Although there are thousands of plant disease, understanding plant disease if you are a gardener, farmer or even a nursery plant owner, it’s necessary that you understand the various types of disease that are likely to attack your plants.
The non-pathogenic diseases are caused by the sudden change in humidity, soil moisture, soil PH, temperature and much more.
On the other hand, the pathogenic diseases are caused by bacteria, viruses, fungi, mycoplasmas, and nematodes.
These pathogens are transferred from one plant to the other through the soil, water, insects, fertilizing, air, farming tools among other agents.
Most of the plant diseases source their energy from your plant’s nutrients. Hence, they are responsible for a great deal of damage and the overall yield of your plants.
And for that reason, this article aims at giving you a comprehensive outline of the common plant diseases as well as other infamous plant diseases that are likely to attack your plants.
Also, inclusive will be some of the control and prevention measures for combating the plant diseases.
Table of Contents
5 Most Common Plant Diseases
Blight is one of the most common plant diseases that is categorized by the sudden death of the plant tissues. It can be the leaves, flowers or the stem.
The wet and humid climatic conditions cause it. There are two categories of blight; the early and the late blight.
⦁ The Early Blight
Early blight is a fungal blight that is known to affect most of the vegetables (potatoes, peppers, tomatoes, kales), shade trees, fruit trees and ornamental plants.
It occurs way early in the plant’s growing season and is known as Alternaria Blight in other words.
The early blight starts out as yellow spots which later enlarge and become brown or black spots on the leaves.
In some cases, the sunken spots can enlarge and form concentric rings pattern. The Early blight starts at the base of the plant.
And as the plant disease spreads out, those small spots join up together and become big black or brown patches.
If the leaves get heavily blighted and the situation is out of hand the plant dries up and dies.
The Late blight or Phytophthora Blight occurs later in the development of plants. It occurs majorly in the summer and its categorized by large dark brown patches on the leaves.
Although many other diseases may cause the dark brown spots, there is a distinctive characteristic in the late blight.
You will notice the presence of the fuzzy mold-spore which occur on the underside of the affected leaves and stems.
To clearly see the fuzzy mold-spores you may have to use a hand lens or view it on a macro photo taken with a digital camera very early in the morning.
Also, you should notice that the spots formed in the late blight have a waxy-looking characteristic.
Cankers are another popular plant disease that majorly occurs on the woody stems of plants.
It is easily identifiable through a dead, discolored section on the stem of a plant, sunken areas, cracks or abnormal tissues.
At times, the Cankers tend to ooze hence may girdle the trunks or shoots hence every other part above the affected area may die.
There is the Cytospora Cankers and the Nectaria Cankers. The Cytospora is a fungal plant disease which attacks the stone fruits, spruces and poplars mostly.
You will notice some circular discolored patches on the bark of a plant.
The Nectaria Cankers is also a fungus plant disease which attacks most of the hardwoods, shrubs, maples, and vines.
It is characterized by some small sunken areas and spore-producing structures which may appear on the bark of plants.
The bacteria cankers kill the plant twigs and branches.
Rusts is another very common plant disease too. To complete their life cycle, the rusts need at least two different species of plants as their hosts
. Rust can be categorized in either tan colored or rust colored coating. There are different categories of rusts, and one of them is the Asparagus rusts.
The Asparagus rust is characterized by browning or reddening of the plant’s twigs and needles. At times the rusts can lead to the release of rusty as well as powdery spores.
This plant disease majorly affects the new shoot in plants during spring, and the leaf stalks too.
Rust can be transmitted from one plant to the other by the wind.
Some of the plants that are prone to this disease include; wheat, cedar, white pine among other plants.
Wilting is a common issue in plants that occurs especially when a plant doesn’t get enough water. At times, fungi or bacteria can clog the conducting water system in plants hence it may cause permanent wilting.
This is often followed by the death of the entire plant or just a part of it.
Symptoms of plant wilting may time resemble that of the blight although with some distinctive difference.
Wilting majorly affects corn especially when flea beetles attack them.
Wilted Leaves due to lack of enough water.
Affected parts during wilting tend to have some long streaks which may at times have wavy margins.
In some extreme cases, the plants may die or may have stunted growth hence you won’t get any produce.
Rots is a plant disease that causes the roots, stems, flowers, and fruits of the plant to decay.
In some cases, the plant diseases may cause the leaves to rot, but this is mainly known as blights or leaf spots.
Rots can either be soft and somehow squishy or hard and very dry.
Bacteria or fungi cause rots, and they are most active in the roots, stored fruits, tubers, and bulbs.
There are different categories of rots including; the fruit rots, root, and stem rots as well as wood rots.
Other Plant Diseases
There are other plant diseases which may not be so famous, but they can still affect your plants. Some of this plant diseases include;
A close-up photo of leaf curls and blisters
⦁ Downy Mildew; the downy mildew majorly affects the vegetables, flowers, fruits, and grass.
The downy mildew is characterized by a white or purple downy growth which may occur on either the underside of leaves or along the stems.
⦁ Leaf Spots; a wide range of fungi causes leaf spots. The leaf spots come with more definite edge and darker borders. When the spots grow together, they may become a blotch or a blight.
⦁ Leaf Curls; Leaf curls are fungal diseases that affect the leaves majorly. They cause the leaves to have a distorted shape.
Often the leaf curls come with some blisters which may have yellow bumps on the upper surface and gray depressions on the lower surface of the leaves.
Preventive Measures for Combating Plant Diseases
Regardless of how much you weed, water and worry about your plants, some plant diseases are beyond your control.
Even the healthiest gardens at times fall victim of plant diseases. And just like the human body, we say that prevention is better than cure.
Therefore, by providing a healthy environment for your plants, this is an essential step in preventing the attacks of plant diseases.
Although we may not get hold of all the plant diseases, there are some preventive routines that we can follow to prevent as well as reduce the chances of plant disease attacks.
Below are some of the basic preventive and control measures for plant diseases;
⦁ Proper Inspection of Purchased Plants
Before you bring any plants home, ensure that you check them out for plant diseases.
This is one of the easiest ways to keep away diseases from your garden. There are a few obvious indicators of plant diseases, and these are; mildew, yellowing, wilting foliage, dark-spotted leaves among others.
Take a pass if you notice any of the above mentioned or any signs of fungal and insect diseases.
Ensure that you plant only the pathogen-free and healthy cuttings, bulbs, transplants and seeds too.
If you are making your purchases through the online nurseries, ensure that you go for the certified disease-free plants.
In some cases, you can opt for the tolerant cultivars which have a genetic resistance to some diseases.
Such cultivars are available at the county extension office where you will be provided with the resistant crops that will do well in your residential area.
Mulches are a very useful form of plant diseases prevention. They maintain the moisture in the soil, and they reduce infestation of weeds hence keeping the garden free of diseases.
With mulch on your plants, you will be able to prevent soil with fungi infections from spreading out the diseases to the plant foliage.
Also, you could try mulching plants which have had an issue of black spots therefore before. Generally, mulching keeps away most of the annoying plant diseases that attack the plants in your garden.
⦁ Good Sanitation in the Garden
Good sanitation is crucial to the health of your plants. This especially applies to the vegetables and fruits garden.
By good sanitation, I mean picking of any plant debris in the garden, trimming and pruning of the unhealthy stems and branches, weeding and proper disposal of non-degradable materials.
Leftovers from diseased foliage’s or stems may result to some recurrent plant diseases in the garden. In case you have any diseased foliage or stems on the garden, there are better discarded rather than composted.
Unless you have a hot compost pile. Ensure that you discard them since the cold composts will invite more diseases and provide a haven for insects.
⦁ Leave the Soil to Warm Before Planting
Fungal diseases get their hooks in cold gardens therefore if you want to reduce the chances of plant diseases, you should avoid planting in cold gardens.
Therefore, to eliminate the fungal diseases, ensure that you wait until the soil is completely warmed in spring.
Invest in a soil thermometer, and this will save you a lot of hassle later on.
Dealing with sick plants is a lot more expensive than buying a soil thermometer. Also, you could use the traditional phenology to know the right time for planting.
⦁ Water your Plants Correctly
Plants spread diseases through water, and that is why; if you want to eliminate plant diseases, you will have to avoid working in the garden when plants are wet.
Therefore, you should water your plants early in the morning so that they are completely dry by mid-day. Plant diseases are likely to crawl in the longer the plant foliage remains wet.
To reduce chances of spreading out diseases through water, opt for the drip irrigation.
It’s a safer way of watering your plants without having to splash inoculum of diseases on to the fruits and plant foliage.
This will also reduce the chances of fungal diseases. Most of the fungal diseases thrive in damp environments.
⦁ Crop Rotation
If you would like to keep away plant diseases in your vegetable garden especially, try out the crop rotation.
If you plant your crops in the same spot for many years, it will be almost inevitable to have the fungal crop diseases.
However, before you begin rotating your crops in the garden, it’s good that you learn the different effective ways of crop rotation.
⦁ Proper Soil and Air Circulation
Powderly Mildew and black spots are fungal plant diseases that mostly attack due to poor air and soil circulation in your garden.
It attacks the plants which are either grown too close to the wall or those that are squeezed together hence have poor air flow.
A congested garden is a home to most of the fungal plant diseases. For that reason, you should try pruning some of the plant branches or dividing the large plants to create a well-aerated environment in your garden.