Early weed control is paramount for maintaining high-profile, quality lawns, as young weeds are more manageable and controllable. Having a plan to address the weeds before their growth will save time and money and improve the health of the lawn.
Stop Weeds Before They Start
The best way to control weed invasion is to prevent weeds from germinating and rooting. This is accomplished by performing a pre-emergent weed control application in the spring before soil temperatures reach 55 degrees consecutively. Pre-emergent herbicides offer different control lengths based on the type of active ingredient within the pre-emergent. Pre-emergent weed control can be applied via granular particles or liquid form each spring and summer to control the weed population.
5 Reasons You Might be Dealing with Weeds After Applying Pre-emergent
Regardless of any pre-emergent weed control applications made, there is always the possibility of weed growth due to many factors.
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Improper timing: Pre-emergent herbicides must be applied before weed seeds germinate. If used too late, weeds may have already sprouted.
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Incomplete or Uneven Application: If coverage is not uniform, there will be gaps where pre-emergent herbicides do not exist within the soil to stop the weed seed from germinating.
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Herbicide Breakdown (Short Residual or Heavy Rainfall): Weather conditions, such as heavy rainfall, may cause surface runoff and translocate or move pre-emergent herbicide from its intended target area, reducing its effectiveness.
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Herbicide Resistance: Some weeds develop resistance to herbicides and don’t respond as well as they once did in controlling them.
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Weeds Germinating from Deep in the Soil: Pre-emergent weed control occurs within the top ½” - 1”. However, certain weed seeds can germinate at greater depths below the protected area.
What are Post-Emergent Herbicides?
Post-emergent herbicides target weeds in the growing phase after germination. These herbicides are absorbed by the weed plant's leaf and root tissues and yield the best result when applied at an early growing stage.
The 4 Types of Post-Emergent Herbicides
1. Selective vs. Non-Selective
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Selective herbicides target weeds without harming turfgrass lawns.
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Non-selective herbicides kill all vegetation, including the lawn.
2. Contact vs. Systemic
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Contact Herbicides kill only the part of the plant they touch (fast-acting).
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Systemic Herbicides are absorbed into the plant and kill it from the inside out (slower but effective on deep-rooted weeds).
Post-emergent Herbicides for Lawn Weeds
Several post-emergent herbicides work on home lawns when used responsibly and according to the manufacturer's label. However, it should be predetermined whether weeds that have grown after pre-emergent applications need to be sprayed, as pulling weeds is always safer for the environment when the population is low. The following types will assist in early weed control if post-emergent herbicides are needed.
Applying post-emergent herbicides in the early stages of weed growth is best, as the weed will absorb the herbicides more effectively. Proper application standards should be practiced for environmental and personal safety when applying pre- and post-emergent herbicides.
Safety Guidelines For Herbicide Applications
Always wear Personal Protection Equipment (PPE) when applying chemical compounds to your lawn, and follow the label instructions. When mixing chemicals, measure accurately and use a calibrated sprayer. Mix in a dry area and always fill with water before adding herbicides or other chemicals. Never mix different chemicals before confirming that the mixture is compatible.
Avoid spraying herbicides when wind speeds exceed 10 mph, within 24 hours of rain to prevent runoff and environmental pollution, and when temperatures exceed 85 degrees Fahrenheit.
Protect water sources and the environment by keeping applications 10-20 feet away from water and not overwatering after application. Pre-emergent herbicides require watering to move consistently on the surface, creating a chemical barrier for weed control.
Storing herbicides is equally essential. When disposing of empty containers, follow the label. Triple rinse the container and create holes in the bottom so it is not reusable. Keep materials that aid in the absorption of herbicides close in the event an accidental spill occurs.
The Importance of Proper Use of Pre and Post-Emergent Herbicides
Pre-emergent herbicides should be applied before weed seed germination in the spring. Once weeds germinate and begin to grow, a post-emergent herbicide can be used if applied in the early stages of growth. Pre-emergent herbicides are not guaranteed to control every weed seed germination, so some select areas will require mechanical removal or post-emergent herbicides for total control. Caution should be used when working with pre and post-emergent herbicides and applied per the manufacturer’s label. Use personal protection equipment (PPE) and monitor the weather before making applications to protect yourself and the environment. When appropriately used, pre and post-emergent herbicides can be an integral part of your lawn maintenance program for seasonal success.
