What's eating my bok choy 'black summer'?

Bok Choy 'Black Summer' is a brassica and shares the full family pest load: cabbage white caterpillars shred leaves, flea beetles pepper seedlings with tiny holes, aphids colonise growing tips, and slugs rasp through young plants at night. Caterpillars are the single most destructive threat to mature plants.

Irregular holes eaten through leaf blades; frass (dark green droppings) visible; entire plants can be skeletonised if unchecked. Cover with fine mesh or fleece from transplanting; hand-pick eggs and caterpillars; apply Bacillus thuringiensis var. kurstaki (Btk) spray as a biological control.

Numerous small, round holes (shot-hole pattern) in seedling and young leaves; severe attacks stunt or kill young plants. Use row cover immediately after sowing or transplanting; delay transplanting until plants are larger; apply diatomaceous earth around plants; sticky yellow traps can monitor populations.

Dense blue-grey colonies on growing tips and undersides; leaves curl and growth is severely checked; honeydew attracts sooty mould. Blast with water; introduce parasitic wasps and ladybirds; spray insecticidal soap on colonies; remove and destroy badly infested tips.

Ragged holes and slime trails on leaves, especially near soil level; worst on young plants in wet conditions. Apply iron phosphate slug pellets around plants; use copper tape barriers in raised beds; hand-pick at dusk; improve drainage to reduce slug habitat.