Knockout roses pests - Ask Extension
These flying pests are all over the knockout roses. They like to gather 6 or 8 together in the blooms and also eat the leaves. They have shiny backs a...
Knowledgebase
Knockout roses pests #659423
Asked July 03, 2020, 2:26 PM EDT
These flying pests are all over the knockout roses. They like to gather 6 or 8 together in the blooms and also eat the leaves. They have shiny backs and fly when I touch them. Can you tell what they are and if I need to worry about them or not? If I need to treat, what are my options? The roses are still putting out new growth and buds but the plants are covered in these pests.
Anne Arundel County Maryland
Expert Response
These are Japanese beetles. They are active for about 6 weeks then the adults will disappear. This pest will not kill your rose but certainly can do a lot of cosmetic damage.
What typically happens with KnockOut roses is that this time of year they take a break from blooming. But then begin to grow again and bloom again into the fall. Once the beetles are gone, you may have to do some light pruning to remove the damaged canes.
Controlling adult Japanese beetles is difficult when populations are high. They feed on at least 275 different plant species and will fly in from neighboring areas. Especially if you have plants that really attracts them like roses.
The least toxic control is going out in the morning or early evening and knocking or sweeping the adults from plants into a bucket of soapy water.
There are no preventative sprays. Insecticides provide only temporary relief when populations are heavy. Some organic sprays contain the active ingredients neem, pyrethrins (harmful to bees), or spinosad (harmful to bees when wet but has little effect when sprays dry).
If you decide to spray, follow all label directions and avoid treating plants when pollinators are present. The following is information from our website, https://extension.umd.edu/hgic/topics/japanese-beetles
Deb
What typically happens with KnockOut roses is that this time of year they take a break from blooming. But then begin to grow again and bloom again into the fall. Once the beetles are gone, you may have to do some light pruning to remove the damaged canes.
Controlling adult Japanese beetles is difficult when populations are high. They feed on at least 275 different plant species and will fly in from neighboring areas. Especially if you have plants that really attracts them like roses.
The least toxic control is going out in the morning or early evening and knocking or sweeping the adults from plants into a bucket of soapy water.
There are no preventative sprays. Insecticides provide only temporary relief when populations are heavy. Some organic sprays contain the active ingredients neem, pyrethrins (harmful to bees), or spinosad (harmful to bees when wet but has little effect when sprays dry).
If you decide to spray, follow all label directions and avoid treating plants when pollinators are present. The following is information from our website, https://extension.umd.edu/hgic/topics/japanese-beetles
Deb
