Pest identification
What's eating my romaine lettuce?
Slugs and snails
Signs: Holes and ragged edges in outer and lower leaves; slime trails through the head base
Control: Iron phosphate pellets; remove dead lower leaves that provide shelter; water in the morning
Lettuce aphid (Nasonovia ribisnigri)
Signs: Dense grey-green colonies deep inside the head; contamination makes the lettuce difficult to wash clean
Control: Grow resistant varieties (labeled Nr); apply insecticidal soap early before aphids penetrate the head; remove outer aphid-bearing leaves
Caterpillars (cabbage looper, Trichoplusia ni)
Signs: Large holes through multiple layers of leaves; frass (droppings) visible inside head
Control: Inspect and hand-pick; Bacillus thuringiensis (Bt) spray on foliage; use row cover to exclude adult moths
Birds (pigeons, sparrows)
Signs: Young transplants pecked and leaves stripped; heads pecked open as they mature
Control: Bird-proof netting supported above the crop; reflective tape as a deterrent
Keep romaine lettuce pest-free
Healthy plants resist pests best. Get the basics right:
Romaine Lettuce pests — FAQ
What is eating my romaine lettuce?
Romaine lettuce's tall, upright heads attract slugs in the lower leaves, aphids on inner leaves, and caterpillars boring through the head. Birds and rabbits target young transplants. Downy mildew (though a disease) is often confused with pest damage. Slugs and aphids are the two most reliably damaging pest groups for Romaine.
How do I get rid of slugs and snails on romaine lettuce?
Holes and ragged edges in outer and lower leaves; slime trails through the head base Iron phosphate pellets; remove dead lower leaves that provide shelter; water in the morning
How do I get rid of lettuce aphid (nasonovia ribisnigri) on romaine lettuce?
Dense grey-green colonies deep inside the head; contamination makes the lettuce difficult to wash clean Grow resistant varieties (labeled Nr); apply insecticidal soap early before aphids penetrate the head; remove outer aphid-bearing leaves
How do I get rid of caterpillars (cabbage looper, trichoplusia ni) on romaine lettuce?
Large holes through multiple layers of leaves; frass (droppings) visible inside head Inspect and hand-pick; Bacillus thuringiensis (Bt) spray on foliage; use row cover to exclude adult moths
How do I get rid of birds (pigeons, sparrows) on romaine lettuce?
Young transplants pecked and leaves stripped; heads pecked open as they mature Bird-proof netting supported above the crop; reflective tape as a deterrent