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Hortiscope: Use a facial sponge, rubbing alcohol to control scale

Q: I have a problem with scale. I have used a detergent and water mix and made sure every little bit got on the bulbs. However, I still have the problem. What can I do to get rid of these pests?

A: Scale insects are difficult to control. It takes a concerted effort on your part to bring their number down to a level that will not be harmful to the plant. If your attempt with the detergent and water did not work, then likely you are dealing with what are known as armored scale.

Try getting a hold of a facial sponge that is not treated with a cosmetic product. Use the sponge, along with rubbing alcohol, to try to wipe the pests out. Normal pressure (not hard pressing) such as you would use on yourself should break the barrier and kill the scale.

Keep in mind that the alcohol will kill these pests, but their bodies will remain. Getting the armor coverings off likely would do more damage to the plant. Judge your success or failure by whether or not the scale population seems to be stabilized or increasing. If it is increasing, then dump the plant and get another one for the holidays. Try a small section of the plant with this alcohol rub to be sure there is not going to be a negative reaction.

Q: I neglected to ask about the red splotches and streaks on the leaves of many of my older amaryllis plants. I just invested in new bulbs and don't want them to become contaminated. How can I treat this redness in the greenery?

A: I think this may be a virus that is embedded in the amaryllis plants. If that is the case, there is no treatment for it. However, while being a distraction, the problem may not be lethal to the plants. To be sure of what the problem may be, a lab culture needs to be taken.

To contact Ron Smith for answers to your questions, write to Ron Smith, NDSU Department of Plant Sciences, Dept. 7670, Box 6050, Fargo, ND 58108-6050 or e-mail