SYMPTOMS
The whole plant wilts. Leaves and buds dry up and are webbed together with silvery webs (usually during flowering). Tiny bugs cluster at flowering tips.
DIAGNOSIS
mites: two-spotted spider mite (Tetranychus urticae), carmine spider mite (Tetranychus cinnabarinus), hemp russet mite (Aculops cannabicola)
SYMPTOMS
The plant may wilt. Leaves turn yellow, pucker, and are distorted. Leaves are coated with a clear, sticky, varnish-like substance on which gray-black mold grows. Small, pear-shaped insects with two “tailpipes” on their rear end cluster on the undersides of leaves.
They can be any color. Ants may also be present; they bring and protect aphids.
SOLUTIONS
• Sanitize
• Use beneficial insects
• Use beneficial mites
• Use beneficial fungi
• Use kaolin
• Use insecticidal soap
• Use neem
• Use horticultural oil
• Manage humidity
SOLUTIONS
• Sanitize
• Use screens on doors, vents, and windows
• Use traps
• Use beneficial insects
• Use beneficial fungi
• Use kaolin
• Use hot-pepper spray
• Use insecticidal soap
• Use neem
• Use horticultural oil
If there are ants:
• Use traps
• Use diatomaceous earth
DIAGNOSIS
aphids: green peach aphid (Myzus persicae), black bean aphid (Aphis fabae), hops aphid (Phorodon humuli), hemp louse (Phorodon cannabis)
SYMPTOMS
The plant wilts turn brown and die. Leaves curl up. Silver-white or yellowish speckles and streaks appear on leaves. Black specks that look like ground pepper cover plants.
DIAGNOSIS
thrips: onion or tobacco thrips (Thrips tabaci), greenhouse thrips (Heliothrips haemorrhoidalis), marijuana thrips (Oxythrips cannabis), Indian bean thrips (Caliothrips indices), western flower thrips (Frankliniella occidentalis)
SOLUTIONS
• Sanitize
• Use screens on doors, vents, and windows
• Use traps
• Use beneficial insects
• Use beneficial mites
• Use kaolin
• Use insecticidal soap
• Use neem
• Use spinosad
SYMPTOMS
The plant wilts turn yellow and die. In the field, this may affect groups of plants. In soil surrounding roots, look for large, C-shaped, white grubs with brown heads and three pairs of jointed legs.
SOLUTIONS
• Use beneficial insects
• Use beneficial nematodes
• Use beneficial bacteria
DIAGNOSIS
beetle grubs: Japanese beetle (Popillia japonica), European chafers (Melolontha spp.), black scarab (Maladera holosericea), African black beetle (Heteronychus aerator)
SYMPTOMS
Plant wilts. Leaves are stippled with pale dots and coated with a clear, sticky, varnishlike substance on which gray-black mold grows. Look for small, wedge-shaped insects on the undersides of leaves that jump and fly away rapidly when disturbed.
DIAGNOSIS
leafhoppers: glasshouse leafhopper (Zygina pallidifrons), red-banded leafhopper (Graphocephala coccinea), potato leafhopper (Empoasca fable).
SOLUTIONS
• Sanitize
• Weed
• Use row covers
• Use screens on doors, vents, and windows
• Use beneficial insects
• Use beneficial fungi
• Use insecticidal soap
• Use neem
• Use pyrethrin
SYMPTOMS
Plant wilts and collapses. Tap roots and stems are hollowed out. The presence of ants or termites confirms the diagnosis.
DIAGNOSIS
ants or termites
SYMPTOMS
Seedling or young plant wilts and dies. You find holes and tunnels in roots. In the soil and on roots, look for ¼-inch-long (6 mm) white larvae with brown heads and three pairs of jointed legs. You may also find numerous small, round holes between leaf veins. Leaves may be skeletonized (soft tissue eaten away but all veins remain).
SOLUTIONS
• Use traps
• Use diatomaceous earth
DIAGNOSIS
flea beetle larvae: hemp flea beetle (Psylliodes attenuate), hops flea beetle (Psylliodes punctulata), striped flea beetle (Phyllotreta nemorum), other flea beetles (Podagrica spp.)
SYMPTOMS
The plant wilts turns yellow, and dies. You find holes chewed in roots, or roots may be missing entirely. In soil, look for whitish C-shaped grubs with brown heads, but not with three pairs of jointed legs.
SOLUTIONS
• Sanitize
• Weed
• Use traps
• Use beneficial nematodes
• Use hot-pepper spray
• Use garlic spray
• Use insecticidal soap
• Use neem
• Use spinosad
• Rotate crops
DIAGNOSIS
weevil and curculio grubs: hemp weevil (Rhinoncus pericarps), cabbage curculio (Ceutorhynchus rapae).
SYMPTOMS
Plant wilts during the day but recovers at night; turns yellow and becomes stunted over time. Roots may be missing or rotten. Tiny, headless, legless, white larvae in soil surrounding sources confirm the diagnosis.
SOLUTIONS
• Sanitize
• Weed
• Use row covers
• Use screens on doors, vents, and windows
• Use tarpaper collars
• Use beneficial insects
• Use beneficial nematodes
• Use neem
• Use horticultural oil
SYMPTOMS
Plant wilts during the day but recovers at night; turns yellow and becomes stunted over time. Roots may have holes, be missing, or be rotten. In soil, look for large, dark crickets with shovel-like front legs; they burrow through the soil like moles and eat roots.
DIAGNOSIS
mole crickets: northern mole cricket (Neocurtilla hexadecyl), European mole cricket (Gryllotalpa gryllotalpa), African mole cricket (Gryllotalpa africana).
SOLUTIONS
• Weed
• Use row covers
• Use beneficial nematodes
• Use neem
• Use diatomaceous earth