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Mad Mandarins, July 10 2020

Get a Fresh Start: How to Control and Get Rid of Sooty Mold on Citrus Trees

Do you have black soot on your citrus leaves or fruit? Does it look darker than dirt or yard dust? Chances are, your plant or tree might have sooty mold. Below are some photos of what sooty mold looks like:

Most people assume that the sooty mold you see on citrus plants is a disease. Conversely, sooty mold is actually more common than most think. Sooty mold is a black, powdery fungus that grows on the branches, leaves, and fruit. 

This fungus is unsightly and does little harm to the fruit. Even while the plant has sooty mold, the fruit is still edible. However, severe coating of the fungus can block light, therefore affecting plant growth. 

Citrus with sooty mold is a definite sign that harmful insects have invaded your citrus tree. Continue reading to find out a few tips for helping to control sooty mold and the insects that create conditions ripe for fungal growth.

Citrus Sooty Mold

Citrus with sooty mold is the result of an infestation of aphids or other types of sap-sucking insects such as bees. While these insects dine on the sweet juices produced from the citrus, they excrete a sticky “honeydew” that attracts the growth of ugly black mold. These insects can not properly digest all of the nutrients from the citrus, so their bodies excrete the remainder in the form of honeydew. 

The sooty mold fungus can grow wherever the honeydew substance drips: sidewalks, lawn furniture, pots, etc.

How To Treat Citrus Sooty Mold

To get rid of sooty mold on citrus, the first step is to eliminate the honeydew-producing insects. Aphids are usually the main culprit, but other honeydew-producing insects include psyllids, leafhoppers, soft scales, mealybugs, and whiteflies. Neem oil, horticultural soap, or insecticidal sprays are very effective ways of helping control the pests, though eradication generally requires more than one application. 

Our favorite recipe is neem oil, water, and mild dishwashing liquid, natural preferred. Follow the concentrated neem oil directions, then per every gallon, just squeeze a teaspoon per every 2 gallons. The dishwashing liquid acts as an emulsifier. It’s not required, but does help. 

Lets not forget to keep ants in check. Ants love sweet substances like honeydew, and they will actually protect the honeydew-producing insects from ladybugs, lacewings and other valuable insects, ensuring a continual supply of the gooey stuff. 

To help control the ants, we suggest placing bait under the tree. You can also use sticky tape wrapped around the trunk to prevent the ants from crawling up into the tree. Once all pests are controlled, the sooty mold will usually wear away on its own. You can help speed the process by spraying the tree with a strong stream of water, or water with a little detergent mixed in. 

A timely rainfall will do a world of good. To improve the appearance of the tree, don’t forget to prune for damaged growth. While neem oil is natural, it does hurt and kill good insects like bees and ladybugs. You’ll want to apply this before flowering time to avoid our pollinating friends, the bees. Additionally, the oil can burn the tree if applied during the hot temperature. To be safe, apply in the morning or right before the sun comes down.  

We hope these tips have helped you understand the importance of controlling sooty mold on citrus trees and get you going in the right direction to treat it! Don’t wait too long, treat sooty mold ASAP! 

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Mad Mandarins

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