Mistletoe, Lichens, Ball Moss and Spanish Moss

Ball moss, Spanish moss, lichens and mistletoe are commonly found growing on shade trees in Texas. Of these, only mistletoe is classed as a parasitic plant on ornamental shade trees. Lichens, ball moss, and Spanish moss, although found on trees, are not feeding on the tree, but only using the tree for support.

Mistletoe
(Pharadendron engelmanni)

Mistletoe is a tree parasitic plant that derives its food directly from trees. The haustoria or "feeding structures" of the mistletoe grows into the vascular system of the tree and derives their nutrients from the sap flow of the tree. Mistletoe is spread by birds feeding on the berries and spreading the seed in their droppings onto other limbs. The seed germinates into the rough bark of the tree and the haustoria then grows into the vascular system.

Mechanically removing the mistletoe from the tree is the only control method currently recommended. Mistletoe is removed with a hoe or knife from a limb. If the removal is to last for a period of time, it is necessary to take a knife or some other type of sharp instrument and remove that part of the wood where the haustoria is located. To merely cut the mistletoe from the tree at the bark layer will eliminate it for a short time but recovery will begin immediately.

Lichens

Lichens are bluish-green to gray paper-thin plants that grow on the outside bark of the tree. Their growth becomes very dense and upright on some plants, while on others they are flat on the bark of the tree. Lichens can be found on rocks and other inanimate objects indicating that they are receiving no nutrients from the host tree, as is the case with mistletoe. Lichens are a combination of algae and fungi growing together in what is known as a symbiotic relationship. The trees are involved only in that they are the object on which the lichen is growing.

Although found in most areas of Texas, lichens are more of a problem along the Gulf Coast and in the more humid areas. Lichens are most often thought of as an indicator of poor tree vigor. Lichens have a requirement for a certain amount of sunlight so if the tree is healthy and has dense foliage, the lichens do not have a chance to grow and develop. When the trees are weak due to other causes, lichens can proliferate and cause a great deal of concern. Thus it is very important that trees be maintained to insure maximum foliage. Currently there is no chemical control for lichens. In the past, such compounds as copper bordeaux have been used for control. Re-growth occurred soon after the chemicals were washed off. Even though the copper bordeaux will eliminate the organisms for a short period of time, it is not recommended due to its short term effect, and because its use is not currently cleared by the Environmental Protection Agency (EPA).

Ball Moss
(Tillandsia recurvata)

Ball moss is the grayish-green "pincushion-like" or tufted growth seen on the bark of a number of Texas shade trees. Ball moss is an epiphytic plant, meaning it derives its nutrition from the air, not from the tree. It causes a great deal of worry for homeowners who fear that the ball moss is killing their trees. Trees heavily infested with ball moss have been observed to undergo a slow decline, because the moss can smother lower limbs of a tree simply through shading of buds. In general though, moderate populations of ball moss are not harmful to a healthy, actively growing tree.

If your trees have a heavy infestation of ball moss or you simply don't like the look of the moss in your trees, there are effective control measures that can be taken.

When there is only a light infestation of ball moss present, just take good care of your trees and don't worry - no chemical sprays are needed. However, if large numbers are present, here's your ball moss battle plan:

1. Prune out and destroy dead or severely weakened branches, especially those encrusted with the moss.

2. Treat with Kocide 101 in spring (February through May).

3. Use Kocide 101 at 6 lb./100 gallons of water or 6 tablespoons per gallon of water.

4. Invigorate trees with an application of a slow-release fertilizer such as 19-5-9. Apply 2 pounds (2 cups) per inch diameter of the tree trunk. Irrigate deeply and regularly throughout both the growing and dormant seasons.

5. Re-treat any tree with signs of active ball moss after 12
months.

When controlling ball moss using Kocide 101, it is important that all of the moss be covered and saturated with the spray solution. To be effective, applications must be made before or during the rainy season, usually mid-February to early May. This insures that the Kocide is on the ball moss and waiting to be absorbed into the moss with the next spring rain. Spray equipment such as a 50-gallon skid mount sprayer which applies chemical 30 to 40 feet high is available from some equipment rental stores. Of course, you must have a pickup truck available to haul the sprayer.

Two cautions about using Kocide 101: 1) the chemical has a bluish color and can stain brick walls, roofs and driveways, and 2) Kocide will damage foliage of peaches, plums, nectarines and apricots.

Ball moss treated with Kocide will die over a 6 to 12 month period but will remain in the tree because of its "hold fasts," which attaches it to the tree. In most cases, it will take 18 months for these "hold fasts" to decay sufficiently so that the ball moss will be dropped from the tree. Once Kocide has been applied and the moss is killed, it will become dark gray in color and the "leaf like" structures will point downward rather than be in an upright position.

Even though baking soda has been shown effective for ball moss control at the rate of 40 pounds of baking soda per 100 gallons of water, Mr. Arm & Hammer has not put it on the label SO WE CAN'T RECOMMEND IT! However, if it is used, it should be applied exactly as Kocide 101 is.

Another recommended method to control ball moss is "de-mossing." This procedure consists of pruning out dead or weak branches, plus physically scraping or picking all of the moss throughout the tree. This procedure will give good control for about 2 to 3 years. Since some of the tiny moss tufts are unavoidably missed, a new crop of ball moss will eventually appear again.

Spanish Moss
(Tillandsia usneoides)

Unlike ball moss, Spanish moss does not develop the very dense growth around the limbs and for that reason is not considered to be a problem on trees. In Texas, Spanish moss is associated with an atomosphere of the "old South". The "old South" is the area in which it is found normally and there it is prized by the homeowners. No control is suggested.