Keith Hawkins, LSU AgCenter Area Horticulture Agent (AHA)
Figure 1. Crape myrtle leaves infect with cercospera fungus. Photo by LSU AgCenter.
Figure 2. Shumard oak, a native oak and attractive shade tree. Photo by LSU School of Renewable Natural Resources.
Figure 3. Louisiana Home Citrus Production is a handy, downloadable publication for homeowners and gardeners.
Jimmy of DeRidder came by the AgCenter office to discuss his concern about his crape myrtles and leaf spots. Jimmy had attended Master Gardener classes and was able to identify his problem as a fungal disease caused by the cercospera fungus.
This condition is generally a cosmetic nuisance and unlikely to cause death to a tree. Leaf spots on any plant happen because of prolonged wet weather. Jimmy wanted to prevent future infections, but also wanted to avoid spray drift because his trees are near water. We discussed using soil drenches under the tree for a systemic treatment to be in the tree’s leaves. We also discussed removing leaves to remove any the risk of spores causing more infection. However, some leaves fall under the canopy of azaleas so using a spray wand to treat under the azaleas seemed to be a tactic to minimize these infections.
Mara sent a question about an attractive landscape tree, “Tell me please, if you know---do Shumard oaks drop leaves first, then acorns later? I think so but can't remember. There's a Shumard a few blocks from here. They produce giant acorns that my squirrels love. “AHA researched this question on the website of the US Forest Service and a couple of reliable online site and was unable to find an answer regarding when leaves and acorns drop.
Dan Gill, retired AgCenter horticulture agent, likes the Shumard oak and another related tree in one of his articles, “Two native oak species I’m recommending a lot these days are the Nuttall oak and Shumard oak. These oaks have moderate growth rates, faster than live oak but not as fast as water oak. They live longer (over 100 years) and are not so prone to trunk rot as the water oaks. The Nuttall oak is particularly well suited to the lowland areas while the Shumard oak is native to more upland sites.
Both oaks have upright, oval growth habits, about 50 to 60 feet tall and 30 to 40 feet wide, which fit well in urban landscapes. They lose their large, deeply lobbed leaves from late November through early December. Both will achieve some fall color; the Nuttall oak turns a dull yellowish-orange while the Shumard oak turns a more attractive burgundy red.”
James in Vernon Parish asked, “What citrus plants trees can grow here?” AHA referred to an AgCenter publication shown below for information regarding home citrus production, and this document says, “Citrus in Zone III [including Vernon Parish] would freeze regularly. Home growers may risk planting satsumas and kumquats in Zone III. Citrus in Zone III should be grafted on a trifoliata rootstock and be protected in winter.”
One way to grow citrus in area prone to freezes is to plant on the south side of a building where the citrus tree has protection. Also, the building will absorb the sun’s heat and then radiate that energy at night to provide another layer of protection.
This publication is available online at no charge. Homeowners and gardeners may go to www.lsuagcenter.com and search for “Louisiana Home Citrus Production” to obtain this handy reference.
If you want to contact Roots, Shoots, Fruits and Flowers, please send your questions and pictures to Keith Hawkins, Area Horticulture Agent (AHA), 337-463-7006 or email@example.com. Also, you can be on the “green thumbs” email list by emailing your request to the address above.
“This work has been supported, in part, by the USDA National Institute of Food and Agriculture, Renewable Resources Extension Act Award, Accession Number 1011417.”