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Pests Threatening your Landscape this Summer

Posted on: June 17th, 2016

Pests threatening your landscape this summer, could very well affect the health and beauty of your trees and shrubs.

This is typically when insects emerge from inactivity, funguses begin to breed and a lack of moisture and nutrients are common stressors.

It’s critical that homeowners and property managers are aware of problematic symptoms that could be developing – discolored leaves, premature leaf drop, dead branches and a thinning canopy.

Swingle has compiled a list of possible problems, which might affect trees and shrubs across the Front Range in the summer of 2016. Regular inspections will help catch problems early for the most effective treatment.

Pests Threatening your Landscape this Summer


Pests Threatening your Landscape

Aphids (from the aphididae family) are tiny, soft-bodied insects that literally “suck” the sap out of tree and shrub leaves. The aphid female is quite unique – giving birth to live females, who themselves are already pregnant with many more generations of the insect. It’s this anomaly, which enables the population to explode in numbers.

Aphids can cause foliage to curl and distort unnaturally, causing stunted growth and stress. Perhaps most frustrating is the sugary waste (called honeydew), which drops from the insect leaving unwanted deposits on windows, cars and anything below it.

A kind of sooty mold often breeds on the honeydew deposits, causing the surface of the foliage to look black in appearance. This is typically the first warning sign for homeowners and property managers that aphid activity is present.

Treatment options include both soil injections and topical sprays – the latter becoming a less common application in an effort to help protect and preserve the pollinator population in Colorado.

Emerald Ash Borer

Pests Threatening your Landscape - EAB

The emerald ash borer (EAB) population is still building rapidly in northern Boulder, with no signs of slowing down. Proof of that comes as Longmont detected its first active case of EAB in early June 2016.

The Denver Parks and Recreation (DPR) Forestry Division is rolling out a public education campaign about emerald ash borer (EAB). They now understand the severity of the situation and are being proactive in educating the public of the long-term effects of EAB and why treatment is important.

“Ash trees in Denver can be found throughout residential properties, public rights-of-way, parks and green spaces. These ash trees perform important functions; including cooling the landscape and mitigating air pollution and storm water runoff. It is critical we activate a public awareness campaign to help stop the infestation of Emerald Ash Borer in our community.” – Rob Davis, Denver City Forester

What does that mean for you? If you have an ash tree, you will either need to treat it, remove it, or you can choose to do nothing (however, the tree will likely die). Waiting to treat until AFTER the borer is discovered on your property or an adjacent property is NOT a good strategy. Remember, once the borers are found, it’s likely they’ve already been there for two to three years, causing significant if not irreversible damage.

Japanese Beetle

Pests Threatening your Landscape

This beetle is becoming more established in the northeastern part of Colorado. The beetle commonly feeds on turf grass, roses, Virginia creeper, crabapple, linden, elm and many others.

Beetle grubs attack healthy lawn roots, causing irreversible brown patches, which appear during the early summer months. While brown patches on lawns can be caused by many reasons, they are more easily identified on trees, shrubs, and roses due to their bright green appearance and damaged foliage.  Japanese beetles, both in lawns and on trees and shrubs, require additional treatment or the damage will be permanent.

Pine Sawfly

Pests Threatening your Landscape

The sawfly infests Ponderosa pine trees. The larvae are caterpillar and worm-like, while the adult sawfly looks like a stingless wasp, which will not harm humans. The larvae feed on pine needles for about two to three weeks – stripping the foliage down to the branch. They may chew on the branches if there is no other available food, impacting the tree’s health even more.

Large populations of sawflies will require treatment to protect the tree and its health and should be performed as soon as the infestation is noticed. If trees are left untreated, defoliation to the tree may be permanent. It can take only a few days or a couple weeks for the tree to be damaged.

Tussock Moth

The Douglas-Fir Tussock Moths are defoliators, which affect blue spruce and white fir in our Colorado urban environment. During the larvae or caterpillar phase of the insect’s life, it begins eating newer foliage located at the top of the tree. As they grow larger, they begin to move down the tree eating older needles, resulting in a brown or red cast on the affected area.

It’s much easier to treat young larva, as treatment is most effective right after the eggs have hatched. Typically you want to have your trees sprayed no later than mid to late June.

Elm Leaf Beetle

Pests threatening your landscape

Leaf beetle larvae damage begins with the leaves taking on a transparent appearance. Eventually, the leaves turn brown and begin to drop from the tree early in the summer. Adult beetles chew holes in the leaves giving them a “B-B” hole appearance. However, their feeding is far less damaging than the larvae’s. Adult beetles often invade homes in the fall as they seek shelter for the winter.

European Elm Scale

Pests threatening your landscape

In spring, as the temperatures warm, the females feed on branch sap, which results in conspicuous honeydew production. Young yellowish-green crawlers emerge in late June into July migrating onto leaves to feed. This feeding causes premature yellowing and shedding of leaves. The leaves that fall will be very sticky from honeydew. A black sooty mold will form on twigs and branches – branches may be killed by heavy scale populations.

Of course, other issues might be lurking on your trees and shrubs. If you suspect any abnormalities, contact Swingle today for a free property evaluation.


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