By David G. Hallauer

Jefferson County Extension Agent, Agriculture

Crabgrass preventers are another name for preemergence herbicides that prevent crabgrass seeds from developing into mature plants. Many people have a somewhat foggy idea of how they work. They don't actually keep the seed from germinating; rather, the germinating plant takes up some of the herbicide and is killed. Crabgrass preventers are just that--preventers. With few exceptions they will have no effect on existing crabgrass plants. Therefore, preventers have to be applied before crabgrass germinates. Additionally, they don't last forever once applied to the soil. Microorganisms and natural processes in the soil begin to gradually break them down soon after they are applied. Therefore, if some products are applied too early, they may have lost much of their strength by the time they are needed. Most crabgrass preventers are fairly ineffective after about 60 days, although there is considerable variation among products (products with the active ingredients of dithiopyr and prodiamine are longer lasting).

For most of Kansas, crabgrass typically begins to germinate around May 1, or a little later. Therefore, April 15 is a good target date for which to apply the preventer; this gives the active ingredients some time to evenly disperse in the soil before crabgrass germination starts. Additionally, weather varies from one spring to the next, and with it the timing of crabgrass germination. For this reason application timing of preventers is sometimes based on the bloom of ornamental plants. For example, when the Eastern redbud trees in your area are approaching full-bloom, apply your crabgrass preventer. A follow-up application will be needed about 8 weeks later, unless you are using one of the aforementioned longer lasting products.

Dithiopyr and prodiamine containing products are the only two that will give season long control of crabgrass from a single application. In fact, they can be applied much earlier than April 15 and still will have sufficient residual strength to last the season. Prodiamine can even be applied in the fall for crabgrass control the next season. Dithiopyr can be applied as early as March 1. Because of the added flexibility in timing, these products are favorites of lawn care companies that have many customers to service in the spring.

Though dithiopyr cannot be applied as early as prodiamine, it is the herbicide of choice if you must apply later than recommended.

Dithiopyr is the exception to the rule that preemergence herbicides do not kill existing weeds. Dithiopyr can kill crabgrass as long as it is young (2 to 3 leaf stage). Therefore, if you are late applying your crabgrass preventer, use products with the active ingredient dithiopyr. Remember, when using any pesticide, read the label and follow instructions carefully.

Ways to cut back on your energy bill

As the warmer weather approaches and gasoline prices skyrocket this summer, there is a way to fight back on the rising cost of living. With air conditioners humming, and fans spinning, cutting back your energy consumption benefits the environment as well as your bank account.

According to the Environmental Protection Agency (EPA), lighting accounts for up to 25 percent of all electricity sold in the United States. To cut down on your electric bill, it is recommended you apply a sensible approach to lighting both inside and outside your home. Even the simplest steps can have a dramatic impact on reducing your energy costs. Here are some ideas to get you started.

--Turn off lights when you leave a room or when they aren't needed.

--Keep bulbs and lighting fixtures clean for maximum lighting output.

--Install energy-efficient compact fluorescent lights. These give off less energy than regular bulbs.

--Pull the plug on instant-on appliances (such as television) when you don't plan to use them for a few days or more.

--They draw current even when they're switched off.

--Use task lighting directed at a specific area instead of overhead lighting.

--Turn off unnecessary light since much of the energy used is given off as heat. Your air-conditioner will have to work harder to compensate for it.

--Keep windows clean so daylight can come through better. You'll use fewer lights.

--Install outdoor motion detectors to light walkways and outdoor areas. This spares the expense of leaving floodlights on all the time.

--Install electronic timers to control fans, heat lamps and indoor and outdoor lights. You can program these to remain on for a specific interval and then shut off.

--Install occupancy sensors to automatically switch on lights when a person enters a room and off after the area is unoccupied. These are ideal for walk-in closets and hallways, laundry rooms, basements, work areas, tool sheds and garages--all the places where lights may be needlessly left on for hours or even days at a time.

--Install dimmer switches in place of light switches. Dimmers not only enhance the atmosphere of a room, but also use less electricity. For example, a light bulb at 50 percent brightness uses approximately 40 percent less electricity. A dimmer switch also extends the life of your bulbs. A bulb at 50 percent brightness will last approximately 20 times longer.

Date: 4/21/05