Bagworms

Information, pictures and control of bag worms on ornamental trees and shrubs.

Types of Bagworms    Life Cycle    Feeding and Damage    Bagworm Pictures 

Control of Bagworms 

There are three types of bagworms found the North America:
The Evergreen bagworm, the Snailcase bagworm, and the grass bagworm. 
Evergreen bagworms are the most common and are found in the Eastern United States from New England south through Texas and west to Nebraska. 
The Snailcase bagworm is currently found throughout the mid Atlantic and is making its way to the Pacific coast.  Each type of bagworm creates a specific type of bag relative to its feeding habits.  Often, people will confuse Bagworms with Tent Caterpillars.  

The Bagworm is a perennial insect that gets its name from the silken bag it constructs around itself.  As a caterpillar, in the larval stage, this insect is rarely seen.  The Evergreen Bagworm and the Grass Bagworm are the only species to produce male moths that are capable of flight.  They are black, furry, clear-winged moths that have a one inch wingspan.  The adult female remains inside her bag until she dies.  Females are creamy white and lack wings and legs. 

Life Cycle 

Bagworms pass the winter as eggs inside a spindle shaped bag found on a variety of trees and plants.
The Evergreen Bagworm prefers deciduous and evergreen trees while the Snailcase Bagworm prefers vegetables, ornamentals, legumes, fruit and other trees.  There can be up to 1000 eggs in a single bag.  The eggs hatch in mid May and the tiny larval use silk and plant material to construct a small bag around its hind parts.  As they feed and grow, so does the bag. 

Bags are made of silk and plant materials like sand, soil and lichen.  In early fall, when the bags are one to two inches big, the larvae suspend the bags pointing downward from twigs during which time they transform into the pupae or resting stage before becoming adults.  Evergreen Bagworms attach their bags mainly to evergreen trees making it look like pinecones.  Grass Bagworms are attached to grass until they pupate, then it attaches its bag to the sides of fences and buildings.  The Snailcase Bagworm constructs their bags when larvae drop to the ground on silken threads and make c-shaped cases around themselves.  They are made of silk and soil particles and look like small round pieces of dirt.  This bagworm is odd because it reproduces parthenogenetically (without males). 

The Adult male Evergreen bagworm emerges in early fall when they fly in search of females who are still in their bags.  Females produce a scent or pheromone that attracts the males to her.  The male inserts his abdomen into a hole in the bottom of the bag to mate.  The female lays several hundred eggs in a sack and then drops from her bag and dies.  The eggs remain in the bag until May when the life cycle starts all over again.  There is usually one generation per year.  Adult male bagworms survive just long enough to mate, due to underdeveloped mouthparts that prevent them from feeding.

Feeding and Damage 

As young larvae, Evergreen Bagworms spin strands of silk that can be carried by the wind to plants to feed.  When disturbed, larvae will retract back into their bag and hold the opening closed.  The larvae feed on needles and leaves and as young caterpillars, they feed on the upper parts of plants leaving holes in the foliage.  They damage orange trees in Florida as well as junipers, spruce, pine, willow, apple, maple, elm, birch and cedar trees across the US. 
As a large population, they can cause damage by stripping plants of foliage.  Leaf damage is usually noticeable in June to late July and August.  Infestations usually go unnoticed in pine trees because the bags look like pine cones. Some bagworms feed on specific plants while others eat a variety of leaves from different plants. 

The Snailcase Bagworm was introduced into the United States in 1940 and discovered in Albany, New York in 1962. They are most often seen hanging from the exterior of houses, sheds and fences.  Their bags are very difficult to get rid of and can cause damage to fences and houses when removed.  The Grass Bagworm is considered a relative cousin to the Evergreen bagworm because it feeds on grasses and creates one-inch long silk bags that are found attached to grass.  Their bags aren't considered a nuisance.

Bagworm Control Measures

When infestations of bagworms are detected early, control is much easier.  Once population numbers begin to multiply and spread to numerous locations, control will require more work.  If bagworm infestations are not noticed until late summer, not only will their numbers be higher but the bagworms will have aged enough to make them more difficult to kill with an insecticide.

Sometimes, hand-picking of the bags or cocoons can save your trees and shrubs.
Most have had success using a proper insecticide to spray infested trees or shrubs, especially if treatment begins early in the season (before their numbers are too high and the bagworms have matured into a tougher pest to kill.)

There are certain Permethrin and Acephate products used to kill and control bagworms.  However, best results have been obtained by using Talstar One.  Talstar is a concentrated product that works at very low rates, with no odor and a label which allows use of product on many plants, shrubs, lawns and buildings.
Talstar for Trees and Shrubs Information.

Bagworm Pictures

Bagworm Emerging    Snailcase Bagworm   Snailcase Bagworms on House

Bagworm on Juniper    Bagworm Moth Bag  

Bagworm Emerging

Snailcase Bagworm

Snailcase Bagworms on House

Bagworm on Juniper   

Bagworm Moth Bag

Credits:
Our thanks to Lani Powell for research and writing which made this Bagworm information page possible!

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Bagworm Pictures    Bagworm Information    Feeding and Damage    Life Cycle of Bagworms