Mealybugs cannot be controlled with a single application of alcohol/water. The life cycle of these insects dictates that you'll have eggs, nymphs, and adults at the same time and some of those life stages are difficult to control. Plain water will do little or nothing to control mealies. Wiping them off may even spread the eggs or nymphs via the cloth. I prefer an alcohol and water mist applied every few days, even after you cease to see the insects. You might also try a horticultural oil, so effective against scale (mealies are extremely closely related to scale, if not a type of scale insect) insects.

Yikes! You've got a challenge ahead of you, but I don't need to tell you that. I'll suggest what I would do if this were my plant. First, I would cut the fern all the way down to the soil level, or nearly so. Then, I'd gently pries it out of the container so that I could scrub the pot and give the root system a little examination. Back in the pot (with little disturbance at this time of year), I'd examine what little sticks are left for any sign of mealies. As your fern regrows over the winter, you'll need to be very vigilant about inspecting it frequently. Since ferns can be spot treated with alcohol, be prepared to do battle. You can also use insecticidal soap on ferns as long as you follow the directions. By the way, it doesn't sound like you 'won the battle' with the cacti. ;-) I'd not let them anywhere near the fern. By the way, I've used an alcohol mist quite successfully on cacti that I have grown. You might try it on your cacti, in case you're missing the small eggs and crawlers. I'll not suggest the alcohol mist for your ferns, but only because I haven't used it on that plant. Perhaps someone else has experience with that.

We need to know more about this tree. How long have you had it? How long has it been in the same container? What kind of potting medium do you have? Does your greenhouse remain steadily at 71 or is that a day OR night temperature? Is your plant watered adequately/properly? Insect infestations can cause stress for a plant. They have to use considerable energy resources to withstand and recover such attacks. My favorite method of mealybug control on citrus (and most other plants) is to keep a misting bottle filled with a solution of one part isopropyl alcohol to three parts water so that you can attack the critters on a regular basis. You can also go after them with a cotton swab dipped in the alcohol out of the bottle PLUS mist them. Don't use the alcohol on bright, sunny days...or anything else, for that matter.

White fly maybe? I have the same thing, but I can't spray (butterfly garden) and they don't seem to be causing any problems. I just blast them with the hose. I don't think that either mealy bugs or white fly would cause this. My daylily repeat bloomer had the same problem this year. We had very strange weather, though, and I thought it was from the temps fluctuating so much. Susan