Spring Pre-Emergent Application Timing and Benefits

February is here, and that means the weather is getting warmer. This is the perfect time to talk about one of the most predominant issues in golf course maintenance - weed control. Being the southernmost part of the U.S., South Florida starts to get warmer earlier than the rest of the country. This means that the growing season also begins earlier. 

The seeds of the weeds will start to germinate as early as mid-February in South Florida and the end of February in Central Florida. This means preventive methods of weed control need to begin before this. The most fundamental method for this is applying pre-emergent herbicides, which is the foundation of weed control and has been so for over 30 years.

What Are Pre-Emergents?

Pre-emergent herbicides are specially composed chemicals that target the growth of unwanted weeds and leave the other greens undisturbed. Since this is a preventive method, it is applied before the weeds sprout.

The herbicides mix with water and spread inside the soil layer. Then, they release an enzyme that inhibits the growth of the root cells in the weeds. Without any roots, the seedlings fail to feed and grow leading to their death. 

Timing Of Application

It is important to apply pre-emergent herbicides before germination starts. Typically, germination begins when the temperature is consistently in the 50-55 degrees Fahrenheit range.

For South Florida, this could mean that pre-emergent herbicides need to be applied by early February. For Central Florida regions, it should be applied by the middle of February at the latest. Temperatures start to get warmer in Ohio in March. So the time for pre-emergent application is March in South Ohio and April for North Ohio.

For South Carolina, the temperatures start reaching the desired range around the middle of February. So pre-emergent applications should be applied between mid-February and the end of February.

Early application gives the product enough time to seep into the soil and begin releasing the enzyme to inhibit the growth of roots as the weed seeds start to germinate. Applying the herbicide too late will be completely ineffective as the weeds would have already developed a strong root system. In such a situation, you will have to invest in post-emergent methods, which are far more expensive and time-consuming. It is important to note that applying the pre-emergent too early will allow it to seep too far down the topsoil for the tinier roots to reach it. So correctly timing the application is crucial.

Watering in the herbicide so that it reaches deep enough to create a protective barrier against germination is a good tip to keep in mind. 

Types Of Weeds 

Annual Weeds

Annual weeds are weeds that live during one growing cycle. There are two kinds of annual weeds. The summer annual weeds that sprout during spring or early summer, and the winter annual weeds that germinate in fall or early winter. 

Florida

Some examples of summer annual weeds are broadleafs such as knotweed, pigweed, prickly lettuce, garden spurge, Florida pusley etc.

Winter annual weeds include Virginia pepperweed, common chickweed, southern plantain, etc.

Weed grasses are bunching grasses that grow on the turfgrass in clusters. Annual weed grasses include goosegrass, witchgrass, crabgrass, annual bluegrass (poa annua), etc.

Ohio

Common annual weeds in Ohio are speedwell, black medic, knotweed, spurge, purslane, crabgrass, bittercress and chickweed. These include both summer and winter annual weeds.

South Carolina

Some common annual weeds in South Carolina are common lespedeza, common mallow, curly dock, black medic, chickweed, crabgrass, carpet weed, cheatgrass etc.

Perennial Weeds

Perennial weeds are hardy weeds that are very good at surviving year after year. They reproduce via vegetative means like rhizomes (a crawling stem that lies underneath the layer of soil), stolons (stems that grow at the soil's surface), and through seeds. They can be very difficult to kill.

Florida

Some examples of perennial weeds are dandelion, white clover, yellow woodsorrel, matchweed, etc.

Perennial weed grasses and sedges include yellow and purple nutsedge, dallisgrass, smut grass, hurricane grass etc. 

Ohio

Common perennial weeds in Ohio include wild violet weeds, thistle, dandelion, oxalis, white clover, nutsedge and ground ivy.

South Carolina

Some common examples of perennial weeds in South Carolina include broadleaf plantain, broadleaf dock or bitter dock, dandelion, dallisgrass, etc.

Biennial Weeds

Biennial weeds finish their cycle in two years. In the first year, they grow. During winter, they are dormant, and in the second year, they reproduce via seeds and spread. Their life-cycle is similar to annual weeds.

Florida

Some examples of biennial weeds in Florida are mallow, bull thistle or cotton thistle and wild carrot. 

Ohio

Common biennial weeds in Ohio are giant hogweed, musk thistle, poison hemlock, and wild carrot.

South Carolina

Some common examples of biennial weeds in the Carolina region are cudweed, cutleaf evening primrose, oldfield toadflax, prickly lettuce, etc.

How To Combat The Weeds?

Barricade brands of herbicides with an active ingredient of prodiamine are effective against annual weeds like crabgrass, chickweed, oxalis, annual bluegrass (poa annua) and garden spurge. They are efficient and offer proper weed control when applied at the right time, which is the beginning of February for most Florida.

Dimension, which includes dithiopyr in its composition, provides effective crabgrass control with flexibility in its application period as it can also be used as a post-emergent application.

Late germinating weeds like goosegrass cannot be controlled by early February pre-emergent applications. Ronstar, which has oxadiazon as the active ingredient, is the most effective for goosegrass and should be applied around March for adequate control.

Specticle herbicide also provides control over warm-season annuals, but this needs to be applied right before the weed seeds germinate for it to be effective. This will not provide control if applied after germination.

Sequential application of pre-emergent herbicides will provide the best results. If the first application is during early spring, the next one should be 4-6 weeks later. The same applies to winter annual weeds as well. If the first application is during early fall, then another application should definitely follow it after 4-6 weeks. This will make sure even late germinating weeds are killed.

Benefits Of Pre-Emergent Applications

There are various benefits of pre-emergent herbicide applications.

• Pre-emergent applications kill the weeds before they grow, thus eradicating the problem before it becomes one. 

• This kind of preventive technique saves a lot of time as pulling out weeds that have already developed a strong root system takes more effort.

• Pre-emergent applications also save money as you don't have to invest in post-emergent herbicides, which could be more expensive.

• It allows your grass to look healthy and green as no weeds are making your turfgrass turn brown.

• It also saves precious soil nutrition for the turfgrass as weeds are not using them all up.

If you are looking for golf maintenance services that will provide customized services to your greens after proper analysis of your soil profile and turfgrass, then DTE Golf® is here to help you. Contact us today for more information.