Rosemary: Most important pests and diseases

If I tell you to think of any aromatic plant, I’m sure rosemary comes quickly to mind. In today’s article, we will focus on identifying what are the most common pests and diseases of this plant and how to control them.

Rosemary: Most important pests and diseases
Rosemary plant

Rosemary: What is it used for?

Its scientific name is Rosmarinus officinalis and its natural habitat is the Mediterranean region. It grows in any type of soil, preferably dry and somewhat sandy soils. As you know, it is shrubby, woody and its leaves are perennial (they last in the plant all the seasons of the year). Its flowers are violet, pink or white.

This aromatic plant is used in many situations. Among them: rosemary tea, oils, alcohol, soaps, etc. In addition, like many other aromatic plants and flowers in the garden, it is very useful because it attracts beneficial insects: pollinators (such as bees). The bees settle on the different flowers depositing the pollen of some on the pistils of others, and making easier the fertilization that produces the growth of fruits.

Rosemary: Most important pests and diseases
Bee on rosemary flower

The truth is that it is a plant quite resistant to pests and diseases. The most common are fungal diseases. It is not advisable to water it too much and excessively fertilized soils can also be harmful.


Rosemary diseases


Root rot: Rhizoctonia spp.

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The roots of the rosemary plant can be affected if they receive too much water from irrigation. Therefore, the soils in which they are grown must be permeable. Otherwise, the roots will rot.

It is a fungus that affects the roots and the neck of the plant. The attacked areas show discolorations and later rot. Normally, young plants are the ones that present this type of disease. This is because they do not yet have well-formed tissues.
Black spots on rosemary leaves: Alternaria spp.

Again we are faced with another fungus. In this case, the symptoms appear on the leaves. If you observe on your rosemary, some black spots like the ones shown in the photo… Alternaria is in your orchard.

Rosemary: Most important pests and diseases
Rosemary leaf affected by Alternaria spp

Rosemary pests

This plant is not spared from the main outdoor pests, among which the following stand out:
White bugs on rosemary: mealybugs.

Although the picture does not show it well, mealybugs can also appear. Remember that males do not feed on plants and have wings. On the contrary, the females (which are the ones we see in our crops) are larviform, have no wings and are permanently attached to the plants they parasitize.

There are many species of mealybugs, but the most dangerous one is the ribbed mealybug. It can kill our plants in a short time because it reproduces very quickly and feeds by sucking the sap.

Rosemary: Most important pests and diseases
Ladybug larva (left) and adult ladybug (right) feeding on grooved mealybugs

They can be controlled by natural predators and parasitoids of mealybugs such as Criptolaemus montouzieri, Anagyrus pseudococci or Leptomastix algirica. In addition, we can apply chromatic traps or ecological products such as potassium soap or neem oil.

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Red spider mite on rosemary leaves

Although it is known as spider mite, it is a species of mite. They are usually generalists and mainly affect grapevines, horticultural and ornamental crops. They are located on the underside of leaves and can be identified by dark spots on the sides and a large number of silks.

Rosemary: Most important pests and diseases
Tetranychus urticae or red spider mite

Does rosemary repel insects in the garden?

The smell of rosemary is also not pleasant for some pest insects. We can take that into account for crop associations in the orchard. Crop association is one of the most used techniques in organic farming. It consists of strategically placing plants close to each other because of their compatibility or benefits. An example is rosemary which, thanks to its smell, repels some garden pests, such as thrips.

Therefore, a good association of rosemary is with plants attacked by pests that it can repel, for example:

  • With CARROTS. Useful association because it repels the carrot fly and thrips, typical pests of this crop.
  • With BEANS. The smell of rosemary does not like the Chrysomela bean pest.

Author

  • James Jones

    Meet James Jones, a passionate gardening writer whose words bloom with the wisdom of an experienced horticulturist. With a deep-rooted love for all things green, James has dedicated his life to sharing the art and science of gardening with the world. James's words have found their way into countless publications, and his gardening insights have inspired a new generation of green thumbs. His commitment to sustainability and environmental stewardship shines through in every article he crafts.

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