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Weather Conditions Perfect for Palmer Pigweed

More than 10 inches of rain inside of a month is beginning to create some weed problems according Dr. Wesley Everman, NC State Extension Weed Science Specialist:

“People that have pre-emergence herbicides down have had really good control. Some of our sandier soils the pre-emergence herbicides have been moved far enough down the soil that we are seeing some of the larger seeded broad leaves start to emerge and the folks that didn’t get a pre down are really behind because the weeds are really liking the hot temperatures and abundant rain.”

Once fields dry enough to actually get into, Everman has these recommendations:

“First we need to be scouting to see what is out there. If its soybeans or sorghum we will be looking at palmer amaranth or some grasses. I’ve seen some rag weed out there as well but for the most part we need to know what is out there so we can pick the herbicide for the appropriate weeds and for the right size of weed.”

Everman mentioned the 800 pound gorilla…Palmer Amaranth. Unfortunately, this is the weather that particular weed just loves:

“You couldn’t ask for a better situation, warm temperatures, a lot of humidity and the moisture.”

The Weed Free NC Campaign began at the first of the year, an effort to control weeds by reducing the seed bank, therefore the number of weeds. Everman says the program will really be put the test:

“This is the time for us to start implementing the program and getting people to scout more and make sure they are on top of the pigweed. This will really put it to the true test as this is the worst situation to try to get on top of the weeds with the wet weather. A lot of people are putting in crops as fast as they can and not getting back to spray it in a timely manner.”

So, what should be done now to get weeds under control? Everman explains:

“The most important thing is to get the right product at the right rate at the right time. For pigweed you want them when they are 4-6” tall and spray them with a product that will control them. In soybeans, that product is most likely going to be a PPO inhibitor and there are several varieties to choose from. They will do about the same job post emergence and a few have residual activity. Then make sure you are getting out there quickly enough so we are not getting behind. If the pigweed get to big we are not going to get that good control and we will have to come back with a clean up program or a hand crew.”

We’re at that time of year when it could rain on any given day, especially after 4:00 pm. Everman explains that dry time after application of herbicides depends on the product:

"In general you want an hour to two hours minimum. Some of the products have a surfactant that makes them safe in 30 minutes but others may need longer.”

NC State Extension Weed Specialist Dr. Wes Everman. is dedicated to serving the agricultural industry in the Carolinas and Virginia with the latest ag news, exclusive regional weather station readings, and key crop market information. The website is a companion of the Southern Farm Network, provider of daily agricultural radio programming to the Carolinas since 1974. presents radio programs, interviews and news relevant to crop and livestock production and research throughout the mid-Atlantic agricultural community.