By Cynthia White, UC Master Gardener
THE CULPRIT IS THE ELM LEAF BEETLE
In case you are wondering what is happening to the majestic elm trees in town – here is the answer. Elm Leaf Beetle! The pest isn’t normally a big problem in California but this year we have been struck when the leaves are usually providing the best canopy for our late summer heat. Some trees are nearly in a state of total defoliation! We do have help available. The UC Master Gardener Pest Notes has a clearly written set of instructions and information that will relieve a great deal of anxiety but also let us know we have to be proactive. Link to the article https://ipm.ucanr.edu/legacy_assets/PDF/PESTNOTES/pnelmleafbeetle.pdf.
The small but nasty beetle prefers the American elm over the other two varieties we have in Colusa but be warned that if it really likes our mild summer, it might just spread its wings and move on to the Siberian elm and the English elm, and if they are still at it before cooler weather it can move on to the zelkova or saw-tooth elm. The easiest way to tell what kind of elm you have is by examining the bark configuration. On the west side of 10th Street here in Colusa the largest and most damaged of the elms are primarily American elm. These trees are over 100 years old and are a valuable asset to our community.
If you are considering new trees in your landscape, be sure to read about the potential issues and search out one of the newer elm varieties that have been developed to avoid pests. If you need help with the process, contact the University Extension Office and we will walk you through the process of improving your landscape and reducing the heat of summer.