They are vulnerable to certain diseases and pests, and mine gets them all.

The heat doesn’t seem to be a problem - it has valiantly continued to flower, and they are a hardy plant, native to warm-temperate, subtropical and tropical regions. I looked up a few pests and thought I would share how to get rid of them.

Aphids and Whiteflies – These are common sap-sucking garden pests that target hibiscus. These tiny insects excrete honeydew, a sticky substance that encourages the growth of sooty black mould. Misshapen or stunted growth is another symptom of an aphid infestation. Get rid of them naturally with a good forceful spray of water, or make a homemade aphid spray by mixing a few tablespoons of pure liquid soap (no degreasers or moisturisers) in a small bucket of water. Eliminate whiteflies using biological controls, insecticidal soap, and horticultural oils, or again use a hose to dislodge eggs and adults from your hibiscus. Whiteflies thrive in warm weather, so be vigilant during the summer.


Leaf Spot - These fungal infections can impact hibiscus plants and thrive in warm, humid conditions. Yellow or black spots appear on infected leaves, or greyish-white fungus may develop on the undersides of infected leaves. Leaf spot diseases interrupt photosynthesis, causing your hibiscus to produce weak or stunted growth. Eliminate using organic fungicides and give your hibiscus plants plenty of space to promote good air circulation.

Mealybugs - These are slow-moving, sap-sucking insects with oval-shaped bodies covered in white wax that can impact hibiscus plants. Symptoms include clumps of fluffy white wax and weak or stunted growth. Mealybugs also produce honeydew, which can lead to the appearance of sooty black mould. According to a survey on these critters, they were considered key pests, occasional pests and potential pests in 15%, 62% and 24% of the cases, respectively. The Algarve, Beira Litoral, Ribatejo e Oeste and Madeira are regions where mealybugs were considered the key pests. To control them, they say a 70% or less solution of isopropyl (rubbing) alcohol in water may be dabbed directly on mealybugs with a cotton swab to kill them or remove them. Test the solution out on a small part of the plant 1 to 2 days beforehand to make sure it does not cause leaf burn (phytotoxicity).

Credits: Pexels; Author: @ravikant;

Powdery mildew - This is a fungal disease that can infect hibiscus plants. Symptoms include powdery white growths on foliage and curled or discoloured leaves, and can also cause stunted growth. It thrives in humid conditions, so avoid overwatering, and promote good air circulation by leaving plenty of space around your plants. Remove infected leaves and any leaf debris around your hibiscus.

Credits: envato elements; Author: Grigory_bruev;

Scale insects - are another type of sap-sucking pest that can infest hibiscus plants. These small bugs with waxy armoured shells can be spotted crawling over leaves. Symptoms include deposits of honeydew, sooty black mould, and white eggs on the undersides of leaves. Get rid of scale insects using insecticidal soap or horticultural oils. Use biological controls or organic pesticides to eliminate large-scale insect infestations.

Wilt disease – This is caused by fungi entering through the roots, preventing your hibiscus’s ability to circulate water properly. Wilt disease affects the entire plant, causing wilting, dying leaves that turn dark green or black. Fungi love soggy, wet soil, and if you keep your hibiscus too wet, you are inviting fungi to grow there. Most wilt disease strikes in winter when gardeners fail to reduce watering enough and the soil stays too wet, and if your hibiscus is fully wilted, you may not be able to save it, but as a last resort, the internet will provide options to help.

And lastly, a non-damaging pest – ants! They love the nectar produced by hibiscus blooms and lap up the sugary honeydew that sap-sucking insects excrete onto hibiscus leaves.

Author

Marilyn writes regularly for The Portugal News, and has lived in the Algarve for some years. A dog-lover, she has lived in Ireland, UK, Bermuda and the Isle of Man. 

Marilyn Sheridan