Published Mar 15, 2025
It is caused by the fungus Septoria lycopersici. This fungus can attack tomatoes at any stage of development, but symptoms usually first appear on the older, lower leaves and stem when plants are setting fruit. Symptoms usually appear on leaves but can occur on petioles, stems, and the calyx.
The first symptoms appear as small, water-soaked, circular spots 1/16 to 1/8" in diameter on the undersides of older leaves. The centers of these spots then turn gray to tan and have a dark-brown margin. The spots are distinctively circular and are often quite numerous. As the spots age, they sometimes enlarge and often coalesce.
A diagnostic feature of this disease is the presence of many dark-brown, pimple-like structures that are readily visible in the tan centers of the spots. When spots are numerous, affected leaves turn yellow and eventually shrivel up, brown, and drop off.
Defoliation usually starts on the oldest leaves and can quickly spread progressively up the plant towards the new growth. Significant losses can result from early leaf-drop and often leads to the subsequent sun scalding of the fruit when plants are prematurely defoliated.
Management of Septoria leaf spot (Septoria blight):
The above cultural practices for bacterial spot and specks can also be applied here.
Chemical control to be used here may include:
Triazoles: Defenacozole eg Score https://www.agropests.co.ke/products?s=score
Tebunaconazole eg Folicur https://www.agropests.co.ke/products?s=folicur ,
Nativo https://www.agropests.co.ke/products?s=nativo ,
Klassic https://www.agropests.co.ke/products?s=klassic
Uster Top https://agropests.co.ke/products?s=uster%20top
Azoxystrobin e.g Ortiva https://www.agropests.co.ke/products?s=ortiva
Fluopyram eg Luna Sensation https://www.agropests.co.ke/products?s=luna