Crop damage from pre-emergent herbicides has become a bigger issue across North Carolina with farmers seeing stunted plants, deformed leaves and even stand loss with worries the injury will lead to yield loss.
For the most part the injuries are primarily cosmetic and don’t harm yields, but Wes Everman, North Carolina State University Extension weed specialist, says farmers still need to take steps to avoid pre-emergent herbicide damage.
“We can see injury from our PRE herbicides for a number of different reasons. Our rate can be high. We could have sprayer overlaps. Maybe more commonly, especially with the heavy rains we’ve seen in the spring, we can have soil movement. Some herbicides stick to that soil a little more tightly than others, and they can move with that soil,” Everman said during an Extension weed management webinar.
Cool weather and moisture exasperates injury because plants aren’t able to grow as well and break down the herbicides. “When it’s cool, everything slows down. Even we slow down. On cool mornings, we’re not moving as fast as we are in regular mornings,” Everman said.
“Generally speaking, most of the time, we’re going to see a plant outgrow that injury as the growing conditions improve. If it’s a temporary cool spell or a wet spell, once that water dries off, the temperature comes up, that plant will start growing again. Metabolism will kick in and it will come out of it, and oftentimes we don’t’ see any effect from that injury in terms of growth and yield later on,” Everman said.
Everman said all PRE herbicides have the potential to cause crop injury to crops. Generally, injury is not a problem under ideal conditions and is more of an issue under adverse environmental conditions such as cool, wet weather.
Everman urges farmers not to cut rates to avoid herbicide injury. Reduced rate does reduce injury, but reduced rates also give weeds a better chance to survive as well.