Best spray for bagworms in arborvitae

[Brian Tymchak]

Seeing Tom's post in the Weed Killer thread for recommended sprayers brought to mind that I need to start doing my own treatments. I've been having a service do it for several years but they've just become too expensive. That money can be more helpful in other ways, like tool upgrades in the shop, or better yet, going towards a bigger shop... (I can only dream..)

Anyway, what are best recommended products to spray arborvitae for bagworm?

Thanks!

[Stan Calow]

I dealt with them at parents' house for a few years. My experience is that any available household pesticide you can buy at the local hardware store will kill them. Its a matter of hitting each of them directly so that the pesticide can get into their protective layer. So my choices were based on how easy to was to spray. Its easy for the ones at eye level. I used a hose-end sprayer with whatever concentrate I had on hand (one of the xxxx-thrin derivatives) to spray higher in the trees. The standard recommendation is to just pick them off by hand and dispose, but that's not as satisfying as watching them die in place.

[Bruce Wrenn]

Best answer is to check with local Ag Extension office. Sprays are most effective when they are just hatching, which varies by location.

[Tom M King]

When I was a teenager, one of my jobs was to burn bagworms. We'd wrap rags around the end of a long stick, put some kerosene on it, light it, and put the flame up at the bottom of a tent to burn it up. I never saw anyone spray them. You don't want to put enough kerosene on the rag for it to run down the pole..........

[Brian Tymchak]

Thanks guys. The arborvitaes are ~20 ft tall so spraying is the only practical solution.

Bruce, appreciate the tip about the timing of spraying. I hadn't thought about that. I'll do some more research.

[Ted Calver]

I sprayed for bagworms with Sevin in early May here in tidewater VA and again in early June to kill the larvae before they form their protective bags. There is a difference between bagworms and webworms/eastern tent caterpillars. Burning (does more damage than good), or a really strong stream of water work for webworms/tent caterpillars, (I used to love burnng the tent caterpillars out of our apple tree when I was a kid--think Bevis and Butthead yelling FIRE, FIRE!), but spraying in early spring and hand picking works best for bagworms.

[Mark Bolton]

Tom's advice for burning them out sounds more like what we use to do for gypsy moths (tent caterpillars). We had a beautiful specimen tree hit hard by bagworms. There is no way to burn them out without burning the entire tree down. They hang their "bags" like christmas ornaments all over the tree. We sprayed with Captain Jacks Deadbug... it knocked them down but the poor tree has been barely struggling back for years. Looks kinda like a haggered bonsai. She keeps telling me to cut it down but Im persistent in seeing if it starts sending off some new chutes up high. Looking better this year but not by much.

[Tom M King]

Yeah, they were Tent Caterpillars that I used to burn out.

[Erik Loza]

A biologist-friend said that all you need to do is punch a hole in the tents and then, native wasps will come in an get them all.

Erik

[Brady Watson]

Part-time farmer here....I've got 140+ Thuja Green Giants about 20' tall. They were about 18" tall when I planted them back in 2011.

Answer: It depends...

BEFORE YOU DO ANYTHING chemical related - You must do due diligence as an adult and access the situation. Pesticides are no joke and should be used sparingly. Walk around and sample the bags by squeezing them. Is there anyone in there? Did it squirt out? (Worm inside) - If no - it's just an empty bag and there's nothing to treat. If yes, then they are in there and active. Bags should be physically removed whenever possible as they can contain eggs for the next cycle. I've monitored my trees over the years and after the Preying Mantids got established, I've witnessed trees covered in bags one week and a week or two later - all gone (empty) with Mantid egg deposits everywhere.

It should be mentioned that bagworms are MUCH less of a problem when your beneficial insects (and birds) naturally eliminate them for you. If you want to kill EVERYTHING, you can apply Sevin @ homeowner concentration as directed. However, it is much more effective to use a professional strength variant of Sevin, with the active ingredient being Carbaryl. This can be applied nearly any time of the year and covers a host of pests...Make friends with a farmer and ask them to help you.

HOWEVER - If you have an active infestation, You should really try to knock them out at the RIGHT TIME using BT (Bacillus thuringiensis), a bacteria which specifically targets the digestive tract of caterpillars in their larval stage. This will starve them to death AND save your beneficials like Preying Mantis insects and other predatory 'helpers' as it leaves them unaffected. You have to do this typically in the spring - Read up on BT to find out the best time in your zone.

I'm not dispensing advice - simply sharing what has worked for me and the cautions I abide by to make the most adult decision. Just throwing chemical death around like it's nothing is not a good thing and in many cases is applied incorrectly or at the wrong time. We've all seen the RoundUp cancer commercials...

[Mark Bolton]

I'm not dispensing advice - simply sharing what has worked for me and the cautions I abide by to make the most adult decision. Just throwing chemical death around like it's nothing is not a good thing and in many cases is applied incorrectly or at the wrong time. We've all seen the RoundUp cancer commercials...

You BT advice is the route I most often take along with a myriad of other non-sevin options. Indiscriminate spraying of anything is always a no-no in my book but we have people laying waste to their sidewalks with Roundup, Crossbow,... dredging thier brassicas in Sevin dust, on and on.

It usually doesnt take a rocket launcher to knock these things down. Even BT is an indiscriminate acting on all caterpillars.

While they may require multiple, dilute, applications.. a lot of the more benign sprays will weaken the pests enough to knock them down to where mother nature can rebound.