White spots on magnolia leaves & sandspur control in lawn

Q. My magnolia tree leaves have small white spots on them. I can scrape them off with my fingernail. What is this and will it damage my tree?

A. More than likely this is a scale insect. It’s probably False Oleander Scale, which is common on magnolias. If the tree is otherwise healthy, the scale will not cause permanent harm. But if the tree has been weakened by other factors such as construction damage (adding or removing soil around the roots, paving over the roots, soil compaction, etc.), storm damage or if the tree has been damaged from weed and feed applications in nearby lawn areas, then the scale could be the “last straw” for this tree. You’ll find this scale on native magnolia trees out in the wild. You can spray the infested leaves with one of the horticultural oil sprays but good coverage of infested leaves is important. Make sure it is summer oil, not dormant oil. If the tree is too large to spray, you may get some control with a systemic insecticide containing imidacloprid. If the tree is otherwise healthy, the scale should not be a problem for the tree. For more information on this scale, visit http://edis.ifas.ufl.edu/in306.

Q. I have a large infestation of sandspurs. Is there anything that I can use in my lawn to get rid of this weed?

A. Sandspur or sandbur is a warm season annual grass. As such, it comes up from seed during spring. In the seedling stage it blends in with the lawn grass. Later in spring and summer, it produces the stickers (burs/spurs), which contain seed. The parent plants will die as a result of the first killing frost or freeze. The seed remain dormant throughout winter and germinate the following spring to start the cycle all over again. Because sandbur is a true grass, there are few to no effective and safe postemergence choices for controlling this weed in a lawn. So, the best option is to apply a preemergence herbicide for lawns during February to early March. This provides a very narrow window to achieve control. Timing is extremely important when using a preemergence herbicide. You may also need to apply a second application six to nine weeks after the initial application to achieve season-long control based on directions on the product’s label. Always follow the label directions and precautions when using any pesticide, including herbicides. For more information on growing a Florida lawn, including weed control, visit http://hort.ifas.ufl.edu/yourfloridalawn.

Larry Williams, UF/IFAS Extension Agent, Okaloosa County, July 19, 2017

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