Moth sightings in Colorado are on the rise, but why?

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SOUTHERN COLORADO – You’ve probably noticed swarms of moths flying around your doors, sneaking inside your home and infiltrating your garden over the last few weeks. That’s because moth season is in full swing in Colorado. And, according to experts, you’ll be doing more swatting than normal this year. 

Entomologists with Colorado State University say moth populations are larger this year. This comes after four straight years of below-average numbers for the winged creature. CSU Professors Whitney Cranshaw and Frank Peairs explain the uptick in moths across Colorado. Both entomologists are professors in the Department of Agricultural Biology and CSU Extension Specialists.

“Flights of the moths crossing through into eastern Colorado on their annual migration to the mountains first became noticeable the first few days of May, much earlier than 2019, when noticeable numbers were first observed in late May,” the entomology team writes in its CSU Extension article. “They originate from fields across eastern Colorado and adjacent areas of western Kansas and Nebraska on a yearly westward migration, ultimately arriving in the mountains to spend the summer, and returning to the plains in September. Peak moth flights may last five to six weeks, generally starting the last week of May or early June. Already, the moths have damaged crops in Colorado, Nebraska and Kansas.”

Landscaping plants offer food and shelter for miller moths, which can increase populations locally during migrations. Moths tend to favor plants, found along the Front Range, such as lilac, cherries, spirea, raspberry, cotoneaster, horsechestnut and Russian olive. They also seek shelter in shrubs, spruce and pines around your home. In fact, the reason behind why some homes have more moths than others, comes down to the plants available in each yard.  

While these moths are a huge nuisance, especially once they sneak inside your home, there is some good news. Moths don’t feed or lay eggs during their migratory flight, so that’s one less thing you have to worry about. They also don’t feed on any household furniture or food. Once a moth gets inside your home, it will eventually die without reproducing or have to find its way back outside.

So, why exactly are there so many miller moths flying around this year? Cranshaw and Peairs say less moisture during fall, winter and spring is one big factor in the spike. When moths make their westward migration across Colorado in early May, they follow flowering plants for nectar and energy sources. Good moisture leads to an abundance of flowering plants, but a drier season gives these moths less room to roam.

In other words, the moths can’t spread out across Colorado and feed the way they usually do. Instead they’re concentrated in areas where a lot of flowering plants are, such as yards and gardens. Neighbors along the Front Range also had a freeze in mid-April, killing blossoms that would normally be in peak bloom right now. Both factors combined are contributing to a higher moth concentration in Colorado. 

Since moths avoid daylight, they hide out in small cracks in doorways, garages and cars before daybreak. At night, they’re ready to come out, feed and resume their migratory flights. They’re attracted to lights at night because they naturally use the moon or stars to orient their flights.

There are a few things you can do to help control the moth party outside your house. Try to seal any obvious openings, particularly around windows and doors. You can also reduce lighting at night around your house by either turning off unnecessary lights or replacing them with non-attractive yellow lights. 

“Once in the home, the best way to remove the moths is to swat or vacuum them or to attract them to traps,” according to the CSU Extension article. “An easy trap to make is to suspend a light bulb over a bucket partially filled with soapy water. Some wetting agent, such as soap or detergent must be added or many moths will escape, the water beading readily off the scales of their wings and body. Always use a grounded plug and extreme caution when using any electrical device near water!”

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