Bagworms

A large bagworm infestation can lead to almost complete defoliation of trees.

Bagworms are destructive insects that attack many deciduous and evergreen trees and shrubs. Young bagworm caterpillars feed on needles and leaves. A large infestation can lead to almost complete defoliation of trees. Bagworms can be recognized by the characteristic case or “bag” that they construct around themselves. The bag is made from silk and plant material from the plants they are feeding on.

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Treatment Strategy

Physically removing and destroying as many of the bags as possible can significantly reduce bagworm populations. Depending on the size of the trees and shrubs, this may or may not be feasible. We do not recommend using ladders!

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Bagworms Treatment Option 1

Controlling caterpillars when they hatch in the latter part of May is another method. You can spray the tree for bagworms with an insecticide containing bifentherin such as Up-Star® Gold as the insects emerge in late May.  It is important to apply insecticides that control lepidopteran insects.  Most insecticides do not control this insect type.

Application Type - Foliar spray

DIY Product/Equipment Needed:

• Up-Star® Gold

• Pump up tank sprayer with wand

• Gloves/safety glasses

Bagworms Treatment Option 2

Applying the insecticide Lepitect,  to the soil at the base of the tree in May or June is another option. Using Lepitect™ allows for broader window of time to make the application as it systemically moves into the plant and has a residual of 30 days.

Application Type - Soil injection

DIY Product/Equipment Needed:

• Lepitect

• Soil injection kit

• Safety glasses

• Gloves

Bagworms Treatment Option 3

Another less aggressive sprayed approach is Conserve® SC.   The active ingredient in Conserve® SC, spinosid, is a naturally occurring bacterium found in soil. Conserve® SC can be applied as a foliar spray and is considered non-toxic to people, yet is effective on moth and butterfly insects.

Application Method - Foliar Spray

DIY Equipment/Product Needed:

• Conserve® SC

• Hand pump sprayer with wand

• Gloves

• Safety glasses

Bagworms DIY Kit

Option 1:

Application Type - Foliar spray

DIY Product/Equipment Needed:

• Up-Star® Gold

• Pump up tank sprayer with wand

• Gloves/safety glasses

Option 2:

Application TypeSoil injection

DIY Product/Equipment Needed:

• Lepitect

• Soil injection kit

• Safety glasses

• Gloves

Option 3:

Application Method - Foliar Spray

DIY Equipment/Product Needed:

• Conserve® SC

• Hand pump sprayer with wand

• Gloves

• Safety glasses

How Is It Spread?

Eggs of bagworms hatch in late May and early June from bags constructed the previous season. The larvae (caterpillars) build a bag around their hind parts after hatching and carry it around as they feed on needles and leaves throughout the summer. In August, the mature larvae attach their bags to a branch (looking a lot like small pine cones) where they stay for about 4 weeks in a pupa stage. The adults emerge and then lay their eggs.

Susceptible Trees

While any tree can be infested with bagworms, the most common are arborvitae, hemlock, juniper, pine, spruce, bald cypress, locust, sweetgum, and sycamore.

Symptoms

Visible bags on the branch ends.

Lookalikes

None

Related/Similar Problems

None

Timing

When visible or in May for chemical treatments

Urgency

Moderate

Risk of Spreading

Low

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