Dear,

Basically, Cercospora arachidicola (early leaf spot) causes brown lesions (spots) surrounded by a yellow halo. In general, early leaf spot can be found as early as 30 days after planting. Early leaf spots produce spores mainly on the top of the leaf.

Late leaf spot caused by Cercosporidium personatum, generally is most aggressive. Late leaf spot causes dark brown to black spots that may or may not have halos. Late leaf spots produce dark brown spores, usually on the underside of the leaf.

You can find attached some pictures of both diseases.

Greats,

Nelson Suassuna

This is very difficult to distinguish between symptoms of early and late leaf spot. Early leaf spot usually causes brown lesions (spots) that are surrounded by a yellow halo. Although early leaf spot can be found as early as 30 days after planting, first lesions often are not observed until mid-July.

Early leaf spots produce tufts of silvery, hair-like spores on the top of the leaf. These spores can be seen with the help of a good magnifying glass. 

Late leaf spot has become more common recently and has been the most important leaf spot the past few growing seasons.

Late leaf spot causes dark brown to black spots that may or may not have halos. Late leaf spots produce dark brown spores, usually on the underside of the leaf. The mass of spores can be seen without magnification and give the spot a velvety appearance. It is important to determine if late leaf spot is present since it can be more difficult to control.

while agreeing with the commentary above, I would like to add that early and late connote appearance time in the plant developmental process and their separation if not time-bound may be made by microscopy. Field observation may be confusing if based on the color and overall nature of spot because these might have been influenced passively by convergent environmental influences making field diagnosis vague. Please isolate and use microscopy otherwise the explanation of my learned collegue Dr Suassuma suffices. 

Agree with Dr. Nelson Dias Suassuna as  Cercospora arachidicola appears early stages of  plant growth and development as brown lesions (spots) surrounded by a yellow halo while,  Cercosporidium personatum at later stahges as dark brown to black spots that may or may not have halos.