Let it cure (dry) for several weeks. I wouldn't cut it in two, but you could -- then let cure for two weeks. After two weeks, stick the end in a pot of very well draining fairly dry soil. Do not water until roots are beginning to form. There's lots of information on-line about propagating epiphyllums from cuttings. This post was edited by dave_in_nova on Wed, Aug 13, 14 at 12:55

Those look to be 'Iceberg' roses, the best and easiest roses for Southern California, which might shock you since you seem to be having trouble with them. Most plants that flower need to have the old flowers removed. You don't need to remove all the flowers individually, you can take off the whole cluster when most of the flowers are finished. The bugs you are talking about are probably aphids. Stop spraying them with insecticide. It only makes things worse. Spray off the aphids as much as possible with a strong blast of water from the hose. In time, predators will take care of all the aphids if you don't use insecticide. Insecticide kills the beneficial bugs just as fast as the bad ones. The white stuff on the foliage is powdery mildew (PM). It's been a late and rainy spring and PM is rampant this year. Make sure your roses are getting enough water, because thirsty roses are more vulnerable to powdery mildew. As summer comes on the PM will go away. You could shorten the roses a little by cutting them back and that will remove a lot of the PM. It looks like someone has trimmed the roses into a hedge like shape. They are in a very narrow bed. Think about widening the bed in the future. It will look a lot better and you will have less lawn to mow that way. Congrats on the new house!

This time of year in cold weather zones you don't deadhead to encourage bloom production because it is too late in the season for this to happen. It is best to prune for the end of the season which means get rid of excessive leggy growth and bad and old canes. The good canes you leave will get thicker and heavier and hopefully will mostly make through the winter and be the basis for the rose next year. New growth begun at this point will likely be killed by the winter.

It sounds like relations with your brother aren't so great, either, or else he has a bad conscience about his wife's behavior. For the sake of family peace, I'd be tactful, but I'd be clear and firm: express a willingness to share cuttings and explain how to get them to root, but make it clear that your sister-in-law is not to take cuttings without your permission, so that she doesn't damage rare and vulnerable plants. It might help if you explain that these roses didn't come for the nearest big box store, as lagomorphmom said. If you can work in an implication that she'll have a better garden in the long run if she has you as a friend and gardening ally rather than as an enemy, so much the better, but unfortunately a lot of people don't understand this line of reasoning. Good luck!! Melissa