As we move into the heart of the growing season, two very different, equally important questions have made their way into my inbox several times already this year. Those questions being about identifying and managing poison hemlock around the home landscape and handling or preparing to manage bag worms.
Bagworms are a familiar nuisance for many homeowners, especially those with arborvitae, juniper, or cedar. These caterpillar pests are best recognized by the spindle-shaped bags they construct from silk and bits of foliage. These bags, often 1½ to 2½ inches long when mature, allow the larvae to remain well camouflaged as they feed.
Bagworm feeding can cause significant damage, particularly on evergreen hosts. As populations increase, larvae consume needles and buds, leading to branch dieback and, in severe infestations, plant death in the following season. Unlike many insects, female bagworms do not fly, so infestations tend to build locally and intensify year after year if left unchecked.
Understanding the bagworm life cycle is key to effective management. Bagworms produce one generation per year and overwinter as eggs inside the protective bag of the female. Each bag can contain hundreds of eggs—sometimes up to 1,000—that hatch in late May or early June. Newly hatched larvae disperse by “ballooning,” using silk threads to catch the wind and move to nearby plants, where they begin forming new bags and feeding.
By mid- to late summer, larvae mature and firmly attach their bags to branches for pupation. At this point, control becomes much more difficult, which is why timing is everything when it comes to management.
For light infestations, simply picking off and destroying bags is highly effective. Late fall through early spring is an ideal time because foliage has dropped and bags may be easier to spot on evergreens. Be sure to cut the silk attachment band to prevent future branch girdling.
Bacillus thuringiensis (Bt) is a bacterial insecticide that works best on young larvae. Applications should be made in late June after egg hatch is complete. Specifically, Bacillus thuringiensis var. kurstaki (Btk) does not kill natural enemies, such as predators and parasitoids that help provide natural control of bagworm populations.
Keep in mind, Btk is most effective on small bagworms and becomes much less effective when bags surpass 3/4" in length and is totally ineffective once the bagworms have completely constructed their cocoon bags and stop feeding. Btk is a stomach poison which means it must be consumed to kill the caterpillars, and it has relatively short residual activity. Thus, two applications may be required. Once bags exceed 2/3" in length, standard insecticides will need to be used to suppress heavy infestations.
For larger infestations, insecticides can be effective if applied when larvae are actively feeding. Thorough coverage is essential because the insects are protected inside their bags.
Monitoring your landscape in early summer is critical. Catching bagworms while they are still small can make control simpler and far more effective, preventing long-term damage to valuable ornamentals.
While bagworms threaten plant health, poison hemlock poses a serious risk to people and animals. This tall, invasive weed (Conium maculatum) has been spreading widely and is increasingly found in disturbed areas such as roadsides, fence rows, and occasionally home landscapes.
Poison hemlock belongs to the carrot family, which makes identification tricky because it resembles plants like wild carrot (Queen Anne’s lace). However, there are several distinguishing characteristics to watch for:
-Smooth, hairless stems marked with distinctive purple blotches
-Hollow stems and a tall, upright growth habit (often 6–10 feet tall)
-Finely divided, fern-like leaves
-Clusters of small white flowers arranged in umbrella-shaped groups
The plant has a two-year (biennial) life cycle. In the first year, it forms a low-growing rosette of leaves. In the second year, it “bolts,” producing tall stems and flowers before setting seed and dying.
The primary concern with poison hemlock is its extreme toxicity. All parts of the plant contain harmful alkaloids that can be dangerous if ingested and may also pose a risk through skin contact or inhalation during handling. Because of this, proper identification and cautious management are essential.
Small infestations can be controlled by hand pulling or digging, especially when plants are young. Always wear gloves and protective clothing to avoid contact with plant sap. Remove as much of the root as possible to prevent regrowth. Targeted herbicide treatments are most effective when applied during the early rosette stage or before the plant bolts. Avoid allowing plants to flower and set seed, as a single plant can produce thousands of seeds that remain viable for several years.
One important precaution: never burn poison hemlock plants. Burning can release toxic compounds into the air, creating an inhalation hazard.
Both bagworms and poison hemlock highlight the importance of timely identification and intervention in the home landscape. While bagworms can quietly weaken prized evergreens, poison hemlock presents a more immediate safety concern that should not be ignored.
Regular scouting, whether for insect pests or invasive plants, remains one of the most valuable tools for homeowners. By staying alert and taking action early, you can keep your yard and garden healthy, attractive, and safe throughout the season.
Frank Becker is the Agriculture and Natural Resources Extension Educator with Ohio State University Extension – Wayne County, and a Certified Crop Adviser, and may be reached at 330-264-8722 or becker.587@osu.edu
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This article was previously published in The Daily Record.