Sunday, August 26, 2012
The Heartbreak of Bagworms
The little "bags" that I saw actually contain these caterpillars, hanging from the branches by their own silk threads. This pest can quickly decimate an arborvitae, as it has done here. This is the first time I've seen this pest. It can also affect junipers and pines. Often, it will concentrate on one plant, leaving others in close vicinity somewhat untouched.
In July I applied the organic, biological control BT (Bacillus thuringiensis) which is a bacteruim known to kill the caterpillars, but which is safe for birds, animals and other insects which are not caterpillars (be careful near known butterfly colonies, as it will kill them). It appeared most had died after the application (as the spinning I noticed earlier was not the wind, but their own wriggling - nasty!), but short of hand-picking all of the "ornaments" off the tree, there is still the threat of a new infestation next year. This is because when allowed to mature and drop to the ground, each of the bags can contain literally hundreds of offspring for next year's crop.
The jury's out on whether this arborvitae will survive; the others adjacent to it only had small infestations, so they have a good chance, especially with an application of BT next spring before they are attacked again. So if you're out in your garden, and see these bags, start pulling them off. It's recommended that you burn them, but I'm not a big fan of fires in the garden(!). So I just dropped mine in a bucket of water laced with organic insecticidal soap. Good riddance, bagworms! Hope I don't see you next year!
Posted by Lisahct at 6:17 PM