Go Early with Pre-emergents in 2020!


2019 was another year of record-making weather in the United States. The country experienced the second wettest year on record since statistics began to be logged over 125 years ago, eclipsed only by the year 1973. To make matters even worse, 2019 ranked as the 34th warmest year in the same period. Over the past ten years, we’ve experienced the hottest and wettest decade than any other 10 year period. And there’s no sign of this startling trend changing anytime soon.

So what impact does this alarming weather pattern have on our industry? Quite simply it means that you should be preparing to apply your pre-emergent herbicides earlier than what traditional thinking is telling you. Dr. Fred Yelverton at North Carolina State University has already issued a recommendation of applying pre-emergent herbicides two weeks earlier than previous recommendations, based on this emerging weather pattern.

We all know that crabgrass germinates when the 24-hour mean soil temperatures average about 53-55 degrees at a depth of 2 to 4 inches for several consecutive days. Clearly each of us has a slightly different micro-climate which will somewhat vary the timing of reaching this critical soil temperature. Each of us must decide our own comfort level when to comes to playing the annual game of “chicken” with Mother Nature as it relates to application timing of this very important weed management practice.

And let’s be very clear about one thing, there’s very little downside to applying pre-emergent herbicide earlier than normal. Pre-emergent herbicides are primarily degraded by soil microbes, which, during early spring when the temperatures are in the 40’s and 50’s, are not very active in the soil. So, at worst, there might be minimal degradation of the herbicide layer when pre-emergent herbicides are applied earlier in the year.

To me, the “risk vs. reward” equation when it comes to controlling crabgrass always favors less risk. Dealing with crabgrass post-emergently is never a fun job or a cheap one. Consider yourself duly warned as we begin to head into early spring.

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