The most powerful of the systemic pesticides doesn't need to be used against scale on indoor plants. Entry level organic pesticides such as horticultural oil or insecticidal soap get the job done, slowly but surely and safely. The oil may need a summer and two winter applications. It's particularly effective against the egg stage in the scale life cycle.
Insecticidal soap may be home made or store bought. Basically, it's just dish washing [not dishwasher] soap and water. It's particularly effective against the soft bodied crawler stage of the scale life cycle.
In coming up with a battle plan, it's important to identify the particular plant and the particular scale. In fact, there are many different kinds of scale. Generally, they ultimately respond to the above mentioned treatments. But there are exceptions. For example, insecticidal soap tends not to be effective against Japanese, lecanium, oak kermes, obscure, tuliptree or wax scales.
Also regarding a battle plan, it generally isn't advisable to use pesticides inside. The problem lies in their residual nature. Specifically, different pesticides last different amounts of times after their application in the environment. But horticultural oil and insecticidal soap aren't long lasting. That's why they tend to need a couple of applications to do the job.
You can buy them from a number of plant catalogs or buy the plants/bulbs online. They come in red, yellow and white.
This is like asking why do Mexican eat tacos. The history plays big role where the french has contributed the revoluiton on wine. They have been to ups and down of the wine culture. The staple drink has been evolved there as some of the drinks have been created. The soil itself in France has very suitable nature of abosrbing water capacity. The wine need good limey stone character and soil which can absorve water at max. The bottle of wine need 300 bottle of water iteslf. The french has been very keen with the idea where they have separate appellation and striction of growing grape varities in certain region. That may be reason why they focus on growing particular grape varities for example........bougrone stand more for pinot noir, where as chablis ofr chardonnay.
The certainly history and culture plays a good role. It is one of the major reason why french make wine...for french day without a wine is like day without a sunshine.
sommelier Sandeep Kumar K.C.