Copper Soaps: what orchids should it be used on

[cluelessmidwesterner]

Hi All,

I have a Oncidium complex hybrid that has scale. I remember reading that certain species and hybrids of orchids you shouldn't use copper based products on but for the life of me I cannot find the article nor remember which type of orchid it

[SouthPark]

I have definitely seen some online material mentioning issues with copper and thin-leaved orchids ----- and saw comments about issues with dendrobium and copper. It probably depends on what type of orchid it is, or even what type of dendrobium ----- that's if copper really does cause problems with them.

I tested copper solution - sprayed on all leaves of a Den. moschatum - and no problem with it. I sprayed quite a fair bit too. I used Yates liquid copper.

Click Here.

And still no problem with it even today.

This link here says something about dendrobium ---- as in not good for dendrobium - but doesn't say why. It also mentions possible issue with 'other sensitive genera', which is quite vague. https://staugorchidsociety.org/PDF/O...ySueBottom.pdf

[Roberta]

One thing to keep in mind... match the treatment to the problem. Copper-based treatments are fungicides and bactericides. So these could be useful if you are treating a fungal or bacterial situation. Some types of orchids are more sensitive than others, don't know which are the sensitive ones. (Like some Dendrobiums, but not all)

If you are treating for scale, however, you want to be using an insecticide, favoring a systemic formulation. The only benefit a "copper soap" would have would be the "soap" part... which has no lasting effect. Use a product that is designed for scale and other sucking insects.

[cluelessmidwesterner]

Thanks everyone.

Roberta this Oncidium has had scale since I purchased it a year ago. I've total changed the media, used insecticidal soap, spot treated with alcohol as soon as I see them but the little blighters keep coming back. Because of the scale I have a lot of leaf spotting. I know some Oncidiums do have leaf spotting but it could be due to fungus.

I'm a bit leery about using systemic product because 1. it's in s/h and 2. my resident felines occasionally get at my orchids and if I don't catch them in time will "graze" on the leaves.

[Roberta]

Scale is tough... if you treat with soap (or neem oil or any other topical treatment) you might kill most adults ( but they also have hard shells to protect themselves) but you won't get the eggs. So at the very least, you will need to treat at least once a week for several weeks. (with mild treatment like you're using, maybe make it part of your weekly routine...) You need to nail the successive generations. And it only takes one survivor to replenish the population. So I'm afraid that you have a sisyphean task there.

[Ray]

The fact that they are in semi-hydroponics plays no role in the treatment or use of systemic insecticides.

If you really want to eradicate them - and you should, as insects are a major vector in disease spread - you need to treat the plants 3 times at one-week intervals, as Roberta suggested.

Find a way to isolate the plants from your cats for a month, even if the growing conditions aren’t ideal in the temporary location.

[HardWood]

If you have a very bad, resistant scale infestation, you may need to immerse the entire plant and pot and media in a solution of oil. yes you will lose the flowers but you can save the plant. yes you do need to do it three times one week apart. the oil will suffocate the adult scale. scale can anywhere on the plant including the roots. Follow the dilution on the bottle. You may need to treat your entire collection. scale can crawl when they are young. this treatment is drastic but it does work. Immersion covers the entire plant not just the leaves and the top of the media.

[SouthPark]

For scale - could possibly try imidacloprid, and see how it goes. But noting that this substance is deadly to bees.