Sweet leaf suffering from chlorosis
Public DomainSweet leaf suffering from chlorosis - Credit: Jim Conrad

Greensickness is another word for chlorosis, a condition affecting plants wherein their leaves don't produce enough chlorophyll, turning pale yellow. Such plants are unable to manufacture carbohydrates through photosynthesis, and will eventually die.

Chlorosis is generally caused by a lack of nutrients. This could be due to a lack of minerals in the soil, a lack of nitrogen, a problem with the soil pH, waterlogged or damaged roots, pesticides or exposure to sulphur dioxide.