March 2020 Articles

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What’s that hanging in my tree?

What’s that hanging in my tree? Editor: Rick Bogren at 225-578-5839 or rbogren@agcenter.lsu.edu By Heather Kirk-Ballard LSU AgCenter Horticulturist Some 20-plus years ago when I was an undergraduate at LSU studying horticulture, I first began to notice the strange new gray growth on the limbs of the trees across campus, especially the live oaks and crape myrtles. No, it wasn’t Spanish moss as we are all accustomed to here in Louisiana. It was something similar, yet different. This structure did not hang low or sweep from the limbs like Spanish moss. It clung tightly to the branches in tiny balls on the limbs of the trees. Fast forward, and now it’s become more prevalent and a bit of an issue for some heavily infested trees. This structure turned out to be what is called ball moss (Tillandsia recurvate), and it is a true flowering plant. Interestingly enough, it is related to Spanish moss and is classified as an epiphyte from the family Bromeliaceae, more commonly known as bromeliads. It is a rather large family. Epiphytes are organisms that grow on the surface of plant structures such as limbs and branches, using them strictly as a structural support. Ball moss photosynthesizes its own food and absorbs water from the air that is collected on its leaves while absorbing minerals and other nutrients from dust in the air. They do not really affect the host plant in a negative way unless the growth of the moss gets out of control. Ball moss can compete with the tree it’s on for sunlight and some nutrients. It also can restrict photosynthesis by reducing the available surface area on the leaves and branches it attaches to. Ball moss is not a parasite. It does not typically harm host plants unless the moss completely covers the majority of surfaces, inhibiting the plant from making its own food. The more concerning issue with ball moss is that infestations can lead to overall decline and susceptibility to secondary disease or infection, or it may cause plants to succumb to insect pressure. Ball moss creates small, round golf ball- to baseball-sized growths. They produce tiny "pups" that all grow together to appear as one large growth. Seeds are dispersed mainly by wind. Ball moss produces many seeds containing fine, straight hairs that adhere to older, wet or rough surfaces of trees or shrubs. Seeds germinate and then thrive in areas with low light and low airflow with high humidity. Although ball moss will not typically kill them, heavily infested plants may experience a slow decline resulting in death that occurs over several years. Very slow growing, ball moss does not become mature and produce seeds until year four or five. So taking notice early on of the smaller growths and removing them by hand is your best defense against a heavy infestation. Unlike Spanish moss, ball moss is less tolerant of pollution. Thirty years ago, the live oaks and crape myrtles surrounding the LSU campus were covered in Spanish moss. Now, the Spanish moss has disappeared from the trees only to be replaced by ball moss. If the growth has gotten out of control and you cannot sensibly remove it by hand, you can control ball moss by spraying it with a baking soda solution. Mix it in a 2:1 ratio of water to baking soda or 5 pounds of baking soda to 10 gallons of water. To effectively kill the ball moss, it is important that you get good coverage of the moss with the spray solution. The most effective treatment is to thoroughly saturate the ball moss. Trees that are heavily infested with ball moss should be resprayed 12 months later. Applications made in the late winter or early spring when the ball moss is flowering have proven to be much more effective than those made in the fall or in the summer. The ball moss will die, but it will remain attached to the structure of the host plant. Dead ball moss will appear dark gray to black and will no longer look viable. If the baking soda solution does not cut it, you can try a copper fungicide as recommended by Raj Singh, director of the LSU AgCenter plant diagnostic lab. Read the label carefully to apply the recommended dose and follow directions on the product label. Excessive use of copper-containing products may cause injury to the host plant. Search for Publication No. 3421 on the AgCenter website for more information.