Black spots on leaves of shrubs are always a bad sign, and often most it means a disease of sorts. Well, there is more than a single answer to this question.
In this article, we will help you find out the culprit and define the best way to deal with the problem of brown and black spots on your shrubby plants.
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What Are The Causes of Black Spots On Shrubs?
The causes of black leaves on shrubs are due to fungal leaf spot disease, or blight and canker. Moreover, it may also be due to bacterial leaf spots. These are the key reasons why your shrub has black spots on its leaves.
Some shrubby plants will be more prone to diseases than others, but almost all of them will have a sort of disease in their lifetime. Of all the shrubs, the rose has to be the most damage-prone and this is why you must know all of these that can attack your bushes, but that doesn’t mean that they cannot affect your other shrubs.
– Fungal Leaf Spot Disease
Black-leaf spot diseases are almost always caused by some type of spot fungus and are the most widespread shrub diseases. The pathogens usually can survive harsh winters in infected debris, buds, and young twigs! Once the growing season has begun, the pathogens will use rain and wind to spread in the canopy and other nearby plants!
This black disease will come in many shapes, forms, and sizes, often beginning at the lower branches of your shrubs and slowly creeping to the top canopy. Black spot problems will appear randomly on leaves and in a variety of sizes, ranging from yellow, orange, black, and brown spots.
If we’re talking size, then you should know that the bigger your leaf spots are, the longer your shrub has the disease, such as the spot disease that would result in black little dots.
Blight and canker are diseases that are specific subspecies of the before-mentioned disease and are too caused by a fungal infection. In addition, this matter is worrying because it would ruin the beauty of the leaves of any shrub.
Blight will typically attack younger and green offshoots, and they typically don’t progress to attack the older growth. This can seriously affect your shrubs because most of that new growth will produce the highest energy. This way, blight stunts and slows growth until you act and mitigate the disease.
Unlike the blight disease, canker won’t be so picky and will spread and work its way on shoots, leaves, and branches, but on stems and bark as well. This issue is a serious disease and if you spot it on your trunk, you may also have to say goodbye to the entire growth above the place where it’s bitten, because it will damage it severly.
Branches and leaves will have discolored bark and will ooze dark sap when cut. Cankered areas will have a mushroom-like appearance on the bark, and they will have a black center, but a yellow or white surrounding.
– Bacterial Leaf Spot
Bacterial spots on leaves are most commonly caused by Pseudomonas or Xanthomonas pathogens which live on plant skin without any immediate effects. When the conditions are right, these pathogens germinate and spread, and this is how they trigger the diseases that would infest wholly.
This one usually starts as brown or dark spots with a yellow halo around each spot. If you’re dealing with serious cases, the centers of spots may dry up, causing entire leaves to disintegrate or have holes.
On the other hand, if the rainy and humid weather persists, bacterial disease symptoms will often grow, merge, and cause leaves to go completely black. Bacterial blight can infect buds, flowers, and entire shoots too.
How to Stop Black Spots Growing on Shrub Leaves?
To stop black spots from growing on shrub leaves you should first care for the hygiene of the place, and start pruning the infected areas on the shrub. You can also try to manage the watering properly, decrease the feeding, use fungicides, and spray insecticidal fluid
– Care for the Hygiene
If you spot your shrub infected by black leaf diseases, you should assess the situation both on the ground and in the canopy.
Start by gathering infected and fallen leaves from the ground to make sure no pathogens are left for the next growing season.
Make sure tha you would give proper care to the hygiene of the place, because they will spread the disease to the new shoots if you don’t clean it properly with some alcohol.
Cut off sick branches and foliage as much as you can and burn or destroy the gathered plant material.
Pruning should allow air to flow better in the canopy and sunlight to penetrate those hard-to-reach places inside.
As you do so, you will be cleaning off the damaged parts and foreseeing healthier shoots.
– Proper Watering
If the disease progresses into the warm and airy weather and your tree is desperate for water, mind that you water your shrub only at the base where the stem enters the ground so that no water touches leaves. In addition to this, you must also avoid exposing your tree to any water stress. Tap water is fine as long as you purify it!
Always maintain moist soil, and don’t let your tree dry up completely, because it’s already weakened by the disease. If you cannot water your shrub diligently, providing mulch on the topsoil and maintaining it throughout the growing season is a good option.
– Decrease the Feeding
Don’t feed your trees and shrubs that suffer from leaf disease. People often do this as a response, but this can overload the roots without doing any benefit to the plant.
The plant doesn’t have the same ability to transport nutrients, but the roots will still take them in, and they will crystallize at the base.
– Using Fungicides
Fungicides should only be applied to help a struggling tree or shrub that’s been infected for a few years in a row.
These are the chemicals that are used to only work on healthy plants and are protective, not to be applied as medicine, which means that after you have pruned the infected parts well, you can now apply them to the clean parts.
Always use a pressurized sprayer to cover entire canopies with fungicides.
– Spray Insecticidal Fluid
Small sap-sucking insects will spread diseases and bacteria and quickly introduce them to your healthy plants. Just make a nature-friendly pesticide that can help you get rid of these pesky critters.
For instance, neem oil works best in this regard, along with some rubbing alcohol or your regular dish soap. Mix any of these with a large amount of water and spray your plants heavily! Remember that pesticides also work best when applied preventatively at the beginning of the growing season.
Nobody likes to see that black spot issue on our garden plants and shrubs! But what may come as a small relief is knowing that these don’t have to be entirely harmful to the shrub, so let’s review what we’ve said in order to keep your shrubs happy:
- Always inspect your plants to see what’s bugging them, as diseases and insects will leave somewhat the same marks, but won’t be dealt with in the same manner.
- Fungal leaf spot disease and wilts or blights don’t have the same damaging effect as canker or bacterial spot can have, so with some, there’s no need for a speedy reaction.
- Always deal with diseases preventatively: Regularly prune your plants to allow air and sunlight to be present and spray fungicides early on in the growing season.
Now we have it all covered when it comes to those nasty dots, and you know so well how to prevent black spot diseases, and we’re sure your shrubs will be thankful for this new-found knowledge.