VIRUSES -Virus symptoms often include color changes in the leaves such as a mosaic or mottled pattern of light and dark green.  Other color changes could appear as ring patterns of light green to yellow.  Additional symptoms include stunted or malformed new growth, unusual flower colors, and dieback of terminal growth.  However, it is easy to confuse these symptoms with nutritional deficiencies, environmental effects such as air pollution, and especially this year, drought stress. At the Morris Arboretum, we have noticed a mosaic causing distortion in the leaves of some of our rose plants. Most plant viruses cause systemic infections and there is no cure for infected plants. Plant viruses are commonly spread from plant to plant by insects that feed on sap such as aphids, thrips and white flies. Other common ways the virus is spread include infected seeds, sap, divisions, grafted plant varieties, bulbs and pollen. Viruses can also be spread by horticultural activities such as vegetative propagation and pruning.  Many viruses can survive in weeds adjacent to the horticultural plants that become infected in our gardens. Controlling virus diseases often involves removal of infected plants prevent the virus from spreading to adjacent healthy plants.  Insect management is critical as viruses can  move through the garden in insects feeding on infected plants before feeding on near by healthy plants.  Weed removal is also very important since they can be the primary source of infected plants where insects breed or overwinter before moving onto healthy plants in the garden.  To avoid planting virus infected varieties in your garden, purchase certified virus clean stock and be prepared to remove plants that exhibit disease symptoms.