Knockout Roses are being attacked - Ask Extension
My knockout roses are being attacked by something. The leaves are being chewed sometime just hole othertims down to the stem. The blooms are still com...
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Knockout Roses are being attacked #869508
Asked May 21, 2024, 5:40 PM EDT
My knockout roses are being attacked by something. The leaves are being chewed sometime just hole othertims down to the stem. The blooms are still comin in. I don't see an insect, a beetle or "rust" on the leaves. I've tried rose dust and even Sevin (ugh) Please help me get these plants well. Some ofthem have been here for several years and some are new this season. Tank you
Franklin County Ohio
Expert Response
From your picture it looks like your rose bush is a victim of Leaf-cutter Bees. Leaf-cutter bees are 1/2 inch long with gray to black stout bodies. They are very hairy and the abdomen has white stripes. They are not aggressive and will not sting unless handled.
Leaf-cutter bees make semi-circular or circular notches on leaves of many broadleaf plants, such as rose, ash, lilac, and Virginia creeper. They are active from May through August.
While damage to leaves may look bad, it is only cosmetic. The bees do not eat the leaf pieces. Instead they take them back to the nest to line cells where eggs are laid. The bees are beneficial pollinators and chemical treatment is not recommended. Placing physical barriers such as cheesecloth on the plants is a successful solution to preventing damage. These barriers should be used when leaf cutting is first observed.
Following are a few links to Univ Extension sites with more info about these bees:
https://yardandgarden.extension.iastate.edu/encyclopedia/leafcutter-bees
https://bygl.osu.edu/node/1705
Leaf-cutter bees make semi-circular or circular notches on leaves of many broadleaf plants, such as rose, ash, lilac, and Virginia creeper. They are active from May through August.
While damage to leaves may look bad, it is only cosmetic. The bees do not eat the leaf pieces. Instead they take them back to the nest to line cells where eggs are laid. The bees are beneficial pollinators and chemical treatment is not recommended. Placing physical barriers such as cheesecloth on the plants is a successful solution to preventing damage. These barriers should be used when leaf cutting is first observed.
Following are a few links to Univ Extension sites with more info about these bees:
https://yardandgarden.extension.iastate.edu/encyclopedia/leafcutter-bees
https://bygl.osu.edu/node/1705
