Pests of Geraniums

[tiedam wendy]

For the second year running our geraniums have been attacked by a small moth which seems to lay its eggs on the plants,shortly after the geraniums and a couple of pelagoniums have started to die, some of the stems have a black gooey stuff in them.Can anyone help please.We live in Spain and the affected plants are in pots or baskets in our garden.