What Causes Black Spots On Lemon Tree Leaves?

Lemon trees are susceptible to fungal and bacterial infections that cause them to have spots, curl, turn brown, or wilt. Does your lemon tree show any of these signs? Why do your lemon tree leaves have black spots? Here is the answer.

Your lemon tree leaves turn brown because of sooty fungi. Sooty fungus is a discoloration on leaves and other parts of the lemon tree, producing powdery black spots.

What causes your lemon tree to have sooty fungi? How to treat it? We dug for the answers to your questions. Continue reading throughout this post.

Citrus Canker a deadly plant disease in citrus plants - What Causes Black Spots On Lemon Tree Leaves

What Is The Cause Of Black Spots On Lemon Tree Leaves?

Sooty fungi cause black discoloration on lemon tree leaves. These fungi accompany mites, ants, and aphids. Sooty molds produce powdery black spots on branches, trunks, and foliage. Sooty fungi don't feed on plants but destroy the tree's beauty and wear them out.

Unripe citrus fruits with sooty mold fungi, as a result of the activity of Citrus scale mealybug, Planococcus citri

How To Remove Sooty Fungi?

You can use a sponge soaked in a mixture of water and black soap. Clean the foliage and trunk of the infected plants and trees. However, sooty fungi comes from insects, such as whiteflies, aphids, scales, blackflies, and mealybugs. Getting rid of these insects will control the problem of black spots.

Check out this African Black soap on Amazon

How To Eliminate Sooty-Causing Insects?

Insecticide application helps kill insects that cause sooty fungi in lemon trees and other plants in your yard. It is advisable to use specific insecticides for edible fruits.

Here are the best insecticides you can use to destroy harmful insects:

BioAdvanced Citrus And Vegetable Insect Control

BioAdvanced has a specific formulation for citrus plants and vegetables to kill insects such as aphids, whiteflies, psyllids, and more. It has rainproof protection and is long-lasting. Check the label for instructions.

Click here to check BioAdvanced on Amazon.

Natria Neem Oil Organic Disease Control

Neem Oil helps control pests and diseases. This product is an effective repellant of insects for plants. You can use Neem Oil on indoor and outdoor plants. Since Natria Neem Oil is organic, you can apply it to edible fruits and vegetables.

Click here to check Neem Oil on Amazon.

Garden Safe Insecticidal Soap

Garden Safe Insecticidal Soap is organic, which is why this is ideal to use on fruits and vegetables on harvest day. You can also use this on ornamentals, flowers, shrubs, and more. This insecticidal soap can control mealybugs, leafhoppers, psyllids, aphids, scales, thrips, and other harmful pests.

Click here to check insecticidal soap on Amazon.

Monterey Horticultural Oil Concentrate

If you are looking for pest control insecticides that can kill aphids, thrips, leafhoppers, spider mites, whiteflies, leaf miners, and more, Monterey Horticultural Oil Concentrate is ideal to use.

You can apply this insecticide to plants and trees, such as apples, citrus, almonds, corn, figs, pineapple, pecans, avocados, potatoes, and many more. Horticultural Oil Concentrate is organic and registered with Organic Materials Review Institute or OMRI.

Click here to check oil concentrate insecticides on Amazon.

Mighty Mint Plant Protection Peppermint Spray

This peppermint spray kills mites, insects, spiders, and fungal diseases. It is safe to use around plants, humans, and pets—ideal for indoor plants, crops, and gardens.

Click here to use peppermint spray on Amazon.

What Are The Gray And Brown Spots On Lemon Tree?

Citrus Canker a deadly plant disease in citrus plants

Botrytis Cinerea is a fungal pathogen that causes gray and brown spots on a lemon tree. This fungus quickly germinates in extreme humidity and spreads through rain and wind. Botrytis attacks the leaves, branches, flowers, and fruits.

Fungicides can help control botrytis cinerea. Ensure that your plant is listed on the label. Here are the recommended fungicides:

Spectracide Multi-Purpose Fungicide Spray

Spectracide fungicide spray is rainproof and can't be washed off once it dries out. You can use this fungicide on fruits, vegetables, nuts, lawns, ornamentals, and trees.

Click here to check fungicide spray on Amazon.

Root 98 Warehouse Southern Ag Organic Bio Fungicide

Bio Fungicide is ideal for controlling plant diseases of fruits, trees, lawns, shrubs, flowers, potted ornamental plants, and more.

Click here to check bio fungicides on Amazon.

What Causes Brown Spots On Lemon Tree Leaves?

Bacterial leaf spot diseases often start as small dark brown to black spots with a halo of yellow tissue surrounding each spot.

Citrus anthracnose, also known as brown leaf spot, is another fungal disease that causes brown spots on leaves and spreads quickly on the tree and the nearby trees. Fungicides can control brown leaf spots.

Listed here are recommended fungicides against anthracnose:

Bonide Fungicide Concentrate

Bonide Fungicide Concentrate is an extreme protection of vegetables, ornamental plants, and fruits against diseases. It controls diseases caused by botrytis blights, anthracnose, powdery mildew, rusts, scabs, and more.

Click here to check fungicide concentrate on Amazon.

777 Concentrate Revitalize Fungicide

Revitalize fungicide is organic and can be used on fruit, vegetables, nuts, ornamental plants, flowers, trees, shrubs, and more. This fungicide can control fungal and bacterial diseases such as spots, molds, mildews, and rots.

Click here to check the Revitalize Fungicide on Amazon.

What Causes Black Spot On Lemon Tree Fruits?

Close up green brown with black rust mold spotted lime citrus round fruits on green tree bush, under warm yellow sunlight shade and shadow background

Citrus black spot is a type of fungal disease from Guignardia citricarpa. This black spot affects all citrus species and hybrids. Most commercially grown cultivated citrus showed citrus black spots and was unmarketable or sold at a discounted price.

The black spot looks like a round, black lesion with a grey center. You will also see a freckle-like lesion on matured citrus fruits after harvest or in storage. Use fungicides with copper to control citrus black spots.

Dr. Earth Disease Control Fungicide

Dr. Earth is 100% organic and is ready to use a fungicide. It controls black spots, peach leaf curl, leaf blotch, dollar spots, brown rot, scab, and other plant diseases. 

Click here to check disease control fungicides on Amazon.

Southern Ag Liquid Copper Fungicide

Liquid copper fungicide controls plant diseases caused by fungi and bacteria. This product contains a 27.15% of copper diammonia diacetate complex, which controls leaf spots, blights, rust, and more.

Click here to check copper fungicides on Amazon.

How To Treat Lesions On Lemon Tree?

Citrus Canker a deadly plant disease in citrus plants

Citrus canker is a deadly plant disease common in citrus trees. This disease is caused by Xanthomonas axonopodis. You can find lesions on stems, leaves, and fruits of citrus trees. These lesions look like craters with aligned circles around them.

Cankers spread through rainwater from one plant to another plant and are highly contagious to animals and humans.

How To Treat Canker On Lemon Trees?

The old-fashioned way of treating canker is burning the tree to avoid the bacteria spreading. Copper-based bactericides can now treat citrus canker alongside proper pruning during summer and fall.

Another method of controlling canker spread is the restriction on bringing or taking infected fruits to other states.

Earth's Ally 3-In-1 Plant Spray

Earth's Ally 3-in-1 plant spray concentrate is a fungicide, insecticide, and spider mite control in one. This product controls plant diseases, such as leaf spots, black spots, downy mildew, canker, and blight.

3-in-1 plant spray kills harmful insects like aphids, spider mites, mealybugs, scale, and many more.

Click here to check 3-in-1 plant spray on Amazon.

Bonide 811 Copper 4E Fungicide

Copper fungicide controls rust, spots, downy mildew, powdery mildew, peach leaf curl, and other plant diseases. Specially formulated for fruits, vegetables, nuts, herbs, roses, ornamental plants, and turf.

Click here to check copper 4E fungicide on Amazon.

What Are The Treatment For Lemon Tree Fungi?

There are precautionary measures to prevent and treat fungal diseases on a lemon tree.

  • Provide well-drained soil for the tree. It is necessary not to make the soil soggy because it will attract bacteria and fungi.
  • Pruning helps in controlling the spread of fungal infections. Cut the infected dead leaves and branches.
  • Remove low branches that ground spores can reach.
  • Proper disposal of fallen, dead leaves around the tree base.
  • Use fungicides and insecticides to prevent the spread of fungi and insects. Always follow the instructions on the label before using any commercialized product.


If you see that your lemon tree leaves have black spots or other signs of fungal infections, take immediate precautions and treat the disease to avoid spreading and causing more damage. Write your suggestions and questions below, and we will respond the soonest as possible.

If you want to find out more about plant diseases, pests, and other helpful tips, you may visit and read these posts:

Why Are My Hydroponic Plants Wilting? How Can I Fix It?

Can I Mix Fungicide & Insecticide? Are They Compatible?

Pesticides Vs. Insecticide; Which Is Best For Your Home Vegetable Garden?



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