Pest Watch: Bagworms!

by Susan Ndiaye, Community Horticulture Educator

pinecone like structure hanging on an evergreen tree

Have you ever noticed one of these structures hanging on a Colorado blue spruce or an arborvitae?  They kind of look like pine cones, but not exactly.  Well, they aren’t pine cones, but silken bags spun and decorated by bagworms (Thyridopteryx ephemeraeform).

Bagworms are moths whose larvae feed on evergreens such as spruce, juniper, pine and arborvitae.  The larvae can also feed on deciduous trees such as maple, elm, birch and sycamore.  Bagworms defoliate the trees and shrubs they infest.  In large numbers, bagworms can cause significant defoliation, which can lead to the death of the plant.

Bagworm Lifecycle

In late spring, bagworm eggs, which overwinter in their mother’s silken bag, hatch and caterpillars emerge.  These caterpillars begin to form new silk bags, and as they eat, they cover it with bits of leaves.  As the caterpillar grows, it expand its bags.   Then in late summer the caterpillar firmly attaches its bag to the plant and pupates.

Adult male bagworm - clear winged moth with furry brown body
Adult male bagworm

Complete metamorphosis from caterpillar to moth takes about four weeks.  Adult male bagworms emerge from their bags as clear winged moths and begin to search for a mate.  Adult female bagworms are wingless moths and never leave their bags.  After mating females produce 500-1000 eggs before dying.  Their eggs overwinter inside their mother’s silken bag and the whole cycle begins again.

Management

Because bagworms are protected by their silken bag, management can be tricky.  For smaller trees and shrubs the best tactic is to remove and destroy the bags by hand.  Unfortunately, this is not possible in all instances, especially on larger trees and shrubs.  Insecticides are most effective right after bagworm eggs hatch, when the caterpillars are small.

But how does one know when the eggs are going to hatch?  Well, it turns out that there is a “Bagworm Forecast” that you can check in the spring to determine  the best time to apply insecticide.  The maps provided by this forecast are updated daily and available six days in the future, so you can plan ahead.

For recommendations on pesticides, check out the resources below.  And as always, make sure you read and follow all the instructions on the pesticide label including the use of personal protective equipment.  The label is the law!

If you need to spray a larger tree, you may need to contact an arborist.  Click here to find a certified arborist near you.

Fun Facts

As females don’t fly, you may wonder how bagworms spread.  Bagworm caterpillars can balloon, or use their silk threads to catch the wind and travel long distances.

Despite relatively little protection for overwintering bagworm eggs, research at Purdue University found that it takes a 24 hr period at -0.6 ° F or below to kill the eggs.  So if you live in Orange County New York don’t expect a cold winter to kill off your bagworms.

Here is a video of a bagworm feeding!

Video from Purdue University Landscape Report (https://www.purduelandscapereport.org/article/824/)

Resources

Bagworm – Penn State University

Bagworms – Cornell University

Bagworm Forecast – USA National Phenology Network

Bagworms on Landscape Plants – University of Kentucky

Cold weather in January 2018 may have killed bagworms in some parts of Indiana – Landscape Report, Purdue University

Urban Sanctuary

Urban Sanctuary

By Cecelia Lillard, Florida Master Gardener Volunteer and James Alton Thomas, Greenville Township Senior Master Gardener Volunteer

This article appeared in the August 2019 Issue of Gardening in Orange County. Click here to subscribe!

This article profiles an urban lot that was transformed into an oasis for body, mind and soul as well as for wildlife.  This lot belongs to a local Master Gardener and illustrates how much privacy, beauty and biodiversity can be created with thoughtful design and considered plant choices.  We’ll review the design principles employed in this yard and then take a look at the ecological needs fulfilled through the design and its implementation.

A bright green garden - houses in the background and bright lush green garden in the foregroundFirst and foremost, this design provides privacy and the sense that the space is an outdoor room.  The lot is 50′ wide and faces southeast.  The edges of the property are bordered by deciduous and evergreen trees.  The tall Norway Spruce provides a strong anchor for the southern border and creates a shade garden for almost half of the yard, while the mature deciduous trees provide both frame and boundary for the property.  Given that this garden is in shade much of the time, plant textures are emphasized in throughout the space.  Since the plants are in groups instead of individual plants, the various textures become harmonious and interesting rather than chaotic to the eye.  The repetition of plants by massing gives the design a simplicity that helps quiet the mind and gives one an opportunity to linger in areas and simply enjoy the beauty of a plant’s texture and color.

A beautifully green garden with trees in the background and a small grassy area with a large planter in the foreground
The central planter provides the main focal point of the yard and is the only place where we find a traditional lawn.  The repetition of red in the plants helps to unify the yard and gives the focal point additional structure.  The use of evergreen boxwoods around the base of the container ensures that the focal point will be held even in winter when the planter is moved indoors and allowed to go dormant.

The lawn around the focal point draws the eye to the back of the circle where a stone path peeks between the low shrubs and groundcovers.  The curving shape of the path gives the landscape a sense of movement and entices one into the farther spaces.  The copper birdbath provides another focal point that draws the viewer’s eye and invites the viewer to another part of the garden that is more private.  The red pole, which supports an unseen, yet occupied birdhouse, gives us a hint that there is more to that part of the garden than we can see and provides a touch of mystery.

A lush green gardenThe yard evokes a feeling of balance with the shrubs softening the borders of the property and the understory trees filling the gaps between the shrub layer and the canopy of the deciduous trees.  The varying heights of the plants provide visual interest and contribute to the feeling of privacy that is created in such a small space.  The repetition of color throughout the garden contributes to the sense of balance, with the yellow-greens contrasting with the darker greens, yet not competing with them.

Seasonal interest was also a major consideration in the design of this space.  There is year-round interest provided by many elements of the garden.  The plants were chosen not only for their texture, but for their bloom times and flower colors as well.  There is a continuous supply of flowers in the garden throughout the spring and summer and into fall.  The changing color of the leaves of the trees and shrubs during the autumn supplies the visual interest that flowers provided the rest of the season.  In the winter, the evergreens take center stage, furnishing a stark contrast to the more delicate structures of the deciduous plants.

Overall this garden creation has a feeling of unity, where all of the parts work together to create a coherent whole.  The massing provides a rhythm that is relaxing and the multiple textures provide interest within that rhythm.  The reiteration of certain colors also unifies the space by visually connecting different areas of the property.

green stripped caterpillar with a red head on a leaf stem
Rosy Maple Moth Caterpillar  (Dryocampa rubicunda)

Looking at the yard from an ecological point of view, the property provides all the layers of a forest garden:  tall tree layer, low tree layer, shrub layer, herbaceous layer, ground cover layer and, of course, the root layer.   The tall tree layer consists of both deciduous and evergreen trees.  These trees provide food in the form of seeds and shelter within their branches to birds and squirrels.  The leaves of the deciduous trees also supply an important habitat for insects, including butterflies and moths, providing spaces to lay eggs and food for growing larvae.

A back beetle with orange stripes and long antenna on the white florets of a Queen Anne's Lace flower
A longhorn beetle on the umbelliferous flower of Queen Anne’s Lace

Since the garden was designed to be in continuous bloom for more than half the year, it can be considered an insectary.  There are various flower shapes throughout the garden, providing food for many different types of insects.  Some insects prefer umbelliferous flowers, while others prefer flowers with central florets like asters.  The diversity of flower shapes and bloom times helps ensure that beneficial insects will have a continuous food supply and will help keep invasive and/or problem insects at manageable populations.

As we have spent much of this issue discussing soil and the soil food web, we need to look at our garden through that lens.  In addition to providing mulch and habitat for overwintering insects, fallen leaves contribute to the soil structure and organic matter content in the soil.  These photos were taken in spring and we can see how full and lush the vegetation is early in the season.  This verdure is due not only to the care of the gardener, but more so to the health of the soil where these plants are growing.  The soil food web is very dynamic in an environment like this and the result is the beauty that we see in these photos.  May you be inspired to use these design principles and nourish your ecosystem to build a beautiful garden of your own.Drawing of a carm with icons highliting different management practices, soil health benifits, and soil organisms that are important to soil health. Click on the picture to learn more.

For links to resources that will help you design your own urban sanctuary, check out Cornell University’s “Site Assessment for Better Gardens and Landscapes“.

Click here to learn more about Backyard Conservation.