If you purchase an item through links on this page, we may earn a commission. Our editorial content is not influenced by commissions. Read full disclosure.
Let’s eliminate it early. You will be experience black spots in your garden at some point. Black spot is not only common, but it affects so much more than roses, which most people don’t know.
It is a widespread fungal disease that can appear on many plants when the conditions are right, especially on plants with fleshy foliage in humid conditions.
Don’t worry, we’ll cover everything you need to know about black spot fungal disease and what to do about it.
Contents
What is the black spot?
Black spot is a disease that causes black spots to form on plants. Many species are affected, but you will commonly see it on roses, citrus fruits and apples.
Pink black spots (pink diplocarpon) is a common fungal disease well known to rose growers. Once it appears, it is likely to spread quickly and return the following season. At this point, management is the best approach.
Citrus black spot (Guignardia citricarpa) affects citrus. Black spot on citrus fruits results in reduced fruit quality and quantity. Lesions appear on fruit and foliage. Citrus black spot is common in subtropical areas, but as environments warm it is something to watch out for.
Apple scab, caused byVenturia inequalis, affects apples and close relatives such as crabapples, pear trees, firethorns and mountain ash, among others. Spots appear on leaves, fruits, flowers and even new green shoots.
You can see fruits opening as they develop, and they will often fall from the tree prematurely. The leaves of apple trees suffer greatly from spotting and can also fall from the tree.
Black spot begins in the spring when new shoots and buds appear. Weather, humidity and environment play a big role in the spread of this disease. If you have a wet season, watch out for black spot disease.
In addition to the pathogens listed above, black spot can also be caused by bacteria in the Pseudomonas gender.
- Glomerella cingulata infect apples
- Stegophora ulmea infects elm trees
- Stevensea wrightii infects succulents and cacti
- Placosphaeria spp. infects various species
Plants susceptible to black spot
When black spot spreads, it can cover foliage, flowers and fruit. This is on both evergreen and deciduous plants.
Black Spot Life Cycle
The fungal disease overwinters on dead leaves and debris, as well as on lesions still present on the soft wood of the infected plant.
In the spring, spores are produced in large quantities and are splashed onto plants by rain and water and in windy conditions.
When the spores receive seven hours of humidity and temperatures ranging from 75 to 85° with high relative humidity, infection occurs.
Within two weeks of infection, combined with ideal conditions, even more spores are produced and neighboring plants are infected.
This cycle can repeat itself several times in a season, as long as humidity levels remain long enough in humid conditions.
How does black spot spread
I’m going to jump in here because the black dot is a fungal zoo, to be honest. The main thing to remember is that when black spot appears on your plants, the conditions causing it are usually the same and the treatment is pretty much consistent.
The small spores of blackhead fungi are called condida. They are spread by splashing water, and leaves and fruits are affected.
A wetting period between 24 and 48 hours is necessary for the infection to take hold, especially in humid conditions.
Once the plant is infected, the disease may lie dormant and take several months before signs of infection begin to appear. In citrus fruits, it usually appears when the fruit begins to ripen.
In apple trees and rosebushes, when spring arrives, the mushrooms of V. inequalis And d.pink which have spores of overwintering shoots in the air. The wind carries the spores to newly developed foliage, twigs and flowers.
The spores need several hours of humidity in humid conditions to begin infection. Within 15 days, the first spots begin to appear.
The spores of the new infection are spread by wind or rain and irrigation splashes to other parts of the plant, as well as to new plants and trees.
The tree can suffer from small harvests and poor quality fruit if this cycle repeats itself over several seasons.
Signs of black spots on roses and other susceptible plants can appear in as little as four days after infection. Repetitive infections can result in fewer and fewer flowers as the plant’s energy is dissipated through leaf drop and defoliation.
Recognize the signs of blackhead
Although we cover a variety of black spot and fungus varieties, the symptoms are the same. Pay attention to your plants, especially when the weather is wet, with lots of wet and dry periods combined with high relative humidity.
The black spots are circular with rough edges. The edges can be smooth or feathery and the spots vary in size. They can be small dots or up to 1/2 inch in diameter.
Sometimes they are light brown, other times they are dark black.
Usually the lower leaves, foliage, flowers and fruits are infected first. However, it does not take long before the whole plant is infected.
Over time, the black spot on the foliage will turn the leaves yellow, and then they will fall off. Defoliation is common with black spot, especially when the infection is severe. Repeated infections affect plant vigor over time.
How to deal with blackheads
It is a mixture to provide plants with proper growing conditions and preventive measures once infection occurs.
1. Good airflow
When planting your plants, don’t space them as far apart as possible in one area. Air circulation is important to keep pests and diseases away; the black spot is no different. Pay attention to the required spacing of the plants you use and prune them to make sure they don’t get too dense in the center.
2. Garden hygiene
Blackhead prevention is a year-round process. It overwinters on leaf litter on the ground, so rake and dispose of the leaf litter as soon as possible. This should be done year round if you live in humid environments.
Regularly clean all garden tools with water and bleach.
3. Size
Prune infected plants as best you can. Remove severely infected leaves from the plant and from the soil when they drop. Prune any branches or stems that show infection.
This is important because spores can sit on parts of a plant to spread when conditions are right and it rains or you water overhead.
4. Plants sensitive to mulch
Apply a thick layer of mulch around the base of the plants. The mulch will stop the splattering of infected soil if spores are present. In humid or subtropical areas, do not use wood as mulch, as it can cause many types of fungi to form.
5. Spray with sulfur
Sulfur is very effective in preventing fungal diseases like black spot. I include sulfur in my spray regimen because it also targets many issues. I prefer to spray it, so buy a powder that can be mixed with water. It smells a little, but it disappears quickly.
6. Copper sulphate
Use a fungicide that contains copper sulfate. It’s best if you use it preventively in the spring before symptoms appear, but it can also limit or stop the spread. You probably won’t completely eliminate a blackhead infection with copper.
7. Neem Oil
It’s my favorite tool in my garden shed. It is an organic pesticide and fungicide made from natural ingredients. It penetrates inside a plant and coats the foliage. Regular neem oil sprays help prevent many problems like blackheads. It does not control black spot, however.
Do not spray in sunny conditions as it may burn foliage.
Neem oil can harm beneficial insects like bees, so spray in the early evening when the bees have retired for the day.
8. Black spot resistant plant cultivars
Depending on the plant you choose, see if the cultivars are resistant to black spot. This is especially important in humid, wet or subtropical areas.
For pinks, look for “Elizabeth Taylor”, “Lady X”, “Mister Lincoln”, “Peace”, “Princess of Monaco”, “Tiffany”, “Nearly Wild”, “Queen Elizabeth”, “Sexy Rexy”, “Distant Drums”, “Knock Out” and “Wanderin’ Wind”.
‘Finger Lime’, ‘Shatian You’ and most pomelos and bitter oranges are resistant, according to a study published by the American Society for Horticultural Science.
9. Fungicides
There are a few conventional fungicides that are very effective against black spot, especially if you rotate them every two weeks. Manxozeb, captan, and chlorothanonil are all great options if you’re determined to get rid of this disease and nothing else is working.
Home remedies for blackheads?
If you do a quick search on the Internet for home remedies for blackheads, you will undoubtedly come across the so-called Cornell method. This involves the use of baking soda or potassium bicarbonate. This is usually mixed with something like oil, dish soap, or vinegar.
It may be somewhat helpful in stopping or limiting the spread, but it will not eliminate the disease. You should also be careful because vinegar and dish soap can cause sunburn. The best thing seems to be horticultural oil.
Use it sparingly as baking soda is toxic to plants.
Prevention is the best cure for black spot, but if it does appear, be sure to remove as much infected foliage from the ground as possible. Spray regularly, space plants properly, and don’t be afraid to prune infected stems and branches if it’s a bad infection.
Was this article helpful?
Yes No ×
We appreciate your helpful feedback!
Your response will be used to improve our content. The more feedback you give us, the better our pages will be.
Facebook pinterest