Warmer temperatures combined with plenty of precipitation may cause crabgrass to germinate a little early this year
Normally we don’t concern ourselves with applying crabgrass preventer in Fairfield County until early to mid-April. Considering that lawns are now beginning to grow, and tree buds are swelling, it’s apparent that slightly warmer than normal temperatures may cause us to consider moving crabgrass control measures up on this year’s calendar.
Crabgrass is a summer annual grass that will re-establish itself each year from seed that remains near the soil surface from last year’s crabgrass crop. The seed of crabgrass begins to germinate in areas of a lawn where light can penetrate to the soil surface and the soil temperatures warm to nighttime minimum temperatures of 52 – 54 F for at least 5 consecutive nights under conditions of moist soils. The OSU’s CFAES Weather System tells us that on March 20, the average 2 inch depth soil temperature in Columbus was 53.1 degrees. Since then, cooler temperatures caused the 2 inch soil temperature to decline to 45.6 degrees on March 25. Regardless, should air temperatures remain normal or above, we would expect soil temperatures to quickly warm back up also.
When applied in a timely fashion, preemergence herbicides can effectively control the germination of crabgrass. A “timely” application requires that the herbicide be applied and rained into the soil’s surface before soil temperatures are such that germination can occur.
Homeowners are able to purchase crabgrass preventers or crabgrass killers and apply them to their lawn if they wish. Common ingredient names of preemergence herbicides available for home lawns include benefin/trifluralin, pendimethalin, prodiamine and dithiopyr. Dithiopyr, commonly sold under the trade name Dimension, is the product of choice if crabgrass is already germinating at the time of application.
Corn gluten meal is a popular natural fertilizer that also has substances in it that are reported to inhibit crabgrass and other weed seed germination.
Once crabgrass germinates and emerges, although somewhat less effective than “preventers” there are a few postemergence products available to suppress or eliminate it from lawns. Common ingredient names of postemergence herbicides include MSMA (Monosodium methyl arsonate), DSMA (Disodium methyl arsonate), fenoxaprop, quinclora and dithiopyr (which is only effective on crabgrass seedlings).
When applying postemergence herbicides be sure to obtain thorough coverage and do not mow for two days before and after the herbicide application.