303-378-8000‬ info@dlcarbor.com

Tree Insect Calendar

Check out what is bugging your trees!

Common Denver Tree Insects

This handy tree insect calendar helps homeowners identify what’s bugging their trees.  We continuously monitor for new or re-emerging insects or diseases and advise action when necessary.

Got a tree insect problem and need it treated? Click here to fill out a tree service request form, or give us a call at 303-378-8000.

Japanese Beetle

This insect radiated out of Cherry Hills Village several years ago and now found across the Denver Metro area. It overwinters as a grub in lawns. The beetle damages plants, trees, vines, and potted flowers. DLC Arbor Services basis its treatments on the type of plant infected.

Emerald Ash Borer

The time to treat for the Emerald Ash Borer is now. Ash trees have no natural defense against the EAB. Since it can take three to five years for an untrained eye to detect this jewel green insect, by the time the bug is noticed, it is too late to save the tree. DLC Arbor’s experts can provide you with treatment options.

Ash/Lilac Borer

This common parasitic wasp plagues young Ash trees with trunks less than 12 inches in diameter. Our arborist says it is difficult to find an Ash tree without it in Denver. Although fatal if left untreated, it is controlled with a combination of insecticide and fertilizer.

Ips Beetle

The Ips Beetle is killing Colorado Blue Spruce again. Prevention is the only treatment. Once Ips Beetles attack a tree, they are unstoppable. They will eventually kill the tree and requiring tree removal. Ips Beetles spread when the temperature rises above 50°. Treatment consists of two sprays per year.

Kermes Scale

Kermes Scale attacks the twigs of Oak trees. Symptoms include branch tips falling off in high numbers between May and September. Kermes Scale is often confused with squirrel damage. DLC Arbor treats this tenacious insect with a combination of systemic insecticides.

Oystershell Scale

Oystershell Scale infests aspen trees. Their shell (scale) protects them from insecticide sprays, so the best control method is systemic insecticide injections or difficult-to-time trunk sprays during their “crawler stage” from May to June. If left untreated, Oystershell Scale eventually kills the trees and require removal.

Elm Leaf Beetle

The Elm Leaf Beetle plagues most Elm trees found in Denver. Both the beetle and its larvae eat leaves. Contact DLC Arbor for available treatment options.

European Elm Scale

The European Elm Scale attacks American Elms and secretes honeydew that blackens a tree’s bark with sooty mold. Branch dieback is typical. Contact DLC Arbor because new treatment options are available.

Pine Borers

Pine Borers include Mountain Pine Beetle, Zimmerman Pine Moth, Piñon Pitch Mass Borer, and Turpentine Beetle. They all dig tunnels into the tree and causing limb breakage and sometimes tree death. Pine Borers are treatable if detected early.

Peach (Fruit) Tree Borer

The Peach Tree Borer damages or kills Peach, Cherry, Plum, and other Stone fruit trees. Symptoms include jelly-like ooze at the bottom of the trunk. Spring is the best time to start treatment.

Boxelder Bugs

Boxelder Bugs sometimes appear in large numbers. The adults try to over-wintering in homes and become a pest. Systemic insecticide application in the spring controls this insect.


These soft-bodied tree insects suck on sap and live on almost any type of plant. They cause the curling of leaves and branch dieback. Also, the insects produce honeydew, which is a nuisance. DLC Arbor bases its control methods on the plant species affected. So, call to understand all treatment options.

Fire Blight

Fire Blight is a bacteria that infects pome fruit trees such as Apple and Pear trees. Stone fruit trees, such as Peaches and Plums, are immune. Fire Blight is challenging to treat. But, DLC Arbor is successful in treating fire blight with a combination of treatments.

Mountain Pine Beetle

The Mountain Pine Beetle (MPB) has returned to pre-outbreak levels and is no longer warrants treatment. Treating for MPB now is a waste of money.

Ladybugs - The More the Merrier

The Ladybug is the only nice bug on this list! We love them so much; the Ladybug is our mascot! Look for the giant Ladybug logos on DLC Arbor trucks. In the spring, buy several packages of live Ladybugs and let them loose in your yard. Your plants will love it because they eat soft body insects like Aphids, Tree Mites, White Flies, and Scale Insects. 

logos and ladybug


DLC Arbor Services

123 Vallejo St.

Denver, CO 80223