New buds falling off a healthy plant

[CatE17]

Help! All three of my orchids have recently been repotted and are in rude health, especially the one in a glass pot which is throwing out new spikes like crazy but all the flower buds that emerge are turning yellow and falling off. The leaves are a healthy green. I'm watering with tepid water one a week and they live on light windowsills. PLease help!

[Ray]

If the buds are yellowing and falling off, the first thing I'd look for is mites. They are difficult to see, but may have telltale webbing associated with them. Wiping the underside of the leaves with a dry tissue will sometimes develop a yellow or red "smear", indicating their presence.

The second thing that comes to mind is ethylene. It is released by ripening fruit, growing tomato plants and their relatives, or by incomplete combustion of fossil fuels, usually as a result of a dirty, or improperly-adjusted burner.

[CatE17]

Thanks Ray. I'm not sure it's your second suggestion as the plants aren't near fruit and/or sources of fossil fuel; however, I had a look at the undersides of the leaves and while two seem to be fine, the third has a ring of sticky drops round the underside of each leaf! When I work out how to post photos I will do so but do you have any idea what that might mean in the meantime?

Re. the other two, should I be feeding them? Would that prevent the bud drop? I'm just wondering if the reason that the buds form well then suddenly yellow and drop off is because the plant doesn't have the reserve to sustain a flower. Thank you

[CatE17]

As you see, the leaves of one plant are covered with this rather revolting sticky stuff although the spike seems healthy enough. The picture of the whole plant is to show that about 6 weeks ago there was only one spike-the rest have all suddenly sprouted since then and it seems healthy apart from this bud drop problem. Any help much appreciated!

[Paul Mc]

WOW, yeah you've got something going on there. I'll leave it to others who are more experienced to help you with determining the pest you might have. Best of luck to you though on that front.

So, you say you repotted it. What did you pot them in, media used, etc... I'm assuming they were not looking sad when you got them, or had any visible issues such as those beads under the leaf. I am also assuming all three are phalaenopsis orchids, is that correct? I'm wondering if the move from whatever medium it was originally potted in may have shocked the plants a bit. This can happen if it's going from a medium that retains water really well to one that does not retain much at all. I'm not saying this is what has happened, but I am putting it out there as something for you to consider.

I don't want to scare you with this next one though I do feel you should be aware of it. Phal's tend to produce spikes and keiki's (babies) when they are in danger. If it's producing spikes like crazy then this might be a sign. I'm surely not saying this is what is happening, but I have had this happen to me on a few phal's when I first started and was learning how to grow them.

[Merlyn]

Use a 5x magnifying glass or loupe and look under the leaves closely. Like Ray, I suspect mites.

[johnblagg]

you have definatly got some sort of bug on them.some sticky sap on the edges of leaves and buds is just normal but when the spots are all over the leaves like this is then it is from where the inscets have pierced the surface to feed

[Connie Star]

Welcome to Orchid Board! You've come to the right place.

[CatE17]

Gosh, you are all so knowledgeable! This is a whole new world for me, I normally deal with vegetable plants.... So I couldn't see any insects on the affected plant but enough people told me that it would be mites to make me go and buy some insecticide. Just started using it, I'll keep you posted! Re. the other two phals with the bud problem, I'd repotted them in normal soil which, I must say, they didn't seem to mind at all apart from this bud drop problem. Then someone pointed out that they probably didn't much like being on an English windowsill in the middle of winter! I've moved them to where they can still get some sun but they aren't exposed to so much cold and they seem to like it as they haven't dropped any more buds and the existing buds are growing and are about to open. Should I repot them in this special orchid compost I've bought or leave them?