Mulch a small spot in your yard as the dog's toilet. Collect the dog's wastes and move them to this area. When the dog uses this spot, reward him generously with praise and treats. We planted it, and it is now nearly 9 feet tall in a pot in our solarium. The plant now has spider mites, but it is very difficult to spray a 9-foot tree while it is indoors.
Mites love citrus plants but hate high humidity.
Mist your grapefruit often if you keep it indoors through the summer, and occasionally take it outdoors for a quick simulated thunderstorm from your garden hose. If none of these measures keeps the mites under control, you'll have to spray them. Nothing is more effective in killing mites than horticultural oil. Oil kills all stages of mites from egg to adult, so one very thorough spraying might be all that is needed. Use it at half the rate specified on the label.