What’s The Cause And Treatment for Black Citrus Tree Leaves?

black sooty citrus mold

So your citrus has started to bloom, and you’ve gone out to visit your orchard only to find leaves covered with a black coating and white fuzz. The black coating is one or more genera of fungi called sooty citrus mold. The white spots are from mealybugs laying eggs and freshly produced sugary honeydew secretions as they poke along eating your citrus tree. Although the sooty mold blocks sunlight, it doesn’t feed on the plant tissue and alone won’t destroy your citrus, but ignoring the pests that attracted it just might. Aphids, mealybugs, scale, and whiteflies are the soft-bodied usual insect suspects with their honeydew excretions that must be addressed for your citrus health and end the sooty mold.

Treat the mold and pests with your mix of insecticidal soap or a premixed one available at the garden center. Other available treatments include horticultural oil, fungicides, and pesticides. Hanging sticky traps in your citrus trees can attract and capture some of the perpetrating pests such as whiteflies but won’t rid the trees of existing sooty mold. Rinsing the leaves with a strong stream of water can loosen and remove the mold and some pests.

Insecticidal soaps are soap salt from fatty acids in animal fat, coconut, olive, and palm oil. Some online recommendations for making insecticidal soap claim you can use dishwashing soap. Yet, many brands are detergents with none of the necessary salts from fatty acids to be an effective treatment against the sooty mold and fruit tree pests. Rely on actual soap such as olive oil based unscented Castile soap that contains soap salt as the basis of your DIY Insecticidal soap production. Add a tablespoon or two into a gallon of water, or purchase the premixed insecticidal soaps in ready-to-use spray bottles.

Applying the Insecticidal soaps will loosen the mold, which will eventually dry and flake off. Soak the leaves to loosen the mold and coat the insects as it only works when wet, and there is no systemic benefit to this treatment. Be careful with Insecticidal soap overspray and don’t apply to azaleas, begonias, succulents, and various other plants. Use caution with your citrus understory plantings, as fruit trees have shallow roots that can suffer from too much competition for space and nutrients. Such adverse growing conditions for your citrus trees can result in nutritional deficiencies and stress that attract more pests. Consider practicing companion planting under the citrus with plants such as legumes that return nitrogen to the soil and flowering species like daisies and cosmos that attract beneficial insects. Only use plants underneath your citrus that can withstand your citrus pest control protocols.

Put an added kick in your homemade insecticidal soap with a tablespoon or two of cayenne pepper to further fortify the attack on the soft-shelled honeydew releasing pests. Dried pepper sprinkled around the base of trees is also an effective pest deterrent without the pepper spray risk of leave burn on some plants. Cayenne pepper is not only toxic to targeted pests but beneficial insects such as honey bees. Research the interactions of these concoctions with other desirable flora and fauna in your garden or landscape.

Horticultural oils are petroleum or plant-based oils that include neem oil. These oils make it difficult for the mold to cling to the plant and clog the breathing and other insects’ functions. Precautions are necessary when applying horticultural oils as they can burn non-targeted sensitive plants and your skin. Horticultural oils are non-selective pesticides that kill both pests and beneficial insects. Pond owners beware as horticultural oil is toxic to fish. It is crucial to limit overspray, prevent intrusion of the oil into your pond, and other water bodies via stormwater runoff.

There are also various systemic pesticide treatments available for treating your lawn and garden. Our lawn care spray techs can provide more information and set you up with a quote for service.

Once the sooty mold is gone, it is essential to maintain a healthy ecosystem for beneficial insects to thrive in and around your citrus trees, including companion planting, limiting the use of harmful chemicals, and proper fertilization of your trees. Some of the predators of these pest species include Ladybugs, Lacewings, and some predator wasp. If you don’t have them in your yard, consider purchasing them from Arbico organics. Earth Works garden center has the organic treatments mentioned in this article available for purchase, and our lawn care department is ready to serve you.

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