Scale on my cymbidium

[bil]

Originally Posted by Mainwaring

You can also try Hydrogen peroxide 3-5%
It is not poisonous at all, for you, the plant or the environment. You might need to apply it a few times, but eventually it will do the job. It kill all bugs on a plant, including fungus

The only problem I have with peroxide is that it is an indiscriminate oxidiser. It will destroy plant tissue as easily as it does pest.

[Whimgrinder]

I believe that there is often a disadvantage to thinking that you are somehow doing yourself a favor by embracing the use of "organic" alternatives to engineered pesticides. Chemistry that has been carefully engineered to do a specific task often means using far less of the ingredient to do the job, and the risk of damage to your plants is far less as well.
For example, dumping sulphur on your plants may prevent fungi from happening, but the risk of damaging your plants is far greater, and you don't get the systemic benefits of a fungicide designed for the task. The "home remedy" approach to pest control is often (note that I don't say "always") far less ideal than the smart, careful use of chemicals specific to the problem. This is especially true when you are faced with dealing with a serious, persistent pest like Scale. You could spend the next decade hosing your plants down with alcohol and/or H2O2 and never rid yourself of the pest. It's important to remember that insects like Scale have a shell that is very effective at keeping the creature inside from being exposed to chemicals. This is why systemic pesticides are pretty much mandatory for the eradicatin of scale: they have to ingest it through the plant sap.

If you have to pound a nail into a board, which would you prefer: a hammer, or a twenty pound chunk of granite?

[estación seca]

Imidacloprid is a nicotine-like chemical. Nicotine is a natural, organic product that is far more toxic than almost anything humans have invented. Insects have not become resistant to nicotine through what seems millions of years, except for a few genera of beetles and butterflies that feed on Nicotiana and relatives. If not for the ubiquitous presence of tobacco mosaic virus, chewing and smoking tobacco extracts would be extremely effective insecticides.

Mammals are not especially sensitive to imidacloprid so it is somewhat less dangerous than organophosphate insecticides. Nevertheless, when using sprays, be sure there is excellent ventilation, and wear mask, eye protection, long clothing and gloves.

By the way, pyrethrum is a natural, organic product that acts the same way organophosphate insecticides like malathion act.