Spooky pinecone-shaped cocoons spotted in Ontario and should be drowned on sight

If you're out for a stroll this spring and you come across what looks like an innocent pinecone hanging from a tree, you might want to take a closer look, because what you're seeing could actually be housing thousands of tree-killing eggs. 

Although they closely resemble pinecones, bagworm moth cocoons can contain up to 1,000 eggs that have the potential to defoliate evergreen plants. 

The destructive pests are native to North America (primarily the eastern United States) and attack over 120 tree species, including cedar, hemlock, juniper, pine, spruce, and fir. 

The pesky insects have become increasingly common in Ontario, with multiple new sightings already reported this season and shared on the biodiversity social network, iNaturalist. 

Photo: amelie_s/iNaturalist.

Based on the type of tree they decided to call home, bagworm moths can wreak havoc, rapidly stripping foliage and leaving entire branches (or even whole trees) weakened or dead. 

On evergreen trees, the pests will eat lots of foliage, causing the tree's branch tips to turn brown and die, while on deciduous trees, they'll chew small holes in the leaves, which can cause defoliation. 

The insects spin cocoons during their larval life, constructing them with pieces of plant material, including leaves and twigs, from the trees they feed on. Eggs typically hatch in late spring or early summer, after which tiny black larvae emerge. 

Photo: ezgrower/iNaturalist.

These tiny tree invaders stay in their bags until late summer or early fall, until adult males emerge to mate. Adult females are wingless and tend to spend their entire lives inside their bags, while male bagworm moths are ashy-black in colour and have transparent wings. 

If you come across these cocoons, your best bet is to cut them off by hand and place them into a plastic bucket filled with a mixture of dish soap and water, making sure that the sacks are fully submerged. 

Following this step, you can transfer the soaked bagworms into a tightly sealed plastic bag and throw them in the garbage. Bagworm infestations can also be treated with an insecticide that contains Bacillus thuringiensis.

While the removal process can be done at any point during the season, you'll want to do so before new bagworms hatch, which typically occurs in late May to mid-June.