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The Grass is Greener
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Doing the right thing at the right time can save a lot of work later.

Pre-emerge herbicide applications can control 95 percent of weed problems with one application. If per-emerge treatments are not applied, one is left fighting weeds throughout the growing season with repeated post-emerge sprays.

Proper timing of one pesticide application supplants monthly post-emerge sprays. Less is more. The pre-emerge for winter weeds was applied back in October. Now the pre-emerge for summer weeds is due. Our warm-season lawn grasses started going dormant around Nov. 13 when soil temperatures at 4 inches dropped below 65 degrees.

Last Monday on Nov. 26 we had a brief excursion down to 50 degrees, which may have been enough to pull the trigger of summer weed seeds. Pre-emerge herbicides do not work unless they are applied before (pre-) the weeds break through the soil (emerge).

Some of our toughest insect pests to control during the growing season are vulnerable to dormant oil sprays. One or two properly timed and applied sprays now can knock out scale insects, which are very difficult to control during the balance of the year. This is especially true for fruit trees, for which systemic insecticides are largely unavailable and contact insecticides are largely ineffective.

In researching dormant oil use, I found the following column from Jeff Cook, extension agent in Taylor County, which is half way between Columbus and Macon, near Fort Valley. I cannot improve on it, so here is what Jeff has to say about dormant oil sprays:
“Oils are a good way to control a wide variety of insects. However, most of the year, it is too warm to apply them. Dormant oils should be applied while plants are dormant or have hardened off for the winter and prior to bud break in the spring. Applying these oils in high temperatures or before dormancy can cause unacceptable injury, and applying during wet or freezing weather can decrease control.

“Most of these oils are combinations of highly refined petroleum oils (or plant-derived oils) combined with an emulsifiying agent. They are safe and effective when used properly. Timing of applications and repeated applications are critical for success.

“Various oils have been used for centuries to control insect and mite pests. Oils remain an important tool to manage certain pest problems (e.g., scales, aphids, mites) on fruit trees, shade trees and woody ornamental plants. Several recently developed oils extend this usefulness to flowers, vegetables and other herbaceous plants.

“Oils have different effects on pest insects. The most important is that they block the air holes (spiracles) through which insects breathe, causing them to die from asphyxiation. In some cases, oils also may act as poisons, interacting with the fatty acids of the insect and interfering with normal metabolism. Oils also may disrupt how an insect feeds, a feature that is particularly important in the transmission of some plant viruses by aphids.

“Oils pose few risks to people or to most desirable species, including beneficial natural enemies of insect pests. This allows oils to integrate well with biological controls. Toxicity is minimal, at least compared to alternative pesticides, and oils quickly dissipate through evaporation, leaving little residue. Oils also are easy to apply with existing spray equipment and can be mixed with many other pesticides to extend their performance.

“The main limitation of spray oils is their small but real potential to cause plant injury (phytotoxicity) in some situations. Oils also can stain some surfaces, particularly dark-colored house paints. Some of the newer spray oils can largely eliminate these problems if they are properly applied.”

Some of the pests that we can control with dormant oil applications include: aphids, mites, scale and any overwintering eggs. In our area and on our woody ornamentals and fruit trees, scale insects would be the major pest that we need to focus on.

Now is the time to apply oils so that you can make a couple of sprays this winter and reduce pest populations for the following spring.

Don Gardner is the UGA extension agent in Glynn County, serving South Bryan.

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