Protecting Pollinators & Groundcovers

Field site in Ashe County

If you follow NCSU Christmas Trees on Facebook, you saw that Jeff Owen, Brad Edwards and I treated some groundcovers -- mainly purple deadnettle -- with either Roundup, Stinger or Goal last Friday.

Why is this important? After all, the groundcovers are just now starting to grow. Typically, growers wait until late April or into May before doing any type of herbicide application. These little purple deadnettles certainly aren't impacting tree growth. When the weather gets warm, they die back naturally.

The goal of these treatments is to burn back the flowers so that bees won't be in the trees.  On warm days, bees have been in this particular field  for the past month. If the grower needed to treat with an insecticide and had to spray during the day with a high pressure sprayer, bees in the area would be at risk.

Early spring is a tough time for bees. The population of a bee hive fluctuates through the year according to the season and resources. The number of worker bees declines at the first of the year, reaching the lowest number in February/March. This is the time of the year the queen is starting to lay eggs when there are fewest bees to feed and take care of the young. A queen may produce 1,500 bees daily. Honey and pollen resources have been depleted and there are few places for bees to forage. They work red maple when it's blooming which provide both pollen and nectar. In tree fields, purple deadnettle and wild mustard bloom early and bees will be foraging in the trees.

The hope is that by using a suppressive rate of a herbicide over the top of the trees the flowers will be burned back, but the good groundcovers -- especially the clover -- won't be killed out. We tried 3 commonly used herbicides at the typical suppressive rates to determine if they would knock back the purple deadnettle and how long flowering would be suppressed.

Of course it's too early to tell completely, but I went back today to see if any materials had made a difference. It's been five days after treatment.

The only treatment that worked so far was the Goal at 13 ounces per acre. The purple deadnettle had been burned back and there were few to no flowers. So this appears to be a quick way to clean up a field of flowers. Of course, Jeff reminded me that this would only work up until the time the trees break bud. After that the Goal will burn the new growth as well.

Purple deadnettle after treatment with Goal.

The Roundup was starting to have some effect, but there were still quite a few flowers. We'll check back next week to see if it's working any better.

Purple deadnettle after suppresive rates of Roundup.

The Stinger hadn't worked at all yet on the purple deadnettle. It looked like the check. It appeared that the deadnettle had grown since Friday in these rows.

Purple deadnettle after suppresive rates of Stinger.

We'll be trying these and other materials on other spring groundcovers and other weather conditions, as well as following how long it takes for the groundcovers at this site to green back up. But it looks like Goal at suppressive rates will burn back some flowers.