Knockout Roses, Bugs, and Foxtail Q&A

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I want to share a few questions that were asked recently at the N.C. Cooperative Extension, Caldwell County Center. I hope you find these questions and answers helpful. If you have specific questions not answered here, please contact me and my team at the office. We look forward to hearing from you.

Question: Can I prune my knockout roses this weekend?

Answer: My advice is wait until we have had two good hard freezes. This will ensure the plants are dormant. Some sources suggest waiting until the spring to prune. However, if we have a big winter storm, the roses may not be able to support the weight of the ice or snow. Pruning in the fall keeps the roses from being damaged by winter storms.

Before the roses start growing again in the spring, check the canes. Prune back any canes that look damaged or dried out from the winter.

Proper pruning opens the plant up to light and air movement. This makes the roses more productive. Make pruning cuts at a 45-degree angle away from the bud. And to keep from spreading disease, dip the pruner blades into alcohol when switching between plants.

When I prune, I always start by removing all of the deadwood. Also, prune out sickly, dying, or diseased canes. Then select three to six strong basal shoots to keep. Remove all other growth canes. Then prune back the three to six selected canes to the desired height.

Question: When I was out in my yard today, I brushed up against a shrub, and I got some colorful bugs on me. I looked at the seed pods on the bush, and I saw a lot of the weird little multicolored bugs.

The scentless plant bug, rhopalid bug, is commonly found on hibiscus, but these bugs do not cause damage. (credit Eddie Pitts)

The scentless plant bug, rhopalid bug, is commonly found on hibiscus, but these bugs do not cause damage. (credit Eddie Pitts)

Answer: This insect is a scentless plant bug. The specific name of this insect is the rhopalid bug (Niesthrea louisianica). Our most common and most annoying scentless plant bug is the boxelder bug. However, rhopalid bug does not cause a problem like the boxelder bug. It is just something that exists and really does not cause a problem for plants or people.

These insects are common on hibiscus. They are more noticeable later in the season when overlapping generations feed on the fruit of the host. Since they do not cause damage to the plant, I don’t recommend any control.

Question: Do you know what kind of spider this is? It was found in our pantry and bit my wife.

Fishing spiders are large enough to bite. The experience is described as similar to a bee or wasp sting. (credit Jacob Vance, Emory University, Bugwood.org)

Fishing spiders are large enough to bite. The experience is described as similar to a bee or wasp sting. (credit Jacob Vance, Emory University, Bugwood.org)

Answer: This is a fishing spider (Dolomedes tenebrosus). Spiders bites are rare but occur when the spider is pinned down and feels its life is threatened. These spiders are large enough to give a painful bite. However, despite it being unpleasant, there is nothing about the venom that is dangerous to humans. If complications around the bite or allergic reactions occur, seek medical attention immediately.

Question: How do I control foxtail grass in my horse pasture?

Foxtail is a weedy annual grass. Foxtail can be controlled in the spring with Prowl H2O, a preemergent herbicide. The brown bottle brush seedheads in the foreground are foxtail.

Foxtail is a weedy annual grass. Foxtail can be controlled in the spring with Prowl H2O, a preemergent herbicide. The brown bottle brush seedheads in the foreground are foxtail.

Answer: Foxtail is an annual grass that germinates in the spring. Annuals come back from seed each spring. Foxtail can be controlled in the spring before it germinates. Very soon, the foxtail will be killed by freezing temperatures.

The way to control foxtail is with a preemergent herbicide. A preemergent herbicide stops seed from germinating. Applying a preemergent herbicide in the spring before the foxtail seed germinates will control it.

Foxtail germinates when the soil temperature is warm enough in the spring (65 degrees for three days). This is typically mid to late April. Applying a preemergent herbicide before April 15th (or earlier) will control foxtail.

There is only one preemergent herbicide labeled for use in pastures and hayfields in North Carolina. This product is Prowl H2O. (It was approved for use in 2017). This product is degraded by soil microorganisms, so when soils are below 65 degrees, there is very little biological activity and the preemergent does not degrade. So making an application early does not reduce the efficacy of the herbicide. Be sure to always read and follow the labeled directions for pesticides.

For answers to your agriculture questions, call the N.C. Cooperative Extension, Caldwell County Center at 828-757-1290 or visit us online.