Why You Should Be On The Lookout Now For Armyworms


As we approach September in West Tennessee, Armyworms are always a concern for turf grass managers. Armyworms can quickly destroy a lawn in a matter of hours, let alone days. This reminds most of us of the quick decision we had to make in 2014 when we experienced one of the worst Armyworm outbreaks ever.

BEFORE there is a severe outbreak of Fall Armyworms across West Tennessee again, why wait until the last minute to have a plan?  And if you need help, call us at 4-EverGreen or Okeena to schedule your armyworm treatment before the outbreak is here! We were bombarded in 2014 with calls and want to be proactive as far as what homeowners should be looking for, before it’s too late! Here are some interesting facts about this lawn damaging pest.

Armyworms are stout-bodied, hairless, striped caterpillars that chew on the foliage of grass and/ or plants. They are named because of their habit of crawling in large numbers from field to field when they have exhausted their food supply. Several species of armyworms attack turfgrass. Homeowners are understandably concerned when their turf is literally mowed down by a mowing “army” of caterpillars that seems to appear overnight. There are three major species of armyworms that attack turf in the U.S.  Fall armyworms cause more damage over a broader area.  These destructive pests can eliminate your plants or turfgrass in a day or less. People will say “I’m going to let the worms cycle through because most are pretty big.” This is usually a mistake because a larva will consume over 80% of its total food needs in the last few days before it pupates. First generation caterpillars cause the most damage in an area but can be prevented.

A little info about their lifecycle:  Armyworms spend the winter as mature lavae or in a pupal stage amid plant debris or down in the soil itself. As the name indicates fall armyworms are most numerous in late summer or early fall. On certain occasions with severe outbreaks, armyworms can occur as early as mid-April but this is unusual. It is in this feeding period that the larvae cause the most destruction. After pupating, they will emerge as moths ready to mate, lay eggs, and continue their cycle. A female moths can lay up to 2000 eggs. There can be anywhere from 2-3 generations per year, with some areas having 4 if the conditions are favorable.

Fall armyworms are typically most active early in the morning, late afternoon, or early in the evening, but on taller grass, can be observed feeding throughout the day. They feed and destroy crops and since much of this activity is done at night, they are often hard to discover before extensive damage has already been done. When they have devoured a field or your lawn, they will move together to a new area with fresh food. Armyworms pass the winter in partially grown larvae in the soil or under debris in grassy areas. Activity and growth are continuous except during VERY cold weather.

Armyworm damage proceeds at a faster rate because of the large sized caterpillars, synchronous egg laying, and subsequent population growth. In epidemic years,  the generations of fall armyworms overlap, allowing for almost continuous egg laying, which means that caterpillars of ALL sizes can be found in any given lawn. Fall armyworm moths usually fly between the hours from dusk til dawn. If you see clouds of moths, with a wingspan of about an inch, check your lawn 7-10 days later for fall armyworms. Insecticides with longer residuals are a better choice for outbreak years. An application of insecticide may be necessary if the infestation is extremely severe and/or the plants are under stress.

So, what can we do for control?

Pyrethroid insecticides generally provide excellent control of Fall Armyworms.

Apply Sevin Dust to lawn to prevent Armyworm damage.

If you have other questions or concerns about armyworms or any other pest inside or outside the house, please call our office for a FREE consultation. 731-264-0088

 Thanks, have a great week!

Scott Riley

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