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Publication #HS1305

Epiphytic Weeds of Citrus in Florida1

Ramdas Kanissery and Mongi Zekri2

Introduction

The thousands of acres of citrus groves in Florida provide an environment for many epiphytic weeds. “Epiphytic” is a Greek term meaning “on the plant,” and is most commonly used to describe plants growing on trees and shrubbery. Epiphytes growing on trees are also referred to as “air plants” because they have no physical contact with the land. Epiphytic plants are an important addition to biodiversity; however, they are considered weeds among agricultural tree crops (including citrus) in wet and humid areas. Even though these plants may not harm the citrus trees directly, severe infestations will shade parts of the tree and interfere with normal sunlight interception and air circulation. Additionally, their growth on the stem and branches of citrus trees may reduce the effectiveness and reach of pesticide and nutritional sprays. In some cases, the presence of these weeds makes fruit harvest difficult.

Epiphytic weeds affecting Florida citrus can be classified into three broad categories:

  1. Tillandsias (or bromeliads), members of the pineapple family

  2. Orchids

  3. Nonflowering plants (ferns, true mosses, and lichens)

Vine weeds are not listed among the epiphytes, as they are terrestrial (ground-growing) in origin.

Tillandsias

The five major species of Tillandsia are found in citrus groves. These flowering plants are commonly referred to as “bromeliads” and are all members of the pineapple family (Bromeliaceae). These plants use their hosts for anchorage and support and are not parasitic. In addition, there has been no evidence of these species acting as a host for citrus pests and pathogens. The major Tillandsia species found on citrus are as follows:

Spanish moss (Tillandsia usneoides) is a flowering plant, not a moss like its name suggests. The half-inch-length tubular flowers are purple in color, and the plant flowers throughout the year. Of all the epiphytic weeds, this species is the greatest nuisance. Colonies of this plant grow so prolifically on citrus trees that sunlight availability is reduced.

Figure 1. 

Spanish moss.


Credit:

Mongi Zekri, UF/IFAS


[Click thumbnail to enlarge.]

Ball moss (Tillandsia recurvata) is, again, not a moss. This close relative of Spanish moss is found growing in spherical balls on everything from host plants, like citrus trees, to electric utility wires. Although not as noxious as Spanish moss, severe infestations may occasionally be seen on citrus and other host species.

Figure 2. 

Ball moss.


Credit:

Mongi Zekri, UF/IFAS


[Click thumbnail to enlarge.]

Bartram’s airplant (Tillandsia bartramii) is also found extensively throughout Florida’s citrus-growing regions. This plant grows on a variety of hosts and has gained popularity among ornamental plant enthusiasts.

Figure 3. 

Bartram's airplant.


Credit:

Mongi Zekri, UF/IFAS


[Click thumbnail to enlarge.]

Wild pine (Tillandsia utriculata) is the largest of Florida’s native bromeliads, with the inflorescence growing up to six feet in height. The plant is also exceptionally long-lived on host trees.

Figure 4. 

Wild pine.


Credit:

Robert Riefer


[Click thumbnail to enlarge.]

Cardinal plant (Tillandsia fasciculata) has an inflorescence that produces an attractive red color in strong sunlight, hence its name. Large clumps may be observed in a wide variety of host trees, including citrus.

Figure 5. 

Cardinal plant.


Credit:

Robert Riefer


[Click thumbnail to enlarge.]

Orchids

Orchids are another category of common epiphytes on citrus trees. They are most prevalent in the citrus-growing regions that receive high rainfall. Although these orchids are not parasitic in nature, severe infestations will shade parts of the tree and interfere with normal limb development and air circulation. In many cases, these epiphytic orchids attract ants in such numbers that they may impede fruit harvesting. Two species of orchids (the butterfly orchid and the jingle bell orchid) have been found mostly in both abandoned and well-maintained groves in Florida.

Butterfly orchid (Encyclia tampensis) is named after the Tampa Bay area, where it was first discovered, and is ubiquitous in the state of Florida. This plant grows in an assortment of host trees and plants, as well as terrestrially in rock areas filled with leaf litter.

Figure 6. 

Butterfly orchid.


Credit:

Julie Carson, UF/IFAS


[Click thumbnail to enlarge.]

Jingle bell orchid (Harrisella porrecta) is named after the tiny seed pods this orchid produces, which turn orange-brown when mature. It is one of the species of “leafless” orchids. The seedlings produce only one to two leaves when germinated; these leaves are quickly shed as the plant matures.

Figure 7. 

Jingle bell orchid.


Credit:

Roger Hammer, UF/IFAS


[Click thumbnail to enlarge.]

Nonflowering Plants

Nonflowering plants are the third category of epiphytic weeds found on citrus trees. These plants include ferns, true mosses, and lichens. They may give an unappealing appearance to citrus trees, and their prolific infestation is destructive to the hosts.

Resurrection fern (Pleopeltis polypodioides) appears dead and dehydrated during periods of dry weather, but springs to life with even a brief rainfall. As with all of the aforementioned epiphytes, there is no evidence that this species harbors any deleterious pests or pathogens to citrus.

Figure 8. 

Resurrection fern—growth stage.


Credit:

Julie Carson, UF/IFAS


[Click thumbnail to enlarge.]

Figure 9. 

Resurrection fern—dry stage.


Credit:

Mongi Zekri, UF/IFAS


[Click thumbnail to enlarge.]

True mosses (several genera and species) are predominantly found growing on mature citrus groves where the tree canopy provides a lower light level environment. True mosses do not grow well in open, full light exposure.

Figure 10. 

True moss.


Credit:

Mongi Zekri, UF/IFAS


[Click thumbnail to enlarge.]

Lichens (several genera and species) appear as circular-to-oval patches on the trunk, branches, and twigs of the citrus trees. Lichens are not a single plant, but two organisms: a fungus and algae in a symbiotic relationship. The algae provide the fungus with food, and the fungus provides the attachment and anchorage, as well as absorption of water and nutrients from the surface layer of bark or leaves where the lichen grows. Old or diseased citrus trees appear to have more lichens than healthy ones, as the bark of weak trees is more conducive to fungal growth.

Figure 11. 

Lichens.


Credit:

Mongi Zekri, UF/IFAS


[Click thumbnail to enlarge.]

Control

Sprays containing copper compounds are an effective method for controlling most epiphytic weeds. Spanish mosses and other bromeliads are allergic to compounds that contain copper. Because many groves are routinely sprayed with copper to kill pathogens, such as citrus canker, these epiphytic weeds are unable to gain a foothold in well-maintained citrus groves. The best control measure for eradicating orchids is physical removal from the trees. Mosses, ferns, and lichen can be controlled by spraying the tree with copper-sulfate. Copper-sulfate sprayed on lichens on trees will kill the fungus side of the symbiotic association.

Conclusion

Although directly harmless to citrus trees, epiphytic weeds give an unsightly and unhealthy appearance to the trees and may interfere with the grove management practices and harvesting. When trees are severely infested, these weeds proliferate to the point of reducing sunlight interception by the tree. Physical removal and copper sprays are effective methods for controlling epiphytic weeds.

Footnotes

1.

This document is HS1305, one of a series of the Horticultural Sciences Department, UF/IFAS Extension. Reviewed September 2017. Visit the EDIS website at http://edis.ifas.ufl.edu.

2.

Ramdas Kanissery, assistant professor, UF/IFAS Southwest Florida Research and Education Center; and Mongi Zekri, multi-county Citrus agent IV, UF/IFAS Extension Hendry County; UF/IFAS Extension, Gainesville, FL 32611.


The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county's UF/IFAS Extension office.

U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.