Thrip Damage

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Jun 6, 2006
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Sacramento, CA. Outside w/ Southeast Exposure
I thought it would be useful to post a couple of photos of what thrips can do to one's plants.

This is one of my besseae species, and yes, all of them look about like this. This is one of the worst though. You can see how the leaves have grown in a fashion so that there is a portion that was stunted in growth, making the leaves appear wavy. The second photo shows what the underside of the leaf looks like. Pretty huh?


SlipperFan said:
I didn't know they could do that much damage.

That's why I thought some photos would be useful. It sounded as though people were generally not that familiar with thrips as an orchid pest, and they've turned out to be the worst I've experienced, hands down. I think I probably had them for quite a while before it got warm and the population exploded enough for me to realize what was going on.
Thrips confirmation

I have some besseae hybrid phrags that have similar simptoms that the photos you posted show. The problem is mostly on new growths of second bloom seedlings but some are mature plants as well. How do you know that the problem is with thrips? Others (established dealers) who looked at my problem plants never suggested thrips.
I didn't know what was wrong for a long time, until I saw some bugs moving around. They were nothing I'd seen before, yet I recalled hearing that thrips could be problematic for orchids. I pretty much figured, if the aren't some other orchid pest, maybe that's what they were, so I talked to Likespaphs here, since he's the resident "bug guy" ;) and we agreed that I probably had thrips, based on the descriptions of the bugs and the damage (and the fact that the chemical he recommended nuked 'em!)
I note that there are three heavy duty insecticides for thrips: Avid, Conserve SC, and Orthene. Is any one of these recommended, or do you need a rotation of products?

Also my problem (symptoms as shown on the photos) only seems to be appearing on phrags, mostly new growths. Paphs have not developed the problem. Are phrags more susceptible to thrips than paphs?
you always need a rotation of pesticides to avoid building resistance in the insects. i think conserve is best as it's less toxic, has only a 4 hour rei (re entry interval), and is fairly gentle on plants, though apparent, not on blooms...
there are other pesticides too. one is called botanigard. it's a parasitic fungus that infects the exoskeletons of soft bodied insects. pretty good stuff, the bugs can't really develop a resistance to it. if you use it, though, it'd probably be better to get the wp (wettable powder) instead of the es (emulsified solution) as there is often more phytotoxicity associated with the petroleum products in an es than there are with wp's, which have none.
i don't know which are more susceptible, paphs or phrags, though....
I had problems with sandarianum, purpuratum, philipensis.

I used malithion to get it under control.

Problem Phrags

I'll try posting some pictures typical of the problems I am having with my phrag collection. First the new growths start out OK, but soom they acquire a definite yellowish cast and the downhill process starts.

Later the problem is exacerbated and the whole plant is in decline, although as shown the roots are fine. At this point or shortly thereafter I usually discard the plant. Neither Physan or Phyton 27 seem to help.

I use RO water with Peters 12-3-15 RO type fertilizer and pH adjuster at about 100 ppm N. Will try dropping that down. It is a new problem to me. I have been growing phrags successfully for several years without a problem. Any suggestions?
Hmmm, I haven't had quite as much yellowing, but I agree, that second photo looks quite similar to the issues I've been having that were thrip related. I would look really closely into the crown of the plant. The damage seems to start deep in there so that by the time the leaf has grown out you can really see the damage that's been done. I've also had new leaves just break off (as if they were weakened from sucking/chewing) when I go to inspect the crowns.

Curious to see what others might have to say.
I just got rid of thrips a couple months ago in my collection as well. Couldn't believe that damage they did and how fast they spread. Where they came from is still a mystery but I suspect they came in on a plant I bought at a show in the spring. I nuked them with Orthene and that took care of things. If you find them in your collection gt rid ofthem fast....they can do so much damage in a short time.:mad:
i would just check in the bracts of the leaves to make sure there are no long-tailled mealybugs in there
Chas, do you spray your Phrags with Physan regularly, or do you ever use Pro-Tekt in their watering solution? I've had the same symptoms (as your first photo) on a few Phrags, and am beginning to suspect that one or both of these may be the culprit. But I'm still gathering data at this point.

Matthew Gore
very interesting Heather, thanks ! a vendor here showed me similar damages on plants and said they were indeed caused by thrips. That was on paphs however. Still I find it hard to know if the sort of brown "crust" on the leaves is due to thirps themselves or to treatment against thrips.....
gore42 said:
Chas, do you spray your Phrags with Physan regularly, or do you ever use Pro-Tekt in their watering solution? I've had the same symptoms (as your first photo) on a few Phrags, and am beginning to suspect that one or both of these may be the culprit. But I'm still gathering data at this point.

Matthew Gore

Matthew - please keep us posted on your research - I am not a Physan user really, but I do use Pro-Tekt....more frequently with my Paphs but still...

Brian - re: the Conserve, FWIW, one of the three plants I sprayed that was in bud bloomed just fine. The other two were significantly more stressed to begin with so it may be purely circumstantial that I sprayed and lost two sheaths.
One sure way to tell if the damage is due to thrips is to look for silvery colored trails and little black spots on the UNDERSIDE of the leaves. They seem to prefer Phrags to Paphs, but will attack any tender seedling or flower. A relatively non toxic control that has worked for me is pyrethins. I will try to find a picture of what I am talking about.