This year perhaps more than almost any other year, the same questions have kept popping up on the air, on my Facebook page and pretty much everywhere that I’ve turned. I decided, glamorous and beautiful as they aren’t, perhaps we ought to address some of these issue here. I hope they answer some of your dilemmas.
“What has happened to our Italian cypress trees? Big areas look like they have died.”
That’s a disease called Seridium canker. It’s the same pathogen that has essentially ruined Leyland cypress trees across Texas. Large parts of the trees are killed, and by the time you prune to remove the dead, oozing wood, the growth form of the trees has been ruined. Unfortunately we have no chemical control or preventive for it. Some feel that improving drainage will help slow its spread, but it’s unwise to spend a great deal of money trying to correct it.
“Why is my St. Augustine yellow in big patches? What can I do to get it growing again?”
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That sounds like Take All Root Rot (TARR). It was a common problem in 2012, and it seems to be back again this year. The grass is yellow in broad sweeps, and fertilizer does nothing to help green it up. Severely impacted areas pull loose easily from the soil. Their roots will have rotted, and it will appear that grub worms might have devoured them. In reality, it’s more likely this year to have been caused by the TARR fungus. Dr. Phil Colbaugh, retired pathologist with the Texas Agricultural Experiment Station, recommends application of 1 inch of sphagnum peat moss to create an acidic layer across the top of the lawn. That seems to retard the development of the fungus much more effectively than fungicides.
“Why do my crape myrtles look so sparse? Most of the growth seems to be from new shoots coming up from the ground.”
Some of our crape myrtle varieties were hurt badly by that one really cold spell in early January. Their tops are either dead or they are dying, which accounts for the vigor of those basal sprouts. Trim out the dead wood and retrain the new growth. You’ll have really attractive trees very quickly. Varieties most impacted: Natchez, Muskogee and Tuscarora.
“My Indian hawthorns and redtip photinias look like they’re dying. What can I use to save them?
That is Entomosporium fungal leaf spot, and like a couple of the other issues here, there is no good control other than to replace the plants with another species. It starts out with maroon “freckles,” and it soon causes weakened, yellowing foliage. Within a couple of years the plants are sparse and starting to die.
“What are these growths on my trees’ leaves? What kind of damage do they do? What can I do to stop them?”
Those are insect galls. The adult insect stings the leaves or twigs and implants her eggs. The gall tissue forms around the eggs and then the larvae develop within the galls. The good news is that they don’t do much damage. They are almost entirely cosmetic. There is no effective prevention or control. They will soon be done for this year. There is no call to action.
“Why are leaves at the ends of the branches of my pear tree turning black?”
That’s the bacterial infection called fire blight. It attacks only members of the Rose family, including apples, pears, cotoneasters, loquats, photinias and pyracanthas, among others. You can usually see the point of infection a couple of inches back from the dead area. Prune to remove all the blackened section including that area of infection. Disinfect your pruning tools between each cut by dipping them down into a bucket filled with 10 percent chlorine bleach and 90 percent water. Rinse and oil them after you finish the trimming. And mark the calendar to spray the plants with agricultural streptomycin during peak bloom season next time around. That’s when bees carry the bacteria into the flowers as they are pollinating the blooms.
“What are the symptoms of the Rose Rosette Virus I hear about? What plants can I use to replace them if mine have it?”
Rose Rosette Virus (RRV) is one of those problems that becomes very identifiable once you have seen a confirmed case of it. You will typically see all or most of these symptoms: buds that fail to open properly, reducing the overall bloom greatly; extremely thorny canes on all or part of the plant; strong “bull” canes that are several times the normal stem diameter and that outgrow all the other stems; a deep reddish cast to the leaves and stems in the affected portions; an overall appearance that the plants have suffered drift of a weedkiller spray. Plants will grow weaker over the ensuing months and eventually will die within one to two years. Rosette is spread by a wind-borne microscopic mite, and there is no control for the mite or the disease. Affected plants should be removed immediately, roots and all, and sent to the landfill in black plastic trash bags (tied shut to keep the mites inside). No one is sure just yet how long the bed will need to be planted with other shrubs or flowers. Very detailed research is underway at Texas A&M and elsewhere.