Selective Weed Killer Application

How to treat turf weeds with a selective herbicide

Turf weeds can suddenly appear at ant time, no matter how well we manage the turf or lawn. However it has to be said that well managed turf is less susceptible to weeds than neglected turf. However, correctly managed turf is still not imune to weeds.

When weeds start to appear there are two main types of control, hand removal or chemical control. Although hand removal is fine for a few weeds on a relatively small area, it is nigh impossible on larger areas such as large lawns and sports fields. This is where chemicals are used, as they save time and money.

When weeds are treated with chemicals in turf, a selective weed killer or selective herbicide should be used. Never use a total weed killer, such as round up, as this will not only kill the weeds, it will kill the grass too. So ensure that you are using the correct product for controlling weeds in turf. Although it may seem obvious, many people have used the incorrect product and killed both grass and weeds.

Timing of weed control using a selective herbicide

When using a selective weed killer the weeds need to be actively growing for the best results. In fact the stronger the growth, the quicker and better the kill will be. The ideal time for weed control is usually anywhere between April and September duing periods of strong growth. Avoid periods of weak growth and drought as it can lead to poor results and also damage to the lawn.

The months of May and June are typically ideal times of the year for controlling turf weeds as growth is usually very strong during this period. Many turf care professional apply a nitrogen based feed to the turf, about a week before spraying weeds, to encourage strong grass growth and encourage a good kill. However, any time of the year when the grass is growing strongly is perfect for controlling weeds.

Choosing the correct product

Practically all selective weed killers available contain 2 or more active ingredients, to cover a broader spectrum of control. However, different ingredients are more effective against different weeds. For instance Mecoprop-p is good for controlling clover, Fluroxpyr can be effective against speedwell. Therefore, once the weeds have been correctly identified, it is important to choose a product that will control the weeds causing you trouble.

How to treat weeds in turf

Although selective herbicides can be applied through both a sprayer or a watering can, you will achieve better results using a sprayer. This is because a sprayer produces finer droplets that will stick to the leaves of the weed. Although it is perfectly acceptable to use a watering can, much of the solution runs off the weed as the droplets (even with a fine rose or dribble bar) are quite coarse.

So the growth is strong and vigorous and it is ideal to treat the weed in the turf, we still need to consider a few more things before treating the weeds.

When spraying weeds we need to mow the turf of lawn, leave it for at least 3 days, spray the weed killer, then don’t mow the lawn again for at least another 3 days.

When we mow the lawn we often remove much of the weed leaves. Therefore by leaving the grass for 3 days after mowing we allow the leaf to grow back. This gives the weed killer a large target area in which to attach its self to the leaf, which ensures more chemical enters the weed.

Again, by leaving the grass another 3 days before we mow again, we allow the chemical to be absorbed right into the plant, ensuring a more effective kill. If we mowed right after we sprayed, we would again remove the leaves and the chemical that was attached to them.

Spray when the surface of the turf or lawn is dry. This ensures that the chemical will stick and not run off the leaves. If we spray during a heavy dew or following rainfall, then the leaves of the weeds will be damp and covered in water droplets. If we spray in these conditions, then much of the chemical is liable to run off the leaves and into the soil, thus reducing the effectiveness of the weed killer.

Spray when there is no rain forecast, as a shower of rain following weed control may wash the chemical off the weed leaves into the soil, again reducing the effectiveness.

Last but not least, follow the instructions on the label, including the health and safety precautions. Always wear the correct protective equipment and clean or dispose of any empty containers or contaminated clothing afterwards. Remember to store chemicals correctly, under lock and key.

When to avoid treating weeds

  • Don’t spray in frosty conditions.
  • Avoid treating weeds during drought conditions. The turf will already be stressed and an application of weed killer will only add more stress and possibly damage the lawn.
  • Avoid spraying during windy conditions, as the chemical may drift and contaminate fish ponds, flowers and other garden plants.
  • Avoid treating weeds during periods of extreme heat, as this may scorch the grass.