Have you seen signs of pests on your cannabis leaves? Here’s what to do.
The cannabis plant is susceptible to pests, leaf damage, and disease. While some pests can be tolerated with little effect on yield, others may compromise the quality of your crops. In general, preventative care is the best way to ensure the health of your plants.
You need to check if it’s not too late for treatment. If you notice tiny dots on the leaves, use an insecticidal soap spray. You can also use organic insecticides but they may have harmful effects on bees and other beneficial insects. In case of infestation, try removing affected leaves so that they don’t harm other parts of the plant.
SYMPTOMS
Ants march along plant stems. They bring aphids, scale, and mealybugs. Leaves are coated with a clear, sticky, varnishlike substance on which gray-black mold grows.
DIAGNOSIS
ants
SOLUTIONS
• Use traps
• Use diatomaceous earth
SYMPTOMS
Caterpillars, from ⅜ to 2 inches (10 mm to 5 cm) long, are green, brown, pinkish white, pale brown, or almost black. Rows of dots or alternating light and dark stripes run along the length of their bodies. Their heads are yellow-green, brown, or dark yellow-brown.
DIAGNOSIS
leaf-eating caterpillars and budworms: cotton bollworm (Helicoverpa armigera), corn earworm (Helicoverpa zea), flax noctuid (Heliothis fireplace), hemp bagworm (Psyche cannabinella), silver Y moth (Autographa gamma), dot moth (Melanchra persicaria), cabbage moth (Mamestra brassicae), garden tiger moth (Arctia caja), common hairy caterpillar (Spilosoma obliqua), beet webworm (Loxostege sticticalis), hemp dagger moth (Plataplecta consanguine)
SOLUTIONS
• Weed
• Use screens on doors, vents, and windows
• Use cutworm collars
• Turn off lights at night
• Remove pests by hand
• Use beneficial insects
• Use beneficial nematodes
• Use beneficial bacteria
• Use beneficial protozoa
• Use insecticidal viruses
• Use hot-pepper spray
• Use garlic spray
• Use insecticidal soap
• Use neem
• Use spinosad
• Use pyrethrin
• Do not plant near corn (maize)
• Rotate crops
SYMPTOMS
You see caterpillars on leaves and the main leaf veins are eaten away. You may also see irregularly shaped holes in leaves, entire leaves missing, or tiny, black pellets of caterpillar poop. Also look for caterpillars, curled into C shapes, hiding in the soil.
DIAGNOSIS
cutworms and armyworms: black cutworm (Agrotis epsilon), paddy cutworm (Spodoptera litura), beet armyworm (Spodoptera exigua), playback cutworm (Agrotis gladiatorial), common cutworm (Agrotis segetum), bertha armyworm (Mamestra configurator)
SOLUTIONS
• Use cutworm collars
• Remove pests by hand
• Use beneficial insects
• Use beneficial nematodes
• Use beneficial bacteria
• Use insecticidal viruses
• Use hot-pepper spray
• Use garlic spray
• Use insecticidal soap
• Use neem
• Use spinosad
SYMPTOMS
You find copper-colored, metallic green beetles or beetles that resemble brown ladybeetles on plants. Large, ragged holes appear in leaves, which may be skeletonized (soft tissue eaten away but veins remain).
DIAGNOSIS
large leaf-eating beetles: Japanese beetle (Popillia japonica), Indian bean beetle (Epilachna dodecastigma)
SOLUTIONS
• Weed
• Use row covers
• Remove pests by hand
• Use beneficial fungi
• Use hot-pepper spray
• Use garlic spray
• Use insecticidal soap
• Use neem
• Use spinosad
SYMPTOMS
As you walk among plants, large pests leap away from you. You find large, round, smooth-edged holes in leaves. Plants may be stripped of leaves.
DIAGNOSIS
grasshoppers: two-striped grasshopper (Melanoplus bivittatus), sprinkled locust (Chloealtis conspersa), clear-winged grasshopper (Camnula pellucid), elegant grasshopper (Zonocerus elegans), citrus locust (Chondracris rosea)
SOLUTIONS
• Weed
• Use row covers
• Use screens on doors, vents, and windows
• Remove pests by hand
• Use beneficial fungi
• Use beneficial protozoa
• Use neem
• Use diatomaceous earth
SYMPTOMS
Pale green, ½-inch-long (13 mm) caterpillar-like larvae are on leaves. Leaf edges have ragged holes, or leaves are skeletonized (soft tissue eaten away but veins remain).
DIAGNOSIS
hemp sawfly (Trichiocampus cannabis)
SOLUTIONS
• Use row covers
• Use screens on doors, vents, and windows
• Remove pests by hand
• Use neem
SYMPTOMS
You find dark red-brown, ½-inch-long (13 mm), flattened, segmented insects with two large pincers on their rear ends. Tender new leaf blades have holes in the middle.
DIAGNOSIS
common earwig (Forficula auricularia)
SOLUTIONS
• Use earwig traps
• Use insecticidal soap
• Use diatomaceous earth
• Use spinosad