Spraying for weeds before they sprout

Published 6:04 pm Saturday, September 8, 2018

By Terry



I’m a fan of made up words. Years ago a buddy came up with oversueded as a reason someone might do something he shouldn’t. I didn’t ask for examples.

It was also way back in my early working years that university agriculture folks morphed the hyphenated pre-emergent into simply premerge. This one refers to chemical herbicides that are applied before weeds sprout, i.e. emerge.

These products work underground to keep weed seeds from germinating and emerging from the soil. It used to be that every acre of the major agronomic crops like corn, soybeans and cotton were treated with premerge herbicides. But the amount of premerge herbicides used now is much less than 30 years ago.

That is in a big part due to genetic engineering technology that allows young crops to be sprayed after they are up and growing with products that don’t have the soil persistence of the premerges.  The total amount of herbicides used per acre has been significantly reduced by the gene technology.

It might seem odd to bring up premerge herbicides this time of year, especially when nearly all column readers don’t farm. I do so as a reminder for those who complain every spring about the weeds growing like crazy in their lawns.

Those big weeds in the spring are about to sprout soon. They won’t be very visible in the fall and early winter, but they are down there in the turf.

But I know few among us are going to do anything about it now, including me.  But lawn premerge herbicides, if used, need to be diluted in the soil when the weed seeds attempt to germinate here in a few weeks.

Applying a premerge just prior to the storm rain we had would have been ideal.  But right now is in time.

One thing that makes it difficult for homeowners to spray their own yards with premerge herbicides is the equipment needed.

These herbicides need to be applied fairly precisely. It’s not like spraying tomato plants with fungicides or the patio with an insecticide.

The common hand pump-up sprayer with the adjustable nozzle won’t work with premerges. The pressure with those is steadily dropping while spraying and then goes way up when re-pumped.

Plus the small circular spray pattern makes it impossible to get close to even coverage.

There are more and more people using battery-powered sprayers mounted on ATVs and those can do a decent job with practice to maintain the same speed.  But this is only an option for large turf areas where there is ample turning room and room to get back up to speed before activating the sprayer.

For us walkers, the backpack sprayer with the hand pump lever can maintain reasonable pressure and nozzle output.

As with the 4-wheeler sprayer, this one also takes practice. And do all the practice with just water. Don’t add in the herbicide until you’ve gotten good at it.

Still, the most reliable way to premerge a lawn is to hire a professional with the right equipment and state license.

Terry Rector is spokesman for the Warren County Soil and Water Conservation District.