Is it crabgrass season yet?

With the arrival of yet another spring season, many homeowners are beginning to think about those annual chores involved with getting that lawn in shape. Once again, the battle is on for the best lawn in the neighborhood, but where do you begin?

A trip to your local discount super-store will usually add to the frustrating process of what to use and when. There are a number of excellent products available, some on fertilizers, some on clay particles. Most are spreadable granules, some need to be sprayed. The following guidelines will hopefully clarify what you need to do and when to keep those summer annual weeds out of your own little piece of heaven.

Annual weeds, such as crabgrass, goosegrass, etc., are typically very easy to control. Along with preventative measures to keep these weeds out of your lawn, we also suggest a number of cultural practices first to maintain a healthy, fast growing turf plant to compete against weeds and help combat turf

Crabgrass with seedheads. Detailed color photos can be found at the Missouri Weeds website at http://www.psu.missouri.edu/fishel/, select Weeds of Ornamentals and Turfgrass.

diseases. Spring fertilizations of 1 pound of nitrogen per 1,000 square feet of a complete fertilizer (N, P & K) can be made as soon as the ground thaws, some time in March. We have found that fertilizer applications alone can give 50 to 60% control of crabgrass just due to healthy turfgrass competition. We always recommend a soil test to determine what your soil needs are and to determine if any lime is required to adjust pH (6.5 to 6.8 is optimum). Aerification and proper soil moisture will greatly benefit turfgrass roots and help maintain a healthy plant. Think about plant health care and what all can be done first in growing excellent turfgrass. It’s only after this has been done, that we can decide if a herbicide is still needed for annual weed control. Crabgrass is the primary annual grassy weed we have to deal with every spring. Therefore, crabgrass makes it very difficult to go without some type of preventative in early spring.

Crabgrass preventers on the market today will also give control of many other annual grasses and broadleaf weeds. Crabgrass, goosegrass, annual bluegrass, foxtails, barnyardgrass, and fall panicum are the annual grasses usually listed on many product labels. An additional bonus includes control of many annual broadleaves such as carpetweed, purslane, spurge, knotweed, pigweed, and lambsquarter. Crabgrass preventers are usually applied as a pre-emergence (before crabgrass and annual weed seed germinates) herbicide. Be sure to read the label of the product you select to determine the specific weeds controlled and the rate required to control those weeds.

Most people do not realize that the best time to overseed thinned out turfgrass areas is in the fall. So, many are faced with wanting to seed in the spring and control crabgrass. Most crabgrass preventers cannot be used at time of spring seeding; however, there is a solution.

The best success with spring seeding should include a product named Tupersan (common name - siduron). It is the only pre-emergence herbicide for annual grass control that can be used at time of seeding. Seed can be planted and then followed immediately with an application of Tupersan. It’s always best to plant grass seed as early as possible in the spring, so you may want to plant seed early (when ground thaws) and apply Tupersan by the 1st of April. Be sure to water in according to recommendations on the label. Tupersan can be purchased as a granular material for easy applications through a cyclone-type spreader.

Homeowners can make applications of other crabgrass preventers to lawns that do not require any spring seeding during the first 2 weeks of April for central Missouri. Applications can be made as early as the third week of March in southern Missouri to the third week of April in northern Missouri. A good rule of thumb, is to have crabgrass preventers applied by tax day, April 15th, for most of the state. Crabgrass preventers on fertilizer, clay granules, or as a sprayable material are all effective if applied in a timely manner and watered in correctly. Some products have better residuals than others and only require one application. Those include Ronstar (oxadiazon), Barricade (prodiamine), and Dimension (dithiopyr). Other products that contain Balan (benefin), Team (trifluralin + benefin), or any product that contains pendimethalin may require a split application 6 to 8 weeks apart for the best full-season control of annual grasses. Many of these products in a sprayable formulation should be applied by a professional lawn care operator to ensure proper sprayer calibration and application rates. Many homeowners may have had their crabgrass applications already made in March by their lawn care operator. This is not unusual due to the large customer base they have to deal with each spring. They typically make the split applications of crabgrass preventer and back their guarantees to maintain control.

You can make pre-emergence applications of crabgrass preventers at the most optimum time by watching soil temperatures. Make applications when soil temperatures (1 inch deep) reach 55 degrees F for 4 to 5 consecutive days. This will ensure the longest possible control of annual grasses for that season.

Several products can be used as a post-emergent (after crabgrass emerges) if you experience some weed escapes or problems in late spring. The best control is achieved when crabgrass is in the 1- to 3-leaf stage of growth. Dimension (dithiopyr), Acclaim Extra (fenoxaprop-ethyl), Drive (quinclorac), or MSMA will control annual grasses as a post-emergent. These applications should be made by a professional lawn care operator. Post-emergence applications for crabgrass control will usually be made in early June. Dimension and Drive show label recommendations for crabgrass control up to an early tiller stage of growth.

So, even though it’s crabgrass season there are still options for dealing with this and other weeds.

Brad Fresenburg, Turfgrass Research, UMC