By Stan V. Griep
American Rose Society Consulting Master Rosarian – Rocky Mountain District
Spider mites can be tough customer pests to deal with in the rose bed or garden. One of the reasons that spider mites become a problem in the garden is the use of insecticides that kill their natural predators. One such insecticide is carbaryl (Sevin), which pretty much wipes out all natural predators of the spider mites, making your rose bush a virtual playground for these annoying pests.
Symptoms of Spider Mites on Roses
Some symptoms that spider mites are at work on your roses would be discoloration or bronzing of the leaves/foliage and scorching of leaves. Left untreated, foliage injury can lead to leaf loss and even the death of the rose plant. When the spider mite population on roses is high, they will produce some webbing on the plants. It will look like a rose with spider webs on it. This webbing provides them and their eggs with some protection from predators.
Controlling Spider Mites on Roses
To control spider mites by chemical means will require what is called a miticide, as few insecticides are effective against spider mites and many can actually make the problem worse. Most miticides will not actually get to the eggs so another application 10 to 14 days after the first application will be required to gain control. Insecticidal soaps work well in controlling spider mites too, just as in the control of the tent caterpillars, but will typically require more than one application.
A key note to make here is that no insecticides or miticides should be applied to rose bushes or other plants during the heat of the day. The cool of the early morning or evening are the best times for application. Another very important rule is to make sure the plants and bushes have been well watered prior to the application of any pesticide. A well hydrated plant or bush is far less likely to have an adverse reaction to the pesticide.