Wet Spring Breeds Aphid Problem – What You Can Do

Swingle experts are predicting a significant increase in the aphid population this season – a result of unseasonably wet weather along the Front Range of Colorado this spring.

Though it’s long been said that Colorado receives 300 days of sunshine a year, many areas of the state saw more precipitation than sun in April and May of 2015 – resulting in greener lawns and accelerated growth of trees and shrubs. The rain also creates the perfect environment for aphids and other insects like mosquitoes to thrive at an unusually high rate.

Aphids (from the aphididae family) are tiny, soft-bodied insects that literally “suck” the sap out of plant and tree 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.

Given the already large population due to abnormal moisture and the resulting growth, aphids could easily overtake your landscape if plants are not properly treated.

Aphids can cause foliage to curl and distort unnaturally, which can further distort growth and put undue stress on the plant or tree. 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.

Additionally, ants and hornets are naturally attracted to the honeydew deposits – increasing their population as well.

Aphids are typically found on almost all types of plants and trees across Colorado including: aspen, red twig dogwood, elm, Norway maple and green ash trees (the most common ash tree in the Front Range). While green ash trees are susceptible to aphids, white and autumn purple ash are typically not affected, but should be inspected with the rest of your landscape.

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. The good news is a soil injection can keep the aphids at bay and protect your ash tree from emerald ash borer (EAB).


  • For green ash trees, a soil injection treats for aphids and emerald ash borer – one solution for two problems
  • Treat & Inspect: By treating at the appropriate times through the year, this Swingle program protects your trees and shrubs from aphids, spider mites, and caterpillars

Each situation is unique, which is why consulting a certified arborist is important.

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