How to Manage Pests
Pests in Gardens and Landscapes
Ammonia injury to lettuce
Leaves with ammonia injury temporarily wilt and may turn dark green or gray green. A cross section of
the taproot shows that the center has turned yellow, red, or brown. Smaller roots may be dead.
Ammonia injury occurs when fertilizers break down to form free ammonia in amounts toxic to lettuce. This
is most common with aqua ammonia and urea fertilizers. Chicken manure can also be a problem. Cool, waterlogged,
compacted soil exacerbates the situation. Keep ammonium forms of nitrogen out of the seed row. Avoid overfertilizing.
taproot due to ammonia injury