Scale on Two Newly Purchased Saguaros

[Rich-King of Angmar]

Hello All!

I'm the proud plant parent of two saguaros recently purchased online. Overall, they're healthy but they both have scale and that is concerning. In the past I've treated scale with systemics but I'm a little hesitant with these two. The transplanting process was rough, they both weigh ~100 lbs and I replanted by myself and it was a struggle to say the least LOL. I was as careful as could be but I'm sure the roots incurred some damage so I wanted to give them a little time to heal before watering.

However, these scales are tough and will not come off with the rubbing alcohol/cotton swab method. The alcohol definitely loosens them up but I still need to apply some pressure with a little tool to pry them off. Plus, it took me about 1-2 hrs to clean the scale from 1 rib. So I'm not sure if this method is the way to go. But if that's what needs to be done then so be it.

Will the newly transplanted saguaros be ok if I start watering them now so I can apply the systemic?

And just to confirm, rubbing alcohol itself does not kill scale, it just loosens their grip?

Thanks so much!

[esp_imaging]

Photos please! Is it definitely scale, not corking or other scarring?
Also, where are you based?

I'd guess that the roots need some time to recover before watering?
It's possible that aggressive treatment of the scale could be quite traumatic - maybe wait a few weeks to treat it, until the roots have had a chance to recover? If it's a bad infection, it will have established over a long time, so panic measure to remove it may not be justified.

[Rich-King of Angmar]

I'd love to share pictures, thanks for asking.

The first two attachments are of the same plant, before and after application of ispopropyl/H2O mix. The solution really brings out the smaller marks which show up red when wet. They also pop off when I pry them and leave little white suck spots behind.

The third attachment is of the second plant.

Thanks for the advice! Overall they really do seem healthy and happy so I don't want to overdo it. How long should I wait for the roots to rest?

About me: I'm in Brooklyn, NY and the plants are containerized, indoors, and in a south-facing window.

[hegar]

Those are in my opinion not scale insects, but scab. These small, round lesions are often found on columnar cacti and are not pathogenic.
They are the result of some kind of injury, be it of animal origin or some other means.
You can go ahead and just observe your plants. If the lesions are either produced by fungi or an insect, they will increase in size and number (fungus) or increase in number (insect).
Armored scales of the family Diaspididae are easily removed from a host plant. The scale cover can be pushed aside or lifted off the insect that is underneath it with the use of a toothbrush for example. You can click on the tab named "Pests, Diseases, etc." above and take a look, in order to see what scale insects look like.
So, in short: I would not do anything at this time, not even try to remove these blemishes. Your plant will thank you for leaving it undisturbed.
Even when prying off what you believe are scale insects, you do a little bit of damage to the epidermis of your plants. These wounds are portals of entry for plant pathogens. So, please do not do anything further, because it is most likely not necessary and thus beneficial to your plants.

Harald

[esp_imaging]

Agreed. Healed puncture wounds can look like this, from being next to other spiny cacti in the nursery or during handling/transport.

[Rich-King of Angmar]

What a relief! THANK YOU SOOOOO MUCH!!!!

[CACTUSCANADA]

Those are in my opinion not scale insects, but scab. These small, round lesions are often found on columnar cacti and are not pathogenic.
They are the result of some kind of injury, be it of animal origin or some other means.
You can go ahead and just observe your plants. If the lesions are either produced by fungi or an insect, they will increase in size and number (fungus) or increase in number (insect).
Armored scales of the family Diaspididae are easily removed from a host plant. The scale cover can be pushed aside or lifted off the insect that is underneath it with the use of a toothbrush for example. You can click on the tab named "Pests, Diseases, etc." above and take a look, in order to see what scale insects look like.
So, in short: I would not do anything at this time, not even try to remove these blemishes. Your plant will thank you for leaving it undisturbed.
Even when prying off what you believe are scale insects, you do a little bit of damage to the epidermis of your plants. These wounds are portals of entry for plant pathogens. So, please do not do anything further, because it is most likely not necessary and thus beneficial to your plants.

Harald

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