by Mary Salinas | Jun 21, 2013
We love our native magnolias in part because they are tough, easy to care for trees. The mainstay of southern gardens, they grace us with attractive thick, waxy leaves year round and sublimely fragrant and graceful blooms.
However, this past spring brought conditions that encouraged a fungal leaf disease known as anthracnose, most noticeably on the southern magnolia, Magnolia grandiflora. Affected leaves develop large irregular dead patches with a clearly defined border. The dead patches are a brownish gray and will flake and eventually deteriorate and fall away from the rest of the leaf. Fortunately it is rare for the disease to affect all branches of the tree and infection is somewhat spotty as you can in the photograph below.
Credit: Mary Derrick, UF/IFAS Extension
Conditions that favor the development of anthracnose in magnolia are the cooler, moister conditions that the panhandle experienced this early spring. Spores overwinter on affected branches and in leaf litter and travel to their new hosts through rain, wind and splashing water.
View this article to learn more about the Southern Magnolia
[important]The good news is that this disease is rarely a serious threat to the long term health of the magnolia. [/important]
Credit: Mary Derrick, UF/IFAS Extension
But in order to avoid another infection next spring, remove and dispose of as many affected leaves as possible from the tree and certainly those that have fallen. Avoid irrigation that wets the leaves because the consistent presence of moisture on the leaf is a perfect incubator for anthracnose. Ensure that there is sufficient air flow around the trees. Fungicidal treatment is generally not warranted.
by Matthew Orwat | Jun 17, 2013
Although black or white streaks are shocking when they appear on an otherwise healthy lawn, the incidence of slime mold is rarely harmful.
Closeup: Slime Mold in Centipedegrass. Image courtesy Matthew Orwat
Slime mold is actually caused by the reproductive structures of an array of different organisms, classified as plasmodia or Protista, which are regularly present in the soil. They are often mistaken for fungi. The different types are referred to as myxomycetes or dictyosteliomycetes. They usually appear on warm humid days in late spring or early summer after extended periods of rain. This extended period of heat and humidity, as is currently being experienced in the Florida Panhandle, initiates the perfect climate for slime mold development.
Slime Mold in Centipedegrass. Image Courtesy Matthew Orwat
As depicted in the picture above, slime mold makes the lawn look like it was just spray-painted with black or grey paint. The round fruiting bodies, called sporangia, carry the spores which will give rise to the next generation of the “mold”. After a few days the sporangia will shrivel up, release the spores and leave no noticeable trace on the lawn.
Slime Mold Sporangia. Image Courtesy Matthew Orwat
Currently, no fungicide exists to control slime mold because chemical control is not necessary. An excellent method to speed up the dissipation of slime mold is to mow or rake the lawn lightly. This will disturb the spores and hasten their departure. Another effective removal method is to spray the lawn with a forceful stream of water. This process washes off the slime mold sporangia and restores the lawn to its former dark green beauty.
Excessive thatch accumulation also increases the probability of slime mold occurrence.
For more information consult your local county extension agent or read the Alabama Cooperative Extension publication Slime Mold on Home Lawns.
