make sure you pick off all affected leaves and burn them. dont know if you have any pesticides available to use.
Are they heavily infested? or just the odd leaf. if its most leaves then I'd tear the affected bit off the leaf.

It occurs on every leaf, but the growth seems to accelerate beyond it. It makes the plant very untidy and ugly, the blossoms do however keep blooming. All of the plants are volunteers and come up at various times of the year, but there are always plants growing at some stage and they almost immediatley show infestation. I do have some "organic" pesticides like BT and Spinosad but not sure they will work with leafminers since they will be in the leaf as larvae and not on the outside.

a systemic insecticide should still see the little blighters off as they eat the leaf. at least they still flower well.