A crabapple stressed from too much watering.
Photo: Gyneth Simmons, LA Master Gardener.
Gyneth sent an image and an image, “A friend of mine has a crabapple tree, pictured, and is wondering what to do about the browning leaves. She planted it in March. She fertilized when they planted it and put Epson salt out a month or two ago. She is watering it 45 minutes a day. I told her I thought it was getting too much water. If that is the case, what can be done so she will not lose the tree?”
Based on the email, there are several items affecting the health of this newly planted tree:
The optimal rate of watering for vegetable, grass and trees would be one inch per week. This rate is equivalent to normal rainfall in Louisiana. If you water with a sprinkler, then place an old measuring cup to catch the water. When a gardener attains one inch of water then its time to stop for the week.
If a gardener uses a soaker hose, place a square pan under a place under the hose and then stop when the pan has an inch of water. The sides of cup and the pan would have slight angle so the actual measure would be slightly more than an inch, but that slight amount would be acceptable.
If the crabapple tree fails to survive, digging up the tree and examining the roots would be useful in diagnosing why the tree failed. Are the roots smelly and soft? If so, then root rot has set in.
Mimosa branches with and without leaves.
Photo: Keith Hawkins, LSU AgCenter.
DeWayne of New Llano called the AgCenter and described the symptoms affecting his mimosa tree. AHA visited the home to examine the tree and captured some pictures.
The symptoms, loss of leaves and a weeping crack, shown in the images are consistent with a fungal disease called “mimosa wilt”. The Florida Forest Service (FSS) reports, “Mimosa wilt infections arise because of direct penetration of roots by the fungus pathogen. Once inside the host root, the pathogen grows into roots of ever-increasing size, ultimately into the tap root, and from there into the stem and branches of the tree.” Furthermore, The FSS says, “No proven treatment for infected trees is known.” This mimosa will eventually succumb to this wilt disease. As of this writing, tissue samples will be collected and sent to the Plant Diagnostic Lab in Baton Rouge to confirm the presence of MW.
A foamy, seeping wound on a mimosa trunk.
Photo: Keith Hawkins, LSU AgCenter.
Final growth stage of the walnut caterpillar.
Photo: LSU AgCenter.
Frank sent this email about what is a regular July pest, “I have a friend who has very large pecan trees. Every year the trees have worms that strip a great deal of leaves from top to bottom.
They are black with white fuzzy tips. She calls them walnut worms. At this point she has tried all the Insecticides she knows of.
Would you know what the worms are and what is best the best option to stop the swarm? Thanks for your help.”
Based on Frank’s email, his friend has the walnut caterpillar (WC), and it is difficult to treat because most homeowners do not have the ability to project a spray application up into a mature tree.
Loretta, a homeowner, shared her success story in combatting WC in her landscape, “[I] just wanted to let you know that something worked, not sure what, [ but I] don’t really care.
We have … no worms to be seen. Webs continue to fall every day. We have never had this happen so early in the 25+ years we have been here! We used the [Tanglefoot™] sticky tape & used the [insecticidal soil] drench twice, about 1 week apart, & almost no [WC]! Please pass the information on to others. It works! Thanks again for the suggestions!”
Tanglefoot™ is an insect barrier that attaches to a tree, and the migrating caterpillars stick to the tape and prevent the caterpillars from going up to the canopy. A homeowner will have to replace the sticky tape once there are so many caterpillars that the other caterpillars crawl over the dead bodies.
AHA had suggested the use of Martin’s Dominion ™ Tree & Shrub insecticide as a soil drench. For his own trees, AHA had used this product by mixing it in a bucket of water and the pouring the mix around the base of the tree. The roots of the tree take up the insecticide, and the leaves would resist the attack by WC. AHA observed that the top leaves of the tree seem to have been more susceptible to WC than the lower leaves.
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 firstname.lastname@example.org. 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.”