So just thought I would start a thread dedicated to a neat way to quickly hunt down some of our worst enemies. I rarely see this discussed but it was taught to me by the old timers. Pictures are for reference and not taken by me.
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Very neat idea for bugs.
But I prefer not to know the degree to which my couch is soiled by bodily fluids 
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I was going to add , don’t look into the light and be carefull what you choose to inspect 
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We use UV to scout plants when something is amiss. This year used to check on our eight or so tomato plants that were slowly disappearing. You know something is up when entire branches are defoliated over night. But man, the camouflage on some of these creatures is outstanding. Normal light, nothing. And, these things aren’t small.
Scanning the plants with UV, a dozen hornworms and cocoons glowing in the dark. It works. A good tool to have in the toolbox. Ours is around 365nm.
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I bought one recently. Should have never looked at the carpet downstairs. I found out my dog slipped down there to pee when she was a pup. 
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Hunting worms with a black light sounds like tweaker shit. Sorry. Couldn’t help it.
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But in all seriousness, good trick. I loved hacks. Wait…I am a fucking hack. Ask @shag , he’ll confirm.
One word……. Ewwwwwww!
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NEAT! Didn’t realize bio-flourescence was a thing really with insects! Lots of critters / corals on the reef are bio-fluorescent, and I have two different wave length dive lights for it (one more blue, one is more purple). Its amazing how they just JUMP out at you under “blacklight”. Gonna have to pull them out now and scout both the canna and veggie gardens 
(ps. some people think night dives are scary when using regular bright dive flashlights. I love the effect of diving with JUST the “purple light” and no other lights. Sure its dark, but its a whole other world!)
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Awesome idea to spread the word an ol timer helped me out with this trick this year !
Hornworms can really reek havoc and quick !
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I’ve had great results with this method for the last month or so. Wound up getting a larger flashlight, it helps quite a bit to scan quickly Amazon.com: Lepro 51 LEDs UV Light Handheld Blacklight, UV Flashlight Black Light, 395nm Detector for Pet Urine, Stains, Bed Bug and Scorpions, Battery Not Included : Pet Supplies
Not sure if it messes with the photoperiod so I do it in twilight just before or early dawn.
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Thats actually an excellent point to bring up. Humans just associate bright light with something that can interrupt a photo period, because red lights won’t and they are dim. Well, clearly these are in the “dim” class as well, and many might assume they won’t interrupt a photoperiod.
But
They have used these UV flashlights in diving for a few years now (had my lights 6 years now). And they are noticing a direct correlation with bleached (read: weak / sick) and lower numbers of anemones at several dive resorts “house reefs” (reefs just off the beach of the resort, usually can swim to them), and the decline in anemones directly relates to the timeline and usage of the lights. They are otherwise healthy in nearby areas where they don’t have the UV lights on them on a regular basis, and the decline of them on the house reefs correlates directly to when the resorts started offering “blacklight snorkeling” or rental of the lights. The anemones glow and don’t move much, so they are easy targets.
They have cautioned operators about the over-usage of these lights, especially on close, frequently accessed sites.
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Interesting. I think underwater the natural UV is very significantly attenuated - it’s probable the creatures underwater are less exposed to solar UV and may be more sensitive to it. It’s unfortunate to hear about our inadvertent impact on the reef systems using these tools.
In any case, it’s certainly something that I thought about before I got the big flashlight. The 300-400nm light is diminished by the atmosphere somewhat heavily, but I live at high altitude (~4K feet) where the natural UV is higher. So, during the day, without question, there is a higher amount of the same UV spectrum. I use the relative brightness of it to scan during twilight, and I think the total effect is less plant upset - because it’s bright it’s really quick to scan the plant. With my little UV flashlight, I had to really spend time going over the plant.
I haven’t found any concrete info on what it takes to upset the photoperiod, people use small flourescents to interrupt dark period for early outdoor planting, so I don’t think it takes much. In the abscence of evidence, I’ll stick to doing it on a schedule that would not severely affect flowering anyway - on the edges of natural light, dawn/dusk. I like dawn because it’s the best time to notice problems and do IPM anyway, especially if you are using foliars.
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Thanks for sharing that old timer knowledge 
I ordered a uv headlight right away. First caterpillars of the year were spotted and manually picked. I refuse to spray anything, especially in flower, so this could be a great addition.
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I have found a few small types of caterpillar that don’t show up but the large majority will light up like a glow stick .
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Good to know! Very happy to have stumbled upon your thread when researching ways to deal with caterpillars. Hopefully my order arrives soon and then I hope to not see the whole plant light up 
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