I had this cactus(unidentified)for a couple of years, on an east facing window(indoor)
a few days ago i started to notice these white patches, and difference in color between the 2"poles" of the cactus
can you help?
Hi Amjad, the difference in the color is normal; the top of the plant is getting more light, so it's darker. I don't know if that is a cause for concern, unless the base starts to get soft as well.
In this case, it might mean that you have either been overwatering or it's in the wrong kind of soil.
The white patches are odd.
Are these dried out parts of the skin of the cactus?
They look like scorch damage, more than anything. If your sunlight is really intense, and through a window, this could be what's happening.
Move the plant away from the window a bit, if possible, or put a thin curtain between them and the window for a bit of protection.
Although these plants require bright light, when it's magnified through a window, it can burn the tissues.
Alternately, (because I can't really see enough detail) if these are actually fuzzy or waxy, you most likely have mealy bugs - I'm not sure this is the issue, because mealy bugs generally cluster around the aureoles and spines of cactus, not out in the middle.
Check this by seeing if you can scrape them off. If this is the problem, you should be able to use a toothpick or similar and scrape them off, or use a Q-tip with rubbing alcohol (isopropyl alcohol) to dab them.
This removes the waxy coating and kills them. There are very few sprays that are recommended for cactus, so follow the instructions if you're going to try this.
Hope that helps,