Springtail look-a-likes eating young leaves, new growths

[whygreenberg]

Hello there!! Been a while since I've been around the OB, but am currently stumped and hope I can get some help/advice.

Something is munching on the young leaves that some of my plants are currently growing, mostly thinner leaved genera (a few Dendrobiums, a Phal, and Sedirea). I can see these little guys, mostly hiding down in where the new leaves come out, and they look all the world to me like springtails. (They are also way to small for me to photograph.) Now, I was always under the impression that springtails don't really munch on the plants, and mostly content themselves to cleaning up algae growth, etc. But these little guys are *definitely* munching and or sucking on the leaves.

I have been doing my usual regimen of spraying the affected plants with a soap + rubbing alcohol solution, a few times a week. And it's been a few weeks now and these little nasties are not going away.

SO. Any advice on next steps, and particularly thoughts on what these little crawlers may be, (or if I'm wrong that springtails won't eat the leaves), would be much appreciated.

[camille1585]

Whatever they are they certainly aren't springtails, those only feed on decaying material. As to what they could be, I'm stumped, even though plants and insects is my field of study. What does the damage look like? Too bad they're too small to photograph, that would have been really helpful.

If your treatment isn't working it may be time to pull out the big guns and hit them with a chemical pesticide.

[whygreenberg]

I can probably try to photograph some of the leaf damage tomorrow. On the Dens, it starts as just little patches of yellowing, but (I guess) as they eat or suck on more of the leaf, the entire leaf eventually yellows. On one Den you can see first some white/silvery pitting before the yellowing sets in. The afflicted Sedirea and Phal show little bands of yellowing—I think because the critters sit down in the crown and as the new leaf grows, eat just along the base of the new leaf. (I dunno if that made sense.)

But the insects I'm seeing really do look like my concept of what springtails look like—they're tiny, black, thin and slightly elongated, and on some you can see two little white spots on the back. I may have been fooled, but I even thought that as I went to put my finger down on one of them, it kinda jumped away a little bit.

Anywho. I'm afraid too that they are currently eating on a couple of Den. laevifolium buds.

[camille1585]

Silvery white markings mean that they are cell content feeders. True suckers get to the phloem to feed, while these will insert their stylet into a cell and drain the contents. The damage and description of the insect sounds like it might be thrips. Do you see some tiny black speckling on and right around the damaged areas?

[whygreenberg]

Hmm...haven't noticed the black speckling (I assume you're talkin' droppings). But I've just done some image googling and thrips do look correct. Blergh.

I always thought that thrips were winged insects, but apparently not?

Guess I am going to have to get more hard-core with the eradication methods. Poot. Do you have any specific suggestions for what to get? I've never used anything more chemical than soap & rubbing alcohol, and have my sweet cat to be mindful of.

Merci merci merci!

[camille1585]

Thrips are winged, but their wings are very fringed and nearly transparent when they have them against their body. Thrips don't frequently fly once they've found a place to feed. Sadly enough I know their biology pretty well after having studied them for 8 months.

Unfortunately thrips are quite hard to eradicate because of their tendency to hide in crevices, like the crown for example. They'll feed on leaves, but flowers are their preferred source of food because of the pollen. Normally the most effective way to kill them is with a systemic insecticide. I understand you're worried about your cat, so I'll see if I can find some effective and plant friendly treatments.

We're still assuming it's thrips at this point. If you can get pics of the damage, that would be great. Won't give a 100% ID, but will help.

[whygreenberg]

Thanks so much, Camille! Didn't realize you were so familiar with the thrip. I will attempt damage photos tomorrow. (Been looking around online a bit more, and the way one of my Dens leaves are becoming deformed seems consistent with some of what I'm seeing.)

[whygreenberg]

Damage pics attached...

In order: A couple pics of a Den hybrid (this 'chid probably has the most damage of any), pic of the newest Sedirea leaf, pic of newest Phal lobbii leaf, and a couple pics from the Den laevifolium.

[camille1585]

The damage looks pretty typical of thrips, although I have to admit I'm not familiar with the insects that may do similar damage. Have you tried increasing the amount of soap in your mixture? You'd have to try to get every crevice of the plant, including drenching the crowns. Application would probably need to be repeated on a weekly basis for a while, since thrips go through a complete cycle in 2-3 weeks depending on the species and temperature.
If the affected plants are near other orchids, you might want to give those a quick spray as well since thrips move around quite a lot.

If that doesn't work, you may be forced to go to chemicals.

[whygreenberg]

Thanks so much for the advice, Camille. I am increasing the amount of soap in my spray, and am going to increase the frequency of spraying.

Unfortunately, I thought that that Den hybrid was worst off—seems like almost overnight my Den laevifolium is a bustling hive of activity. I think you're totally right about them being thrips. I'm seeing larvae now on the laevifolium which are basically same size as the adults but orange colored. A lot more feasting is going down on the laevifolium than I thought. That one may be a losing battle.