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Denver, CO Armyworms are a type of turf damaging insect pest typically found east of the Rocky Mountains, but can be found throughout Colorado. In North America there are a few different types of armyworms: the Common Armyworm, Fall Armyworm and Yellowstriped Armyworm. The larvae feed on all types of turf and can damage ornamentals, and vegetables, as well as forage crops and cereals. Armyworms are thought to be semitropical in origin likely from Mexico or Central America and now have taken up permanent residence in along the Gulf States. The adults which resemble moths will migrate north and westward during the spring and summer. Large infestations have occurred further north after large populations of adults have been blown north due to tropical storms. Turf that is damaged by armyworms will appear dry and wilted as stems of plants are completely consumed

Denver, CO Armyworm Larvae


Armyworms feed on the grass anytime during the day and are known for their voracious eating habit. They have been seen moving en masse from one turf grass area to the next eating everything that is green, leaving only a few stems. Normally the damage appears as drought damage with a wilting yellowy appearance. Starlings can sometimes be an indicator of armyworm as they like to scavenge the lawn looking for the larva to feed on.

Life Cycle

The armyworm overwinters in the larva or pupa stage in the southern regions of the United States and in the north some larva may overwinter but most adults are blown north with spring weather fronts. In the spring the larva pupate and or the adults that arrive will mate and the females will lay clusters of eggs 100-300 usually on grass tips, hanging trees and shrubs or structures. Females can lay 1000's of eggs. The eggs will hatch into larvae and feed on the grass until they devour the entire plant and then they will spread out feeding ion the grass at anytime during the day. Over a period of 20-48 days depending on the temperature they will go through 6-9 instars before pupating in the thatch and soil. Depending on the location there can be several generations usually 2 in the north to 6 in the south.


Proper fertilization is extremely important and Weed Man Denver, CO's exclusive brand of granular slow release fertilizer ensures that the turf remains healthy all year long. Adequate nitrogen levels will help the plant recover more quickly if it is thinned out. Proper watering is also important follow Weed Man Denver, CO's proper watering instructions to help prevent Armyworm on your turf! Ensure when the turf is mowed it is at the recommended mowing height for your turf species, and with a sharp mower blade when the turf is dry.