Knockout Roses, aka Rosa Knockout, are characterized by their cluster of low-maintenance shrubs that contain single or double rose flowers that generally bloom into blush or vibrant red color with a few blooming yellows.
Though the plant is incredibly resistant to diseases like mildew and black spot, people have noted issues with finding holes in the leaves on their Knockout Roses.
The Knockout Rose is very good at fighting off common plant diseases; however, many insects and pests enjoy eating on these plants’ leaves. When insects and pests feast on the leaves of a Knockout Rose, the plant can end up with unsightly holes in the leaves that need to be dealt with.
Which Pests Commonly Feast On Knockout Rose Leaves?
There are quite a few pests and insects that chew holes in Knockout Roses’ leaves, but some are more common than others.
In the warmer months of May and June, a pest called a Rose Slug targets your plant. These pests are sawfly larva that enjoy feeding on roses’ foliage, leaving them transparent.
Over time, this transparent layer turns brown. As Rose Slugs develop, they may begin to chew large holes in the leaves, eating everything except the mid-rib.
To spot a Rose Slug, search on the underside of the foliage when scouting. They are smooth with heads that are a yellow-brown color and translucent greenish-yellow bodies. Typically, you can drown them in a bucket of soap and water, but you may need to consider a more potent insecticide if you have a heavy infestation.
If you do not notice foliage damage until June or July, you likely have adult Japanese beetles feasting on your Knockout Roses. These beetles will eat the flowers and foliage, leaving your plants with a lacy appearance.
Japanese Beetles are fairly pretty bugs. They have metallic green bodies and wing covers that are a shiny bronze color. The best way to get rid of these bugs is to handpick them in the mornings and evenings when they are less active.
It is not ideal to use insecticide spray on them as the strength required to kill them is toxic to bees.
If you notice that the holes in your Knockout Rose leaves are perfect ovals or circles, you probably have active Leafcutter Bees. Though the damage is relatively minor, the cuts in the leaves are unsightly and can be avoided.
These bees are solitary and do not live in colonies, so infestations are not likely. They are crucial to pollinating crops and native wildflowers, so you should avoid using chemical means of control. Since the damage is minor, consider leaving them alone and allow them to thrive.
Deer love roses. Generally, deer will chew on the leaves, flowers, and stems of your Knockout Rose plants, which can severely damage the bush.
If you have deer trouble, the best way to keep them away from your plants is to install a fence. You can also spray the area with deer repellent spray. Spraying the plants is a good option because it rarely causes harm to the rose bush and keeps deer away for quite a long time.
How Can I Prevent Pests From Eating My Knockout Roses?
Since these pests are very attracted to Knockout Roses, you need to prevent them from showing up.
The first thing you need to do is prune your Knockout Roses in the later spring or late winter months to remove all dead growth. Search for canes that tend to rub against each other because these areas attract pests.
Check on your rose bush once or twice a week to keep pests from getting comfortable. If you find any pests, fill a cup or jar with warm water halfway up and add a few drops of dish liquid. Handpick the pests and drop them into the pot. If you do this a few times a week, you can control the infestation.
Spraying water from the hose directly onto the areas where insects are heavy will help you manage your problem. Knockout roses are less susceptible to water spots than other roses, so you will not damage them.
Sprays of Neem oil or insecticidal soap offer some control. When spraying cover the underside of rose leaves for the best results.
Fertilize Your Knock Out Roses
Regularly fertilizing Knockout Rose is a fantastic way to ensure your plants stay healthy and strong. Apply the mixed fertilizer around the plant base monthly throughout the entire growing season to keep your plant pest-free and healthy.