Cutworms are the larvae of several noctuid moths, notably the black cutworm (Agrotis ipsilon). They are plump, greasy-looking grey to brown caterpillars, up to about 4-5 cm long, that curl into a C-shape when disturbed. They hide in the top layer of soil by day and feed at night.
In practice
The giveaway is a seedling or young transplant cut clean through at or just below the soil line overnight, often with the top lying beside it. Digging gently around the stem usually turns up the culprit. They are an outdoor and greenhouse problem, worst in fields that were weedy or grassy the season before. Simple stem collars of card or plastic pushed into the soil around transplants stop most damage. Hand-picking at night with a torch works in small gardens. Entomopathogenic nematodes and Bacillus thuringiensis are biological options. Check what is registered for cannabis locally.
Don't confuse with
- Damping-off: the stem rots and pinches at the base; it is not chewed through.
- Slugs: slime trails and ragged leaf holes.
- Corn earworm: feeds in buds later in the season.
A seedling is a young cannabis plant from emergence of the cotyledons until it has several sets of true leaves, typically the first 2-3 weeks.Transplanting moves a plant and its root ball into a new container or the ground; done gently it causes little shock, but GenetixBay advises against it for autoflowers.An entomopathogenic nematode applied as a soil drench whose infective juveniles enter fungus gnat larvae and thrips pupae and kill them with symbiotic bacteria.A soil bacterium whose crystal proteins kill caterpillars after they eat treated leaves; subspecies kurstaki and aizawai are the strains used against budworms.The collapse of seedlings or cuttings when soil-borne pathogens such as Pythium, Rhizoctonia solani and Fusarium rot the stem at the soil line.Helicoverpa zea, a moth caterpillar that bores into developing cannabis flowers outdoors, leaving frass that triggers bud rot; growers call it budworm.The larval stage of moths and butterflies (order Lepidoptera); on cannabis, leaf-chewers, stem borers and bud-boring species whose frass seeds bud rot.
