The Lantana species, also known as Irene plants, feature yellow, pink, red or purple flowers from early in the growing season until a killing frost strikes. These bright flowers, as well as the dark green leaves, attract butterflies to gardens. While Lantana plants can grow in many conditions, including near drought and thick soil, they are susceptible to black or brown leaf spots, caused by fungus or bacteria. These spots spread quickly from leaf to leaf by water and insects, so treat the infection as soon as you notice it to prevent the spots from infecting the entire plant.
Stop watering the plant as soon as you notice the black spots on the leaves. Water dripping from an infected leaf onto another leaf or plant will spread the disease. Allowing the plant to dry out for a few days will also help to limit the fungus.
Wear protective gloves when working with the Lantana plant. Prune away any infected leaves once the plant dries out, after three to four days without water. Snip off all leaves that show the black spots and dispose of them away from all healthy plants.
Collect any leaves that have fallen to the base of the plant and dispose of them immediately. The fungus and bacteria can also spread through the soil.
Treat fungal infections with a fungicide designed to treat black spot. A variety of products for this are available at garden centers and nurseries; follow specific product instructions regarding treatment, as methods will vary by product.
Water the plant in the future by pouring water directly onto the base of the plant instead of watering from overhead. Overhead watering allows water to sit on the leaves, potentially attracting the fungus or bacteria of leaf spot.