What's eating my napa cabbage 'bilko'?

Napa Cabbage 'Bilko' is particularly attractive to the diamond-back moth and imported cabbageworm, which target the dense folded leaves. Slugs favor the soft inner head. Aphids and flea beetles complete the main threat list. Bt-k sprays and row covers are the primary controls for this crop.

Small windowpane holes on leaves as young larvae skeletonize from the underside; older larvae eat clean holes; attacks inner head leaves Bt-k spray at first instar; spinosad rotation to manage Bt resistance; row cover before moth flight

Ragged holes through outer wrapper leaves; frass contaminates the head; caterpillars hide deep in folded leaves Regular Bt-k application every 7–10 days; inspect and remove egg clusters; encourage Cotesia glomerata parasitoid wasps

Holes and slime trails on outer leaves; slugs work inside the head overnight causing significant internal damage Iron phosphate pellets placed around each head; remove debris; use beer traps at field margins

Grey colonies deep in the head wrapping; impossible to wash out completely, can make heads unmarketable Row cover to prevent colonization; strong water spray early; avoid planting near older Brassica stands