Holunder wrote: ↑Sat Nov 05, 2022 5:25 pmIf I do the same in winter while they are dormant in a cool place I probably would risk rot and I am just guessing that the systemic insecticide will not be absorbed by dormant plants. How is the best way to deal with that?
You're correct on both counts -- soil soaks are effective only while the roots are in growth during the spring and summer, doing it in the fall and winter guarantees rot. If you see stem and/or spine mealies, you have 2 options:
- Gently remove them with tweezers. This option can be a bit "labor-intensive" if you find a lot of them.
- Spray the affected plant(s) with Isopropyl alcohol or methylated spirits.
Stem and spine mealies won't tolerate persistently cool conditions, so I don't think you'll see them at all in the winter. Root mealies are another matter -- you've already seen my presentation (thank you for that, by the way!
), so the following quote from
Cactus Nursery in the UK is for people who haven't:
"Root mealybugs (Rhizoecus falcifer) are among the worst pests of cacti and other succulents. They live almost exclusively on roots and the parts of the stem that are below the surface. They are similar to stem and spine mealybugs in that they also secrete whitish, woolly, or powdery wax. Root mealybugs prefer dry substrates.
They multiply particularly rapidly during the dry winter dormancy period. Affected plants look pale, become sickly, and gradually die. Plants damaged and weakened by root mealybugs are especially susceptible to fungal diseases."
Cacti undergo a certain amount of shriveling in winter, and that's normal. The tricky part is knowing the difference between shriveled skin
colors that are normal vs. abnormally pale and/or sickly. Unfortunately you haven't been with your new cacti long enough to know what they should normally look like over the course of their winter shriveling. However, if your gut intuition tells you that things may not look right, unpot the plant and do a thorough root inspection. If you do see a root mealy infestation, soak the roots in warm soapy water to kill the mealies, let the roots dry out completely, and repot the plant in clean,
dry potting medium. (For new growers out there -- as much as you may be tempted into doing it during the winter, don't even think about watering until the next growing season begins.) Regular dish soap is fine, although insecticidal soap wouldn't be a bad idea.
jerrytheplater wrote: ↑Sun Nov 06, 2022 1:13 am
I had Root Mealy bugs in my cacti discovered in January, the heart of my winter. I took them all out to their pots and washed off all of the potting mix. I then soaked them in a 2% soap solution to which I added Malathion according to the label directions. In the US a sprayable formulation is sold by Spectracide. I don't remember which brand I used, but it was a sprayable formulation.
After soaking them, I drained them on newspapers to speed up the drying. I remember I stored the plants in a cool low light room bare root. What I don't remember is if I treated them again to get newly hatched Mealy bugs. Whatever I did worked.
This brings up an interesting question -- if we soak the roots with nothing more than soapy water, will it kill root mealy eggs too? My only encounter with root mealies took place at a time when the growing season allowed me to do Imidacloprid soil soaks, killing the mealies and their eggs in one shot. I've been around my cacti long enough to know what looks normal and what doesn't when they go through the fall/winter shriveling process, so if I see the telltale signs of a root mealy infestation this winter, it'll be time to unpot cacti and knock the infestation down before it goes too far. Such being the case, it's possible that soapy water won't be enough to kill root mealy eggs. When I had my first collection way back in the 1970s, Malathion was the only game in town, and I did soil soaks with it every spring (I still remember that nasty smell). Will it kill root mealy eggs? Certainly, but I'd rather stay away from Malathion, and now that I think about it, I'm leaning toward either insecticidal soap or a solution of water, dish soap, and Imidacloprid. Your 2% soap solution sounds good, Imidacloprid does kill root mealy eggs, so all we need to know is how much Imidacloprid we should add. Here's the recipe I have in mind:
- Per quart of water -- 4 teaspoons dish soap (a little more than 2%, but that's fine), and 1 tablespoon of 1.47% Imidacloprid.
A couple of questions for you, Jerry. #1 -- does the water have to be warm when we soak the roots of infested cacti? #2 -- after you soaked the roots, did you rinse them in running water before you let them dry out? My guess is that rinsing would be counterproductive, although I didn't want to make any assumptions here.