Tree Insect Calendar

Please review the tree insect calendar below to identify the bugs that might be affecting your trees. If one of these tree pests look familiar, contract Ross Tree Company for professional and environmentally sound tree insect control. Click here to fill out a request service form or call 303-871-9121 to discuss Fire Blight treatment options with Ross Tree.

At Ross Tree Company, keeping trees healthy is our passion. When insects invade your trees and professional help is needed, we’re here. And, we abide by our motto – Integrity in Action, so property owners can expect that Ross Tree will use only the tree insect control products needed for the job and nothing more. We have three Qualified Supervisors (QS) licensed by the Colorado Department of Agriculture to handle pesticide products.


Emerald Ash Borer

The Emerald Ash Borer (EAB) came to Boulder in September 2013. As a non-native insect, EAB lacks predators to keep it in check and has killed tens of millions of Ash trees east of the Mississippi. Metro-Denver’s Ash Trees are at risk. Homeowners with high-value mature Ash trees in their yards should consider treatment now. EAB treatment is less expensive than removing a large tree.

Lilac Ash Borer

The Lilac Ash Borer is native to Colorado and attacks White and Green Ash trees. Stressed and recently transplanted Ash trees are susceptible to these borers. Larvae damage the trees by tunneling into the trunk and lower branches, leaving ¼-inch holes in the trunk or lower branches of an infected Ash tree.

Ips Beetle

Ips Beetles are common to Colorado and are also known as Engraver Beetles. They damage Pine and Spruce trees. Ips Beetles grow under bark and eat girdling tunnels that cause dieback and kill trees. Trees at risk are newly transplanted trees and trees suffering from root injuries. The Beetles are small and have reddish-brown bodies. Under the right breeding conditions, they can attack surrounding trees.

Kermes Scale

Kermes scale is a Pin and Red Oak pest. They grow over winter as nymphs and, in the spring, molt and become immobile scales. During spring and summer, the scales suck on the sap of the trees. We use oil sprays in early spring when Oak trees are dormant and before they leaf out to treat Kermes Scale. Other options include spraying in the fall or soil applications.

Tree Aphids

It is normal to find Aphids on yard trees since the insect is the most common insects found on trees in Colorado. Most Aphids feed on specific trees, which makes them easy to identify and treat. Aphids produce honeydew when feeding on trees. This sticky substance can be a nuisance. Call Ross Tree to find out the best way to control these pests.


Japanese Beetle

Adult Japanese Beetles attack Linden, Horsechestnut, apple, American Elm and Norway Maples. Japanese Beetle leave a characteristic skeletonizing pattern on leaves when feeding. They lay their eggs in turfgrass and their grubs damage lawns. Mid-summer is the best time to treat for Japanese Beetles. Homeowners should use a treatment method that lowers the risks to bees. Call Ross Tree to find out the best way to control these pests.

Mountain Pine Beetle

The Mountain Pine Beetle is ubiquitous to the Colorado mountains. This beetle has killed millions of pine trees in the mountains. They can also attack trees in mountain yards of urban areas. The Mountain Pine Beetle develops in Ponderosa, Lodgepole, Scotch, and Limber Pine Trees. Homeowners who see popcorn shaped masses of resin on their trees should give us a call.

European Elm Scale

European Elm Scale is a soft scale insect that attacks Elm and Hackberry trees. Heavy infestations produce large amounts of honeydew which turns into a grayish/black-colored sooty mold. Homeowners should call us when honeydew falls from affected trees onto patios, decks, and vehicles. We’ll apply soil products to treat European Elm Scale in early summer.

Tree Mites

Mites affect shade trees such as Honey Locust, Elm, Mountain Ash, and Oak. There are also Mites that infest Pine and Spruce trees. Signs of Mites include discoloration of leaves, leaf curling, and premature dropping of leaves or needles. Ross Tree uses insecticide soaps and horticultural oils to control Mites.


Walnut Twig Beetle

The Walnut Twig Beetle is a carrier of a fungus that causes Thousand Cankers Disease (TCD) in Walnut Trees. TCD is lethal. The very small Walnut Twig Beetle carries the fungus from tree to tree. The fungus causes small, dead areas in the bark called cankers that girdles the branches until the tree dies. There are no effective treatments to save Walnut trees once infected. The best course is tree removal and it is important that the tree debris be processed professionally to avoid the spread of TCD.


Oystershell Scale

Adult Oystershell Scales are 1/8 inch long, grey or brown in color, and shaped like an oyster shell. When the eggs hatch in early spring, the nymphs move around on legs looking for feeding sites. This is when they colonize trees. After a few days, the nymphs molt and lose their legs and become a scale. We use horticultural oils when trees are dormant to kill scale eggs. We recommend using other control products during scale outbreaks.