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Dallas Morning News - July 15, 2021

Leafcutting Bees


What's up with the leaves of Virginia creeper being spotted and shredded looking? It's a good vine and groundcover, even though becoming too aggressive and even invasive sometimes. I use it and have quite a bit of it in our residential and commercial gardens, but there is one little flaw.


Every year, mid to late summer its foliage develops small yellow spots and develops a shredded looking appearance. The spots are fungal but usually no more than a slight cosmetic problem. Garlic or garlic pepper tea sprays will limit them but it's probably not worth the trouble. The cut-up leaves are courtesy of leafcutter bees also known as the plug bugs.


Leafcutter damage on Virginia creeper



About the size of honeybees, adult leafcutters are dark brown to black, sometimes with yellow or beige markings. Wings are clear or smoky. They range in size from about as large as honeybees to about half as large.


These solitary insects use pieces of leaf tissue to line their nests in cavities in the ground, dead wood, hollow stems, snail shells, pipes and other openings. Leafcutters cut neat circles or partial circles out of the edges of leaves to get material for their nests. You've probably seen this damage on your roses, hollies and fruit tree foliage. For some reason they make messier cuts on Virginia creeper foliage.


Leafcutter damage on rose


Mason bees are close kin. They are metallic blue or green and also use cavities in wood, soil, masonry, pithy stems of plants, keyholes and snail shells. They line the holes with cement made of clay, sand and a sticky secretion from their mouths instead of using leaves, as the leafcutters do.


Leaf-cutting bees, mason bees and plug bugs are all helpful even though they do some cosmetic plant damage


Both are excellent pollinators for many flowers. Honeybees will collect pollen on their bodies, mix it with saliva creating a paste and push it into pollen baskets located on the legs. Mason bees and leafcutters are more messy pollen gatherers. They land less delicately on flowers, spreading pollen everywhere. Pollen sticks all over their bodies like velcro making it more likely to be redistributed to other flowers. Mason bees and leafcutters have about 95% pollination rate, where honeybees have more like a 5% pollination rate.


This helpful bee doesn't sting unless you try to grab one – so don't do that. Leafcutters can be troublesome around machine shops and homeowner equipment because they will plug up any exposed pipes or openings. Mechanics have learned to tape over the ends of pipes, fuel lines and other openings.


Leafcutter damage on holly leaves


Despite these bee's irritating little habits, you shouldn't attempt to control them. Spraying anything that would kill them would affect only a few and mostly hurt other beneficials. Good biodiversity in your organic garden will keep them from being too abundant. Use the soft-working natural products and techniques so birds, praying mantids, dragonflies, lizards and other wildlife will stay healthy and help maintain the balance of nature.





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