SERVICES | TREES & LANDSCAPING - TREE MAINTENANCE - TREE DISEASES AND INSECT PROBLEMS

The City has a very limited pest control budget and can only respond to mass pest infestations throughout entire neighborhoods, as budget permits. However, you may call an independent pest control company or use various other methods to control infestations in individual trees.

Suggestions for treatments:

Elm Leaf Skeletonizing Beetle on American Elms (May to October)
The ideal treatment time is late May to early June. A professional pest control company should be contracted for proper control.

Anthracnose and Scale on Sycamores and Ashes (early Spring)
These pests attack sycamore and Modesto ash trees in the early spring with a resulting early leaf loss. Have your pest control company treat the trees prior to bud-break and after bud-break in early spring. Also, keep the dead wood removed from your tree.

Fall Webworm on Liquidambar, Mulberry, Walnut and Elms (September to October)
These caterpillars occur on liquidambar, mulberry, walnut, and elm trees. They do not seriously harm the tree since the foliage they feed upon grows back in the following year. However, the webs they build may be regarded as unsightly or bothersome.
If so, the web can be cut out of the tree and destroyed by burning or shredding, or a long pole can be used to destroy the web while still in the tree. A substrance called Bacillus thurigiensis (B.t.; trade names: DipelR, ThurcideR, or BiotrolR), a naturally occurring bacterium, can be used to spray the web and kill the caterpillars.

Oak Moth and Tussock Moth (early spring and summer)
The caterpillar or larval stage of the oak moth feeds only on foliage of oak trees and does not harm other plants; whereas, tussock moths eat most vegetation. In the outbreak year, populations of oak moth and tussock moths may grow large enough to cause widespread defoliation; however, healthy oak trees will not be unduly stressed or killed by this leaf loss. The best way to suppress the oak moth and tussock moth is by spraying the tree with B.t., a non-environmentally polluting bacteria (Thurcide), when the caterpillars are actually feeding in March and April, or in July and August before they begin crawling down the tree trunks in search of pupation sites.

Aphis Insects on Maples, Tulip Trees, Elms, Ashes, Lindens (early spring and summer)
These insects cause trees to drip sticky honeydew. Aphis can be controlled by:

• Water washing the tree
• Introducing beneficial insects that feed on aphis
• Spraying with insecticidal soap
• Having your pest control company spray the tree canopy according to pest control recommendations.

If you have any questions or comments concerning the care and maintenance of your street tree, please feel free to call the City Arborist at 277-2762.