Question
After moving my cacti outdoors for the summer, I noticed that there is a spider-web looking material on a couple of them and it looks like they have been eaten away in places.  Would this be a spider mite infestation?  If so, what product can you recommend to use on cacti to kill them but keeping the cactus healthy and looking nice?  

Answer
Dear Marika,

It could be a spider mites. If it is, I would use a "natural" control method so that the plant does not have further damage. The following website has some good control methods, please check it out.

http://www.ext.colostate.edu/PUBS/INSECT/05507.html

Hope this helps, good luck.

Sincerely,

Greg