moisture on a plant's leaf to prevent giving these diseases the habitat they love. This is done using sponge hoses and drip irrigation. Hold the foliage out of the way when you water the roots if you are watering by hand.
The least desired option is overhead spraying, as the most common leaf issues are made worse by wet leaves. However, if you go with this method, water the leaves when they are about to dry out quickly, but the roots still have time to soak up the water before it evaporates.
9. Don’t crowd plants
Carefully consider the distance between transplants and monitor the spread of existing plants. Because crowded plants make their own humidity, diseases like downy mildew, rust, and downy mildew can grow. This high relative humidity can be lowered by increasing airflow around your plants, which also speeds up the drying of the leaf.
Plants grown too close to one another compete with one another for light, water, and nutrients, which results in poor growth. These vulnerable plants are more easily attacked. When plants are close to one another, it is more probable that an infected leaf may come into contact with a normal one, a second way that diseases can spread.
Trim off crowded, damaged, or old stalks on plants like Phlox paniculata that are prone to powdery mildew to reduce the risk of illness. When your plants require it, you should divide them or rearrange them.