Safe Weed Control
The goal of chemical control materials is the elimination of the greatest number of weeds while using the least amount of chemical and the fewest repeat applications. This involves the use of the proper materials at the correct stage in the weeds growth cycle.
Weed identification is very important. Some weeds are easily controlled while others are more difficult to control. Spend some time getting to know your weeds. This will improve your ability to get adequate control of the weeds in your customers lawn and will help you to answer simple questions on weed control effectiveness.
Weed control materials work when the weed is young and actively growing. Weeds under stressful conditions such as drought are more likely to escape control since they are not actively absorbing and translocating the materials applied to them. In addition, the more competition from the desirable lawn grasses the more effective weed control materials will be in controlling the weeds. That makes a healthy vigorously growing lawn the first line of defense against a weed infestation.
SELECTIVITY OF WEED CONTROL MATERIALS
Weed control selectivity can be defined as the ability to use a chemical material to kill one or more plants in a mixed stand of plants without injuring the desirable plants. Selective weed control materials are formulated so when used according to label instructions they will not cause noticeable injury to turfgrasses. This means that they selectively kill the weed growing in the presence of the desirable grasses.
Non-selective weed control materials eliminate all existing vegetation, weeds and turfgrasses included. They are use primarily during lawn renovation projects, fence row spraying and controlling the growth of grasses and weeds in parking lots.
Weed control materials also can be classified as either contact or systemic by the nature in which they kill weeds. Contact weed materials break down plant cells on contact, moisture is lost and the plant dies through dehydration. Contact materials are not translocated through the weed, this leads to top kill leaving plant roots and rhizomes uneffected resulting in the regrowth of the target weed.
Systemic weed materials are absorbed and translocated throughout the plant. Absorption occurs through open stomates or through the leaf surface. After absorption the materials move through the plant to leaves, roots, and lateral stems disrupting the growth of the plant and causing it to die.
Weed control materials should never be applied at rates higher than those recommended. Not only does this increase the likelihood of damage to the desirable grasses, but could damage the vascular system of the weed. This then would not allow the complete movement of the materials through the weed allowing less efficient weed control and possible regrowth of the weed.
EFFECTIVENESS OF APPLIED WEED CONTROL MATERIALS
The effectiveness of weed control materials depends on the amount of the chemical that reaches the site of toxic reaction within the plant. There are many barriers that can prevent a herbicide from controlling undesirable plants in a home lawn.
The first and most important is poor contact between the leaf surface of the weed and the weed control material being applied. Taller vegetation surrounding the weed may intercept the spray before it reaches lower growing weeds. In addition, some plants have leaves that are positioned so they are difficult to spray or positioned so the materials will runoff the leaf before it's absorbed into the leaf.
Once enough material has reached the surface of the leaf, it must enter the plant to control it. So the second limiting factor to effective control is penetration into the plant through the leaf surface. Penetration occurs through leaves, stems, and roots however, penetration through the leaves is the most common way of entry. Penetration of the leaves and stems may occur either through the leaf surface or cuticle or through the stomates.
If the stomates are open, morning or cool moist days, enough weed control material will enter the plant within six hours to achieve the desired control. If the stomates are closed, hot, dry weather or when the plant is showing signs of wilt, entry time into the plant increases delaying effective control of the weed plant.
Penetration through the cuticle is a slow but continuous process, and some plants have cuticles that resist material penetration. Many weeds can absorb enough weed control materials through the cuticle to achieve the desired results unless the material is washed off by rainfall or irrigation.
Weed controls also may enter the plant through the roots. Absorption through the roots depends upon whether the weed control material is designed for root uptake or not.
After the weed control material has entered the plant it must move within the plant to the sight where it will disrupt some life function of the plant. Therefore, factors that limit the translocation of the weed control materials within the plant are the third barriers to effect weed control. Many plants can detoxify or break down with enzymes within the plant the weed control materials before they reach the site of activity.
After the weed control materials reach the site in the plant where it can disrupt some of the life processes, death occurs. The mode of action of herbicides is to disrupt respiration, block photosynthesis and limit nutrient uptake, causing twisting, curling and chlorosis of the leaves, leading to the death of the weed plant. Death also may result from anyone or a combination of these factors. Death may occur indirectly because of the weakened plant is susceptible to infection from disease organisms.
Weeds are our biggest reason for service calls back to a lawn. They also rank high on reasons customers cancel our lawn service. Understanding how they grow will help you get better results with the weed control materials you use.
WEED CONTROL MATERIALS USED:
We apply the following weed control materials as a normal part of our lawn care program:
A 3-Way Product containing: 2,4-D
This weed control product has synergistic action from the combinations of the 3 materials. Synergistic means the power of the whole combination is greater than any one of the parts.
In the past, we also “spiked” our mix of herbicides with Confront (triclopyr and clopyralid) to achieve even greater synergistic action on hard to kill weeds like clover, violets and ground ivy.