I use Bayer 12-month shrub and tree systemic which is Imidacloprid (derived from nicotine, I believe). Works like a charm. There are plenty of indoor plant systemics available, which you should be able to find at a good garden center. The Bayer I use did not previously be recommended for indoor use, but this year it has directions for indoor potted plants. Go figure. I agree that systemics should be used as a last resort, but when carefully used should be "safe". I have three cats who chew a little, but have not had any problems for the past three years.
To kill insects such as scales, leaf hoppers, and aphids and not place harmful toxins in your immediate living environment:
Mix 3 ounces of mild shampoo per gallon of water ( 3/4 oz per quart / liter) and spray down the infected plant. Wash off the plant with clean water a few hours later (keep it out of hot sunlight).
Cheap shampoo such as Suave or VO works well.
Using cheap shampoo works well, as it clogs the holes in the insects' back, which it breathes through, and suffocates them. There is no resistance to suffocating from shampoo coverage, as there is with insecticides that affect the insects' nervous system.
Using deadly toxins to control insects on plants is not worth the risk to family, friends, neighbors, and pets.
This is something I wrote in response to a question directed to me a little while ago. You might find it of interest.
I often see recipes of various mixtures of dish detergents and other ingredients as equal substitutes for insecticidal soaps, but there is a considerable difference between the two. What we refer to as a soap is a substance made by combining a fat with an alkaloid, like sodium hydroxide, which will yield a hard soap - or potassium hydroxide, which yields a soft or liquid soap, like insecticidal soap(s). Of the wide array of fatty acids often used to make various soaps, only a certain few have the insecticidal properties that give them inherent value to gardeners.
With that thought in mind, and contrary to abundant rumors, you should realize you can’t employ common kitchen/dish soaps and expect effectiveness equal to what you can expect from actual insecticidal soaps, like Safer’s, Bonide, and other brands. To be sure, most household soaps/detergents are at least mildly phytotoxic, some to a sufficient degree that they can actually kill plants. Do you know which ones might be safe and which ones dangerous to plants?
One of the most fundamentally important chemical properties of soaps used as insecticides are the number of carbon atoms in the hydrocarbon chains. Soaps with many carbon atoms are long-chain (usually potassium) fatty acids and have insecticidal properties. The fatty acids in insecticidal soaps alter the structure and destroy permeability of insect cell membranes. This causes leakage of the cell contents and quickly leads to death of the insect from dehydration. Kitchen/dish soaps are usually formulated for their grease cutting ability and are usually made from a combination of chemicals that yield a detergent, or in some cases from a combination of detergent(s) and a soap made from short-chain fatty acids unsuited to use in insecticides. These soaps are more often than not phytotoxic and can damage leaves and bark by destroying cuticular wax. This puts them more accurately in the category of ‘herbicide‘, rather than ‘insecticide‘.
Even if the detergent or dish soap itself should prove not to be phytotoxic, dyes and perfumes that are added to these soaps usually are. The frequency with which these additives are altered so the words ‘new‘ and/or ‘improved‘ can be added to the label leaves us unsure whether or not the brand we used today will still cause no apparent issues tomorrow. The soaps for pesticidal applications are safe, tested/proven effective, relatively inexpensive, and a better choice than the home concoctions we so often read about.
Still, it is good practice to test even commercially prepared insecticidal soaps on a part of the plant before spraying it entirely. They work best when mixed with distilled or conditioned water because a precipitate may formed when the metal ions (e.g., Calcium, iron or magnesium) found in hard water bind to the fatty acids in the soap. A short list of some of the plants known to be sensitive to soaps and detergents are J maple, jade, lantana, gardenia, bleeding heart and crown of thorns. Some cultivars of azalea, poinsettia, begonia, impatiens, ferns, palms, and succulents should also be tested. End
I'll leave you to what you'd like to use, but topical insecticides, insecticidal soaps, and home remedies are usually not very effective against scale except those in the crawler stage. Neem oil, over the long term, can be effective because it not only acts as an anti-feedant, but as an oviposition deterrent (anti-egg laying), a growth inhibitor, a mating disrupter, and a chemosterilizer. Azadirachtin, a tetranortriterpenoid compound, closely mimics the hormone ecdysone, which is necessary for reproduction in insects. When present, it takes the place of the real hormone and thus disrupts not only the feeding process, but the metamorphic transition as well, disrupting molting. It interferes with the formation of chitin (insect "skin") and stops pupation in larvae, thus short-circuiting the insect life cycle. It also inhibits flight ability, helping stop insect spread geographically in applications where that is a consideration. Mixing the neem oil in a 50/50 mix of hot water and rubbing alcohol provides some immediate knockdown of most pests and scale in the crawler stage. If you do decide you wish to try neem oil, use only pure, cold-pressed neem, such as that packaged by Dyna-Gro. Steam and alcohol extraction methods destroy the effectiveness of the azadirachtin that makes neem oil so valuable as an insecticide.
Great post, Al. Also to note is that Neem should always be tested on a small part of a plant before using on the whole plant. Some are sensitive to Neem. Never spray plants in direct sunlight. It does work, and I've never found the odor offensive after using it in my sunroom.
With all the hubbub on trying to get rid of scale, I still find it most effective to use a systemic, which seems to be the most effective. In examining the labels of many commercial systemics, some even labeled "organic", a most common ingredient is Imidacloprid, derived from nicotine.
When you buy almost any potted houseplant or summer annuals, they almost certainly have been treated by the grower with with a granular systemic called Marathon. The active ingredient? Imidacloprid.
If the bay laurel were small enough, using Q tips dipped in alcohol takes care of scale in most cases. Otherwise, I would think that insecticidal soaps (see above discussion) and/or horticultural oils would be safe to use; they would smother the scale. I'm pretty sure Neem is OK for food plants.