Laurel is a very easy plant to maintain. I have one I can corroborate it: it takes care of itself! I only watered it occasionally the first year it was on the ground; later ... not even that. It is very resistant, enduring a summer drought that more times than desired begins in late spring and lasts until the fall for some seasons. For all these reasons, talking about laurel diseases is a bit strange to me.
But it is also true that this does not mean that it does not have or can have; rather the opposite: things like watering it excessively, exposing it to the sun without being acclimatized, or having it in a pot with a substrate that is not adequate makes it a very vulnerable plant to infection. So that, Let's see what are the problems you may have and how to fix them.
The diseases that this tree, often grown as a large shrub or small tree, can have are those that we are going to see below:
bacteriosis
Although it is in the first position of this list, it is really very rare for laurel to have bacteriosis. Now, that it is rare does not mean that it cannot end up affected, so it is important to say that if your plant has spots on the leaves, or the fruits look bad, with wounds, and if the branches also have cankers, Pseudomonas bacteria may be hurting you.
The treatment consists of prune affected parts, using tools that are disinfected and clean. Likewise, you have to deal with copper-based products, such as this one that they sell here, since they reduce bacterial activity.
Sooty mold or bold
This is a very common fungal disease in many plants, but especially in laurel. It is associated with insects that almost every spring and summer we will see on the leaves if we do not take action in time: mealybugs. These settle on the underside of the foliage, from which they feed on the sap. But beware, you can also end up sick with bold if that pest is whitefly or aphids. Why?
Well, these three insects secrete a honeydew which is what attracts fungi, in particular the genus Capnodium. As the days go by, the leaves turn blackish, since a kind of layer is formed on them. It is not usually a serious illness; that is to say, it is difficult that it is going to kill the laurel; but it will make it quite ugly.
Fortunately, can be treated by attacking the pest. Once the insects are eradicated, the disease almost always goes away on its own. So, do not hesitate to try anti-mealybug insecticides (on sale here), anti-aphids or anti-whitefly (for sale here), depending on what is affecting you.
Root rot
Laurel root rot is a very serious problem, caused by overwatering, too frequent rains and / or a poorly drained soil. There are many pathogenic fungi that attack the root, but without a doubt we have to highlight the Phytopthora. These enter the interior of the roots when they are weakening due to lack of oxygen caused by excess water.
And of course, sooner rather than later this part, which is essential for the plant, will no longer be able to perform its functions. It turns brown and then dies. Then the leaves will turn that color too, and in the end we will have a dry bay leaf. Fortunately, it can be avoided.
The way to get it is watering only when necessary: once a week, or two at most if it is in a pot. Also, the land has to be well drained, otherwise you could run into problems. Therefore, if it is in a container, it will be filled with peat mixed with 30% perlite; If it is going to be put on the ground, it is necessary to make sure before that the water is absorbed quickly, and if it does not, it will be done in a hole of 1m x 1m and it will be filled with peat mixed with perlite in equal parts.
Smallpox
Bay pox is caused by fungus Stigmina carphopila. It is not a particularly serious problem, but If you see that its leaves have purple spots, it is probably this disease.
You can treat it with fungicides that contain copper, following the manufacturer's instructions. In this way, the plant will gradually improve.
Xylella fastidiosa
Image - Wikimedia / Charles J. Sharp // This is the insect that transmits Xylella, whose name is philaenus spumarius.
La Xylella It is a bacterium that especially affects olive trees, although it is estimated that there are some 300 species of plants that can also become ill. One of them is laurel, and like all the others, it can present a sad appearance, as if it lacked water. Namely, We will see that it has brown, dry leaves, and that it has stopped growing.
There is no effective treatment for this disease. But for what it's worth, a biologist who was dedicated to producing plants and then selling them explained to me in his day that when the first symptoms are detected, and once it is known that you have Xylella, what you can do is cut the branch or branches that are affected, since this reduces the risk of the entire plant ending up ill.
We hope that it has been useful for you to know what are laurel diseases, and most importantly, how to treat them.