Leaf spot

Leaf spots or leaf rot is the appearance of round blemishes found on the leaves of many species of plants, mostly caused by parasitic fungi or bacteria.

Symptoms
A typical spot is "zonal", meaning it has a definite edge and often has a darker border. When lots of spots are present, they can grow together and become a blight or a blotch. Fungal spots are usually round or free-form in shape. Spots caused by Alternaria brassicicola tend to be darker and have a more irregular margin than those cause by Alternaria brassicae. Brussels sprout yields can be seriously reduced due to a low tolerance for spots and blemishes.

Chemical
Treat with thiram or iprodione. Destroy diseased crops after harvest.

Prevention
Avoid using overhead watering systems.

Chemical
Iprodione, difenoconazole, tebuconazole and strobilurin are suitable protectants.