EDITOR'S NOTE: A University of Florida faculty member and Nassau County Extension Horticultural Agent, Rebecca Jordi addresses some of the questions she receives about landscaping and gardening in northeast Florida, in GARDEN TALK. The Extension also offers helpful clinics throughout the year, providing assistance to local gardeners on Amelia Island and in the surrounding areas of Nassau County, Florida. __________
QUESTION: What is wrong with my St. Augustine grass? It seems to be dying in large areas all around my yard. JS
JORDI: I have received dozens of phone calls and office visits regarding this very question within the last two weeks. Because of all the rain we have been receiving, it would be best if we all placed our irrigation systems on manual. I have not needed to run my irrigation system in almost two months. I realize we are allowed to run our irrigation twice a week according to St. Johns River Water Management, but it does not mean we must or should.
Please look at the blades of grass and if they are flat and dark green then it is not necessary to run your irrigation. When the blades begin to slightly fold onto themselves, then it is time to irrigate. Part of the diagnosis process is examining the lawn grass therefore it was essential for you to submit a sample to me (12 inch by 12 inch) which includes the roots, stolon, blades and soil.
After looking at your sample it was easy to determine one of the problems was grey leaf spot. If left untreated, it can destroy the lawn but your specimen also show root rot and decline. Once the roots of any plant are destroyed, it is nearly impossible for the plant to recover. In addition, we have no chemical able to correct this type of root damage to lawn grass. Our best method of control is prevention. How do we prevent this problem in the future? We must control the amount of water applied to the lawn. St. Augustine grass prefers to be watered deeply but less often than we would assume. The root rot caused the blades to wilt. This reaction often makes us assume the grass needs more water so we turn on the sprinklers only to be causing the disease to spread even farther.
What can you do now? Rake out any dead grass, reduce the amount of water used, do not apply high nitrogen in the summer and avoid using weed killers in the high temperatures. Plus, call me to set up a time to examine a specimen of your grass at the Yulee satellite office as soon as you notice any problem.
____________ Plant Clinics will be starting back and the next one will be September 14th. Bring in samples or clippings in plastic bags of your sickly, pitiful looking plants anytime between the hours of 10am and 2pm. The last dates for Plant Clinics will be on Mondays, September 14 and 28, 2009 and October 12 and 26, 2009. See you at the Plant Clinic! _____________________________
QUESTION: I was out of town for a few weeks and upon my return I notice my magnolia was totally dead. What happened? DH
JORDI: I am only able to speculate the cause of death since I am examining a small clipping from the tree. However, I noticed a large portion of the bark was missing from the limb you brought to the office. Although I did find scale insects they were not in numbers large enough to destroy the whole tree.
I suspect the tree either took direct hit from lightening or the strike was nearby. Nothing ends the life of a tree as quickly as the intense energy exerted upon it by lightening. A direct hit from lightening will often cause the bark to be blown off similar to what happened to your tree. The removal of this much bark would cause the demise of any tree. I do not believe the bark removal was from an animal or machinery as I see no teeth impressions or machine made marks.
There are ways to redirect lightening from important specimen trees but you will need to contract a tree company which employs certified arborists to help you correctly install proper lightening rods. There are lists of certified arborist for our area at the Florida Chapter of the International Society of Arboriculture at:http://www.isa-arbor.com/findArborist/verifyArbByLoc.aspx Type in the closest city which could be Fernandina Beach, Callahan or Jacksonville. Although I am listed as a certified arborist under the City of Callahan, I do not install lightening rods! Sadly, the tree ultimately will need to be removed.
QUESTON: I found this large butterfly or moth on my Chaste tree. Can you tell me what it is? Do I need to worry about it eating my tree?
JORDI: The large insect you found is actually a moth, which I believe to be the Imperial moth. As an adult, moths and butterflies are generally only seeking nectar from the flowers and they are not chewing on leaves. You do not need to worry about moths or butterflies eating the leaves of your tree.
The larvae or caterpillar of butterflies or moths are the ones eating the leaves of vegetable and ornamental plants. We often try to control the moth larvae because they have a tendency to feed on vegetables and lawn grass. At the same time, we turn a blind eye to the butterfly caterpillars as we know they are important pollinators. However, many of us do not know the difference between butterfly and moth larvae and may be killing the caterpillars we should be allowing to live. These larvae feed on oak, maple, pine, sycamore, sweet gum and sassafras along with many other plants.
The caterpillars of this size usually do little damage as they are seldom gregarious, which means they are not found in large groups. Large groups of larvae can defoliate a limb or tree quite readily. But these large, lumbering caterpillars eat slowly and are easy for prey to capture so many never reach the adult stage. The photo you see is one I found recently in the UF/IFAS Nassau County Extension Demonstration garden. (The larva picture is from the University of Kentucky). The adult moth photo is mine.
Rebecca L. Jordi
University of Florida/IFAS
Nassau County Extension
Environmental Horticulture Agent III
543350 U. S. Highway #1
Callahan, FL 32011
904 548-1116 or 904 879-1019
http://nassau.ifas.ufl.edu
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