Are your leaves turning brown?
Wet Spring weather provides the optimal conditions for many diseases to reproduce and spread rapidly. Some do not show symptoms until late summer or early fall. Below are disease we have been seeing a lot of…
Anthracnose is a group of diseases caused by several fungi. Spores spread the disease through wind, rain, or by mechanical means. Repeated defoliation reduces growth, weakens the tree, and increases its susceptibility to attack by other pests and to winter injury. Fungi reproduce rapidly during wet spring weather, and damage may appear later. Twig, bud, and shoot blight are more severe if the temperatures remain relatively cool during March and April (below 70°). Warm periods of 2 to 3 days (80°) will prevent the development of the fungus. It will most likely be necessary to treat this condition several times a year.
Hypoxylon Canker is a fatal fungal disease that causes cankers on oaks, elms, pecans, maples, and other hardwoods. It eventually invades the sapwood of the tree, causing premature death. The fungus only attacks trees that have become stressed by drought conditions, construction, root damage, nutrient deficiencies, and herbicide damage. Airborne spores then attack the tree, sometimes after living on the healthy tree for extended periods of time. There is not cure for hypoxylon canker – any treatment application will simply help to maintain the tree and extend its life for as long as possible. Ongoing care will be necessary for the life of the tree.
Fire Blight is a bacterial infection caused by a pathogen called Erwinia Amylovora. It thrives in warm, humid climates, and can double every 20 minutes at temperatures of 70-80°. Fire blight affects plants in the rose family, including Bradford pears, crabapples, Indian hawthorns, roses, and photinias. The disease commonly occurs in wounds and natural openings, spreads rapidly, and leads to decline and death. Treatment is only viable if less than 30% of the canopy is infected. It will be necessary to treat this condition several times within a year.
Iron Chlorosis is a condition caused by iron deficiency in the soil. Iron is involved in the synthesis of chloroplast proteins and chlorophyll in tree leaves. Iron deficiency leads to yellowing leaves (a condition called chlorosis) and a slow decline of the tree. Iron is available from soils at a pH of 6 or less, but is bound in insoluble forms in certain types of soils. Since iron chlorosis is a problem with soil, rather than with the tree itself, this condition generally requires ongoing treatment for the life of the tree.
Bacterial Leaf Scorch
This disease can present symptoms that initially look rather benign, but quickly spread and can fast become alarming in appearance. Bacterial Leaf Scorch is the spread of a bacteria known as Xylella fastidiosa, and many common local species are willing hosts, including: Oaks, Elms, Maples, Sweetgums, & Sycamores. It is spread by insects, primarily leaf hoppers & spittle bugs. These insects pierce the leaves and suck water and nutrients from your tree’s foliage. Any insect that comes in contact with an infected tree will quickly spread this disease to trees in the surrounding area.
Bacterial Leaf Scorch CAN be fatal. It attacks the xylem and as such, damages your tree’s ability to transport water. Infected trees begin to show signs of stress by initially browning around the outer edges while the center of the leaf is still green or has a yellowish border. The leaves quickly continue to discolor and frequently begin to shed. It is critical to identify the problem as early as possible in order to decrease the spread, and diminish the potential damage.
Texans love crape myrtles! And, why not? They have been reliable blooming ornamental trees that seem to love our hot summers and not so ideal soil. However, they now face an insect pest that blackens their lovely bark and reduces their beautiful blooms.
The new pest is crape myrtle bark scale, and its first noted appearance in the US was in 2004 at a commercial property in Richardson, TX. It hit McKinney, America’s crape myrtle city, in 2005. In 2014, entomologists identified the offending insect as Eriococcus lagerstoemiae, previously only found in China, Korea, and Japan. It is hypothesized that it was introduced to the US via an infected smuggled plant. As of early 2015, the pest has spread to at least seven additional states (Louisiana, Oklahoma, Arkansas, Alabama, Georgia, Tennessee, and New Mexico). There’s even a website dedicated to tracking its ugly march across the US, https://www.eddmaps.org/cmbs/distribution.cfm.
Sooty Mold and Scale
Scale insects are often overlooked because once mature they don’t move, look like plant parts, and are quite small. Try to find me now! These minute pests feed by sucking the sap out of plant tissues. Usually the first clue that crape myrtle bark scale is attacking is the presence of sooty mold. The sooty mold is attracted to the bugs’ sticky excretions. Sooty mold may also develop if the crape myrtle aphid is on your plant. However, if you also find white adult scales that ooze a pink blood when crushed, you’ve just encountered the crape myrtle bark scale, not aphids.
Scale Damage on Crepe Myrtles
So, how do these critters affect my crape myrtles? The good news is that even heavy infestations aren’t usually fatal. However, their constant sucking on the plant has significant aesthetic implications. A stressed tree won’t produce as many flower clusters and blooms. The scales’ sticky waste coats the bark and anything else under the tree. And, finally the sticky bark turns black with sooty mold.
How to Get Rid of Scale on Crepe Myrtle
Now that we’re aware of the invader, how do we control it? You can start by washing the trunk and any reachable branches with a soft brush and a solution of water and mild dishwashing soap. This will remove a good portion of the sooty mold, the female insects and their egg masses. Then, give Dallas Tree Surgeons a call and ask for our Crape Myrtle Care Plan. We know the best methods for controlling crape myrtle bark scale and will give your crape myrtle just what it needs to recover and get back to blooming beauty again.
In the last week the Arborist at Dallas Tree Surgeons are seeing Tent Caterpillars all over the DFW metroplex. Just this morning I had two friends call me and ask, “What are these worms on my tree?” We are expecting this to be common question this year.
Tent Caterpillars are social caterpillars that mass on trees after they hatch in the spring. They are known to live on and eat Oaks, Elm, and Cottonwoods. They are often confused with Web Worms, but unlike the Web Worm they make their webs on the trunks of the tree and not in the canopy. There are many species of Tent Caterpillars the four most common are Eastern, Forrest, Western, and Sonoran. The ones we are seeing all over East Dallas are Forrest species. They all are hairy and are colorful. They do not sting and are not harmful. They can be bothersome since they travel from the tree crawling on homes, outdoor furniture, and cars. When the caterpillars mature they permanently leave the tree and make their cocoons in dark places near by. They emerge as small brown moths. Click here for detailed information.
Tent Caterpillar Damage to Trees
Tent Caterpillars eat the leaves of the trees they infest. They do not usually cause lasting damage because they do not usually completely defoliate trees. Since they feed early in the spring the leaves often regrow.
However, if the tree has a very heavy infestation, more than 25% of the canopy has been defoliated, the tree is already stressed or the tree is very young it may be necessary to treat them.
Tent Caterpillar Treatment
If a tree is stressed by preexisting conditions or a large percent of the canopy has been eaten by caterpillars then our arborists recommend using high quality, biologically based soil-conditioners and natural, organic fertilizers that optimize the growth and health of your trees increase the overall health of the tree. If the caterpillars are still active they can be mechanically removed by spraying or scraping them away, the infested branch can be pruned, or they can be treated chemically.
Kretzschmaria Deusta, or That Black Rot at the bottom of Your Hackberry Tree
As an arborist working in and around Dallas, I see Hackberry trees on a daily basis. Lots of them. It’s actually a testament to their species that there are so many, since I’ve never heard of anyone intentionally planting one. But they’re everywhere, nonetheless, especially along fence lines in older neighborhoods. While they don’t last forever, and aren’t beloved by many people, they are fine trees, especially while they’re young.
Hackberries do encounter one serious problem, however: a rot called Kretzschmaria Deusta, formerly Ustulina Deusta. (I don’t count mistletoe because it’s easily controlled and not a health concern if removed at intervals.) Kretzchmaria is an untreatable rot that is common on hackberries in the south and frequently shows up on the base of the trunk, although it can form on openings higher on the trunk as well, such as low joints. The current fruiting bodies are white, and turn gray over time, sometimes oozing droplets of amber. The old fruiting bodies from seasons past are black and dried, and look almost as if someone charred a marshmallow and poured it on the base of the trunk.
Kretzschmaria is a serious rot, and cause for fairly immediate removal. It frequently causes basal failure, or in other words it’s the reason some Hackberries fall completely over. Sometimes you can actually see the progression of the rot through the root system by looking at the canopy, with some branches lush and others nearly defoliated. But Kretzschmaria can easily cause a tree to fall with no such warning, and there may be no signs of ill health at all besides this rot.
My experience is largely as a residential arborist, working in yards where trees rarely have enough space to fall without hitting something the trees’ owner cares about. As such, I always recommend removal when I see Kretzschmaria Deusta (and stump grinding afterward to remove all habitat for the rot to continue growing, especially if other hackberries are nearby). Better safe than sorry!
Fire Blight is a bacterial infection caused by Erwinia Amylovora, a pathogen that is rapidly spreading through the DFW area. The warm winter and humid spring has led to an increase of the bacteria in our area and is transferring itself through wind, water droplets (rain and irrigation), and insects. At temperatures of 70-80 degrees the bacteria doubles every twenty minutes and can cause destruction to a tree in a single season.
Fire Blight not only affects Bradford Pears but also destroys fruit trees, Crab Apples, Indian Hawthorns, Roses, and various types of Photinia.
How to identify Fire Blight
On Bradford Pears and other trees the stems and leaves turn black, die, and stay attached to the branches. It looks like a lot of dead black leaves starting on the ends of the branches and moving inward. The leaves and young twigs curl.
When a Red tipped Photinia has Fire Blight the leaves turn a black or brown, die, and stay on the plant. It usually starts in one area and moves outward.
Control for Fire Blight
For all plants mechanical removal is beneficial. Removing all dead leaves from the plant as well as any dead material that falls will reduce the spread of Fire Bight.
For trees with less than 30% of the canopy infected it is possible to chemically manage the bacteria. Our Certified Arborists use a foliar and root applied systemic fungicide to kill the bacteria. Our goal is to suppress the bacteria through the year until bud break next spring when the treatment can be curative. We expect to repeat treatment three times during the year: once during the spring, once during the fall, and again next spring. If trees are controlled chemically, pruning out the infected sections will not be required because the spores will have already been managed. Treatments may need to be repeated if the tree becomes reinfected.