How To Deal With Plant Disease Problems
There’s nothing worse than watching a plant start to wither and die because of a disease problem. Learn how to spot the early signs of disease so you can keep your plants in pristine condition all season long.
Your plants looks so good, but suddenly they start to turn brown and wilt. The weather is perfect, and everything is getting adequate water, so what’s the problem? You may be dealing with disease. Pathogens can infect plants quickly and show up as a range of symptoms that are tricky to address, meaning you need to know what to look for right away.
Here’s an overview of plant diseases and what you need to know to better protect your green friends.
A plant disease is an impairment in a plant’s normal state that affects its functioning, usually in a negative way. All plant species are susceptible to disease, but cultivated plants tend to have the most problems. That’s because they’ve developed over time through human intervention and didn’t evolve the genetic defenses to fight them off as their wild counterparts did.
There are thousands of plant diseases that could infect your plants today, all of which are split into two categories: infectious and noninfectious.
Infectious diseases are caused by a pathogenic organism that infects the plant material. They can be a fungus, bacterium, virus, nematode, or even a parasitic flowering plant. These pathogens are capable of reproducing within the host and spreading from one plant to another, which makes them highly contagious.
Noninfectious diseases, in contrast, come from unfavorable growing conditions like temperature extremes, inadequate moisture levels, and nutrient deficiencies. They won’t spread from plant to plant, but plants growing in similar situations are likely to develop them.
Environmental conditions make a significant difference in the development and spread of plant diseases. Here are some factors to be aware of.
Temperature: Every disease pathogen has an optimal temperature for growing, which may vary based on the development stage. Generally, warmer weather leads to more plant diseases, as it encourages germination and spore production that causes them to spread.
Humidity: Warm, wet conditions lead to rot and fungal spore production, so high humidity is a leading cause of most leaf and fruit diseases. You can slow down the spread of disease by lowering the air humidity (if indoors) and avoiding spraying plants on their leaves.
Soil Moisture: Saturated soil keeps plant roots wet, which contributes to root rot and other fungal diseases. Refrain from overwatering so you don’t raise the carbon dioxide levels in the soil that encourages the growth of these pathogens. Likewise, other plant diseases are most problematic when the soil stays too dry.
Soil PH: The acidity of your soil affects the kinds of pathogens that proliferate within it. A soil test will give you a sense of its natural pH for information on what diseases are most likely in your conditions.
Soil Type and Fertility: Soil fungi and other pathogens all have preferences for certain soil types. Some thrive in heavy clay, while others need high concentrations of organic material. Elevated levels of certain nutrients can also influence the development of diseases like powdery mildew and leaf blight.
The best way to know whether you’re dealing with plant disease is to look closely at the plant.
Start by looking at the leaves and other foliage. Irregular coloring, size, shape, or signs of blights and lesions are all indicators of fungal or bacterial pathogens. In the early stages of a bacterial infection, you’ll likely see dark, water-soaked spots with distinct margins, almost like a halo. Look for dark specks in these dead areas, as these may be signs of mold growth or fruiting bodies filled with spores.
Viral diseases, like mosaics, show up as discolored, yellowing patches and sections that look dried out.
Next, inspect the plant’s trunk, stems, shoots, and branches. Any sunken, swollen, or discolored sections may be caused by bacterial canker infections, and they can lead to plant wounds that become infected by other pathogens. Galls, overgrowths on the stem, trunk, or branches, are often a sign of crown gall infections.
You can assume the plant is diseased rather than injured from insects or another cause if the change occurs gradually and there isn’t a clear distinction between the healthy and the unhealthy parts.
Below the soil line, root diseases are prevalent and can have consequences for the entire plant. They can come from soilborne creatures known as nematodes as well as bacterial or fungal pathogens. You might see stunted leaves, poor coloring, wilting and dieback, or sudden declines in your plant’s vigor and productivity.
Note: Many of the symptoms associated with plant diseases can be caused by a range of other factors like frost, heat, nutrient deficiencies, and more. In these cases, treating the “disease” won’t have any effect because you aren’t addressing the real symptoms.
One way to tell whether a plant disease is really to blame is to see whether multiple plant species in an area seem to have the same symptoms. Most plant diseases are highly specific and will only affect closely related plant species.
Treating and preventing plant diseases comes down to proper identification and determining what is causing it in the first place. This process takes careful observation and attention to detail to ensure you make the correct diagnosis.
Once you know what kind of pathogen is involved, you can take steps to eradicate it from your plants. In many instances, a topical spray will help kill off the pathogens and restore the plant to full vigor. You may also need to provide it with nutrient-rich compost to give it the strength to fight off the attack. Sometimes, the only option is to cut off the diseased portion to prevent it from spreading throughout the entire plant.
Dealing with plant diseases is an inevitable part of gardening, but they don’t need to be discouraging. Monitor plants closely and understand why infections occur, and you can prevent your plants from suffering from devastating outbreaks.
