It looks like you have a case of root mealybugs. I have a similiar problem and I don't know exactly how many plants are affected so I may have to use some serious chemicals. In your case if you only have a small number you can unpot them, spray off all the soil and bugs with a strong hose sprayer and then soak the plant in water heated to 120 F. I would then let the plants rest in a shaded area or the garage for a few days to let any damage to the roots scab over before replanting. Use a temperature gauge to be sure the water isn't too hot. Dispose of the infected soil. Try to avoid putting plants back in areas where they could be reinfected from infected plants. I had placed a number of potted succulents togerther in a large saucer and all the plants were infected by mealybugs traveling freely in the saucer. I just read that plants housed in greenhouses with wire benches have much less problem with mealybugs. Unfortunately I just finished building new wood benches! Good luck and I hope you can save your plants.

if you just bought them.. return them ... and have a talk with the seller ... and perhaps the county Ag department ...

if not a new purchase ... you seem to be on the right track ..

i would probably go with a systemic product ... if there is one labeled for this ....

ken

As we do not have root mealybugs in my area, does anyone know of a species with a similar appearance?

@gardengal48 (PNW Z8/9) Thanks

You are convinced this is the result of insect herbivory and not evidence of something fungal? Have you identified active insects?

Many entities package Imidacloprid in a 1.47% solution to be used as a soil drench.

If you mix 2 tsp of the 1.47% solution to a quart or liter of distilled water which has been acidified slightly with white vinegar (Imidacloprid is subject to alkaline hydrolysis, which limits its effectiveness), then make sure you moisten the entire soil column, it would quickly rid the soil of any unwanted bugly uggers that chose your containers as the hangout where their dirty work is made manifest.

Al

@tapla (mid-Michigan, USDA z5b-6a) The photo I linked in the original message has three white insects in the middle of the photo.

To remove the issue of starting water pH, what is the target pH of the diluted solution? I can just keep adding white vinegar until that pH is reached without needing to worry about exact amounts.