How do you know if your garden plant has a fungus? Where do fungal infections come from? Plant fungal disease is one of the common problems gardeners and crop growers face. Explore common garden plants affected plus learn how to identify common plant fungal infections, treat, control, and prevent them.
What Fungi Cause Plant Diseases?
Many species of fungi occur naturally, mostly in plant material or soil. Not all of them can cause diseases to any kind of plants. However, under varying but favorable conditions, they multiply. They do so by fragmentation, budding, or producing spores and start to thrive. Due to increased need to feed more, some cause diseases to specific or vulnerable plants.
Most vegetable and some tree plant diseases are caused by various types of harmful fungi. Fungal infections come from infected plants, plant debris (remains after harvest); weed or nearby crop hosts and contaminated seeds. They may also be transferred by farmworkers, planters, and cultivation/gardening tools.
The majority of fungi groups are saprophytic. These don’t cause infections to our garden plants.
A few other kinds of fungi, however, are harmful (phytopathogenic). 85 per cent of plant infections are caused by these fungi group or fungi-like microorganisms.
Common Plant Fungi Diseases
Below is a discussion on various common types of fungus on plants and how to identify each with aid of pictures. We have also given information on treatment, and how to best control them.
1. Powdery Mildew on Plants
What causes powdery mildew? It is caused by many species of biotrophic fungus for example Erysiphe spp., Sphaerotheca spp., etc.
Wind and pollinating insects carry spores. Infection happens afterward when the spores are spread to healthy plants.
Commonly affected plant varieties include sunflowers, melons, pumpkins, grapes, tomatoes and garden peppers. Legumes, fruit trees and roses are other vulnerable groups.
NOTE: Downy mildew, which is caused by Pseudoperonospora cubensis, is an oomycete meaning that it is not a true fungus.
Signs and Symptoms + Pictures
How can you know your plants have been invaded by this fungus? Take a closer look at one or a combination of these signs and symptoms.
- Circular powder-like white spots on the leaves, stems or fruits when infection starts
- Upper leaf sides dusted white
- Twisted leaves
- Leaves may turn yellow or brown, die, and then fall off
- Yellow patches may form on some crops such as onions instead of powdery white spots
You may clearly notice the above signs when conditions highlighted below prevail:
- high humidity
- moderate air temperature
- dry plant foliage
- low light penetrating your garden
The newly formed leaves are most affected. Buds in the plant shoot appear deformed later on in the growing season.
How to Get Rid of Powdery Mildew
Will powdery mildew go away on its own? The answer is no. If you do not apply the most appropriate control, prevention or treatment, this fungus will be there every planting season.
Copper fungicides are widely used in treating and controlling the fungus. Ask for sulfur agents from your nearest stores.
Optimal application of Bacillus subtilis products is one of the best routine practices.
Best Prevention and Control Tips
- Prune your plants properly while removing diseased foliage and fruits
- Do proper spacing for susceptible plants and trees
- Practice appropriate soil cultivation methods to promote drainage
- Bi-Carb Fungicide products can be applied as one of the best preventive measures
Keep in mind that wiping affected leaves or stems and fruits only reduces the amount of the accumulated plant fungus. Doing so does not prevent or treat the infection.
Reportedly, some people allergic to molds may produce body reactions after touching or consuming infected leaves as food.
2. Clubroot Disease
Clubroot is a soil-borne disease caused by a fungal infection. Plasmodiophora brassicae is responsible for clubroot of crucifers. Brassicae family mainly comprises the canola and cabbage family.
Common field crops affected are cabbages, cauliflowers, broccoli, radishes, and brussels. The fungus can invade mustard and sprouts, turnip and candytuft.
Signs and Symptoms
Plant wilting normally gives the first impression of clubroot infection. Observation of the root system is key to identifying the disease.
Deformed, club-shaped roots and stunted growth are typical symptoms of the disease. The older leaves turn yellow, wilt and die.
How does infection occur? As stated the fungus inhabits the soil. After growing your cabbages, the fungus enters them via root hairs. They multiply by the production of spores hence infection. As a result, large galls form on roots giving them club-like swellings. This is what disrupts water and nutrient uptake. That is why cabbages display wilting.
Clubroot of Crucifers Control & Management
The fungus does not tolerate soils above pH 7 but may live for as many as 10 years.
To efficiently get rid of the fungus calls for a more soil-targeted management and treatment.
These include
- Removal and burning of infected plants
- Crop rotation
- Appropriate incorporation of lime fertilizers into acidic soils
3. Leaf Rust Plant Disease
Going on with fungal infections, leaf rust is another plant problem. It is caused by a variety of fungus species. The funguses are unique in that each fungus is specific to its host plant. Therefore do not spread from one type of plant to a different one.
Common crops that it attacks include common bean variety, soybean, clover, black-eyed pea, and wheat. The list of affected plants may be longer.
If you live in a wet and humid area, leaf rust may invade your garden of roses, snapdragons, hollyhocks, crabapples, and daylilies.
Signs and Symptoms
Identifying leaf rust is quite easy. It almost always begins with tiny brown or brick-red spots on both upper and lower leaf surfaces. The disease affects petiole and leaf veins. Petioles have sharp bends. Leaf veins swell and get disfigured.
The spots rarely increase in size as the plant fungus advances. However, under favorable conditions such as dew on leaves, pustules may appear. The pustules are raised. They look either yellow or brown in color. Sometimes they are colorless.
How to Get Rid of Leaf Rust
The use of fungicides is the optimal treatment. However, once established, leaf rust may be difficult to treat. Nonetheless, combine fungicides, and use more resistant plant varieties and cultural practices. These are proven to best manage it.
4. Fungal Wilts/Disease
Fungal wilts are a group of diseases caused by pathogen fungi. They are often identified by wilting of crops.
a. Fusarium Wilt
This wilt disease is caused by Fusarium oxysporum.
Signs and Symptoms
- Yellowing of leaves
- Stunted plants
- Wilting
- Water tissues turning brown
Symptoms may be exhibited on one side of affected plants (often termed one-sided symptoms).
The disease mostly targets young plants as they are more vulnerable to fungal attack. However, Fusarium oxysporum can infect plants of any age.
Common plants attacked include tomatoes, tobacco, legumes, cucurbits, sweet potatoes and bananas,
b. Verticillium wilt
Verticillium wilt is caused by Verticillium fungi species. The symptoms are similar to those of Fusarium wilt with a few distinct symptoms or exceptions.
In addition to wilting, infected plants may lose foliage. The internal stem may lose its natural color. This disease appears to kill seedlings faster than Fusarium wilt.
Unfortunately, there are no known fungicides to control it.
c. Clematis Wilt
Other than the above two, we also have clematis wilt. It is caused by Phoma clematidina fungus.
The pathogen would normally enter the host plant via a physical wound. It mainly affects the stems, leaves and flowering parts of plants called clematis.
How to Identify Clematis Wilt
Clematis wilt is generally characterized by black leaves and purple leaf veins after infection.
This fungal wilt can also be identified by physical examination of stems. Notably, there are “lesions on the plant’s stems which in contact with water, release their spores that spread the infection.”[bbc.co.uk]
Can you Treat Clematis Wilt?
Treating clematis wilt could be stressful due to problems with identification. You can take your affected plants to a reputable center for diagnosis.
You can treat using Myclobutanil or Penconazole products. Otherwise, if you want plants to survive, cut them back to the soil level.
d. Phytophthora Root & Stem Rot
This is a soil-borne fungal wilt disease caused by Phytophthora sojae. As its name suggests, it is responsible for stem and root rot.
Phytophthora root & stem rot starts from the roots up the plant as infection advances.
How to Identify and Manage
You can identify it more easily in young plants by observing the following.
- Yellowing of leaves occurs very quickly
- Plant wilting at a great rate
- Soft rot on the stem that falls off
For more identification detail, carefully cut along the roots of infected plants that have begun flowering. One would see tan to brown discoloration of roots. Similarly, discoloration in portions of the stem just above the soil is evident.
How do you get rid of Phytophthora root rot? Apply 3% hydrogen peroxide to soil around plants that are affected. Treat seeds you intend to use next planting season using mefenoxam and metalaxyl.
How to Treat & Control Fungal Wilt/Disease
Tolerant cultivars and the use of clean certified seeds/cultivars are the most effective when controlling the above wilts.
Managing wilts gives every gardener or farmer an upper hand to get in control of growing and crop production.
- Treat seeds with an appropriate fungicide
- When opting for bulbs as propagation material dip them in liquid curative fungicide
- Use of resistant varieties that are available
- Cultural practices to aid proper soil drainage
- *Fumigation of soils harboring the pathogens
NOTE: Fumigants for soil should be your last measure to adopt due to their potential environmental impact.
5. Blight Disease
Blight as a plant disease is caused by a Phytophthora fungus species. It is also caused by bacteria. Both microorganisms target plant tissue, primarily the cells. When attacked and infected, vulnerable plants are totally damaged and destroyed.
Since there are different types of blight diseases, let us have a look at these two for a better understanding.
a. Early Blight:
What does early blight look like? To identify this plant fungus, the infection starts with the formation of small black or brown lesions on leaves, stems and fruits. Those lesions on stems have a less dark center.
Failure to observe your plants, “the lesions will enlarge and are often surrounded by a yellow halo.”[www.apsnet.org].
This is often referred to as a ‘bullseye’ lesion of early blight. If you don’t treat it, more new lesions form on leaves, stems and fruits. This leads to serious foliage loss. This is enough to cause death. Infected fruits drop off their sheath prematurely.
The fungus mostly invades tomatoes, potatoes, capsicum and eggplants.
How do you treat early blight? The best way to manage and treat early blight is to apply a preventive fungicide to contain the spread of the fungus. Look for brand names such as mancozeb and chlorothalonil.
b) Fungus-like Late Blight:
How can you differentiate late blight from early blight? Just like early blight, an outbreak of late blight is marked by the formation of a small black or brown lesion. These lesions can form on the leaves, stems and fruits too (see picture).
The lesion may be filled with water if you have planted it in humid conditions. In this case, the plant fungus releases more spores. Therefore, you are likely to see tiny white things on the margins of individual lesions.
Gardeners and farmers will likely see a soft rot on stems and fruits after a lesion has been established. This soft rot falls off. The rot is evident in phytophthora root & stem rot disease.
Late blight spreads rapidly causing damage and eventually death of the whole plant within days. The seeds and roots including tubers can be infected too.
NB: Take note that late blight is caused by fungus-like microorganisms. It is not a true fungal disease. We have included it intentionally to better differentiate late blight from early blight.
Prevention and Control of Early and Late Blight
How do you stop early blight and late blight? Controlling and managing blight can be so difficult.
Begin by uprooting and burning the whole diseased plants which you have correctly identified. This prevents the further spread of the plant fungus.
Avoid handling healthy seedlings and planting materials and those impacted by the plant fungus.
Optional preventive measures include:
- Use of clean planting materials such as tubers
- Practice culling to break the pathogen’s cycle from the previous planting season
- Minimize overhead irrigation, especially in humid areas
- Practice crop rotation ensuring you give susceptible plants a 2-year gap
- Avoid excessive application of nitrogen fertilizers
Word on Blight Treatment
Fungicides are very effective as infected plants respond well to treatment.
More importantly, apply copper fungicides as soon as you notice symptoms. Observe good weather conditions and correct timing. These are key to treating blight when using fungicides.
CRUCIAL: Strictly adhere to application rates. Use each chemical with every precaution and instructions as given by the manufacturer.
Plant Fungal Disease Recovery—Home Remedies
Besides antifungal sprays, you can try these natural control means to give your plants chances of quick recovery after fungal infection.
1. Baking Soda for Powdery Mildew
Simply mix 1 tablespoon of baking soda with liter of water. Use the spray once you have noticed drooping leaves.
For improved results, avoid spraying baking soda on plants whose foliage damage is over 70%. Water your affected plants 3 days before. Avoid spraying plants and trees exposed to direct sunlight.
2. Cinnamon
Cinnamon has been used for controlling mold growths, plant fungus and pests. It can also kill soil fungus.
Carry out a simple DIY sprinkling. Use cinnamon powder directly on affected leaves and stems. Incorporate it in topsoil by applying around the inflicted plant.
3. Apple Cider Vinegar
Use apple cider vinegar to help manage powdery mildew symptoms. Add 1 tablespoon of apple cider vinegar to a gallon of water. Shake well before spraying.
4. Milk Spray for Plant Fungus
Milk spray not only controls but is quite effective when the recipes are mixed in the right ratios. For powdery mildew mix water and milk in a 60:40 respectively.
Spray on the buds of plants and trees as soon as you have identified signs of the plant fungus.
Summary
Can a plant recover from a fungal disease? There are very high chances if you identify the plant fungus disease, timely recognize its symptoms and control its spread and progress first.
In some cases, certain conditions must prevail for home DIY remedies to control or prevent growth and spread of fungi. The identification process of the fungi should be rapid to stop it from spreading.
In most cases, many plant fungus (discussed) would not cause or spread illnesses to humans.
Sources And References
- Powdery mildew. Plant pathology. https://www.britannica.com/science/powdery-mildew. Accessed online 20 August 2021
- Schumann, G.L. and C. J. D’Arcy. 2000. Late blight of potato and tomato. The Plant Health Instructor. DOI: 10.1094/PHI-I-2000-0724-01.
- Genetic Diversity and Identification of Wilt and Root Rot Pathogens of Tomato in China. DOI: 10.1094/PDIS-09-19-1873-RE. https://pubmed.ncbi.nlm.nih.gov/32293997/. Epub 2020 Apr 15.
- Nazarov, P A et al. “Infectious Plant Diseases: Etiology, Current Status, Problems and Prospects in Plant Protection.” Acta naturae vol. 12,3 (2020): 46-59. doi:10.32607/actanaturae.11026