Question

Basil with disease   Hello John,

We're from Colombia, and my husband and I started growing our own herb garden not to long ago.  We started with Basil, and now that it's huge and blooming, something started happening to the leaves!  Our local garden shop hasn't been able to help.  Can you please help us identify what is causing this and treatment?  We'd hate to have to rip it all out!  It's gorgeous!

Cheers from COLOMBIA!

Answer
Sorry for the delay in answering.  

Your photograph shows leaf spots which are characteristic of three fungal diseases (caused by _Cercospora_ spp., _Alternaria_ spp._, and _Colletotrichum_ spp.) that occur on basil in temperate and sub-tropical zones. Depending on your altitude, your climate may more temperate than tropical.  To reduce the incidence of foliar disease, always water at the base of the plants and never wet the leaves with sprinklers. Pull off and dispose of diseased foliage at first sign of disease. For minor fungal foliar disease occurrence, basil plants may be sprayed weekly with a fungicide containing potassium bicarbonate, such as Bonide Remedy or GreenCure Organic Fungicide. I am not sure of what brands are commonly found in Colombia.