Natural Remedies for Tent Caterpillars or Armyworms

©Nannette Richford

Whether you call them tent caterpillars or armyworms, these insect larvae can become a nuisance in home gardens and backyards. The nests appear in the spring and are filled with hundreds of tiny caterpillars. The caterpillars venture out of the nest to feed on the tree's leaves during early morning or late evening and return to the nest during the heat of the day.

These caterpillars are Eastern Tent Caterpillars (Malacosoma americanum) and can be found throughout the eastern part of the U.S., including Maine.  They are often referred to as armyworms, but this technically isn't true. According to Merriam Webster, armyworms can be any number of insects larvae that travel in groups and devour crops. Armyworms may devour your garden, but the Eastern Tent Caterpillar typically eats the foliage of the host tree.

​According to the University of Kentucky Entomology Department, the Eastern Tent Caterpillar nest increases in size for 4 to 6 weeks before the caterpillars leave the nest for good in search of a place to spin a cocoon and morph into small reddish-brown moths.

©Nannette Richford

While they do not always pose a problem for homeowners, there is a bumper crop of them them every few years. When this happens, they can defoliate  host trees and can be found crawling on lawns, decks and even in the pool, making them a nuisance. Getting rid of them can be a challenge once they have left the nest.

Natural Methods for Getting Rid of Tent Caterpillars

                                   Physical Removal

Sometimes the easiest method of getting rid of tent caterpillars or armyworms is to physically remove the nest. If you catch them early when the caterpillars and nests are small, physical removal is easy.

• Cut the branch that contains the nest from the tree and dispose of it away from your yard. You can also enclose the nest (after cutting it from the tree) in a garbage bag, seal it  and dispose of it in the trash.​

If physical removal isn't practical or feasible there are other environmentally friendly options., 

       Organic Pesticide Recipes - White Oil Spray

There are several variations of the oil and soap mixture as a natural pesticide. These formulas work because the soap helps the oil stick to the insect's body and blocks its breathing pores. It is unclear how cayenne pepper or ground cinnamon increases the effectiveness. While some sources claim you must use a true soap and avoid dish detergents that contain degreasers, others report success with Dawn Dish Detergent.
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1. ​​Mix 1 cup of canola (or other vegetable oil) oil, 1/4 cup of Dawn Dish Detergent, and a teaspoon of cayenne pepper (or ground cinnamon).
2. Shake it up until it is well blended. The mixture will turn white.
3. To use, mix one tablespoon of the concentrate to one quart of water,
4. Fill a spray bottle or sprayer with the mixture.
   
5. Spray the entire nest with the solution until it is saturated.

Avoid spraying when the temperature is above 90 degrees as it may cause foliage to burn.