The corn earworm (Helicoverpa zea), also called cotton bollworm or tomato fruitworm, is a noctuid moth whose larvae feed in flowers and fruits. On outdoor hemp and cannabis it is the main "budworm": larvae tunnel into colas during flowering. Mature larvae are up to about 4 cm long and vary from green to brown or pink, with light and dark stripes along the body.
In practice
Moths migrate and lay eggs singly on flowers from mid to late summer, so damage peaks just as buds are bulking. Look for small holes, browning patches inside colas and pellets of frass; pull apart any bud with a brown spot. The bigger loss is often secondary Botrytis that starts in the frass. Bacillus thuringiensis sprays aimed at newly hatched larvae, before they bore in, are the usual biological option. Pheromone traps show when moth flights begin. Check what is registered for cannabis locally, including the pre-harvest interval.
Don't confuse with
- European corn borer: bores into stems and branches rather than buds.
- Bud rot alone: grey fuzz and brown tissue with no frass or tunnels.
- Tobacco budworm: Chloridea virescens, a close relative with similar habits.
The dry, single-seeded fruit of cannabis that growers call a seed; a hard shell (pericarp plus seed coat) encloses one embryo and does not split open.Hemp is cannabis grown for fibre, seed or other uses and, in many laws, defined as Cannabis sativa with no more than 0.3% THC by dry weight.The dense, elongated cluster of flowers that forms at the end of a stem or branch; the main cola tops the leader.Botrytis cinerea, the fungus behind bud rot or grey mould, which rots dense colas from the inside in cool, humid conditions late in flower.A soil bacterium whose crystal proteins kill caterpillars after they eat treated leaves; subspecies kurstaki and aizawai are the strains used against budworms.The minimum time, set on a pesticide label, that must pass between the last application and harvest so residues fall to permitted levels.The larval stage of moths and butterflies (order Lepidoptera); on cannabis, leaf-chewers, stem borers and bud-boring species whose frass seeds bud rot.Systematic, regular inspection of plants, traps and roots to detect pests and disease early, identify them correctly and record numbers for decisions.The pest or disease level, set in advance, at which a grower takes a specific control action because waiting longer would cost more than acting.
