Nutsedge in new lawn resisting control efforts

Dear Neil: I have a handsome oak growing in my yard. Every year about this time, its leaves develop tiny holes. Many of the leaves start to fall, although new leaves are also being produced. My tree is the only oak in the area that is doing this. What would cause it, and what can I do?

A. It may be a bacterial leaf spot. They result in what is called "shot-hole" effect on tree leaves, most notably on purple-leafed plums. You'll often see a newer brown spot that is hanging partially attached, as if cut by a dull paper punch. As to why your tree is affected and the others not, that could be something as simple as genetic variation between the trees. I would suggest that you send a sample to the Texas Plant Clinic at Texas A&M for analysis. You can find instructions at their website (http://plantclinic.tamu.edu) or by calling your local county Extension office. There will be a small fee for their services, but that way you would know for sure. I don't believe it is a serious threat. I see it on my own oaks (now that you mention it), and it hasn't been a problem in 37 years.

Dear Neil: I hired a lawn care company this year. The lawn is lush and green after all of their applications. However, it has developed nutsedge, and the control they applied doesn't show signs of doing much in the several weeks since it was put down. Did I make a mistake in hiring them?

A. If your lawn looks the way you want it to, and if you're satisfied with the price, no mistake made. These companies turn out lovely turfgrass. If you had done the same things yourself, you would have had the same (or nearly so) results, but you would have had the work to do yourself - also the timing to figure out. They also have a lot of experience, and they have access to products that we consumers do not. As for the nutsedge, the products that are legally labeled for use in nutsedge control are slow-acting by their nature. Unlike most herbicides that go in through leaves, the good nutsedge controls are taken in through the soil via the roots, then conducted up to the leaves. It's not unusual for it to take four or five weeks to make significant impact on the lawn. You may even need a second application one month after the first treatment. But they do work!

Dear Neil: I have a large avocado tree. It's in a patio pot, but the tree has gotten big enough that I won't have room for it indoors this winter. Can I plant it into the ground?

A. Avocados are extremely sensitive to freezing weather -- even to frost. The only place where they have even a fighting chance would be in the lower Rio Grande Valley near Brownsville. Certainly not here. You can try trimming it significantly to get it inside, but at some point you'll want to discard it and start a new one.

Dear Neil: You can see from the attached photos that my red oak tree is losing the end 12 or 18 inches of several of its branches. I take very good care of my trees, including regular watering. I cannot figure out what is happening to this healthy red oak. Another red oak on the other side of the yard looks just fine. What is going on?

A. I'm going to guess that it's one of two things. Clip down one of the browned twigs (using a pole pruner if you have to). Trim it several inches farther back than necessary, because I want you to look at the interface between the dead and healthy tissues. If you see a swollen area in the twig there, that's the work of a gall-forming insect. She stings a twig when it's smaller and lays her eggs in the young tissues. The plant creates a gall of its own tissue around the eggs. The damage eventually girdles and kills the twig. There is no major damage, and there is no way to prevent or control the dieback. And the second option would be, if the twigs appear to have been chewed, either squirrels or birds have been picking at the twigs. Squirrels are quite active in pecans, live oaks, and this year, in cedar elms. Again, no major harm and no call to action.

Dear Neil: I have a lawn that I would like to be totally St. Augustine, but bermuda keeps moving in. I do not have a sprinkler system, and I can't afford one right now. Could this be lack of nutrition? If so, what should I use and when?

A. Keep telling yourself that "St. Augustine trumps bermuda." Better yet, maybe you need to tell that to the St. Augustine. Given ample moisture and all-nitrogen fertilizer in early April, early June and early September, St. Augustine should be the dominant grass for you. That assumes that you'll protect the St. Augustine from Take All Root Rot in the spring (if it shows up), chinch bugs in the summer (they will show up - always in the hottest, sunniest part of the yard), and brown patch in the fall. It also assumes that you'll never let the St. Augustine get really dry, to the point of its turning tan and crisp. Ramp up the care you give it next year and see if that doesn't help it crowd out the bermuda.

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Nutsedge in new lawn resisting control efforts