Browntail moth caterpillar

[caterpillarhunter]

Hi everyone! I'm a new member here, I don't know anything about lasers, and I'm actually just here asking for advice on a very strange and limited subject.

I live in rural Mid-Coast Maine, and in the past few years we've had a horrible infestation of browntail moth caterpillars. They defoliate trees, and their hairs (which they shed copiously) cause poison ivy-like rashes in many people.

The baby caterpillars overwinter in nests of hundreds by wrapping themselves in a dead leaf that's attached to the ends of branches at the tops of trees. So when I'm staring at those dangling dead leaves in December I'm constantly wishing I had Superman's heat ray vision so I could burn them up. Then I realized that I could!

I've been researching a bit, and I'm leaning toward the Sanwu Challenger 2, 1W 635nm. I like this because I think it's strong enough, and the multimode would let me aim on a safe low power mode before I turn it up to burn those suckers. I'd mount it on a tripod for accurate aiming.

My questions are:
Is this the right frequency to use?
Is 1W powerful enough to set that nest on fire? I want to be able to make it burn up from 100 ft away, as some of these trees are 70 feet tall.
Is there another laser of a similar price that you'd recommend instead?

I'm not concerned about setting other things on fire, since I'd only do it in the winter when there's snow on the ground.
I'm also not that concerned about hitting other things up in the air, as we don't really have planes flying overhead, and I'd watch out for birds and squirrels before I turn up the power.

Thanks in advance!

 

[Mattronium]

Firstly, welcome to LPF.

I'm not sure how practical of a solution it would be.
At the very start, to even consider doing this in practice, you need to have a good understanding of laser safety, and some laws, as the power you are talking about is dangerous.

The main issues I see are:
-Pointing a laser into the air unterminated. (genrally unadvisable even without planes, can be mitigated with diverging beam after focus)
-The time it would take and aiming precision needed (tripod + lots of time? How long would it take to make a significant impact?)
-High Power or large optics maybe? (might need higher power or beam expander/lens contraption)

To your questions, the frequency/wavelength does not matter a whole lot except in the absorption of the target at that wavelength, the main wavelegts for very high power (>2W) power would be blue/445nm-455nm. for medium high power 405nm, 520nm, or 638nm, or IR (808nm, but that would have aiming issues). As long as the intended target absorbs 450nm adequately that is likely going to be best as it can give the most power per $.
1W might be on the low side for 100ft. but if you have a beam expander then 1W might be sufficient.

I don't know if you have looked into other options or not, there might be other solutions that are easier/safer?
I don't want to discourage you from thinking about ideas of maybe trying something, but just make sure you do it safely first.

 

[caterpillarhunter]

Thanks for your thoughtful reply, Mattronium.

Pointing a laser into the sky was my biggest concern too. What's a diverging beam, and how would I add it to the Challenger 2?
Since you think the 1W would be too weak, now I'm thinking the 3W 445nm Challenger 2. But I'm also wondering -- if a 1W laser might not be able to burn a leaf at 100 ft, how dangerous could it be?

The time needed wouldn't be too bad. This year, I'm only seeing about 20 nests on our property. The worst year so far, there were maybe 200.

Believe me, many people have been trying to figure out what to do about this problem. The main solutions are:

1) Aerial spraying of pesticides on trees. The problem with this is that it's very bad for other wildlife.
2) Systemic pesticide injections into the trees. This is what I used after that worst year. It's moderately expensive (it cost me about $1000 that year), and it's also somewhat bad for bees and wildlife. However, it was extremely effective.
3) Manually clipping the nests off, then burning them. This is the safest method for the environment. However, it's also by far the most expensive ($3-5000) because it involves hiring arborists with expensive heavy equipment to go up there and get them. Also, the equipment can only reach about 60 feet, and often can't navigate through the woods to get to the necessary trees.

I have heard of someone attaching a blowtorch to a drone and using that to burn the nests. It works, but it's a bit tricky to navigate it through the branches, and it involves some technical expertise to be able to build it and actuate the blowtorch remotely.

What I like about the laser idea is that, if we can figure out how to do it safely, it would be very cheap, effective, and safe for the environment.

 

[Mattronium]

What I mean by a diverging beam, is lasers naturally diverge(spread out/get larger) as they travel, if a laser were normaly focus to infinity (where the beam stays as small as possible for as long as possible) then the laser poses maximum risk at far distances. If you were to take the laser and focus it so that the spot size at 100ft was as small as possible, then for example; the laser beam diameter might get smaller from the laser to 100ft, and then grow beyond that, but after 100ft the beam would grow larger much quicker than when focuse to infinity, so at very long distances the beam is larger and safer.

The reason to have a beam expander (device usnig lenses to enlarge the beam size at laser) would be that the larger the beam at the laser device the smaller spot one can get at a specified distance.
For a normal laser maybe the smallest dot at 100ft is going to be maybe a few inches? but with a beam expander one could get that down to <inch, and the smaller the dot the less power one might need. Though I am not sure about the exact sizes, I'm just making guesses.

 

[Unown (WILD)]

It's not going to work. Diode lasers do not diverge well. You're looking at a huge line instead of a dot at even 10 feet away. They aren't good for distance. Single mode diodes have the best divergence but are not powerful enough. Maybe a gas laser that is very powerful? Not sure how many watts... maybe at least 10?
I'm also concerned that even with a cheap enough laser you will just burn a hole right through it before the entire thing catches fire. I mean I have a two watt 445 laser and it will just burn through paper with a hole and slightly char around it but to actually make it catch something on fire takes a bit of time and that's up close let alone 100ft away.
Maybe a diode array with some corrective optics might do the trick but will be costly. Then again it's cheaper than the 3-5000 you mentioned.
One thing I can say for sure is that it will not be a simple setup. Definitely not a portable... like not even close

 

[caterpillarhunter]

It's not going to work. Diode lasers do not diverge well. You're looking at a huge line instead of a dot at even 10 feet away. They aren't good for distance. Single mode diodes have the best divergence but are not powerful enough. Maybe a gas laser that is very powerful? Not sure how many watts... maybe at least 10?
I'm also concerned that even with a cheap enough laser you will just burn a hole right through it before the entire thing catches fire. I mean I have a two watt 445 laser and it will just burn through paper with a hole and slightly char around it but to actually make it catch something on fire takes a bit of time and that's up close let alone 100ft away.
Maybe a diode array with some corrective optics might do the trick but will be costly. Then again it's cheaper than the 3-5000 you mentioned.
One thing I can say for sure is that it will not be a simple setup. Definitely not a portable... like not even close

Huh, ok. What about putting a laser on a drone? Unlike the blowtorch, it wouldn't require a big drone, which means it would be much cheaper and easier to navigate through branches

 

[Unown (WILD)]

Do you know how shaky a hovering drone is? You couldn't use a laser any better than trying to do a tattoo. If the drone were to fly out of control that laser would be shining everywhere before it hit the ground. You gotta put some common sense into these ideas. This was worrying at first but now hearing the possibility of a multiwatt laser mounted drone is a huge no no.
Even if by some freak accident this could be done then if you were to set fire to these hundreds of pods could set the entire tree on fire. You might as well just get a chainsaw and cut them down at that point.

 

[caterpillarhunter]

Lol that's quite an image. I don't think I did a good job describing the situation. Each tree has maybe 20 nests at most in a bad situation. When one nest is set on fire, remember it's one dry leaf with a few hundred baby (1/4 inch long) caterpillars and silk in it. Even with a blowtorch they never truly set on fire, they smolder and smoke.

But I am confused here. On the one hand, I'm hearing that these lasers aren't particularly dangerous at any real distance, and that they need time on one spot to do anything. So I thought, "Oh, they're not as dangerous as I thought." But now you're giving the impression that I could cause a huge amount of damage with it. I'm sorry, but I'm getting mixed messages here.

As I said at the beginning, I really don't know much about lasers. But I think the big thing I'm hearing is that lasers are not the solution for this problem. Oh well.

Thank you all very much! I really appreciate your help.

 

[Ears and Eggs]

I don't think the drone is a good idea, it's going to be hard to be accurate, and easy to screw up and have the beam shoot somewhere dangerous. Someone's eyes or near an aircraft would be the big concern even at long range, it's going to be too spread out to be a fire hazard at hundreds of feet.


There are purpose built lasers for this kind of use. These are likely to be very expensive, but they use adaptive optics and can focus on exactly the distance you need, and are mounted to a tripod and have remote guidance so you have much more control and less likely to hit something you don't want to.

 

[julianthedragon]

But I am confused here. On the one hand, I'm hearing that these lasers aren't particularly dangerous at any real distance, and that they need time on one spot to do anything. So I thought, "Oh, they're not as dangerous as I thought." But now you're giving the impression that I could cause a huge amount of damage with it. I'm sorry, but I'm getting mixed messages here.

Handheld lasers only burn at close range when focused to a small point (or if sufficiently powerful focused to infinity). However the beam can go for miles and blind anyone that takes a direct hit or reflection. Obviously both scenarios are dangerous.

While we're talking about drones, why not put another form of ignition on a drone and fly it up there?

The original idea with a laser would work fine if you could get any closer to the nests and you could do it without pointing it into the open air, though you might need a little more than a watt to set it on fire. What color are the nests? If they are lighter colored or damp at all it might be harder to start a fire. Keep in mind lasers can also cut things if you get close enough to start a fire, maybe that would work? It would involve getting 10-15ft away from the nest still unfortunately

 

[caterpillarhunter]

Handheld lasers only burn at close range when focused to a small point (or if sufficiently powerful focused to infinity). However the beam can go for miles and blind anyone that takes a direct hit or reflection. Obviously both scenarios are dangerous.

While we're talking about drones, why not put another form of ignition on a drone and fly it up there?

I understand now, thank you.

As I mentioned, there is someone attaching blowtorches to drones. I believe he's selling them for about $4000 each. I was hoping to find a more economical solution.

 

[caterpillarhunter]

I don't think the drone is a good idea, it's going to be hard to be accurate, and easy to screw up and have the beam shoot somewhere dangerous. Someone's eyes or near an aircraft would be the big concern even at long range, it's going to be too spread out to be a fire hazard at hundreds of feet.


There are purpose built lasers for this kind of use. These are likely to be very expensive, but they use adaptive optics and can focus on exactly the distance you need, and are mounted to a tripod and have remote guidance so you have much more control and less likely to lit something you don't want to.

That's so cool! I can't find a price on the website, but I can't imagine that it's in my price range.

 

[Unown (WILD)]

Like others have said it doesn't take much to blind someone whereas it will take considerably more power to do what you want to do. There aren't any mixed messages but rather a lack of understanding on your part which is perfectly normal for someone just getting into lasers.
I should have explained that more but tbh we get so many new members on here asking to do these crazy things (not saying you're crazy) and it gets tiresome. Especially when these lasers are so easy to get.
There's a lot of misconceptions about lasers due to them being in media during the decades such as lasers making sound and in space which you wouldn't hear anyway. Or that they fire in blasts that are slower than a turtle. So it's understandable why it sounds good in thought but not in practice.

 

[caterpillarhunter]

Handheld lasers only burn at close range when focused to a small point (or if sufficiently powerful focused to infinity). However the beam can go for miles and blind anyone that takes a direct hit or reflection. Obviously both scenarios are dangerous.

While we're talking about drones, why not put another form of ignition on a drone and fly it up there?

The original idea with a laser would work fine if you could get any closer to the nests and you could do it without pointing it into the open air, though you might need a little more than a watt to set it on fire. What color are the nests? If they are lighter colored or damp at all it might be harder to start a fire. Keep in mind lasers can also cut things if you get close enough to start a fire, maybe that would work? It would involve getting 10-15ft away from the nest still unfortunately

They're the color of a dead leaf, with some white silk wrapped around it. They're actually quite dry inside, but the caterpillars themselves certainly have moisture in them.

Now that I think about it more, though, neither the leaf nor the caterpillars need to actually burn. Simply punching holes in the leaf would be enough to kill them because it would allow rain to get in, and that would kill them with the next freeze.

Unfortunately, if I could get within 15 feet of a nest, I could cut it down with a pole pruner, and not have to be so high tech.

 

[Unown (WILD)]

What about a bb gun? That would put holes in them. They pretty cheap and you could consider it target practice

 

[bostjan]

Here's an idea.

Wait until night time. Then use your laser to cut the logo of your local pest control company into a piece of cardboard, then shine the laser into the clouds through the cardboard. The pest control company will see their signal and come to your house.

Or just use the telephone.