Change of pace … beware of the bagworm in Pa.

Deceptive, sinister and prolific, a cool and calculated killer lurks nearby. Mastering the art of disguise, he is the smoothest of criminals, a bold assassin who blends into the shadows and decimates his victims in broad daylight. Leaving no trace of regret, the relentless destroyer's work often goes unnoticed by passersby – that is, until it's too late.

Keenly observed by only the most vigilant and watchful eyes – this elusive menace has wreaked havoc on decorative shrubs and evergreens for decades. All who've ever fatefully encountered the malevolent foe will not soon forget him. Yes, they know this master of disaster all too well; he is the formidable bagworm.

Scientifically known as Thyridopteryx ephemeraeformis, common evergreen bagworms are abundant backyard pests in the eastern United States, and here in southern Pennsylvania, they seem to feel right at home. Their favorite delicacies include arborvitae, cedar, pine, spruce and other evergreen species, but they are also known to sometimes dine on certain deciduous trees as well.

In their larvae caterpillar stage, which generally occurs between June and August, bagworms use densely woven silk and bits of plant matter to construct baglike cases for both protection and disguise as they feed for several weeks on host trees, often defoliating branches before landowners even notice an infestation. 

That's exactly what happened at my home, where after two weeks of observing the puzzling die-off of twin arborvitaes, I finally noticed the inch-long wiggling needle sacks and their tree-loving tenants inside. 

Though I consider myself a bit more observant of nature's wonders than most, I must shamefully admit that even I fell for their disguising charade. Realizing this was a subject about which I knew very little, I quickly referred to the Master Gardeners and the local Penn State Cooperative Extension for help.

"A lot of people think they are small pine cones and don't realize they're the reason their trees are dying until it's too late," said Alice Oskam of the Lebanon County Master Gardeners.

"We have received a lot of calls about bagworms in the past," said Oskam. "They are quite common in this area, and most people have become more educated about them, knowing the best way to control them is to simply pick them off by hand and dispose of them."

Extension floriculture educator, Sinclair Adam Jr. mirrored Oskam's advice, stating that removal by hand was the best option for controlling bagworms this late in the season.

"It may be too late to apply chemicals with an effective result," said Adam. "The best time (for pesticides) is when they are crawling about the tree in late June and early July. There are some systemic products that will control them after the bags form, but hand picking is always effective."

By late summer, many of the bagworms begin to enter their pupae stage, where they seal off their bags and rest for nearly a month in an inverted slumber. Around mid-September, the males emerge from their bags as dark moths and fly to female cases for mating. After reproduction, the females lay eggs in their bags before exiting, and then both adults die. The eggs overwinter in the protective sacks and the lifecycle continues next spring.

"It can be somewhat laborious to pick the bagworms off by hand, especially if the tree is large," said Adam. "But next year there will be more. If not controlled this season, they could get out of hand because there could be 500-1,000 eggs in each bag for next year's population."

Taking the experts' advice, I spent more than three hours last week picking enough bagworms from my arborvitaes to nearly fill a five-gallon bucket. I'm hoping my efforts provided enough relief for the trees to successfully regenerate with next year's new spring green-up.

In the meantime, I am thankful to have spotted a few songbirds and one praying mantis hanging around my disheveled arborvitaes, keeping close watch for any bagworms I may have missed in the removal process. My chickens are enjoying the occasional bagworm treat from the few I kept of my pickings, and as a newly informed landowner, my mind can rest easy.

The evergreens are safe from bagworm destruction … for now.

Categories: PenBlogs, Pennsylvania – Tyler Frantz, Social Media

Leave a Reply

Your email address will not be published. Required fields are marked *