Table 1. Common damage symptoms on protected herb crops and possible pest and disease causes*

Primary symptoms Secondary symptoms Affected crops Possible diagnosis

Reference Section
Poor seedling emergence Rotting from root tip upwards and seedling collapse in one direction Wide range Damping-off

(Pythium species)

C.1
Root rotting from soil surface downwards and seedling collapse in all directions Wide range Damping-off

(Rhizoctonia solani)

C.1
Stem base rot Roots sparse, discoloured and rotting Wide range Root and crown rots

C.1
Soft rot of foliage Watery rot plus white fluffy growth, often with hard black resting structures Wide range Sclerotinia rot

C.8
Leaf and stem decay plus white/grey furry growth and grey spore production Wide range Grey mould

(Botrytis cinerea)

C.2
Soft rotting, no fungal growth visible Wide range Bacterial soft rot

C.9
Wilting Vascular staining Basil Fusarium wilt

C.6
Mint Verticillium wilt

C.6
Sage Verticillium wilt

C.6
Roots sparse, discoloured and rotting Wide range Root rots

C.1
Roots often sparse, truncated, rotting. Small, semi-translucent, legless white larvae with black heads present among roots Wide range; parsley most susceptible Sciarid fly larvae

B.3
Plants often stunted and yellow. Plump, white/cream legless larvae with brown heads present, among sparse root system or at stem base Long term plants e.g. stock plants Vine weevil

B.10
Stunting Roots sparse, discoloured and rotting Wide range Root rots

C.1
Leaf mottling, vein clearing, distortion or discolouration Umbelliferous crops Viral diseases

C.10
Wilting with vascular staining in the stem E.g. basil, mint or sage Wilts

C.6
Distorted and thickened stems in spring Mint Rust

C.5
Plants often wilting and yellow. Plump, white/cream legless larvae with brown heads present, among sparse root system or at stem base Long term plants e.g. stock plants Vine weevil

B.10
Discoloured foliage Wilting with vascular staining in the stem E.g. basil, mint or sage Wilts

C.6
Leaf mottling, vein clearing or distortion Umbelliferous crops Viral diseases

C.10
Fungal growth visible:
On soil White/pale brown fungal strands growing over soil/compost surface Wide range Rhizoctonia root rot or damping-off
C.1
On stems/plant bases White fluffy growth often with hard black resting structures Wide range Sclerotinia rot

C.8
White/grey furry growth and grey spore production Wide range Grey mould (B. cinerea)

C.2
White/pale pink growth on stems, plus vascular staining Basil Fusarium wilt

C.6
On leaves Sparse, white powdery growth on upper surfaces Wide range Powdery mildew

C.3
White/grey/brown growth on leaf undersides, plus brown/yellow angular lesions on upper leaf surface Wide range Downy mildew

C.4
Brown/red/orange pustules on leaf underside Wide range Rust

C.5
Leaf damage Yellow/brown lesions, sometimes angular, with spore production on leaf underside Wide range Downy mildew

C.4
Water-soaked lesions, angular appearance, sometimes at leaf margin with a yellow halo, vein blackening Coriander, fenugreek Bacterial diseases

C.9
Pale to brown lesions, mainly circular, fungal growth sometimes visible in lesion centre Wide range Leaf spots

C.7
Red or brown lesions, with brown/red/orange pustules on leaf underside Wide range Rust

C.5
Whitish fuzzy-edged spots, usually in groups, sometimes merging to form bleached areas Wide range Leafhopper

B.1
White clearly-defined round or oval spots, often associated with white tunnels or mines Mainly basil, mint Leaf miner

B.8
White or silvery flecks or patches, with small black faecal spots inside the white or silvery areas Mainly basil, chive, mint, parsley Thrips

B.6
Fine yellow speckling, sometimes with yellow or necrotic patches Mainly mint, tarragon Two-spotted spider mite

B.9
Sticky patches, sometimes with sooty moulds Wide range Aphids or whitefly

B.4, B.5
Leaf distortion E.g. Leaf mottling, vein clearing, discolouration Umbelliferous crops Viral diseases

C.10
Mis-shapen leaves, vein distortion, leaf crinkling, small narrow insects may or may not be present on leaf undersides Basil, mint, parsley, tarragon, thyme Thrips

B.6
Mis-shapen or curled leaves, sometimes with leaf yellowing. Presence of aphids and/or cast skins. Leaves sometimes sticky with black sooty moulds Wide range Aphids

B.4
Rolled-up leaves, spun together with silk Wide range, particularly mint Leaf-roller/webber caterpillars

B.7
Holes in leaves or chewed edges Irregular holes, leaf edge shredding. Slime often present Wide range Slugs or snails

B.11
Holes or ‘windows’ (only lower surface removed, upper surface intact). Barrel-shaped droppings often present but no slime Wide range Caterpillars

B.7
Round pits or ‘shot-holes’ in leaves Cruciferous herbs, sorrel Flea beetles

B.12
Notches cut from leaf edges Long term plants e.g. stock plants Vine weevil

B.10
Frass (droppings) present Small, black dried-liquid droppings on leaves. Small black flies often present on compost, plants, pots, floor or bench Particularly basil, mint, thyme Shore fly

B.2
Larger, dry black droppings on leaves, often barrel-shaped Wide range Caterpillars

B.7

*Considers biotic (pest or disease) causes only; possible abiotic factors include drought, water-logging, physical damage or nutritional problems.