Roses are a spectacular blooming plant that require some specialized care. The plants come in floribunda, hybrids, grandifloras and even little tea roses. The same basic care is necessary for whatever type of plant you have. Roses need well-drained sandy soil, at least half a day of sun and good organic matter for nutrition. Rose food is a good addition, and most standard rose foods contain a systemic insecticide. There is some debate as to whether the systemic is necessary in all cases, as it can kill beneficial insects.
The biggest problem on roses is pest damage. There are two main types of pests: sucking and chewing pests. Sucking pests will cause discoloration or necrotic spots on leaves, wilted foliage, deformed leaves and honeydew (which can cause sooty mold). Chewing insects will leave holes and severed stems, as well as cause wilting and discoloration. If your rose shows none of these symptoms you probably do not need to use a systemic to control insects.
Fertilizer is an easy way to boost nutrients in your garden soil. Fertilizers are made up of three basic minerals: nitrogen, which is important for plant growth; phosphorus which enhances root systems; and potassium, an important mineral for bloom production. Roses need all three, but when buds are forming it is important to enhance potassium levels to achieve the maximum number of flowers. Most commercial rose food contains systemic, so it's important to know if you really need it or not to avoid harming the good garden insects.
Fungicides and insecticides can be systemic. They are applied to the root area and worked into the soil, generally as a rose powder or "dust." The systemic gets taken up through the roots and pervades the entire plant. Any sucking insect that ingests the sap of the plant will be poisoned by the systemic chemicals. Similarly, any fungus that is attacking the rose will not be able to grow in the inhospitable environment that the systemic fungicide creates.
Aphids are one of the most common pests on rose bushes. They will breed quickly and suck on all parts of rose plants. They also exude honeydew, which will cover the leaves and cause sooty mildew. Thrips, mites and scale are also common on rose plants. Leaf hoppers (tiny grasshoppers) and leaf cutter bees do much of the foliage damage, excising chunks of leaf tissue and making jagged edges on foliage. White fly also secrete honeydew. Leaf-feeding beetles and caterpillars are foliar feeders that will ruin the attractiveness of your rose.
As an alternative to a systemic, you can wait until pest season and use the spray-wash method of removing soft-bodied insects. On a frequent basis, you can direct a spray of water on the plants and blast off the insects. Horticultural soaps and oils can also help. These other methods can help preserve your spiders, honey bees, ladybugs and other beneficial garden helpers.