Blight
Blight is a rapid and complete chlorosis, browning, then death of plant tissues such as leaves, branches, twigs, or floral organs. Accordingly, many diseases that primarily exhibit this symptom are called blights. Several notable examples are:
Clavibacter michiganensis
The causal agent of bacterial wilt and canker of tomato survives in or on seeds for up to 8 months but occasionally also in plant refuse in the soil. The pathogen can be spread long distances because of its association with seeds. The risk of spreading the bacteria to healthy tomato plants is greatest during transplanting, tying, and suckering or any time when the host may be wounded. Once the bacteria enters the plant through a wound, it will move and multiply primarily in the xylem vessels. Once established, the bacteria may move into the phloem, pith, and cortex. Infection can result in either systemic or superficial disease. Systemic infections appear in 3–6 weeks and the risk of secondary infection goes up with water-splashing. The common occurrence of latent infections – presence of the pathogen within the host yet the host shows no symptoms – makes this pathogen especially dangerous.