From April to May, aphids multiply tremendously due to the dry, hot weather conditions.
Typical for the damage caused by aphids are deformed, discoloured and sticky, shiny leaves. This damage is sustained when an aphid inserts its proboscis into the plant to reach the sap. This is then excreted as honeydew, which encourages the invasion of black spot fungus and other insects.
Preventing aphid infestation
Prevention starts on procurement of your roses. Only buy healthy, strong plants. These must have
a well-rooted ball, at least 3 propagation stems and healthy-looking green leaves.
For bare-rooted roses, undamaged propagation stems and as many fine hair roots as possible should be available. Strong growth is advantageous against pests.
Cultivation based on natural processes and different types of plant compilations (e.g. roses with lavender or onions) also help to prevent pests. Excessive amounts of fertiliser (with nitrogen) or water deficits promote aphid attacks. Please observe the planting and care guidelines when you buy your rose bushes.
Natural methods of control
• Aphids have a whole series of natural enemies in the garden. These include ladybird larvae, ladybirds, lacewings, earwigs or also hoverflies. Deadwood corners, lacewing boxes or insect hotels provide beneficial organisms with a good opportunity of settling in your garden. When the range of food available is large, these aphid hunters can increase greatly in number, and the aphid infestation will be less severe. Ensure that you can provide the beneficial organisms with optimum conditions. An organised garden in which plant protection is constantly being used is not attractive for insects such as ladybirds.
• If the infestation is small, collect aphids by hand or rinse them off with a strong jet of water. Repeat the procedure several times. After treatment, ensure good ventilation.
• Soap solution: Mix 1 tablespoon of soap (unscented) with 1 litre of water. Spray the rose over several days with this mixture.
• Stinging nettle decoction: Use over several days until the affected areas are free of aphids.
• Remove badly damaged parts of the rose.
• Neem: A natural pesticide. Spray roses with Neem. This inhibits egg-laying and thus prevents progeny. Use as early on as possible.
• Use chemical pesticide according to the instructions. It penetrates the plant and is adsorbed by the aphids via the sap. Only use in exceptional cases as such pesticides damage the environment.