Diseases and pests that affect orange trees

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Last updated on January 21st, 2020

Orange trees are an evergreen citrus tree which means they don’t lose their leaves come Autumn. They produce beautiful flowers that are white and scented which results in delightful fruits six months later. Once the fruit is ripe, you can eat it straight off the tree. If you are growing orange trees in Britain, there are a few diseases and other problems that you should be on the lookout for and most can be resolved with a little extra care.

Washington Orange Tree perfect for growing in containers

If worth noting that many problems when growing orange trees are caused by the incorrect growing condition. With this in mind be sure to read our guide on growing orange trees in pots.

Root rot caused by overwatering

root rot causing leaves to fall off and wilt

The critical issue you might face is root rot. This is when you water too much or too often, and the roots are left standing in water. If you notice standing water or you don’t let it dry out in between waterings, start doing so. They can be avoided by simply watering properly which means letting the surface of the soil dry out between each watering session. If you place a saucer under the pot to collect the water its also important to empty the water and not leave the pot sitting in water.

You can read our guide on how to properly water and feed citrus trees including oranges by clicking here.

Pests such as aphids and leaf minors

Aphids attacking citrus tree leaves

While not technically a disease, pests can be equally problematic for citrus trees like oranges. The most common pests you will face are aphids and mealybugs. Both of these hide underneath the leaves, and they suck the sap out from the leaf tissues. This will cause the leaves to curl and eventually fall off. Mealybugs leave small deposits all over the plant, and you will see what looks like tiny cotton wool deposits. Both pests leave a substance that is sappy and sticky on the leaves as pictured above. This substance stops the leaves from properly breathing and if you don’t clean it off and treat the issue it will manifest in a black suit that prevents any sunlight from reaching the leaves and eventually kill your orange tree.

Treat aphids and mealybugs with insecticidal soap or pesticide spray

At the first sign of these pests, you need to wash them off entirely from all the leaves and all the stems, regularly inspecting your orange tree for any indication of them. You will need to wipe down every leaf to remove the sappy secretion and any black suit; otherwise, the leaves will still suffocate. You can use insecticidal soap sprays as well and commercial bug killer designed for fruit, but your overall goal is to remove any and every bug and continue to repeat the process until the problem is eradicated.

If you have leaves that are badly effected we recommend removing them by hand rather than trying to clean them off.

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Leaf drop on orange trees

This problem is one that manifests in the form of a significant portion of the leaves falling off your tree. Now, most citrus trees in Britain has to be grown in pots so that they can be moved indoors over the winter. During this process, you might notice a handful of leaves falling, especially in January and February, and that is perfectly normal.

Orange tree winter care

If a significant number of leaves fall, you need to check the soil. If the soil is too dry it can cause the leaves to fall, so you need to increase watering and mist your plant regularly to increase the humidity.

Be careful here though, as too much water can be equally fatal, so you have to allow the compost to dry out before subsequent waterings. Many people who leave the soil to be too dry and have to contend with leaf drop make the mistake of overcompensating which then causes root rot which is even more fatal.

Being exposed to cold temperatures can also cause leaf drop.

Learn more pests and diseases that affect citrus trees

Image credits –

Last update on 2021-04-12 / Affiliate links / Images from Amazon Product Advertising API

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