'Buck eye rot' is a disease of which crop

'Buckeye rot' is a disease of Water chestnut.
Buckeye rot is one of several fruit-rotting diseases that attack both green and ripe fruit, especially where the fruit touches the soil. The lesion is rounded with alternating bands of light and dark brown in concentric circles. The lesion appears water-soaked at first but later may become leathery on the surface.
Staking or plastic mulch to prevent fruit from contacting the soil is an effective control. The disease is worse in hot, wet weather. Fungicides offer little control to soil-contact type diseases.