Januaris is an expert gardener and author of farming guides. He loves to write about crops, pest control, fish farming, and beekeeping.
Diseases of leafy vegetables can cause devastating effects to your crop. They can completely kill your crop or significantly reduce its quality, which means that you can incur great losses if one of the diseases strikes your garden.
Just in case you didn't know, leafy vegetables refer to crops such as collard greens, kale, cabbage, spinach, broccoli, rape, cauliflower, lettuce, celery, and turnip among others. They belong to the family Cruciferae.
There are several diseases that attack leafy vegetables, and they are majorly caused by fungi, bacteria, or viruses. If you grow greens or planning to grow them, here are the common diseases of leaf vegetables, their causes, prevention, control, and treatment. See clear vegetable disease photos in order to exactly diagnose the problem with your crop!
What Are the Common Diseases of Leafy Vegetables?
- Downy Mildew
- Alternaria Leaf Spot
- Frogeye Leaf Spot
- White Spot
- Powdery Mildew
- Bottom Rot
- White Rust
- Bacterial Soft Rot
- Black Rot
- Root Nematode
1. Downy Mildew - The Most Common Leaf Vegetable Disease
Downy mildew is a fungal disease caused by Peronospora parasitica. It causes white mold and faint yellow spots on the dorsal and ventral sides of the leaves respectively.
The fungus thrives in cold and wet conditions, so you can prevent it by avoiding these conditions in your garden. Some practices that can cause cold and wet conditions are excess watering and over-head irrigation.
You can control downy mildew by uprooting the infected crop and burning it, and you can treat it by using the fosetyl-al fungicide.
2. Alternaria Leaf Spot
Alternaria leaf spot is caused by fungus Alternaria brassicae. The leaves of the infected crop (especially kales) have black or brown circular spots. With time, the spots enlarge and concentric rings appear on them.
You can prevent this disease by planting certified seed or disease-free transplants. You can also prevent it by avoiding wet and warm conditions in your garden as the fungus is very active under these conditions. Cruciferae weeds harbor the fungus, so you should eradicate them from your garden.
The best way to control Alternaria leaf spot is to uproot and bury or burn the infected crop. You can also spray your crops with a suitable fungicide immediately after you see the symptoms.
3. Frogeye Leaf Spot
Brought about by fungus Cercospora brassicicola, Frogeye leaf spot causes pale green, gray, or white spots on the leaves. The spots are bordered by a brown ring and can take any shape.
You can prevent this disease by planting fungus-free seed or transplants. Another great way to prevent the fungus is to improve soil drainage and avoid excess moisture in the garden. In addition, you can prevent it by doing proper weeding and crop residue removal.
You can control frogeye leaf spot by practicing crop rotation. Some copper products and fungicides like Benomyl can treat and control the disease. Use these chemicals immediately after you see the symptoms.
4. White Spot
White spot is a leafy vegetable disease caused by fungus Pseudocercosporella capsellae. The crop infected by the fungi usually has brown or gray spots on the leaves. The leaves later turn yellow and fall off within a few days.
The fungus can survive on seeds, so you can prevent it by planting certified seed. You can also prevent the harmful microorganisms by avoiding cool and damp conditions in your garden.
The best way to control white spot is to eradicate the infected crop. The disease spreads fast, so you should remove the sick crop immediately after seeing the symptoms. The fungus can be killed by suitable fungicides and copper products, which means that you can these chemicals to treat your infected crops.
White spot was a major problem in my garden until I discovered this copper fungicide. It amazes me on how it clears out the disease in less than a week.
Even when the crops are heavily infected, this organic farming-friendly fungicide does the job of killing the harmful micro-organisms, reviving your crops, keeping your garden free from fungus and increasing your yield!
And the best thing about it is that it can deal with other fungal diseases mentioned in this article, including the downy mildew and alternaria leaf spot.
I would recommend that you get it if you have the fungal menace in your garden!
5. Bacterial Soft Rot
Bacterial soft rot is caused by Erwinia carotovora, and it's one of the most common cabbage and collard green diseases. It causes dark, mushy patches on the stems and leaf stalks.
You can prevent bacterial soft rot by avoiding water-splashing in your garden. Farm tools can introduce the bacterium to your garden, so you should disinfect your tools before using them in your garden.
The best way to control the spread of the bacteria is to uproot and destroy the infected crop. Concerning treatment, you can use a suitable bactericide to kill the harmful microorganism.
6. Powdery Mildew
Powdery Mildew is a fungal vegetable disease caused by Erysiphe polygoni. It causes white powdery mold on the upper surface of leaves.
The fungus survives in cool and dry conditions, so you can avoid these conditions in order to discourage the pathogen from developing in your garden.
Powdery mildew can be treated with sulfur, so you can use the chemical on your vegetables when you notice the disease symptoms. As for the control, you can eradicate the infected crops to stop the spread of the pathogen.
Caused by fungus Colletotrichum higginisianum, Anthracnose affects leaves & stems of vegetables like turnips, and causes small, gray, or black spots on these parts.
The harmful microorganism survives in weeds, so you can prevent it by removing any unwanted plants from your garden. You can also prevent the fungus by keeping your garden at a lower moisture level.
The affected crops can spread Anthracnose to the healthy ones, so you need to remove the infected crops from your garden in order to control the spread of the disease. You can try suitable fungicides to kill the pathogen.
Wirestem is caused by fungus Rhizoctonia solani which lives in the soil. The disease is recognized by reddish-brown patches on stems of leafy vegetables. The stem rots and peels off with time, exposing a wire-like wood.
The infectious microorganism is favored by moist soils and rotten plant remains. This means that you can prevent the disease by keeping your soil at the optimum moisture. If you have plant remains in your garden, dispose them to prevent the microorganism further.
The best way to control wirestem is to disinfect your soil. You can also control the disease by discarding any infected seedlings. The pathogen can be killed by fungicides that contain pentachloronitobenzene.
9. Bottom Rot
Caused by fungus Rhizoctonia solani, Bottom rot makes the lower leaves of the infected vegetables to turn black and wilt. The pathogen can move to the roots, causing root rot.
You can prevent this disease by disinfecting soil and planting materials. The infectious microorganism survives in a very wet soil, so you can do away with excess moisture to prevent it in your garden.
Bottom rot can be controlled by crop rotation, so ensure you do not grow leafy vegetables repeatedly in the garden when it strikes. In the case of treatment, you can use fungicides like Terraclor to cure the sick crops.
Damping-off is another leafy vegetable disease caused by Rhizoctonia solani. It is also caused by Fusarium spp or Pythium spp. The fungus causes decay and wilt in seeds and seedlings respectively. The infected seedlings have light brown stems.
The pathogen survives is cold and wet soils, so you need to keep the soil temperature and moisture at optimum levels to prevent the occurrence of this disease in your garden. You need also to use certified seeds.
You should immediately disinfect your soil if you notice any symptoms of the infection. You should also dispose any infected seeds or seedlings. In addition, you can use Terraclor or any other suitable fungicide to treat the infected crops.
Blackleg is brought about by Leptosphaeria maculans which is a fungus that causes small, light brown spots on the stems. The spots are usually sunken and can enlarge, making the stem to deteriorate.
You can prevent the fungus by using certified disease-free seed. The microorganism is active in a wet soil, so you can prevent it by avoiding wetness in your garden.
You can use fungicides such as Thiram and Captan to treat vegetables infected by blackleg. If the infected crops do not respond to the treatment, uproot and burn or bury them in a dry soil.
12. White Rust
Caused by Albugo candida. White rust is a fungal disease recognized by yellow-white spots on the leaves and sometimes on the stems of greens.
You can prevent Albugo by disposing crop refuse before planting your crop. You should not allow cruciferous weeds to grow in your garden as they harbor the infectious microorganism.
The best way to control white rust is to practice crop rotation. This cultivation method prevents the buildup of the pathogen with seasons. Concerning treatment, you can try any suitable fungicide to kill the microorganisms.
Yellows is a fungal disease caused by Fusarium oxysporum con-glutinans, and triggers formation of large, dull yellowish green patches on the leaves of vegetables.
The harmful microorganism survives in warm conditions, which means that you can prevent it by keeping your garden at lower temperatures. The disease can be spread by farm tools, so ensure you clean and disinfect your tools before using them in your garden.
The best way to control yellows is to plant certified seed or disease-free seedlings. You can try to kill the pathogen with fungicides such as Terraclor, Captan, and Thiram.
Clubroot is brought about by fungus Plasmodiophora brassicae, and causes leaves of the infected vegetable crop to turn yellow or pale green. The pathogen spreads to the stem and roots, causing club-like swellings on them.
You can prevent this disease by planting pathogen-free seedlings. The infectious microorganisms can be introduced to your garden by infested irrigation water and soil, so ensure your irrigation water is clean and your farm tools do not have soil particles from other gardens.
The plant sickness can be eliminated by fungicides such as Terraclor, so you can try them if your vegetables are infected. Concerning control, you can minimize the spread of clubroot by removing weeds that harbor it.
15. Black Rot
Black rot is caused by both fungi and bacteria (Xanthromonas campestris). It brings about yellow patches on the leaves of the infected crop. With time, the patches turn brown. The pathogen spreads to the veins and midribs of leaves and the stem, making them black.
The harmful microorganism can be introduced to your garden by contaminated equipment, irrigation water or plant materials. You can therefore prevent it by ensuring that anything you bring to your garden is disease-free.
You can control black rot by removing any infected crop from your garden. You can also practice crop rotation to prevent the buildup of the disease with seasons.
When it comes to bacterial leafy vegetable diseases, there is only one organic bactericide that treats and cures the crops effectively. This is the most trusted bactericide for all bacterial diseases that affect not only leafy vegetables, but also other garden crops and plants.
In my garden, I have had only one incidence of bacterial infection, and it was dealt completely by this bactericide. Never to come back! It can treat fungus, but I would recommend that you leave that for the copper solution mentioned above.
If you think your garden has black rot, soft rot or any other bacterial disease, I would advise you not to hesitate to buy this bactericide.
Mosaic is a viral disease caused by Turnip Mosaic, and it causes dark lines on the leaf veins of the infected crop. The leaves can become discolored with time.
The disease is transmitted by aphids, so you can prevent it by controlling the insects in your garden. Another way to prevent the virus is to keep your garden free from weeds.
The best way to control mosaic is to uproot and bury or burn the infected crops. Crop rotation can also help with the virus.
17. Root Nematode
This is a Meloidogyne incognita nematode that causes knots on the roots of vegetables. The infected crop becomes stunted and can wilt with time.
The nematodes thrive in a warm soil, so you can prevent them by keeping your soil at lower temperatures.
The infectious organisms can survive in the soil for many years. If you think your soil has these nematodes, you can fumigate it to control them. You can also control them by practicing crop rotation.
Leafy vegetable diseases are many, but these are the most common ones. You can easily prevent, control and treat them with the help of the information provided in this article. If there is a disease that you can’t control or treat, you can get assistance from a plant pathologist, botanist or agricultural extension officer.
Questions & Answers
Question: Is it safe to eat the vegetables with a disease?
Answer: It is not possible to suffer from a plant disease, so it is safe!
Question: What could cause curly leaves in okra and fluted pumpkin with an accompanying white powdery substance?
Answer: In addition to the diseases outlined in this article that cause curly leaves, some tiny pests like aphids also cause the problem. See other pests here - https://dengarden.com/gardening/pests-leafy-vegeta...
Question: What virus is turning my lower tomato leaves brown and crispy before they fall off? I put straw down, but it was no help. As a result, I had to cut down three peach trees due to leaf curl as there was sap everywhere and the peaches were the size of grapes with maggots inside.
Answer: It could be the Curly Top, Mosaic virus, or as a result of uneven watering, high temperatures, or dry spells. If your watering and temperatures are okay, then it is likely a disease spread by aphids and other insects. See how to control the insects here: https://dengarden.com/gardening/pests-leafy-vegeta...
Question: My kales have a disease that is affecting the leaves then extends to the stem and finally the stem rots. Which chemical should I apply?
Answer: Symptoms? You can always start with the Copper Fungicide mentioned in the article.
Question: can a viral disease cause Bollworms?
Answer: No, Bollworms can't be caused by a virus.
Question: What causes my Lacinato kale to curl back from the center vein, then curl around a center point?
Answer: It is highly likely to be the Leaf Curl disease, which is usually caused by fungi. Pests like aphids can also cause curling, but if you can't see the insects, then it is the disease. You can get the copper fungicide mentioned in the article to see if you can control the disease.
Question: what are the effects of pests and diseases in the vegetable garden?
Answer: Increased growing cost, low yields, lose of income, etc
Question: Whiteflies have attacked my sponge gourd and also a virus has infected them. How can I protect my sponge gourd from viruses and whiteflies?
Answer: On top of this article, see this also - https://dengarden.com/gardening/pests-leafy-vegeta...
Question: What diseases have the following symptoms: yellowing of leaves, purple leaves and the leaves get soft and fall?
Answer: These symptoms can also be caused by inadequate nutrients or environmental problems. For diseases, there are a number that cause yellow leaves and you can check them from the article, but purple leaves are usually due to lack of certain nutrients like phosphorus, potassium, etc.
Question: What disease turns my tomato's leaves brown?
Answer: It could be the bacterial canker disease, and you can try the BioSafe Disease Control Concentrate Bactericide mentioned in the article.
Question: Why do my potato plant leaves turn yellow then brown?
Answer: There are a number of factors that cause this - ranging from lack of certain nutrients and environmental factors to poor crop practices and diseases. See diseases with this symptom from the article.
Question: Is it safe to eat alugbati with purple dots on its leaves?
Answer: Yeah, as long as the dots don't affect their taste and you cook them properly.
Question: My spinach has black spots on it. What is this and how do I treat it?
Answer: It's a fungal disease and you can treat it with copper fungicide.
Question: what are the green bumps on front and back of leaf lettuce (black Simpson) in clusters?
Answer: It could be downy mildew/edema, frogeye or yellows developing. You can use the copper fungicide mentioned in the article.
© 2015 Fredrick aka JS
Eden Zelalem on August 07, 2020:
this note is good about the leaf vegetable disease it gives me fantastic detail
Fredrick aka JS (author) from Intercontinental on June 29, 2020:
@Kathy see the disease from the article and how to deal with it.
Kathy U L on June 29, 2020:
My tomato plants have black or a dark gray leaf at the top and the leaves are browning around the edges, what is wrong and can I fix it
Fredrick aka JS (author) from Intercontinental on July 11, 2019:
Attaching pictures is not supported in the comment section, so you can just describe the symptoms.
Dennis sisi on July 10, 2019:
May I sent the picture of my kale so you may see the disease and help me?
julius mwansa on June 23, 2019:
I found the presentation on most common leaf vegetables educative and informative.
Fredrick aka JS (author) from Intercontinental on November 23, 2018:
It's likely to be powdery mildew, so try to avoid splashing water on the leaves. You can also try the fungicide included in the article.
Muvela on November 23, 2018:
My kale crop is developing soft leaves as if they havevbeen soakeed in hot water annd the upper side of the leaf turns white while the bottom side remains green and after some it dries up what could be the problem
Chavela on July 22, 2018:
Don't think it's downy on leaf lettuce. The bumps are green and same as plant. When I cut them, the white juice exudes the same as cutting off leaves. I think it might be the leaves nature. I eat it anyway!
Thanks for your support; you surely do know viruses! I will bet some of the copper product I saw on here. Thanks!
Fredrick aka JS (author) from Intercontinental on May 04, 2018:
Mixing your soil with fumigants (special pesticides). I don't sell certified seeds but you can find them in agricultural stores near you. And as I said, you can't eat lettuce or any other crop produce after treating with the fungicide. Alright, this platform doesn't support photos, but I got your description.
Sherry F1 on May 04, 2018:
Thank You So Much!!
How do I fumigate the soil?
Do you sell the Certified Seeds?
Can you eat the lettuce after you treat it with Copper Fungicide?
I tried to attach a photo but couldn't...
Sherry F1 on May 04, 2018:
Thank You So Much..
Do you sell Certified Seeds?
How do I fumigate the soil?
I tried to attach a picture but couldn't.
Fredrick aka JS (author) from Intercontinental on May 04, 2018:
The fungicide penetrates through the crops so give it at least a week. To control the disease, you need to fumigate the soil. Certified seeds only come being disease free, so they can't help in resisting an existing disease. You can send the photo.
Sherry F1 on May 03, 2018:
Hi Januaris Saint! THANK YOU SO MUCH FOR YOUR ARTICLE AND KNOWLEDGE....I have tried for the past 2-3 years to find out what's going with my lettuce/tomatoes crop. I have 5 raised beds. I plants lettuce, tomatoes and cucumbers every year. I have tried to rotate my crop but it's hard since I only have the 5 beds. And for the 1st time by reading your article I think I know what the problem is. I think I have the Frogeye Leaf Spot in the tomatoes bed. But it is kinda yellow too. And White Spot in my lettuce bed. Yikes/HELP...
I ordered the Copper Fungicide like you suggested.
Here's my ?? Is it safe to eat my lettuce and toms after using this product if I wash it real good? Since I am getting this year after year is this in my soil? What can I do about it? You mentioned purchasing Certified Seeds. Would that work if it's in the soil? Can I send you a photo of the fungus on my leaves? Thank You So Much....
Joseph G.Mulbah on November 22, 2017:
Let me utilized this media to officially express my Heartfield gratitude and appreciation for your courageous, delligence and energetic hard work for your brillent elucidation on diseases that affect vegetable crops and their prevention measure. I must applaud you and say congratulations. You are a good agricultural practitioner and laborious agriculturalist. Keep it up
Fredrick aka JS (author) from Intercontinental on August 03, 2017:
It could be pests then! Big pests like rodents can break leaves, and of course, the broken leaves start to rot.
Din Baron on August 03, 2017:
Thanks Jan Saint.
It doesn't look like any of diseases described above. Just overnight, four to six top jung leafs, start to hang down like someone broke it and just below leafs start to rot and attract the flies and stinks badly.
Would like to attach the photos but doesn't allow me on this comment window.
Fredrick aka JS (author) from Intercontinental on August 02, 2017:
Photos of your sick crop can help identify the issue, but it is highly to be one of the fungal infections described in this article! Try the multipurpose fungicide described above. It could also be due to a watering issue or even a weather issue!
Din on August 02, 2017:
Would like to know why is top of my kale plants starting to rot suddenly?
zafa love on July 19, 2017:
this information has been helpful to run my vegetables
Fredrick aka JS (author) from Intercontinental on July 14, 2015:
Thanks WiccaSage for your comment. Most crop diseases in humid areas are fungal. You can use this information to prevent, treat and control the disease.
Mackenzie Sage Wright on July 10, 2015:
I'm not familiar with some of these; I live where it's humid so usually when one plant comes down with a disease it spreads like the plague.