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It’s Miller Time!

Miller moth damage to windowsill

Eastern Plains residents are no strangers to the bi-annual invasion of Miller Moths. The moth proliferates well east of Colorado’s high plains, in fields abundant new spring growth of wheat and corn and then migrate through our communities twice a year.

The Miller Moth is the common name given to an adult form of the army cutworm. The miller derives it name from the dusty scale that occurs all over its body – reminiscent of flour on covering a mill workers clothing. The moth larva (cutworms) typically hatch out well east of our communities in March and then greedily chew through stalks of grain and corn. After eating their fill, the cutworm pupates to re-emerge as the dusty, winged scourge, we’ve become accustomed to and to begin its migration west to mate.

The first migration of the miller moth occurs at the onset of our spring, in May. This first wave is the heaviest, peaking in June, with millions of moths moving through the local area. This spring miller migration proceeds east to west, across the plains and into the high country – ending with the moths taking up position in the cool climate of the Rocky Mountains. Escaping the warm summer temperatures of the lower elevations, the moths will mate and become chum for hungry bears.

As the temperatures drop in the fall the millers once again, return to the plains, to lay their eggs before the onset of winter. The moths then move back through our local communities, fewer in number this time, but no less visible in the community.

While, it sometimes seems that this moth invasion can reach biblical proportions (especially during the spring migration), miller moths are not considered harmful, poisonous, or harbingers of disease. The massive number of moths in migration does however, pose a nuisance to residents in the path of their travels. Miller moths are are infamous for squeezing into any available opening in structures, invading homes, outbuildings and vehicles, where they will spot up widows, curtains and equipment with their red-rust colored secretions.

It is not recommended to use pesticides on the moths and quite frankly the numbers most residents encounter, prohibits this. Most commercial traps that are designed to kill insects with electricity (bug zappers) often feature protective grills that are too fine to allow the miller moth to pass through and be neutralized. Similar devices exist that seek to trap the insects in a mesh container, these devices were actually designed for mosquito control and use some form of UV light as an attractant and a fan to draw the insects into a drying chamber where they die of dehydration. The problem with these devices is that they were not designed to accommodate larger pests and are often too small or have too fine of a collection screen to trap miller moths.

Fortunately effective control solutions do exist, with the most effective being no-kill forms of containment and release. Light traps date back sever centuries and have been used by entomologists to trap, observe and collect insects for study. We offer a modern version of these very same light traps, for use in both study and removal of nuisance moths. Miller moths in particular, are attracted to our UVA light traps. We employ a specialized LED bulb that peaks in the UVA band at 395-405nm. Moths are lured to the light source and as they circle it, they impact the finned structure that surrounds the light. The collision briefly disorients the moth and they fall into the collection funnel where they pass into a containment area. Within the containment area a moth friendly ‘habitat’ is offered – recycled egg cartons work great for this purpose as the moths will rest in the numerous nooks and folds of the carton. It is in this dark containment area that the moths will come to rest, some will leave, but the majority stay on for the night. In the morning, the trap can be opened and the collection observed or released.

UVA light traps collect moths in massive numbers as compared to the ineffective commercial traps and zappers we wrote of previously. The effectiveness of this style of trap makes it ideal for use as a lure – to draw moths away from structures or for use indoors in clearing structures of moths that already see infestation.

When using a UV light trap, the most effective trapping occurs between dusk and dawn. Your catch will depend upon how attractive your light source is made to the moths. For the best results, turn off all other competing light sources in the vicinity of your moth trap.

Miller moths are a vital part of the local food chain, birds, bats and other essential animals all thrive off the miller moth migration. Moths are also good pollinators for our gardens and crops. So the question arises, what to do with your catch? Our traps are unique in that they offer a no-kill solution to the problem of mitigating the human impact of the Miller Moth migration. You can simply leave your moth trap outdoors and allow the moths to come (at night) and go (at dawn). If trapping indoors, you’ll obviously want to remove the trap to the outdoors to release your catch – making this part of your morning routine. Those with chickens shouldn’t pass up the opportunity to treat your special gals to wholesome, natural, high protein and fatty moth treat – we get the best eggs ever during Colorado’s moth season.

Happy moth trapping!


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