This time it's scale

[fanaticactus]

After a full year of trying to eradicate scale attacks on three Epis (which have never flowered--any wonder??), I finally chopped off as many leaves/stems as possible, each 4" - 6" long and will try to root them. I've used rubbing alcohol on cotton balls and paper towels to remove all visible scale "shells". Some I had to gently scrape away with a knife blade. By the small dark spots left on the stems, I can see where the insects have been sucking out the juices. My question is: I don't know where scale insects lay eggs (if, in fact, they do). Would it be inside the stems? If so, will they keep hatching and anchor themselves on the stems again? If I keep on with the alcohol rubs, will I eventually wipe out their population? Is an insecticidal soap effective on them as well? I'm in no hurry to root them.

[Steve Johnson]

After a full year of trying to eradicate scale attacks on three Epis (which have never flowered--any wonder??), I finally chopped off as many leaves/stems as possible, each 4" - 6" long and will try to root them. I've used rubbing alcohol on cotton balls and paper towels to remove all visible scale "shells". Some I had to gently scrape away with a knife blade. By the small dark spots left on the stems, I can see where the insects have been sucking out the juices. My question is: I don't know where scale insects lay eggs (if, in fact, they do). Would it be inside the stems? If so, will they keep hatching and anchor themselves on the stems again? If I keep on with the alcohol rubs, will I eventually wipe out their population? Is an insecticidal soap effective on them as well? I'm in no hurry to root them.

I believe that would be armored scale, and yes -- they lay eggs. The same Imidacloprid soil soaks you'd use on mealies will also be effective against armored scale and cochineal. I have zero experience with jungle cacti, so I don't know if Epis keep growing when they stay warm enough in Winter. If so and you have yours under the right growing conditions for it, you should be able to apply the systemic now. If not, then you'll have to go after scale infestations the hard way before everything wakes up in Spring and they're ready for soil soaks. (I have my doubts about the effectiveness of insecticidal soaps on scale. Then again, I don't have any cacti that are vulnerable to it, so this is only a guess on my part.)

[fanaticactus]

What about the eggs from scale insects? Where are they and how do I get rid of them?

Steve, I have another systemic I used once on my entire collection probably 3 or 4 years ago. I don't know if it poses the same environmental hazards. The one thing I DO know is that the overpowering smell to it is enough to knock anyone off their feet! But I know I didn't have a single problem that whole growing season after just one application in the Spring. It's name, copied exactly from the label is (are you ready for this?): O, S-dimethylacetylphosphoramidothicate, in a 9.4% solution. It's from Bonide. Do you know anything about it?

[Steve Johnson]

What about the eggs from scale insects? Where are they and how do I get rid of them?

Steve, I have another systemic I used once on my entire collection probably 3 or 4 years ago. I don't know if it poses the same environmental hazards. The one thing I DO know is that the overpowering smell to it is enough to knock anyone off their feet! But I know I didn't have a single problem that whole growing season after just one application in the Spring. It's name, copied exactly from the label is (are you ready for this?): O, S-dimethylacetylphosphoramidothicate, in a 9.4% solution. It's from Bonide. Do you know anything about it?

Female scale insects keep the eggs in their bodies. When the eggs hatch, they become crawlers and move around on the skin for a suitable place to attach. Imidacloprid basically scrambles their tiny nervous systems. Toxicity from the plant's juices will not only kill the scale, it'll also break their life cycle.

Now, the problem with Imidacloprid is that it also does a number on the nervous systems of bees when they lose the ability to make their way back to their hives. When that happens, they'll die -- hence why colony collapse disorder has been a major environmental concern due to the use of Imidacloprid in agricultural applications worldwide. While I don't want to minimize that concern, my understanding is that bees are the only beneficial insects targeted by Imidacloprid. (I don't want to be responsible for spreading misinformation either. If anyone here on the forum is aware of toxicity to other beneficial insects, by all means please correct me!)

My history with cactus growing goes all the way back to the 70s, when Malathion was still acceptable for home use in California. Talk about stinky! I still remember the smell of it when I was soaking my cacti as a preventative every Spring. Funny thing to find out many years later that Malathion doesn't act systemically on mealies. Can't tell you anything about the Bonide product you mentioned, since there's no way in heck I'd see it here in California. Knowing the state's environmental regs these days, I think it's only a matter of time before I won't be able to get Imidacloprid either.