City Trees is a premier publication focused on urban + community forestry. In each issue, you’ll learn how to best manage the trees in your community and more!
Issue link: http://read.dmtmag.com/i/57838
A Cassytha species showing the initial green form and the final brown form severely infesting several live oaks in Miami. Photo by Jeff Shimonski and the occasional errant vehicle that finds a tree in its way. Mother Nature certainly does not help with all of the hurricanes that we have to endure here in Florida. With all of these challenges, it is tough for urban trees to survive more than a few years after being planted. T One more problem that trees in Florida face is the occasional plant parasite that somehow ends up in the tree's canopy and begins to bleed the life out of the tree. During the past few years a species of woe vine (Cassytha sp.) began showing up in tree canopies in the City of Miami. Cassytha and dodder (Cuscuta) are two genera in two different plant families that almost look identical and are difficult to tell apart without close examination of the minute flowers and fruit. They can also completely envelop a tree's canopy. These parasites attach to and penetrate foliage and branches via haustoria (root projections) and begin to withdraw fluids from the tree. Unfortunately, neither private nor municipal property owners recognize an early infesta- www.urban-forestry.com he urban forest is constantly under pres- sure from development and redevelopment, poorly conceived designs, brutal maintenance regimes, tion soon enough to control it without drastic action. I have seen mature live oaks literally topped and then the remaining dodder or woe vine infestation removed by hand. This kind of treatment will kill the patient. A group of plants not commonly thought of as parasites are some of the bromeliads. Bromeliads are typically acknowledged as epiphytes (when they grow in trees) and not as parasites; however, there is enough empirical evidence that several species of air plants (Tillandsia) cause decline in mature live oak (Quercus virginiana) along with other tree species. Throughout Florida, tree companies are hired to control infestations of Spanish moss (T. usneoides) and ball moss (T. recurvata). The decline in trees infested by various bromeliad species may be an indirect parasitism attributable to nutrient loss. Instead of invading the vascular system of the tree like dodder or woe vine does, the bromeli- ads might be intercepting nutrients in a liquid form as water precipitates from the foliage, branches, and trunk of the tree. Furthermore, it has been shown that when the lower green leaves of a palm are removed on a regular basis either for aesthetic reasons or "hurricane 21