Trees of Curtis Park: Fall is time to inspect elms, plan for treatment

Fall in Sacramento is my favorite season. No more scorching heat and the fall colors are spectacular. However, fall may have already arrived for some residents with English elms that are practically leafless while the leaves on the neighbor’s deciduous tree haven’t even changed color.

The culprit causing the English elms and also Siberian elms to defoliate is the elm leaf beetle. When beetle populations are allowed to build up, the larvae feeding on the leaves cause a skeletonized appearance. Extended elm leaf beetle damage can have serious consequences for long-term elm health.

Elm leaf beetle has been a persistent pest to Sacramento’s elms for decades but was brought under control by a management program developed by UC Berkeley’s Dr. Don Dahlsten and his graduate student Andrew Lawson. Begun in 1996, their three-year study of monitoring and treatment brought this pest problem under control. The English and Siberian elms were no longer losing their leaves during the summer.

However, this successful program, which reduced pesticide use by 60%, was discontinued. Currently, residents who experience an elm leaf beetle problem with the city elm trees on their block need to contact the 311 Call Center at 311@ to request treatment.

Now is the time to inspect elms and make the request because treatment needs to take place in January and February. A pesticide is applied to the soil, which is taken up by the tree to provide control throughout the summer. The city’s Urban Forestry section will treat elm trees on request.

If a city elm tree requires any pruning that cannot wait for the program pruning cycle – such as low limbs over street, sidewalk and roof or cracked/split limbs – now is the time to submit this request as well.

Best management practice is to prune elms from early November through the end of March because the elm bark beetle, which spreads Dutch elm disease through its feeding and breeding habits, is not active in winter. Pruning elms sometimes occurs during the summer due to the urgency of the request. However, it is better for all of the elms on the block to prune when the trees are dormant.

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