Answer: Probably the most popular home remedy is to swab and daub the pests with a Q-tip or ball of cotton dipped in isopropyl (rubbing) alcohol. Do not use other alcohols, such as ethanol or methanol, that can penetrate the plant tissues and cause considerable damage! The concentration of the isopropyl seems to make little difference; the common 70% available in hardware and drug stores is satisfactory. After dabbing with alcohol, remove each scale, either with your fingernail or with a toothpick. You will need to monitor your plants and repeat the alcohol treatment to remove the tiny yellowish spots which are the recently hatched crawlers. Pay particular attention to the midrib, other veins, and leaf edge areas. Closely monitor your plants to get an idea of the life cycle of the particular species of scale that is your problem, but expect to repeat treatment against the immatures every 1-2 weeks.
Horticultural, mineral, or neem oil solutions smother the insects, as will Insecticidal Soap. So, you have a choice of arsenals but diligence plays the most important part of the treatment and control.
Best wishes with your orchids!
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