10 Common Garden Plant Diseases

Common plant diseases are caused by viruses, bacteria, fungi, and other microorganisms. Many different types of diseases can affect your plants, appearing in various forms. Symptoms can be different depending on the particular kind of disease and the part of the affected plant.

Fungal infections can affect a plant’s roots, leaves, stems, flowers, or fruits. This can cause issues not only to these particular plants but also infect the soil and the rest of your garden.

This article will provide information on identifying common garden plant diseases, the damage that diseases can cause, and the steps you can take to prevent infections from spreading. 

List of 10 Common Garden Plant Diseases:

Rust

Quick Facts

• Common Name: Rust
• Plants Affected: Various ornamental, fruit, and vegetable garden plants.
• Main Symptoms: Rusty-looking spots on leaves.
• Caused by: Fungus
• Time of Infection: This can occur at any time throughout the growing season.

How To Tell Rust Apart From Other Issues

Rust is a common fungal disease that forms rusty-looking spots on leaves. Rust can affect various ornamental and garden plants, such as vegetables, fruits, grasses, flowers, shrubs, and trees. This disease can affect any part of the plant but most commonly appears on leaves. Infected leaves will turn rusty orange, gray, or brown and may eventually drop off.

Damage

Rust mainly affects the leaves of plants. Badly affected leaves will discolor and drop off. Rust, by itself, will not kill the plant, but plants that lose leaves to rust are weaker and will not produce as much as healthy plants. Spores of this infection are windborne, so they can cover large areas and rapidly spread the disease to nearby plants.

Control

The easiest way to avoid this disease is to plant rust-resistant varieties. You can also control the spread of rust using the tips below:

• Plant your fruits and vegetables in healthy soil and maintain nutritional requirements. Feed your plants regularly with organic fertilizer. Healthy plants are less likely to be affected by the disease.
• The fungus overwinters in the garden debris. Remove dead leaves from around the plants and discard them into the trash.
• Disinfect your pruners after use.
• Wind and water can spread fungal spores. Avoid applying water onto leaves. Apply it directly to the soil. 
• Avoid overwatering and overcrowding your plants.

Powdery Mildew

Quick Facts

• Common Name: Powdery mildew
• Plants Affected: Many ornamental and edible plants.
• Main Symptoms: A white powdery substance on the upper leaf surface.
• Caused by: Fungus
• Time of Infection: During warm and dry weather.

How To Tell Powdery Mildew Apart From Other Issues

Powdery mildew is a fungal disease that attacks many plants, including vegetables, fruits, ornamental flowers, shrubs, and trees.

Powdery mildew will display a white powdery substance most visible on the upper leaf surface. This fungus thrives in warm and dry weather conditions.

Damage

Leaves of susceptible plants develop a white powdery appearance that spreads rapidly under warm and dry conditions. If not controlled, the powdery mildew can kill the entire plant. 

Spores are windborne, so they can cover large areas and rapidly spread the infection. 

Control

Powdery mildew can be tough to control as it spreads quickly and does not have a distinct host plant.

• Plant resistant varieties whenever possible.
• Air Circulation. Ensure that plants have enough room to grow by providing them with proper spacing.
• Weed Control. Remove weeds to give your crops more space to grow.
• Provide regular feeds of organic fertilizer to keep your plants healthy.
• Remove diseased leaves as soon as you see them. Do not compost them.
• Disinfect your pruners with a household disinfectant, a bleach solution (1 part bleach to 9 parts water), or soap and water after every use. 
• Keep the soil well-drained but not dry.
• Fungicides. Apply fungicide to the soil around the base of the plant or to the plant’s leaves to prevent infection.

Gray Mold (Botrytis)

Quick Facts

• Common Name: Gray Mold (Botrytis)
• Plants Affected: A wide variety of fruits, vegetables, and flowers.
• Main Symptoms: Dark brown to black blight on plant leaves, stems, flowers, or fruit.
• Caused by: Fungus
• Time of Infection: This can occur any time throughout the growing season, mainly if plants are located in shady, high-humidity areas.

How To Tell Gray Mold (Botrytis) Apart From Other Issues

Gray mold is a fungal disease that can infect many fruits, vegetables, and flowers. It causes dark brown to black blight on plant leaves, stems, flowers, or even fruit and can live on dead leaves and other plant debris. The disease thrives in shady, high-humidity areas and can spread quickly. Plants become infected when spores are carried by the wind, rain, insects, or other organisms from an infected plant.

Damage

Gray mold produces a powdery growth that easily spreads to other plants through wind, rain, insects, or other organisms. It causes leaves to turn brown and eventually fall off. When present on the plant leaves, the foliage looks discolored and wilted. As the disease progress, the plants will get stunted. If the plant is not removed, it rots and the plant dies.

Control

For the control of gray mold, fungicides are not necessary. When dry conditions return, many flowering plants will recover. Use the tips below to reduce the spread of gray mold and speed up plant recovery.

• Use resistant varieties whenever possible.
• Air circulation. Ensure that plants have enough room by providing them with proper spacing.
• Remove and destroy any infected plant parts as soon as possible before it infects the rest of it. Once spores spread, they can be challenging to eradicate.
• Do not compost infected plant parts.
• Avoid overhead watering of your plants. If you must water, do so early in the day.
• Clean the garden equipment with a diluted bleach solution (1 part bleach to 9 parts water).

Bacterial Wilt

Quick Facts

• Common Name: Bacterial Wilt
• Plants Affected: Cucurbitaceae and Solanaceae / Nightshade plants.
• Main Symptoms: The plant wilts and eventually collapses and dies.
• Caused by: Bacteria
• Time of Infection: This can occur throughout the growing season.

How To Tell Bacterial Wilt Apart From Other Issues

Bacterial wilt is a complicated problem to control, and it is the most destructive bacterial disease of Cucurbitaceae plants (cucumber, ground, pumpkin, squash, watermelon, zucchini, etc.). Still, it can also occur in Solanaceae / Nightshade plants (tomato, potato, pepper, eggplant, bean, etc.).

Striped cucumber beetles and spotted cucumber beetles are two insects known to be the biggest spreaders of bacterial wilt in the Cucurbitaceae plants. These beetles eat the foliage from the infected plant and carry this bacteria in their digestive tracts for a very long time. Every time they feed, they infect any susceptible plant.

This disease can also be spread through transplanting, mechanical means (especially using contaminated secateurs), and even seeds.

Note: the wilting of a plant is not always caused by bacteria. There can be many other reasons why your plant is wilting. Some examples are:
-Transplanted plants can wilt and return to normal after a few days.
-Overheated and underwatered plants will wilt but return to normal if watered in time.
-Overwatered plants can become waterlogged, and the roots may rot. The plant can wilt.

Damage

Bacterial wilt affects a plant’s vascular system. When the plant is infected, bacteria multiply until it blocks the plants water transfer system. Then the plant becomes wilted and eventually collapses and dies.

Control

No cure exists for bacterial wilt. Prevention is the only option. [1]

• Early detection of this disease is critical in order to stop the spread of the bacteria and prevent other plants from dying. Remove and destroy diseased plants.
• Equipment sanitization. Clean all your equipment after use with a diluted bleach solution (1 part bleach to 9 parts water).
• Susceptible varieties. Choose less susceptible varieties for your garden.
• Seed selection. Do not use seeds from infected plants.
• Graft your crop onto developed resistant rootstocks, which are varieties of plants that are resistant to the disease.
• Plant spacing. Ensure that plants have enough room to grow healthy.
• Fertilizer. Keep your plants healthy by feeding your plants with organic fertilizer.
• Good weed management will reduce the number of plants affected by bacterial wilt. Thus, it will reduce the possibility of spreading it.
• Crop rotation is one of the most effective ways to control soil-borne diseases and maintain the health of the soil. Rotation with non-host crops like wheat, cowpea, soybeans, and others can help maintain soil health and prevent the development of crop diseases.

The disease can survive in plant debris over winter. Remove infected plant parts. Do not add to the compost pile.

Cucumber Mosaic Virus

Quick Facts

• Common Name: Cucumber Mosaic Virus
• Plants Affected: Mainly cucumbers. However, other vegetables, fruits, and ornamental plants can also be affected.
• Main Symptoms: Mosaic pattern of dark green and light green areas on leaves.
• Caused by: Virus
• Time of Infection: This can occur at any time throughout the growing season.

How To Tell Cucumber Mosaic Virus Apart From Other Issues

One of the mosaic virus species is the cucumber mosaic virus (CMV). This disease can infect cucumber plants and many other plants, including vegetables, fruits, and ornamental flowers. The cucumber mosaic virus is known to have the widest host range of any known plant viruses. [2]

Aphids mainly transmit this virus. These are tiny insects that suck plant sap. Humans can mechanically spread the cucumber mosaic virus on rear occasions. [3]

Damage

The Cucumber mosaic virus causes a mottled appearance in plants. The symptoms are variable, but infected plant leaves usually have a mosaic pattern of dark green and light green areas. Newly formed leaves will wilt and die. This disease can also reduce crop yield by 20%.

Control

No chemicals can remove the cucumber mosaic virus from the infected plants. So, the most effective control is prevention. 

• Seed selection. Use certified seeds or seeds collected from a healthy plant. Do not use seeds from infected plants.
• Resistant varieties. Use varieties that are resistant to mosaic virus.
• Good weed management will reduce the number of plants affected by the cucumber mosaic virus. Thus, it will reduce the possibility of spreading it.
• Remove and destroy all diseased plant parts. Do not compost them, or you can infect the whole compost.
• Equipment sanitization. Clean tools that you use to prune your plants, to prevent the spreading of the virus. Use a diluted bleach solution (1 part bleach to 9 parts water).

Note: aphid population control would seem to be the first thing to tackle, as they are the primary carriers of the virus. But it is neither practical nor realistic. Insects feed on infected perennial plants early in the season. So, by the time you notice aphids, your crops can already be infected. [4]

Fusarium Wilt

Quick Facts

• Common Name: Fusarium Wilt
• Plants Affected: Cucurbits, bananas, legumes, tomatoes, tobacco, and sweet potatoes are the most susceptible.
• Main Symptoms: Plants wilt, collapse, and die.
• Caused by: Fungus
• Time of Infection: During the warm weather throughout the growing season.

How To Tell Fusarium Wilt Apart From Other Issues

Fusarium wilt is a common warm-weather fungal disease that can affect many plants. Cucurbits, bananas, legumes, tomatoes, tobacco, and sweet potatoes are among the most susceptible plants. This pathogen can be spread by water splash, contaminated equipment, or infected seeds and transplants.

Damage

Fusarium wilt causes the plant to appear stunned, with some yellowing or browning. The fungal infection invades susceptible plants, causing them to wilt, collapse, and die. If a stem is cut, discoloration will be visible inside the stem.

Control

There are no effective treatments once fusarium wilt infects your plants.

• Remove and destroy infected plants immediately if you suspect that your plant is suffering from this disease. Do Not Compost Them!
• Prevent. The disease can be prevented by growing plant varieties that are resistant.
• Water your plants in the morning and avoid water splashes.
• Grafted vegetables can be used where the rootstocks are not susceptible to Fusarium wilt.
• Seed selection. Use certified seeds from reputable sources.
• Equipment sanitization. Clean tools you use in your garden to prevent the spread of disease. Use a diluted bleach solution (1 part bleach to 9 parts water).

Verticillium Wilt

Quick Facts

• Common Name: Verticillium wilt
• Plants Affected: Many vegetables, fruits, and ornamental plants. It commonly affects aubergines, cucurbits, potatoes, strawberries, and tomatoes.
• Main Symptoms: Dieback, yellowed leaves, and wilting.
• Caused by: Fungi
• Time of Infection: Any time of the year. Symptoms can quickly develop during the hot season.
• Resistant Plants: Conifers plants and grasses.

How To Tell Verticillium Wilt Apart From Other Issues

Verticillium wilt is a common soil-borne fungal disease affecting many plants, including fruits, vegetables, and ornamental plants. Verticillium wilt enters the plant through the roots and then travels upwards. It is detected when plants show dieback, yellowed leaves, and wilting. The disease is persistent and can stay in the soil for a long time.

The symptoms of Verticillium wilt are similar to those of Fusarium wilt, and it can be difficult to distinguish between them.

Damage

Verticillium wilt can infect any plant in your garden. Still, it is most common in aubergines, cucurbits, potatoes, strawberries, and tomatoes. 

Verticillium wilt will enter the roots of susceptible plants, multiply, and clog up their vascular system. Plants will develop black or brown streaks in the tissue. Wilting usually appears a few days or weeks after the infection. Growing fruits will not ripen properly. The fungus may also cause fruit to drop prematurely.

Any ripened fruits might not taste good as the disease cause nutritional and moisture stress. [6]

Control

• Use resistant varieties whenever possible.
• Soil. The fungus spreads through contaminated soil. If you suspect that your compost or soil is contaminated with verticillium wilt, do not spread it to the rest of your garden.
• Garden hygiene is an essential factor while controlling this fungus. Wash your hands and clean your garden tools regularly. 
• Control weeds in your garden. Some weeds can be hosts for verticillium wilt and not display any signs of infection.
• Remove and destroy infected plants, do not place them into the compost.

There are no available chemical treatments to control Verticillium wilt.

Pro Tip 1: There is a slight chance for plants to recover from verticillium wilt. Water plants heavily and provides ammonium-based fertilizer (nitrogenous). This will stimulate new growth.

Pro Tip 2: The fungi can remain in the soil for many years. Use the infected soil to grow resistant varieties or grass.

Early Blight

Quick Facts

• Common Name: Early Blight
• Plants Affected: Tomato, potato, peppers, and other nightshade plants.
• Main Symptoms: Water-soaked spots on leaves that turn yellow and brown. The center of the spot becomes like an open cup that dries out and turns black.
• Caused by: Fungus
• Time of Infection: This can occur at any time throughout the growing season.
• Resistant Plants: Resistant tomato and potato varieties are available.

How To Tell Early Blight Apart From Other Issues

Early blight is one of the most common diseases of tomato and potato plants. Early blight begins as a small, water-soaked spot on older leaves, then turns yellow and brown. The center of the area becomes an open cup that dries out and turns black.

The fungus spreads by irrigation, splashing rain, garden tools, or insects. The disease can also be spread through potato tubers and tomato seeds.

Damage

The disease produces dark, moist, sunken spots on leaves and then moves to the stem. Blighted plants become weaker. However, plants can tolerate infection if control measures are introduced in time. [7]

Control

• Plant-resistant varieties when available.
• Use mulch such as wood chips or straw under the plants to avoid spores splashing onto the plant.
• Use drip irrigation, a soaker hose, or hand water at the base of the plant.
• Increase airflow by spacing out plants and removing weeds. 
• Prune the plants bottom leaves to avoid water splash. Also, prune off all the infected leaves from the plant.
• Regularly feed your plants with organic fertilizer. This will keep plants healthy and might prevent fungal diseases.
• Maintain good garden hygiene. Clean your garden equipment and wash your hands after dealing with infected plants.

Pro Tip: Fungicides are available to control early blight. However, plants can handle some of the infections if controls are introduced.

Late Blight

Quick Facts

• Common Name: Late blight
• Plants Affected: Tomatoes and potatoes.
• Main Symptoms: Leaves turn dark brown and dry, and fruits rot.
• Caused by: Water mold
• Time of Infection: Late summer and early fall.
• Resistant Plants: Resistant tomato and potato varieties.

How To Tell Late Blight Apart From Other Issues

Late blight is the most destructive mold that affects tomato and potato crops. This disease can quickly spread in the garden, devastating susceptible plants.

It can be identified by dark brown, brittle patches on the surface of leaves. It can infect plant stems, potato tubers, and tomato fruits.

The disease favors damp and cool conditions but mainly occurs in late summer and early fall. Spores can quickly become airborne during these conditions and infect the whole garden. 

Damage

Late blight develops lesions on the leaves, stems, tomato fruits, and potato tubers. These lesions eventually turn dark brown and dry up. If not controlled, this disease will spread to other plants in the garden.

Tomatoes with early symptoms of late blight do not set many fruits. Late blight affects the lower leaves and stems first, which causes the plant to wilt and die.

Control

• Planting resistant varieties are the most effective way to control the disease.
• Seed selection. Plant-certified seeds only.
• Check tomato and potato plants regularly and remove all diseased leaves. Do not compost them.
• Keep the leaves dry when watering. Use a soaker hose or drip irrigation system for plants prone to disease.
• Water your plants in the morning. This way, leaves will dry quicker in the sun.
• Increase airflow by spacing out plants and removing weeds. Also, stake your tomato plants.

Pro Tip 1: Pesticides are not recommended to control late blight in the home garden. Late blight should be controlled with good cultural practices.

Pro Tip 2: If growing potatoes, grow early varieties because late blight occurs during late summer. This way, you will be able to harvest your crop before the start of blight.

Leaf Curl

Quick Facts

• Common Name: Leaf curl
• Plants Affected: Many fruits, vegetables, and indoor plants.
• Main Symptoms: Upward or downward curling of leaves.
• Caused by: Insect damage, improper watering, nutrient deficiencies, heat or cold.
• Time of Infection: This can occur at any time throughout the growing season.

Description

Leaf curl can be caused by fungus, viruses, insect damage, improper watering, nutrient deficiencies, and temperature fluctuation. It is common in some varieties of tomatoes, but other plants can also be affected. 

Damage

Some leaf curling is a natural occurrence in plants, but some strains of leaf curl cause stunted growth and deformed leaves. It can also postpone the fruit sets.

In most cases, leaf curl is not a severe problem for the plant and will recover with proper care. 

Control

The best way to identify this problem is to inspect the whole plant.

• Pests Control. Check if there are pests such as aphids or whiteflies attacking your plant. Control pests if necessary.
• Temperature. During hot or cold weather, plants protect their leaves by curling them. Some plant leaves will recover to their standard shape, while others will stay with this cosmetic defect.
• Water level. Keep your plant watered adequately. Too wet or too dry can cause levels to curl.
• Fertilizer. When using fertilizer, make sure to follow the instructions. Incorrect fertilizing can cause leaves to curl. It can also cause other, more significant issues.

Final Thoughts

Hopefully, this article answers your question. If you enjoyed this article, you could find similar ones in our Plant Diseases section. Learn and help your plants by reading these guides.

Also, check out our Growing Guides to learn more about how to grow plants of your choice.

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