Ask Mr. Smarty Plants

The very first question we need to ask is, is this plant being grown in a pot outside?  We followed this plant link Echinocereus stramineus (Strawberry hedgehog cactus) to our webpage on this plant and learned that it cannot tolerate temperatures below 50 deg F. Plants in pots are only protected by a thin layer of potting soil and a thinner layer of plastic or terra cotta and are more vulnerable to freeze damage. So, if the pot was exposed to temperatures under 50 deg, especially for several hours, that may explain the browning.

The next thing we would consider is your statement that you pruned back a plant that was covering the cactus. Normally, that would be considered a good thing, because this cactus needs full sun, and may not have been getting it. But maybe the sudden removal of that shade has caused sunscald.

From Cactus Art, here is more information on Echinocereus stramineus (Strawberry hedgehog cactus), including this sentence:

"Rots easily; it is sensitive to overwatering (rot prone) needs a very good drainage to avoid rotting, Keep drier and cool in winter." 

Somehow, since the plant is browning from bottom to top, we suspect that rot may be the answer. When we searched on "treating rot in cactus," we found this site, Cactus Expert 2. At the middle of the page is a discussion of how to identify rot in a cactus and what to do about it. From CactiGuide.com is a website on cacti pests and diseases.

We truly salute your bravery. Hope you have some good heavy leather gloves.