What is wrong with my dianthus?
Lynsey Spendlove, by email
Stefan says: Many dianthus have looked like this during the summer and the symptoms are often due to drying out and the heat. However, you say you suspect a fungal disease and you might just be correct.
One of the most common leaf spot diseases of dianthus may give rise to this characteristically extensive, pale straw-coloured discolouration that spreads from the point of attack along the tip of the leaf and downwards. The factor that may mitigate against this is that the leaf spot diseases tend to be most serious in damp, cool summers; not what we have just experienced.
There is no reliable control measure so carefully trim back the damaged growth, give a little high potash feed and see what happens in the spring.