Aphids are sap-sucking bugs that can weaken and kill rose plants. They can be controlled by spraying them with a homemade solution of environmentally friendly washing-up liquid diluted in water. It is important to spray before the aphids have a chance to lay eggs, as the spray will not kill the eggs. Aphids cluster on the leaves and foliage of roses, and symptoms of an infestation include green or pink insects, white cast aphid skins, and sticky honeydew. Natural enemies will normally reduce the aphid population by late summer, but it is important to check roses throughout the entire blooming season for pests such as spider mites.