Early blight -Alternaria linariae (=A. tomatophila; formerly known as A. solani)
Infections begin as small brown spots on older leaves that quickly enlarge. A yellow halo usually surrounds the lesions. The lesions develop a "bulls-eye" pattern of concentric rings that can be seen with a hand lens. Individual lesions enlarge and coalesce and can kill entire leaves. The disease can also move to stems and fruits and produce dark lesions.
This is a very common foliar disease of tomato plants that can result in defoliation and reduced yields. It can also infect eggplant. The fungus overwinters in soil and plant debris and can also be transmitted on seed and transplants. Early blight is typically splashed by rainfall onto lower leaves early in the season.
When leaves die, fruits become more vulnerable to sunscald. Infected, dead leaves may stick to fruits. The disease can spread during wet or dry weather but is favored by rainfall and heavy dews. The disease spores are wind-blown, allowing the disease to spread through a garden or neighborhood.
Early blight symptoms on fruit
Lesions with yellow halo on foliage
Closeup of lesion with bulls-eye pattern
Late stage symptoms on tomato plants