**3.1 Bottom rot disease of lettuce**

Bottom rot disease of lettuce can be recognized by brown spots that initially appear on the midribs of the lower leaves that are in contact with the soil (Figure 5 A). The rot spreads rapidly under favorable conditions to affect larger sections of the midrib and leaf blades, and may affect the inner leaves of the head. Symptoms are more severe during heading.

Fig. 5. Disease symptom of bottom rot (A) and Fusarium wilt of lettuce (B). Photos courtesy of A. F. Sherf (A) and T. A. Zitter (B).
