My terrace has always been embellished with green and flowering plants. For two years now, some shrubs (cherry laurel, viburnum, privet, jasmine, camellia ...) have had leaves that blacken on the tips and edges and then the plants gradually die. I have already completely changed the pots, the soil and I have put new plants but everything repeats itself. I don't think it depends on irrigation because I've never had any problems before ... What can I do? Thank you
Dear Manuela, thank you for writing in the questions and answers section of the gardening column. His plants most likely continue to be affected by aphids. Aphids are a category of insects, usually also called plant lice, within which several species are grouped, all united by having a mouth apparatus capable of piercing the leaf surface and sucking the sap of the plants. These aphids suck the sap and emit a sugary substance called honeydew, which falls on the leaves and on the ground below and is fertile ground for many fungi, in particular for fungi known as smoky, dark in color (black-brown) which they damage the leaves and prevent photosynthesis causing stress and death in the plant. Aphids practically live in symbiosis with the ants which derive an important food source from the honeydew of these and in turn carry the aphids, moving insects from one plant to another and creating a potential vector for fumaggini. Most likely, even if you have eliminated the plants, changed the pots and renewed the growing medium, on your terrace or in the immediate vicinity there are plants affected by aphids that continue to be a source of insects and continuous waves of attacks on your plants. We therefore advise you to check that there are no plants in the vicinity showing an evident attack by aphids. In the event that your plants are again attacked by aphids, there are different methods of struggle. First of all, there is the fight through insecticides, which uses specific or broad-spectrum insecticides that use the following active ingredients :, Quinalphos, Fenitrothion, Malathion, Triclorfon, Diflubenzuron, Endosulfan, Midacloprid, Pirimicarb. Alternatively, a biological control can be implemented, for example by introducing natural predators such as ladybugs (the species Adalia bipunctata in particular) which feed on aphids, or small wasps such as Chrysoperla carnea, which eliminates aphids by laying their eggs in the larvae and in adults of aphid.