Spider Mites are not insects but minute arachnid relatives of spiders that live on the underside of rose foliage. The first sign of spider mites will be a lightening of the lowest foliage as the mites suck the sap from the leaves and other tender parts and can eventually defoliate the plant. You may also see many little webs (webbing) and eggs on the underside of the leaves. You can check for spider mites with a sheet of white paper. Shake damaged leaves over the paper in the sun. If tiny, rusty dots start to move, you have spider mites.
Controlling spider mites with chemicals can be used, but there are two alternative methods. The first choice is to select rose cultivars that have good spider mite resistance. Second, you can use a water wand with a rose-head attachment (like a showerhead) to wash off the underside of the rose foliage every one or two days until there is no problem. It works, so be sure to try it for at least a couple of weeks before selecting spider mite chemicals, which are the third option. There are several miticides available, some more effective than others. Miticides that do not kill the spider mite eggs must be sprayed at frequent intervals for three weeks to eliminate the mature and hatching mites. Eggs will hatch in two to three days at 75 degrees and above. Insecticidal soap and insecticidal oils also work for the control of spider mites. Remove the affected foliage before spraying and direct the spray material to the underside of the foliage.
Mites can become resistant to a chemical, and it may be necessary to change miticides from time totime. Spraying before winter protection is advisable as mites winter over in sheltered spots in the garden. Because insecticides used for other rose pests also kill the natural enemies of spider mites, diminish the use of broad-spectrum insecticides and only spray insecticides when necessary.
Utah Rose Society