Bagworms: Are They Harmful and How Do You Get Rid of Them?

Bagworms: Are They Harmful and How Do You Get Rid of Them?

Bagworms: Are They Harmful and How Do You Get Rid of Them?

Bagworms are Native Pests in North America with heavier populations in the Eastern US, they can also be found globally.

What do Bagworms look like?

Bower & Branch captured video of a rare sighting of a mature bagworm, carrying his bag, while looking for a new home.

Our families of professional growers are very familiar with this pest, but in all their years, they have never seen such a large bagworm be THIS mobile. Creeps us out!

Bagworns upclose and in evergreen tree.

Bagworms can go unnoticed.. unless you are intentionally looking for them. And once you see that first bagworm, all the rest become easily visible to you.  

Bagworms like evergreen trees – like spruce, pine, juniper, cedar and arborvitae. But we have seen very high populations and infestations on Japanese Maples and many other tree types. For control at home and on the nursery, always focus attention to your evergreens. 

Bagworms attacked evergreens in a line

Bagworms moving from evergreen to evergreen

Eggs hatch in early spring, with up to 1,000 eggs per bags that were laid in the fall. These small worms, about pin head size, are blackish little caterpillars that go unnoticed.

Bagworms use their silk to fly through the wind each spring in search of new homes and food sources. 

Bagworm leaving silk behind on evergreen trees

Once landed, they begin to form their bags for the season and then in early fall, they emerge to mate and fly as moths, uninteresting grayish moths. 

Bagworms begin to eat as soon as they land, primarily eating tender buds and young foliage, leaving holes in the leaves and wrapping silk around stems, causing more damage.  By the time you notice the bags hanging like ornaments (sometimes mistaken as cones), they have already begun to wreak havoc on the young tree. Heavy infestations can really harm your tree, and if more than 80% of the foliage is destroyed, the tree may actually die.

HOW DO YOU GET RID OF BAGWORMS?

  1.  Remove by Hand – YUCK! Trust us, we know! Simply go to work cutting off the bags and the silk if possible, one by one. Not our favorite job, but with small numbers, it is practical. These bagworms are also just ugly – so we do remove them at home and on the nursery as soon as we see them.
  2. Spring (May and June) apply an ingestible insecticide.  There are many on the market that easily control the pest. When applications are successful, you may be able to destroy your local population and not experience the problem again for many years. Young worms are easiest controlled, so spring treatment is the preferred method by professional growers. 
  3. In some years, second generations may form, but this is generally not experienced, but worth being aware of. In these cases, a second treatment may be required.
  4. The key is early detection. Trying to destroy bagworms once their bags are formed is not easily accomplished through sprays. Many times, physical removal is the only effective option and waiting until the following season to treat with sprays.
  5. Organic Multipurpose Insect Killers work well, but require multiple applications every 1-2 weeks through spring to get rid of bagworms. 
  6. Dormant Oil applied on bagworms over the winter provides control on these adults. Only the Male Moths fly.
  7. Spread is relatively slow because the wind or crawlers each spring are the only pathways to expansion.

Reach out to our Plant Whisperers for any questions or advice!