Root weevil damage can be easily mixed up with leaf cutter bee damage. Leaf cutter bees are beneficial and use the material they cut out of the leaf to make nests.
“Something is eating the leaves on my lilacs,” cried the caller. She wondered why the leaves looked like someone had nipped the edges with pinking shears or craft scissors. I knew immediately when she described the angular cuts on the leaves that her plants were being eaten by root weevils.
These pesky bugs not only notch leaves, they occasionally come in the house. If you have seen a little black beetle with a long snout crawling around, you have seen a root weevil. Eggs are laid near the crown of plants throughout the summer. These hatch and the larvae develop in the soil. Adults emerge in June to start the process all over. They don’t fly, so they crawl up plants to get at the leaves.
Lilacs aren’t the only plants these pests eat. Euonymus, peonies, roses, sand cherries, rhododendrons and many others entice them. Fortunately, the damage is usually more an aesthetic problem than a threat to plant health. I simply tolerate the damage and tell people I have the lacy leaf variety of lilac.
It’s rare to see root weevils actually eating leaves because they come out at night. One management strategy is to go out in the evening and pick them off your plants by hand. Then drown them in soapy water or squish them. Another nighttime technique is to lay a white cloth under the plant, and gently beat the branches of the plant with a rolled up newspaper to shake the weevils off. They land on the tarp and you can dispose of them. Consider warning your neighbors if you choose this strategy. They might become alarmed if they see a flashlight in your yard at night and hear the sound of trunk beating. Or, they may know your gardening approach by now and just take it all in stride.
Some people suggest painting the trunk of the plant with a sticky substance to trap the weevils when they try to climb the bush. However, if you put the sticky goo directly on the trunk, after a while you will have a disgusting mass of dead weevils stuck to it. Try wrapping the trunk with cardboard or tree wrap first and put the sticky substance on it instead. Then, you can remove the cardboard when it is covered with dead critters. Nurseries sell sticky products for this purpose.
I don’t know about you, but I find my explanation of the lacy variety a much easier remedy.
JoAnne Skelly is Associate Professor & Extension Educator, Emerita at University of Nevada Cooperative Extension. She can be reached at skellyj@unce.unr.edu.
